Landracing Forum
Tech Information => Aerodynamics => Topic started by: Simspeed on April 19, 2019, 09:03:32 AM
-
Does anyone have data or records of frontal area and Cd numbers from top contenders for unlimited wheel driven streamliners? I'm interested in knowing how my body design compares with the best in class liners. Here's an image of the largest cross-section area of the design I'm working with. Thanks again...
-
Oops...I forgot to add the stabilizer fin cross-section.
-
Does it have Wheels.... and tires.... don't forget that racing tires are required and I don't see those...
-
Sure does Stainless but they don't show up in this widest cross section cut. I've used the M/T 24.5 x 7.5 x 16 dimensional profile for all four tires in my design. The spreadsheet showing needed hp for a given speed zeros out the tire Cd for streamliners, so I'm not trying to capture that drag under the body. For now I'm only interested in the given inputs that reflect car weight, rolling resistance, frontal area, and body Cd to see HP required for a given speed. Thanks to whoever made this and all the other spreadsheets available to forum users. So far the ideal data from the spreadsheet is projecting good numbers for my design given current records for unlimited liners. Thanks for your comments Stainless...
-
Though your shape is not a square which would be less than 2 feet a side and your shape is taller than it is wide. Are you sure you can fit everything in there- like you (how big are you) and the tires already mentioned (tires grow at speed, need clearance) not to mention cage etc. Take off 3-4" from width to be the drivers compartment (minimum tube sizes x2 with some padding and etc) and you don't have a lot of space for shoulders. Since your picture indicates power is not some big honking V8 don't have that but how big is the power plant? Having built one packaging gets seriously tight when you start adding systems- fire, coolant and fuel tanks, running gear, electronics, blowers etc etc. Not having the luxury of computer systems and such when I built mine I built a frame from PVC and sat me and engine it it to check dimensions. Still screwed up the cage height (helmet clearance= 3" over the top plus padding on all bars that are in proximity.) So yours becomes a serious lay down driver position- Visibility from same? (over the tires that are 24.5" tall etc- more with growth) Stainless has experience with these issues I think he may comment on. Good luck. Your shape is more like Marlo's car. I don't know if they have posted any numbers. Mine was shaped more like Goldenrod with a bit more nose droop and with mid rather than front engine. Goldenrod was 8.53sq ft frontal with Cd of .1165. The car had negative lift by design so weight was not added. I can provide reference for this if you want.
-
Thanks Jacksoni that would be great. Any info from or about those who have done it successfully would be appreciated. Yes this design is a very tight squeeze for someone of my height. I designed everything around the engines (two turbo 4 rotor Mazdas) and a 6' 2" driver which happens to be my height. The overall length is 36' which I copied from the team Vesco liner. My first design was 22' but I discovered Cd drops with length for the Sears Haack shape which I'm using. Calculated Cd dropped from .08 to .02 with the added length which is needed to fit everything inside.
The chassis I designed uses 1 .75" double hoops for the driver cage, 1.625 tubing for everything behind the firewall. The front half and steering section will use thick wall oval tubing for added strength. So far everything you mentioned fits inside the shell and chassis.
The drive train consist of electric wheel motors to drive all 4 wheels so there's no need for a differential, drive shaft, or transmission to transmit power to the ground (salt actually). The 4 rotor engines will spin axial PM generators that push electrical power to the wheel motors. There will be no batteries on board in this design. The rotary engines, generators and motors I've researched are capable of a combined 2,100 hp in this application which appears to be more than enough to set a few records God willing...
-
There are two SAE papers you might find interesting: The aerodynamic Design of the Goldenrod- to increase Stability, traction and Speed. Walter Korff. # 660390 from 1966.
Also: Aerodynamic Drag Characteristics
of Land Speed Record Vehicles. Alex Tremulis 660387
If you can't get from SAE, PM me an email or fax # and I can scan or fax them.
I have some other stuff but more applicable to cars as opposed to streamliners and you are beyond that for sure.
-
“Calculated Cd dropped from .08 to .02 with the added length..”
Strongly suspect there is something wrong with this statement or the basis on which it is concluded, in going from 22’ to 35’ length. Would be interesting to see the analytical rationale that produced it.
-
Before you go too far I would build the driver's compartment of the car. I'd be using 1 5/8 dom round tubing throughout the main portion of the car. It's going to have more than adequate strength when properly triangulated and you're going to need every fraction of an inch of space to meet the dimensions you're calling for. The next thing you need to invest in is all your safety equipment. Everything has to be within reach and operable when you're belted in TIGHTLY. Remember, helmets are huge these days, suits, boots and gloves are all large and bulky. When you've got all that sorted then you've got to be able to do the mandatory bailout in a minimum amount of time. It's a lot easier to modify the cockpit area before it becomes an integral part of the whole car and the dimensions you're calling out are definitely really tight.
The other thing you might want to think about is that as you age there is a tendency to expand. You might want to think about that a little. Unfortunately, I'm speaking from experience. :-D :-D :-D
Good luck with the project. It sounds fascinating.
Pete
-
X 4 or 5. Exactly what I was trying to say as well.
-
“Calculated Cd dropped from .08 to .02 with the added length..”
Strongly suspect there is something wrong with this statement or the basis on which it is concluded, in going from 22’ to 35’ length. Would be interesting to see the analytical rationale that produced it.
I thought this a bit off as well. There are several folks on the forum here with obvious credentials with respect to your questions, IO and Blue come to mind. Robfrey as well with his liner. I hope they chime in. Me, I just read and copied best I could. But my car has been over 300 and was stable so something worked. ;)
-
Are you planning to be at SpeedWeek to look at cars? With any luck I will have Bockscar 2 there.... You will be welcome to sit in it.... it is 24 wide, 16 tall with 9 7/8 tall x 17 1/2 tunnel on top for driver and all that excess motor room. Since you need to be totally inside the frame rails and roll structure, with internal sheetmetal to ensure your parts can't get out if the external body is lost it seems to me you are allowing less than 19 inches for you... I guess you won't rattle around much :-D
If not making Bonneville, you are welcome to drop by to fit.... if you decide to go with 1 5/8 tube I have a 7.5 inch CLR die for the JD bender you can borrow... if fact anyone on this site is welcome to borrow it if needed... I see it as the minimum size required hoop size based on current helmets and allowing a little for future helmet growth.
You can view Bockscar 2 on the Build Diary section of this website.
Good luck with your project :cheers:
-
Jacksoni: Thanks for the SAE paper leads, I'll find them and study up.
Interested Observer: I was surprised too when I ran the two different lengths and volumes through the Cd calculator at Fxsolver. Here's the link to the Sears Haack body shape https://www.fxsolver.com/browse/formulas/Sears%E2%80%93Haack+body+%28Drag+Coefficient+related+to+the+Volume%29 (https://www.fxsolver.com/browse/formulas/Sears%E2%80%93Haack+body+%28Drag+Coefficient+related+to+the+Volume%29).
I haven't looked at my 22' body in a while, the Cd number should have read .0713 Cd; and the 36' body Cd is actually .027. When you think about it the SH profile is a tube of a given diameter that smoothly tapers down to a needle point at both ends. So if we keep the diameter constant and increase or decrease the over all length the angular movement of air that flows from end to end decreases with length. The Cd therefore grows smaller with length due to smoother air movement over and around the shape. The SH shape has the lowest theoretical wave drag in supersonic flow but may not be the best in subsonic flow. I'm using it anyway because that's the shape I wanted to use before I even knew it had a name.
Peter Jack: Thanks for you logical recommendations; makes perfect sense. I was under the impression however that cage hoops had to be 1 3/4 diameter. Am I wrong? To your other point about size...I'm fairly tall but still under 200 lbs, and I've measured myself for fit which is doable. On the practical side, if I'm able to build this I'll likely need a younger, thinner person to handle the driving chores. Thanks for your encouragement. :-)
jacksoni: 300 mph is a mile stone for sure. Congrats on your accomplishment. I'll copy whatever works if applicable to my goals.
Stainless: I looked through your build diary very impressive work. Thanks for the invitation to visit your shop or look you up at SpeedWeek for a test fit. Great comradery between the users here on the forum; I'm grateful to everyone who offers help and/or constructive criticism. I'm the rookie here and not ashamed to admit it. Thanks everyone...
-
When you think about it the SH profile is a tube of a given diameter that smoothly tapers down to a needle point at both ends. So if we keep the diameter constant and increase or decrease the over all length the angular movement of air that flows from end to end decreases with length. Cd therefore grows smaller with length due to smoother air movement over and around the shape.
Here you're saying the SH equation demonstrates that increasing the length with constant diameter will lower Cd. The SH shape has the lowest theoretical wave drag in supersonic flow but may not be the best in subsonic flow. I'm using it anyway because that's the shape I wanted to use before I even knew it had a name.
Here you admit the SH equation does not apply at subsonic speeds, and you're using the shape just because you like it. Hey, it's your car, no problem. I think, however, you are mistaken that lengthening the car and keeping the same diameter will lower the drag.
-
From fxsolver: “wave drag is a component of the drag on aircraft, blade tips and projectiles moving at transonic and supersonic speeds, due to the presence of shock waves. Wave drag is independent of viscous effects”
So, Cd based on “wave drag” is additive to the normal viscous and pressure drags that we non-supersonic and non-shock wave producing travellers must deal with. May pertain to Bloodhound and others of that ilk. Suggest you forget about that calculation and pay good attention to the info in the papers that Jacksoni has mentioned.
-
Wow...tough crowd tonight. :wink:
Tortoise: Yes, that is what we see from the equations where Cd lowers as the length of the tube increases for a given diameter. That's probably not true for all shapes I wouldn't know. However for the SH shape it is true as I understand what has been studied and written about it. Also it seems quite obvious to me that air flowing around a sphere of a given dimension will have a higher Cd that air flowing around a long pointy end tube of the same diameter. Is that unrealistic in your estimation tortoise?
I don't think I admitted anything of the sort tortoise. Wave drag is a component of transonic and supersonic speed as I understand it, but aerodynamic principles remain valid in subsonic and supersonic air flows where shape, length, and volume determine the Cd of a profile. Far smarter people than me have determined the SH shape is one of, if not the least drag inhibitive aerodynamic shapes. I think its common knowledge that well known and peer reviewed mathematical formulas generally produce accurate and dependable results tortoise...I think I'll stick with those rather than find some counterproductive fault based on...well, who knows what your thinking is based on. :? :? :?
Interested Observer: Independent yes, but not inconsequential given the nature of air flow over and around low Cd shapes which SH is without doubt one of the best. Or is that statement suspect in your opinion? Your suggestions I'm sure have value IO, I'm not so sure however that forgetting what I've researched an studied on your say so alone has any value to me in this context.
I love naysayers...they are like finding metal filings in a pan of break-in oil.
-
Also it seems quite obvious to me that air flowing around a sphere of a given dimension will have a higher Cd that air flowing around a long pointy end tube of the same diameter. Is that unrealistic in your estimation tortoise?
Not at all, but those are not the alternatives we are considering.
In forms like very good streamliners, where the flow stays attached all the way to the back, ending at a point, with little or no turbulent wake behind, the major source of drag is skin friction. The lower the surface area, (note I said surface area, not frontal area), the lower the drag. Smart guys like Costella, when they make their cars long for stability don't lengthen the fat parts, they splice in a skinny part in the middle to keep the surface area as low as possible.
By the way, the good airfoils for subsonic duty are pointy only at the back.
-
Well it's always a tough crowd.... but that is why we race... to prove our theories
I see you are not far from Denver... the lakester may be there in several weeks... Will let you know
-
Simspeed,
If you want to make a car using the SH profile then go to it. Just remember the very first sentence from you link on this shape: "The Sears–Haack body is the shape with the lowest theoretical wave drag in supersonic flow, for a given body length and given volume." Just because it works in supersonic flow is doesn't mean anything at 300 mph. There are a number of unique streamliner shape that are running at Bonneville, Jacks needle nose belly scrapers, Poteet's flat bottom special, Rob Freyvogal's Carbinite liner which is based on "long runs of laminar flow" theory and the a number of the "standard" square section, long with a pointy nose and tails. All have had some success, some much more than others (Poteet and Jack come to mind along with Danny Thompson's "standard" style liner as cars that have run to their potential.)
It takes just as much effort to build a car to a non applicable design parameter as it does to build one that is based upon air flow at your targeted speed. My suggestion is to get a copy of Bruce Carmichael's "Personal Aircraft Drag Reduction" and looks at what it takes to go over 300 mph with less than 150 hp in an airplane, might change your thinking. I do like your engine selection as the Mazda rotary can make big HPs and is very small in cross section and the use of coupling to the drive wheels using the electric generator/electric motor combination is very out of the box thinking.
I am attaching a pic of a new streamliner that has appeared and has done some runs at El Mo that I would guess is pretty much based on some aero work done by Bruce Carmichael. I have not had a chance to see this car personally or talk with the owners, it is entered as the "Salt Shark" and driven by Tom Flattery from the Gear Grinders. Very unique shape.
Rex
-
I will leave the aero stuff to the guys who really know, having said my piece about my car.
To the cage issue. The rule book says 1.625x.120" wall mild steel or .095" wall moly. MINIMUM!!. Every time this comes up folks say more is better and particularly with high mph liners and such and suggest going to the 1.75"x1.34 wall stuff. More is better. Give up a mm or two for strength. Weight is a non issue in all cases. Lot of steel wrapped around you. George Poteet put the Speed Demon on it's head at some big number and of course did fine and built a new and better. Your safety is of paramount importance, particularly in something that will be going really fast and take forever to stop etc etc. Have fun be safe. :cheers: :dhorse:
-
And has already been mentioned, enough clearance around the tires. Bob Dalton had an inner panel come adrift rubbing the rear tire causing this 425 mph "mishap" last year.
Talked to him last Friday night and his new cars is almost ready for the weld jig.
-
I see you are not far from Denver... the lakester may be there in several weeks... Will let you know
Yes, please do Stainless. I'm scheduled for a move to Houston in about 3 weeks so hope to see you before I move. Thanks...
-
Also it seems quite obvious to me that air flowing around a sphere of a given dimension will have a higher Cd that air flowing around a long pointy end tube of the same diameter. Is that unrealistic in your estimation tortoise?
Not at all, but those are not the alternatives we are considering.
In forms like very good streamliners, where the flow stays attached all the way to the back, ending at a point, with little or no turbulent wake behind, the major source of drag is skin friction.
Now that makes sense tortoise...I'll have to read up on the effects of skin friction dealing with Cd...good point.
-
Simspeed,
My suggestion is to get a copy of Bruce Carmichael's "Personal Aircraft Drag Reduction" and looks at what it takes to go over 300 mph with less than 150 hp in an airplane, might change your thinking. I do like your engine selection as the Mazda rotary can make big HPs and is very small in cross section and the use of coupling to the drive wheels using the electric generator/electric motor combination is very out of the box thinking.
I am attaching a pic of a new streamliner that has appeared and has done some runs at El Mo that I would guess is pretty much based on some aero work done by Bruce Carmichael. I have not had a chance to see this car personally or talk with the owners, it is entered as the "Salt Shark" and driven by Tom Flattery from the Gear Grinders. Very unique shape.
Rex
Thanks for the lead on Carmichael's book. I didn't find it in print but I read a review of the book by Piolenc that gave good reason to keep trying. http://archivale.com/weblog/?p=102.
The Salt Shark looks like on wild idea on aerodynamic drag brought to life. I'd love to see that one in person or read about its success or failure whichever ultimately turn out to be the case. Also thanks for your input on my posts and what the realities may be on the SH design. Like I said I'm a rookie in these areas so my comments should be taken with a grain of salt...or maybe I'm the one who needs salting.. :wink: :-) cheers.
-
The rule book says 1.625x.120" wall mild steel or .095" wall moly. MINIMUM!!. Every time this comes up folks say more is better and particularly with high mph liners and such and suggest going to the 1.75"x1.34 wall stuff. More is better. Give up a mm or two for strength. Weight is a non issue in all cases. Lot of steel wrapped around you. George Poteet put the Speed Demon on it's head at some big number and of course did fine and built a new and better. Your safety is of paramount importance, particularly in something that will be going really fast and take forever to stop etc etc. Have fun be safe. :cheers: :dhorse:
Thanks for clearing the tubing issue that up jacksoni. I always used 1 5/8" tubing both mild and chrome moly on drag cars I built and never saw the need for larger tubing. Two cars had big wrecks and both cages held up well with only shakeup injuries to either driver. I'll go back and change out the 1 3/4 for 1 5/8 in my design. That little bit will make a difference. Thanks...
-
And has already been mentioned, enough clearance around the tires. Bob Dalton had an inner panel come adrift rubbing the rear tire causing this 425 mph "mishap" last year.
Wow...big wreck Dynoroom. Thanks for sharing that. I plan to weld in fitted sheet metal panels to the chassis tubes wherever removable panels aren't need for systems access. I always enjoyed doing the bright tin work on drag cars but welded metal last longer and protects better where weight savings is not a big issue. Silicon bronze rod works great on headers and sheetmetal. Thanks...
-
My son, Duke, and I were pitted by Bob Dalton at the WOS meet and I will say that his car is not the greatest aero design (my opinion only) but he makes up for it by a really STOUT motor. He is not afraid to "tip the can" when needed. We were in line behind him on his "last" run and he definitely had a load in it for that run. He had qualified at around 450 an I am sure that if he did not have the tire blow he would have easily gone over his qualifying speed. We looked at the car after they brought the remains back to the pits and it certainly was built stout, which is just what you want at 450 mph! Good guy.
Rex
-
I will leave the aero stuff to the guys who really know, having said my piece about my car.
To the cage issue. The rule book says 1.625x.120" wall mild steel or .095" wall moly. MINIMUM!!. Every time this comes up folks say more is better and particularly with high mph liners and such and suggest going to the 1.75"x1.34 wall stuff. More is better. Give up a mm or two for strength. Weight is a non issue in all cases. Lot of steel wrapped around you. George Poteet put the Speed Demon on it's head at some big number and of course did fine and built a new and better. Your safety is of paramount importance, particularly in something that will be going really fast and take forever to stop etc etc. Have fun be safe. :cheers: :dhorse:
Weight is an issue for certain cars. Speed demon 2.0 went on a big diet from the first version. Weight is a factor on any car that is still accelerating at the 5. If your speed flattens out before that than aero is the biggest problem. If you are still accelerating at the 5 (read fast streamliner) than weight is a big factor in how hard you are accelerating to that point.
-
I take your point and of course you are correct. Rolling resistance and power to accelerate the mass go up with increased weight. What was in my mind when I said that is the traction problem that pretty much all high power cars have and the ballast often added to aid that issue.
-
Weight is a factor on any car that is still accelerating at the 5. If your speed flattens out before that than aero is the biggest problem. If you are still accelerating at the 5 (read fast streamliner) than weight is a big factor in how hard you are accelerating to that point.
If you have the power to get to big speeds, then you probably have enough power at lower speeds so that the limiting factor in acceleration is wheelspin, not power to weight. You need aero downforce for that. Variable aero downforce, ideally.
-
The streamliner design I personally like is front wheel drive with a high front weight bias and reasonably low weight . The traction of a ballasted streamliner with the acceleration of a light one and the safety of directional stability .
-
Interesting concept John. Are there many front wheel drive only liners?
-
Weight is an issue for certain cars. Speed demon 2.0 went on a big diet from the first version. Weight is a factor on any car that is still accelerating at the 5. If your speed flattens out before that than aero is the biggest problem. If you are still accelerating at the 5 (read fast streamliner) than weight is a big factor in how hard you are accelerating to that point.
Has the team benefited substantially from the weigh reduction? Seems like they're trapped in the 450/460 mph range at best. What do you think is the aero limit for their current combination?
-
Yes speed demon is benefiting from the diet. Ask Steve Watt. I don't have the numbers to back it up, but I am certain of the facts. More Weight will never make a streamliner accelerate harder, (weight bias may) it may make it easier to drive and less prone to spin the tires though. Pour throttle control makes the car spin tires easy which slows down the car, it isn't too light. This is based on zero aero lift which should be the case for a liner, now a roadster would be a different discussion. Variable aero drag can work and does work for higher hp cars. I fall into a gray area with moderate hp. Being lightweight and four wheel drive is my choice at the moment although their is some mutual exclusivity here... Being low on hp I don't want any extra aero drag. I have ran the numbers forward and backwards on this, including my own real world experience. Now blown nitro hemi power levels are not in my experience..
-
Weight is a factor on any car that is still accelerating at the 5. If your speed flattens out before that than aero is the biggest problem. If you are still accelerating at the 5 (read fast streamliner) than weight is a big factor in how hard you are accelerating to that point.
If you have the power to get to big speeds, then you probably have enough power at lower speeds so that the limiting factor in acceleration is wheelspin, not power to weight. You need aero downforce for that. Variable aero downforce, ideally.
So far none of the "fastest" cars have varying downforce. Now that may change in the future, but Danny, Vesco, speed demon.... only built in aero, some and none for a few... I tried to build in a certain amount of downforce into the body shape that I could do without sacrificing any additional drag and relied on the 4x4, again fastest 1/4 speeds are 4x cars. Flashpoint was hitting some numbers last year though.
-
The streamliner design I personally like is front wheel drive with a high front weight bias and reasonably low weight . The traction of a ballasted streamliner with the acceleration of a light one and the safety of directional stability .
This was my original plan, I think it is still good up to a certain power and speed level. But people don't factor enough for weight transfer though. Once you start talking 400 plus it really is a long drag race. All the math changes when you talk about acceleration vs terminal aero drag etc..
-
My design has no built in aero drag. I'm shooting for the smallest frontal area and lowest Cd number for the overall shape. I have considered a front lip for down force to keep the nose planted with skid pods on either side but that's just an idea for discussion.
-
Weird what I have to do to add attachments. Post without attachments and then modify the post to add the attachments otherwise I get error message. Oh well...here is my basic design with no aero drag built in and the front lip to add downforce.
-
Here are more views of the chassis, running gear and odds & ends. To refresh...this concept uses dual 4 rotor Mazda based engines to turn 4 electric generator. The electric power is fed to 4 wheel motors to power the car. Generators and motors I've resourced for this configuration can generate and drive the wheels with kW equal to 2100 hp. The two turbo 4 rotors can produce close to 2800 hp for this application. Even considering the energy loss of this power coupling system the car should be competitive all else being equal. At least that's my theory...
BTW...the engines are turned nose to nose for packaging of the 2 turbos and 1 shared intake for both engines with separate throttle bodies. That way output can be programmed to use one or both engines together as needed depending on available traction to the 4 wheels.
-
Prefacing this question with "I know nothing" but: Generally speaking generators to convert 2100hp into KW's and then electric motors to take those KW's and make them into motive force (motors for the wheels) usually are rather sizeable. I'd be interested in some information about those parts which I am sure you have figured out.
-
Here's the steering system I've concocted for the extremely narrow front end. The orange steering frame is hinged at the front and supported in a framed slot at the rear where the steering column attaches with a double pinon lever arrangement. Total movement through the inline wheel steering is 6 degrees lock to lock. The front electric motors bolt directly to the steering frame and the wheels bolt to the motor rotors through a hub/axle arrangement. Power for each wheel is independent of the rest but the motor controller will coordinate all motors simultaneously with wheel slippage metered for each wheel for controlled application of power.
-
Prefacing this question with "I know nothing" but: Generally speaking generators to convert 2100hp into KW's and then electric motors to take those KW's and make them into motive force (motors for the wheels) usually are rather sizeable. I'd be interested in some information about those parts which I am sure you have figured out.
Hi Jacksoni...there are several manufactures of suitable axial flux coreless motors and generators to my knowledge. The motors shown in my drawings are scaled to dimension for Yasa PD400 series motors which can be wired to generate peak 200 kW max each for high rpm use. Each wheel in this design uses 2 of those motors stacked together with a common axle/hub through the coreless middle. Similarly, motors of that type can be use as generators with the same output based on whatever power supply is chosen to turn them. In this case the design uses 4 rotor Mazdas because of the small cross section to power potential.
-
I keep looking at Simspeed 3 and 4, and the long bit of structure on the front, which appears to do nothing but support the bodywork comprising this Sears Haack profile. This nosepiece appears to be a bit concave on the sides. Tell me why this long, tall, concave-sided nose doesn't massively move the center of pressure forward.
-
I would also worry about the effect of side winds.
Regards, Neil Tucson, AZ
-
I've attached a profile view of the body with all the geometric lines that make up the arcs and curves of the body shape. This helps to visualize the "flow" of the aerodynamic shape. At the undercut of the "bow" we go from an sharp point and leading edge to the widest point at the middle of the length. the body eventually narrows and tapers to another point and sharp lower edge at the back. You can see the transition point from the spherical upper body to the tapered slab sides of the lower body along the sweeping arch from front to back. Realize that Simspeed 1 shows the relative sides of the car to a 6' 2" man standing along side.
-
Ok, I said all of that just so we have a common knowledge of what we're talking about. To Neils point side winds are going to be critical given the narrow width of the car and tire track. The real wheel track is only 9.5 inches center to center. Given that my knowdedge of what moves Cp along the length of a body is very limited at this point I have to guess mostly. I will ask what is it about the needle nose shape that leads you to believe the center of pressure of this body would be at the front rather than and the widest spot longitudinally? Will the needle nose matter more in determining Cp than the stabilizing fin at the rear? The width of the underbody at the hinge pin for the front suspension is 4.8".
-
You have obviously put a lot of time and thought into this :cheers:
Wondering about packaging things like chutes, fire bottles, cooling for the engines?
Here is a rather crude way to get an idea of the CP/CG component...
http://1fatgmc.com/car/14-Hooley/14%20-%20hooley-construction-2014-2.html
Do you have a class that you are planning on running in or is this a 'for speed only car'?
Sumner
-
More Weight will never make a streamliner accelerate harder,
That's actually not true if it is traction limited. We were smoking the tires for the first three miles back in the 90's with Betsy (Al Teague) so we started adding weight for traction & kept adding a lot of it while seeing the speeds increase. Traction control was not SCTA legal at that time by the way.
There are a lot of other weighted cars that do better with it than without as well.
Sid.
-
You have obviously put a lot of time and thought into this :cheers:
Wondering about packaging things like chutes, fire bottles, cooling for the engines?
Here is a rather crude way to get an idea of the CP/CG component...
http://1fatgmc.com/car/14-Hooley/14%20-%20hooley-construction-2014-2.html
Do you have a class that you are planning on running in or is this a 'for speed only car'?
Sumner
Sumner- are you thinking that because it is "hybrid" that it doesn't fit in a normal displacement class? I can't find it now but there was language in the rule book about hybrids in the past saying the IC engine was defining for classification- at least that is what I recall. Two 4 rotor engines likely have enough equivalent displacement to put in the higher engine categories.
-
More Weight will never make a streamliner accelerate harder,
That's actually not true if it is traction limited. We were smoking the tires for the first three miles back in the 90's with Betsy (Al Teague) so we started adding weight for traction & kept adding a lot of it while seeing the speeds increase. Traction control was not SCTA legal at that time by the way.
There are a lot of other weighted cars that do better with it than without as well.
Sid.
You left out the "weight bias may" in Eddieschopshop's comment. Where was the added weight?
-
Sumner- are you thinking that because it is "hybrid" that it doesn't fit in a normal displacement class? I can't find it now but there was language in the rule book about hybrids in the past saying the IC engine was defining for classification- at least that is what I recall. Two 4 rotor engines likely have enough equivalent displacement to put in the higher engine categories.
If there is no battery or capacitor energy storage, the generators and motors are really only acting as a transmission. It should be allowed in the internal combustion engine categories.
-
Solid suspension? [excuse me for not reading every word of the thread]
-
You have obviously put a lot of time and thought into this :cheers:
Wondering about packaging things like chutes, fire bottles, cooling for the engines?
Here is a rather crude way to get an idea of the CP/CG component...
http://1fatgmc.com/car/14-Hooley/14%20-%20hooley-construction-2014-2.html
Do you have a class that you are planning on running in or is this a 'for speed only car'?
Sumner
Thanks Sumner, I have given quite a bit of thought to the design and many drawing iterations to get to the present configuration. Although I haven't put the chutes to paper in this latest version I have allowed for room and chassis layout at the rear to house them. fire bottles and engine cooling are in place with 4 fire canisters high on the chassis above the engines. Engine cooling and fuel are also represented in the two tanks sitting atop the rotor housings. Circulating pumps, hoses, fuel pumps and injectors are not shown and I'm not planning on trying to detail, scale and draw those into the design. I believe there's adequate room available for all that without the need to draw them for packaging reasons.
Thanks for the link to Cp/Cd....I'll study that. I'm not sure how rotary engines are classified by the sanctioning bodies. Total displacement for this design is an actual 5232 cc. If the 2:1 ratio for rotary engines is applied then this would represent 638 cu.in. displacement.
-
Sumner- are you thinking that because it is "hybrid" that it doesn't fit in a normal displacement class? I can't find it now but there was language in the rule book about hybrids in the past saying the IC engine was defining for classification- at least that is what I recall. Two 4 rotor engines likely have enough equivalent displacement to put in the higher engine categories.
That was my thinking too Jacksoni...I just don't know how rotary CCs are calculated for different IC motor type classes.
-
If there is no battery or capacitor energy storage, the generators and motors are really only acting as a transmission. It should be allowed in the internal combustion engine categories.
That was my rational for using "electric" motor/gens in this design tortoise. For packaging reasons primarily but there are added benefits in being able to program the system for each wheel motor dealing with traction and application of power issues.
-
Solid suspension? [excuse me for not reading every word of the thread]
Yes Jack, solid suspension. There's just not room or practical ways in my opinion to suspend the wheels in this configuration. I could be wrong of course, there are smarter and more experienced minds than my own in this field.
-
More Weight will never make a streamliner accelerate harder,
That's actually not true if it is traction limited. We were smoking the tires for the first three miles back in the 90's with Betsy (Al Teague) so we started adding weight for traction & kept adding a lot of it while seeing the speeds increase. Traction control was not SCTA legal at that time by the way.
There are a lot of other weighted cars that do better with it than without as well.
Sid.
You left out the "weight bias may" in Eddieschopshop's comment. Where was the added weight?
Weight was equal to not effect balance. The most lead ballast I've ever seen is in the Target 550 liner.
Sid.
-
Sumner- are you thinking that because it is "hybrid" that it doesn't fit in a normal displacement class? I can't find it now but there was language in the rule book about hybrids in the past saying the IC engine was defining for classification- at least that is what I recall. Two 4 rotor engines likely have enough equivalent displacement to put in the higher engine categories.
That was my thinking too Jacksoni...I just don't know how rotary CCs are calculated for different IC motor type classes.
SCTA uses equivalent displacement is swept volume x2. ( used to be X3. Changed in 2011) So your 638 equivalent puts you in AA/(blown or not, fuel or gas)S. Again I don't see the language in the current rule book but when there was a Prius running the class was by the gas IC and the batteries/electric motors were ignored as I remember. But I have looked back a number of years and can't find it so maybe my imagination. But that Prius ran >130mph and rumor was the Toyota engineers said it couldn't be done and as there may have been some factory backing somewhere they wanted the car back to figure out how. :roll:
-
SCTA uses equivalent displacement is swept volume x2. ( used to be X3. Changed in 2011) So your 638 equivalent puts you in AA/(blown or not, fuel or gas)S. Again I don't see the language in the current rule book but when there was a Prius running the class was by the gas IC and the batteries/electric motors were ignored as I remember. But I have looked back a number of years and can't find it so maybe my imagination. But that Prius ran >130mph and rumor was the Toyota engineers said it couldn't be done and as there may have been some factory backing somewhere they wanted the car back to figure out how. :roll:
My guess is they'll go by the IC alone because that's where 100% of the direct energy for the drive system comes from. Technically in my design you could run just one engine or even fewer rotors down to 2 total to qualify for different cu.in. classes. Have no idea if it would be competitive that way but if weight isn't a prohibitive penalty and if the aerodynamics are as competitive as I hope they would be then why not? Again...all things being equal. :-)
-
Here is a rather crude way to get an idea of the CP/CG component...
http://1fatgmc.com/car/14-Hooley/14%20-%20hooley-construction-2014-2.html
Sumner
I read your post on finding the balancing point for Cp Sumner...it was a great help. I'd read something similar elsewhere but yours was better detailed which I found quite useful. I'll do the same for my drawing profile and print out the shape which is easy to do because I can change the screen image perspective to 2D which eliminates the photo problem with a real car. What I can't do is pinpoint the Cg of a drawing. Oh well...something to look forward to one day I hope. :-)
I do have plans to 3d print the body model to some useful scale and see if I can find a wind tunnel or water flow tank that can measure the shape Cd. If the Cd is as small as I'm hoping it will be that might help me find funding to build it one day. Never know until I try...
-
I do have plans to 3d print the body model to some useful scale and see if I can find a wind tunnel or water flow tank that can measure the shape Cd. If the Cd is as small as I'm hoping it will be that might help me find funding to build it one day. Never know until I try...
As long as you're measuring Cd, you might as well compare that long, tall, concave-sided beak with a small, low, rounded one. Or are you thinking maybe the car has trans-sonic speed potential?
-
I've estimated the Cg based on weighted percentages of major components shown within a fore-aft Cg range for total component sets. I started with the premise that the two identical engines balance at the dead center between them and then added Cg points for the furthermost component point back to the rearmost component point. I then calculated percentages for each and plotted those points within the fore-aft range to arrive at the weighted average distance for all components along the range. This puts the estimated Cg for the car at 19.58" forward of the engine Cg. I'll save this and hopefully one day I'll have a finished car to check today's estimate against. :-D
-
As long as you're measuring Cd, you might as well compare that long, tall, concave-sided beak with a small, low, rounded one. Or are you thinking maybe the car has trans-sonic speed potential?
Hahaha...well you never know tortoise...stranger things have happened. :wink:
But will the small low nose give a better or worse Cd given the loss of the tapered shape below the center line? Where's the tradeoff?
-
But will the small low nose give a better or worse Cd given the loss of the tapered shape below the center line? Where's the tradeoff?
Neither of us know about the Cd, really. I'm just thinking about directional stability. I think you'd need more fin on the back to compensate for the proboscis, and that's more drag right there. Speculation, I know, without data. But you'd really want to know how stable it is before you put yourself inside it.
-
I certainly agree with that statement tortoise. I don't believe this design would ever spin...it'd pencil roll almost immediately I'd imagine.
-
Because of a lack of interest in Hybrid vehicles the rules are limited to the PRODUCTION category ONLY. The "dozens" of OE manufactured vehicles that would appear if a class was created have gone the way of the C/AIR class. It looks like you are spending time and resources(?) on a theoretical car that can set only theoretical records.
Best bet? Petition SCTA or FIA for a recognized class.
Good luck,
-
Dan, why wouldn't it fit in whatever class the swept volume of the motors would be. I don't remember anything requiring mechanical connection from the motor to wheels.
Gasoline powered motors.... :cheers:
-
PRODUCTION category only. If we are talking Hybrid power source.
Not my deal any more. Find an advocate in the SCTA.
DW
-
Nobody considers diesel-electric locomotives "hybrids".
-
Reply #59 mentions use of water to analyze aerodynamics. This would be in a flume, is my best guess. The results would be misleading and it is not a good idea for a lot of reasons. Use a wind tunnel or a virtual analysis that is intended for the purpose.
-
If my memory is right, water was used in the design of the famous "Charlie Toy" bodywork. I think the water was moving vertically/the bodywork was vertical, too.
-
This is the type of water tank aerodynamics I'm referring to.
https://www.youtube.com/watch?v=quDLzxmJl5I&t=2697s (https://www.youtube.com/watch?v=quDLzxmJl5I&t=2697s)
-
Nobody considers diesel-electric locomotives "hybrids".
Trains & stationary engines and don't race at Bonneville.
DW
-
True Dan, but as you are fond of saying, "Don't read into the rule book what isn't there" or words like that. :wink:
The passage says " Vehicles using a hybrid POWER (my emphasis) source, such as a gasoline/battery pack, will compete in the equivalent cubic inch class of the gasoline engine." Goes on to talk about the battery pack being sealed and it can't be charged separately or off site etc. Indeed the generators/electric motors are functioning as the "transmission" as has been pointed out- and transmissions are "free, ie unregulated" in all classes.
But as you say, Simspeed better get a formal special construction ruling about this drive train before going beyond computer speeds and horsepower- which of course are a lot of fun and easier to obtain than real ones...…….. Cheaper than building it and have it called illegal. :cheers: :cheers:
-
A project of this magnitude would have one goal: fastest wheel-driven car. Nobody'd much care what SCTA class it fit.
-
I know you heard it before but in case you haven’t for a while, keep thinking of the game this way-
5 mile drag race on very wide dirt road.
Aero is important but it only has to be aero enough. Acceleration, thermal management, proper chute deployment, crash survivability and reliability all come before aero.
Take it from someone that has made this mistake before.
From my testing so far, I’m liking active aero. I think it holds a bit of an advantage over 4x when it comes to the 6.5 mile FIA course but that has yet to be proven.
I’m sure Eddie is liking his 4x as his car is getting very successful!
This diversity is the coolest thing about our sport.
Rob Freyvogel
#496
AA/BFS
-
A project of this magnitude would have one goal: fastest wheel-driven car. Nobody'd much care what SCTA class it fit.
Exactly tortoise...that was my intention from the beginning of this design. Feasible or not is yet to be determined, but from a systems standpoint there's nothing I've proposed so far that falls outside of known capabilities. Aerodynamics and wheels are the greatest unknowns and I'm working on the aero limitations first because that's the least expensive project for me to tackle at this stage. Aero rules in my opinion.
Where we go from there depends on the Cd, Cp, and Cg values and their relationship as drawn or amended. Thanks to everyone for their input and experience in helping a novice like me get up to speed on what it takes to design, build, and hopefully one day drive this design, or something near to it to its full potential. If it's not me that makes it happen then i'd be more than happy for someone else to take the reigns and bring this to life. For me its about seeing my vision fulfilled for that satisfaction alone. I don't need to be the center of attention...the design will hopefully stand alone for better or worse. Thanks again...I am in your debt.
-
...This diversity is the coolest thing about our sport.
Rob Freyvogel
#496
AA/BFS
Thanks for your input Rob...I am a great fan of your design and effort. Best of luck to you and your team on a successful chase to achieve your goals.
-
Today I printed a 30" scaled profile of the 36' body and glued it to a piece of Walmart foam poster board with some Super 77 I had on the shelf. Cut it out cleanly with an Exacto knife and laid it across an triangle architect scale to find the balance point. After some doing I pinpointed the balance center and transferred that to the computer model. Turns out the theoretical Cp using this method is 10.278" to the rear of the theoretical Cg I came up with yesterday (simspeed 9 attachment ). 10 1/4" roughly which is only 2.38% of the overall 36' length.
That's a pretty thin margin but it doesn't take into account the long narrow cross section at the nose relative to the fatter area from the roll hoop back past the real wheels. As Sumner said longer flatter areas should be more heavily weighted toward Cp which in this case I'd guess would probably move the Cp toward the real perhaps another 10". It's all guesstimating but still there's some validity to the technique it seems.
I found an online aerodynamic modeling application at airshaper.com (http://airshaper.com) that I'm checking out. Maybe just what I'm looking for to calculate the model's Cd numbers. If I go that route I post the results to see what everyone has to say.
-
Aerodynamic stability is going to be very important in this design and will generate a lot of input I suspect. You are on the right track looking at it early in design considerations. But to another issue that has been mentioned- packaging. There is not much space in here for the systems that are going to take up a lot of space. Look at the inside of ANY liner. There is no much available. One of those systems is going to involve heat management, not only from the engines but from the generator and electric motors. Granted, a run may be very short (a Speed demon video posted here suggested 70 seconds) longer if you can run on some longer surface (Bolivia for instance) but how are you going to cool this beast?
-
Thanks for the compliment!
The question that too few ask.
How much further back does the cp have to be from the cg?
One of my hobbies is large model rockets. The basic rule of thumb is 1-2 calipers (body diameters).
Some say that is fine for rockets but this is cars. I contend that is one and the same. The road holding power that the tires have with the salt is just about next to nothing compared to the aero loads.
If you can get 1.0 calipers back, the car will be stable and cross winds will have negligible effect on weather vaneing.
In the rocket world, it is pretty cool when you get this right. Rocket pretty much goes right where it is aimed even in strong cross winds. It just gives a little wiggles indicated by smoke trail.
By the way, you might want to pick up Bruce Carmicheal’s book.
“Personal Aircraft drag reduction “.
You will have to search for it. It is out of print. It is very, very good for what we do.
Be aware that so far CFD does not do a great job with separation drag. So far no one has been able to ACCURATELY model what happens behind a semi truck. At least as far as Eric (Blue)and I know.
Remember the textbook equation for calculating aero drag.
Stagnation drag + Separation drag + Wetted area drag = Total Aero Drag
Cross section or displacement is not part of drag equation.
Optimum finess ratio (length to diameter) for subsonic design is a little over 3:1. We ended up at over 9:1 because of the tire choices available. It’s a long story. Lol. Anyhow, our car looks faster as we designed it but it would be much better shorter and fatter.
I’m excited for you! This is the fun part!
I look forward to following this build!
Feel free to reach out to to answer any questions. Tom Burkland did this for me. He called me up and said that he didn’t want to see me make the same mistakes he made. His input was invaluable and I saved and printed all our correspondence. I can’t say enough about Tom.
Rob Freyvogel
#496
AA/BFS
-
I agree that the point of this exercise is being the fastest of the fast. Lets stop talking about recognized classes.
Being involved with a couple of cars using a front wheel set up similar to yours we discovered, actually Richie knew, you need Ackerman effect.
DW
-
At this stage, this appears to be a fantasy CAD exercise with an interesting powertrain. No provision for necessary ancilliaries or a realistic or competent structure. It is doubtful that any kind of a one-off powertrain control system has been worked out. With a razor’s edge nose, no suspension, scary steering linkage, and 9.5” track it would probably fall over in the first 200 yards, if that far.
-
Yep, a lot of paper race cars here. I remember a prop deal from a ways back.
DW
-
Interested Observer- Must you be so negative?
He is just getting started on design!
Btw, YOU are the reason I almost quit posting!
As far as I know, no one ever built a monument to a critic.
Everybody has to start somewhere.
Btw, you were not always wrong but your tone definitely frustrated me.
-
Stagnation drag + Separation drag + Wetted area drag = Total Aero Drag
Cross section or displacement is not part of drag equation.
Can you give us a rough idea of the percentage of the three components of drag on the Carbiliner?
Optimum finess ratio (length to diameter) for subsonic design is a little over 3:1. We ended up at over 9:1 because of the tire choices available. It’s a long story . . .it would be much better shorter and fatter
The long story about how tire availability made the skinny shape necessary would interest a lot of us, I think. If I remember rightly, many of the "critics" found that hard to believe about short fat bodies, with their higher frontal area.
Your kindness in indulging us in these theoretical discussions is much appreciated.
-
I said my piece on naysayers early on but just know that I recognize the need for every voice in a conversation from cheerleaders to doubting Thomases. How you want to contribute to the discussion and/or be viewed by your peers is 100% your choice. This project is important to me succeed or fail; so I welcome input from wherever and whomever elects to do so. I know just enough to get myself in trouble without the support of people who have been there and done this in their careers. So like others I may get aggravated by someone's tone but I appreciate your perspective and what you can bring to the table of ideas. I can't do any of this with out help positive or questioning...so thanks to everyone again.
-
Aerodynamic stability is going to be very important in this design and will generate a lot of input I suspect. You are on the right track looking at it early in design considerations. But to another issue that has been mentioned- packaging. There is not much space in here for the systems that are going to take up a lot of space. Look at the inside of ANY liner. There is no much available. One of those systems is going to involve heat management, not only from the engines but from the generator and electric motors. Granted, a run may be very short (a Speed demon video posted here suggested 70 seconds) longer if you can run on some longer surface (Bolivia for instance) but how are you going to cool this beast?
Right you are jacksoni...packaging is critical in a design this small. It may well make or break my approach if what's absolutely necessary won't fit in the shell. I see heat management in the conventional sense within the envelop job #1. My intention is to design cooling systems for the IC and motor/generators to use pressurized fluids used by Nascar today. The brief run time is the only saving grace on that front. The gen/motors for this application have cooling circuitry built into the housings using either oil or automotive type coolants. The short run time, and scaling power curve to peak output which like you say is measured in seconds rather than minutes, offers a pretty good window for heat soak and cool down time for IC and electrics both. Casings for the rotary engines and gen/motors will both be machined billet aluminum. No cast iron.
On board cooling capacity has to be limited because of the lack of space so my plan is to stage the systems for peak power through shutdown, and then use an external system in the chase truck to plug high pressure cooling lines into the car when it arrives to help lower the temps as quickly as possible. The greatest on board cooling capacity will be to cool the intake charge downstream of the turbos in the fuel/coolant tanks on top of the rotor housings. I'm wondering if there's a more effective cooling system base on compressed gas expansion rather than heavy and space consuming ice and water? Spraying Nitros Oxide for example dramatically drops the temp of surrounding metal and air in those systems. I believe I've read where NOS had been use in the past in some LSR cars. Anyone know more about that?
-
Gary Eaker (owns the Aerodyne and A2 wind tunnels in NC) ran a firebird to 298 mph in 1989 with N2O blowing onto intercoolers for the turbos. Though running on gasoline, because of all the N2O floating around I think he was put in a Fuel class. So yes can and has been done. CO2 could also be used. There are some street setups that do this.
-
Thanks for the compliment!
The question that too few ask.
How much further back does the cp have to be from the cg?
One of my hobbies is large model rockets. The basic rule of thumb is 1-2 calipers (body diameters).
Some say that is fine for rockets but this is cars. I contend that is one and the same. The road holding power that the tires have with the salt is just about next to nothing compared to the aero loads.
If you can get 1.0 calipers back, the car will be stable and cross winds will have negligible effect on weather vaneing.
Remember the textbook equation for calculating aero drag.
Stagnation drag + Separation drag + Wetted area drag = Total Aero Drag
Cross section or displacement is not part of drag equation.
Optimum finess ratio (length to diameter) for subsonic design is a little over 3:1. We ended up at over 9:1 because of the tire choices available. It’s a long story. Lol. Anyhow, our car looks faster as we designed it but it would be much better shorter and fatter.
I’m excited for you! This is the fun part!
I look forward to following this build!
Feel free to reach out to to answer any questions. Tom Burkland did this for me. He called me up and said that he didn’t want to see me make the same mistakes he made. His input was invaluable and I saved and printed all our correspondence. I can’t say enough about Tom.
Rob Freyvogel
#496
AA/BFS
Thanks for you input and encouragement Rob. Like others who have offered their advice and assistance I value and appreciate your and their openness and kindness.
the widest diameter cross section of this body is roughly 22". So having the Cp location between 22" and 44" back of the theoretical Cg is considered ideal for a real world design? I'm guesstimating its at 20" now so that's good to hear.
I understood that cross section (frontal area) did factor into aero drag along with the others you mentioned. Body displacement or volume, along with length factor into Cd based on what I've read on the subject and the formulas I found on fxSolver.
-
Gary Eaker (owns the Aerodyne and A2 wind tunnels in NC) ran a firebird to 298 mph in 1989 with N2O blowing onto intercoolers for the turbos. Though running on gasoline, because of all the N2O floating around I think he was put in a Fuel class. So yes can and has been done. CO2 could also be used. There are some street setups that do this.
Thanks jacksoni...I knew I'd read something about that many years ago. I like the idea for this application so I'll study up on the pros and cons and see if its something that can be used here.
-
Gary Eaker (owns the Aerodyne and A2 wind tunnels in NC) ran a firebird to 298 mph in 1989 with N2O blowing onto intercoolers for the turbos. Though running on gasoline, because of all the N2O floating around I think he was put in a Fuel class. So yes can and has been done. CO2 could also be used. There are some street setups that do this.
The above is true. the missing link was the used four 20 lb. bottles a pass...
-
I agree that the point of this exercise is being the fastest of the fast. Lets stop talking about recognized classes.
Being involved with a couple of cars using a front wheel set up similar to yours we discovered, actually Richie knew, you need Ackerman effect.
DW
Hi DW...as I understand it the ackerman effect deals with steering wheels that turn in two different radii. Where the front wheel and tandem mounted rear wheel such as the Speed Demon and others, use two different axle hubs that pivot or turn on separate king pins, then the two steer wheels in those designs would indeed turn in two different radii likely requiring the Ackerman effect to be taken into consideration in the design.
The design I've applied here uses a non-suspended walking beam type arrangement where both wheels are fixed positioned along the beam and turn as one from a single forward king pin. Therefore both wheels follow a single turning radius based on whatever angle the beam itself takes from the rearward mounted steering mechanism. I've used a dual lever steering mechanism because it was easy to fit and didn't take up much room. The angular movement steering speed can be sped up or slowed down based on the intersecting angles of the two levers at their crossing point. It would be better from a control standpoint to mount a horizontal steering damper at the real of the beam to smooth the input to the driver. Thanks...
-
Gary Eaker (owns the Aerodyne and A2 wind tunnels in NC) ran a firebird to 298 mph in 1989 with N2O blowing onto intercoolers for the turbos. Though running on gasoline, because of all the N2O floating around I think he was put in a Fuel class. So yes can and has been done. CO2 could also be used. There are some street setups that do this.
The above is true. the missing link was the used four 20 lb. bottles a pass...
Well that's not good is it. Use of an expansion valve setup as with conventional A/C systems might help to reduce the need for so much liquid. You don't get the full benefit and capacity of a nitros system unless you heat the bottle to raise the internal pressure. I wonder how that would apply here? I need to study the effects. Thanks Dynoroom...
-
At this stage, this appears to be a fantasy CAD exercise with an interesting powertrain. No provision for necessary ancilliaries or a realistic or competent structure. It is doubtful that any kind of a one-off powertrain control system has been worked out. With a razor’s edge nose, no suspension, scary steering linkage, and 9.5” track it would probably fall over in the first 200 yards, if that far.
LOL...Well IO every wild idea starts out as a fantasy and evolves if it has merit, or peters out if if doesn't. I think I've made provision so far for engine coolant, fuel, motor/gen coolant, IC oiling, driver padding, front and real wheel housings and containment, driver visibility, steering, turbos, intake, and exhaust. What other ancillary systems besides electronics, fuel delivery, and parachutes do you believe are needed IO? Please describe what there is about the structure (I assume you are referring to the tube chassis) that's unrealistic or incomplete?
No, I have not worked out the power train control system beyond the understanding that similar systems are in use today in the automotive world. Ever heard of parallel hybrid drives IO? I'm not knowledgeable or skilled in those systems but I don't have to be a know-it-all of all things that will ultimately be part of this design if it ever comes to light. There are people with different skill sets that if an when appropriate will have to be sourced to make this project fly...I'd dare to say that's true of 90% of all the LSR cars running today. Do you know of any major one man efforts in the LSR community IO?
You are likely correct that this design would be vertically challenged. I have considered that condition and explored a couple of different approaches to keep the thing from falling over. It amazes me that there are so many motorcycle streamliner LSR records on the books. How in the world do they keep those things upright on just two wheels with zero track width beyond the width of each tire?
Ok, I've beat on you enought IO...stability as you've described is a major challenge that needs to be address. I'd appreciate reading any recommendations you care to make. Thanks...
-
I've toyed with the idea of running a front splitter as shown in the attachment below for two purposes. First to provide downforce at the nose of the car to offset any lift that may develop from frontal pressure along the lower concave face of the nose. Second, as a prop to prevent rolling the car onto its side as I and others have given concern for because of the narrow wheel track and solid suspension. The rounded skid pads on the bottom of the splitter ride above the ground at rest but may contact and skid along the surface if the body rolls in either direction. Is a splitter legal under sanctioning rules? Do you see and problems in its use? Thanks...
-
Thanks for the compliment!
The question that too few ask.
How much further back does the cp have to be from the cg?
One of my hobbies is large model rockets. The basic rule of thumb is 1-2 calipers (body diameters).
Some say that is fine for rockets but this is cars. I contend that is one and the same. The road holding power that the tires have with the salt is just about next to nothing compared to the aero loads.
If you can get 1.0 calipers back, the car will be stable and cross winds will have negligible effect on weather vaneing.
Remember the textbook equation for calculating aero drag.
Stagnation drag + Separation drag + Wetted area drag = Total Aero Drag
Cross section or displacement is not part of drag equation.
Optimum finess ratio (length to diameter) for subsonic design is a little over 3:1. We ended up at over 9:1 because of the tire choices available. It’s a long story. Lol. Anyhow, our car looks faster as we designed it but it would be much better shorter and fatter.
I’m excited for you! This is the fun part!
I look forward to following this build!
Feel free to reach out to to answer any questions. Tom Burkland did this for me. He called me up and said that he didn’t want to see me make the same mistakes he made. His input was invaluable and I saved and printed all our correspondence. I can’t say enough about Tom.
Rob Freyvogel
#496
AA/BFS
Thanks for you input and encouragement Rob. Like others who have offered their advice and assistance I value and appreciate your and their openness and kindness.
the widest diameter cross section of this body is roughly 22". So having the Cp location between 22" and 44" back of the theoretical Cg is considered ideal for a real world design? I'm guesstimating its at 20" now so that's good to hear.
I understood that cross section (frontal area) did factor into aero drag along with the others you mentioned. Body displacement or volume, along with length factor into Cd based on what I've read on the subject and the formulas I found on fxSolver.
In the car world they use frontal area x Cd. In the aircraft world drag is measured in flat plate equipment. I think we are actually in the aircraft world and are flying aircraft at zero elevation but we do need to factor in ground effect.
Btw, these are Tom Bs words, not mine and I have to agree with him.
IE frontal area on the Carbiliner is deceptive. I can’t remember what the number is but it was pretty big. The fuselage is actually fairly small even at its thickest point but frontal area is based total shadow cast from front or back. The cross section of the car near the thickest part of the wing and wheel pants are a bit less than the thickest part of the fuselage. These two areas of the car are very different shapes but pass though the same section of air at different times.
It is not “Area Ruled” perfectly but it is not horrible either. We could have done better and I am trying to keep track of the changes for Mark II.
I like the idea of using nitrous as an intercooler. Just inject it right after the turbos. I would not spray it on an intercooler.
I would start off on Methanol as many guys don’t run any cooling system at all and get away with it when running meth. You just need to run it very rich and you will need a killer ignition system to light that wet mixture.
I have thought many times of getting rid of the heavy intercooler and running about 600 hp of nitrous right after the turbos (300 for each).
I would probably not use it until 4th and 5th gear.
Rob Freyvogel
#496
AA/BFS
-
its not a walking beam unless it "walks" from pivot pin between the wheels. To gain the stability of tandem front wheels to be able to resist a "step out" it can't pivot on either end.. As Gary Allen found out on Higginbotham's first attempt.
-
The Carbiliner has absolutely no Ackerman built into it. I did this on purpose.
When you are heading down the track and you have to steer, it is because your back wheels are sliding left or right. You’re not actually making a turn you are keeping the car going straight and you want the two front wheels to stay lined up right down the middle of the course and only countersteer not steer.
I’m very pleased at how our car steers even with aluminum front wheels with very little tread machine into them.
Rob Freyvogel
#496
AA/BFS
-
Rob,
How does the steering feel when turning off course to the return road?
DW
-
Rob,
How does the steering feel when turning off course to the return road?
DW
Perfectly, you can watch the in car camera on YouTube.
There is nothing precise about driving on salt. Also, we do not run a spool which helps a lot.
Rob Freyvogel
#496
AA/BFS
-
In the car world they use frontal area x Cd. In the aircraft world drag is measured in flat plate equipment. I think we are actually in the aircraft world and are flying aircraft at zero elevation but we do need to factor in ground effect.
Btw, these are Tom Bs words, not mine and I have to agree with him.
IE frontal area on the Carbiliner is deceptive. I can’t remember what the number is but it was pretty big. The fuselage is actually fairly small even at its thickest point but frontal area is based total shadow cast from front or back. The cross section of the car near the thickest part of the wing and wheel pants are a bit less than the thickest part of the fuselage. These two areas of the car are very different shapes but pass though the same section of air at different times.
It is not “Area Ruled” perfectly but it is not horrible either. We could have done better and I am trying to keep track of the changes for Mark II.
I like the idea of using nitrous as an intercooler. Just inject it right after the turbos. I would not spray it on an intercooler.
I would start off on Methanol as many guys don’t run any cooling system at all and get away with it when running meth. You just need to run it very rich and you will need a killer ignition system to light that wet mixture.
I have thought many times of getting rid of the heavy intercooler and running about 600 hp of nitrous right after the turbos (300 for each).
I would probably not use it until 4th and 5th gear.
Rob Freyvogel
#496
AA/BFS
All I know about aerodynamics is what I learn from reading and the experiences of others such as yourself Rob. Based on my reading the objective for my LSR project is to reduce frontal area to the least possible number using the best Cd geometry I can come up with. My wheel options are limited, and also limit the body geometry because I have to fit the elec. motors inside the wheel envelop, so thin cross section and profile aluminum wheels are all I see so far that will work. I started with M/T 16" profiles which fit the car shape but didn't leave room to plumb the motor coolant. The wheel profiles as currently drawn fit the car and give plenty of room for the elec. motors. Vertical stability is another challenge.
I remember back when I was a kid on the farm we'd shoot a quick burst of butane gas from the tractor tank to chill our soda bottles for lunch (propane didn't come along until later). Had to be really careful because the ice cold gas would freeze the Dr. Pepper and explode the glass bottles in a heartbeat. We need something similar to cool the intake charge between the turbos and the engine intake.
I spent the better part of yesterday researching the subject and I've come up with a plan to design just such a system using non-flammable refrigerant gas. No compressor, no condenser, no dryer, just high pressure liquid refrigerant, digital thermostatic expansion valve(s) and expansion tank(s) where the compressed air passes between the turbo and engine and an accumulator tank.
I'm looking to combine the methanol fuel tank with turbo-air routing in my currently design with finned refrigerant lines into an air-fuel-refrigerant intercooler to chill fuel, air, and extract heat through the refrigerant gas simultaneously. The methanol would chill first from direct liquid contact with the refrigerant lines, then extract heat from intake tubing before being burned in the engine. The refrigerant lines would also be in welded contact with the intake charge lines to suck heat through thermal conduction. The system would be programmed through the engine management controller to trigger refrigerant flow through the system based on thermal metering of the air intake and discharge ports at the intercooler tank.
Hot refrigerant gas would exit the intercooler and fill an accumulator tank during the run. Between runs the high pressure liquid refrigerant tank and the accumulator tanks would be recharged and/or drained ready for the next run. The system wouldn't be super light but it would definitely be lighter, more effective, and dependable than carrying several hundred pounds of iced water on every run. My design has limited room...I have to combine systems where possible to make everything fit.
-
its not a walking beam unless it "walks" from pivot pin between the wheels. To gain the stability of tandem front wheels to be able to resist a "step out" it can't pivot on either end.. As Gary Allen found out on Higginbotham's first attempt.
True enough Sparky...the beam doesn't walk in the conventional suspension sense but it does walk from side to side through an arc from the kingpin back to a slot in the chassis where the beam rests between and slides along two high density plastic pads directed by the steering levers. I could use a rack and pinion instead of pivoting levers to control the steering motion but that may not be necessary given the simplicity and low cost of this method. With reaction dampers I think this will track straight and work well.
-
What is the mechanical advantage of your steering set up?
-
What is the mechanical advantage of your steering set up?
For this design its a matter of getting everything to fit the body envelop Sparky. The steering design evolved entirely from that aspect. So narrow and so little room to work with as far as fit and resulting turning radius were concerned I just worked with the room given and this mechanical design is all I could come up with that would be structurally sound and doable. Luckly, I think its a practical design and because it trails the kingpin it should be pretty stable with good lateral dampers.
-
On board cooling capacity has to be limited because of the lack of space so my plan is to stage the systems for peak power through shutdown, and then use an external system in the chase truck to plug high pressure cooling lines into the car when it arrives to help lower the temps as quickly as possible.
I would seriously re-think this approach.
You can't always control how fast your crew gets to the vehicle after a run and a slow response could burn down your driveline, ending your event. Events are few and far between and a prematurely ended event could spell the end of your year.
So your plan is to have a crew waiting for the car at the end of the track? Where, at the 7 mile? then when you turn out at the 4 because of an issue, then what? you just burn down? How about them staging at the 5 so they split the difference. Then you blow a chute and roll to the 8. What about when (not if) you stop on track and are waiting for a push off? your crew wont be there. Add 5 minutes at least till you start rolling towards the return road and your cooling system. And before you say, "I'm not going to run at an event where I cant get to the car quickly" then your options for events gets real thin. I believe that designing a vehicle without sufficient cooling from the start is a foundational mistake that you would have a hell of a time recovering from.
Also, how big a crew do you plan on having?
Seems like you are over-valuing aero. It's important, but not so much that it harms the ability to reliably operate of the car, run, after run, after run, in the real world.
-
I would seriously re-think this approach.
You can't always control how fast your crew gets to the vehicle after a run and a slow response could burn down your driveline, ending your event. Events are few and far between and a prematurely ended event could spell the end of your year.
So your plan is to have a crew waiting for the car at the end of the track? Where, at the 7 mile? then when you turn out at the 4 because of an issue, then what? you just burn down? How about them staging at the 5 so they split the difference. Then you blow a chute and roll to the 8. What about when (not if) you stop on track and are waiting for a push off? your crew wont be there. Add 5 minutes at least till you start rolling towards the return road and your cooling system. And before you say, "I'm not going to run at an event where I cant get to the car quickly" then your options for events gets real thin. I believe that designing a vehicle without sufficient cooling from the start is a foundational mistake that you would have a hell of a time recovering from.
Also, how big a crew do you plan on having?
Seems like you are over-valuing aero. It's important, but not so much that it harms the ability to reliably operate of the car, run, after run, after run, in the real world.
Well you've made a valuable point JR...as I said I'm a LSR rookie and everything you noted is certainly valid and I obviously didn't think it through logistically. Since I made that comment I've studied up on refrigerant cooling for the intake charge and I've come to the conclusion that the same can be applied to the IC and motor/gen powerplant cooling. Now I have to see if the approached I came up with can be fit to the car for both systems. Thanks for helping me see the hurdles and keeping my thinking straight... Helpful input from you experienced guys is great. What a sport...
-
As far as cooling goes, it is actually very difficult to beat good old ice water. This goes for a intercooler coolant and ice water heat and exchanger for engine coolant IE radiator in ice water bath.
My other idea was start spraying high pressure ice water misters (from intercooler water) onto the radiator about halfway through the run.
Also be aware that you will need turbo chargers that are 10-15% bigger for a given HP figure for rotary engine.
Rob Freyvogel
#496
AA/BFS
-
Recognizing the preliminary stages of your project I will make a suggestion that is common when someone comes to the forum with ideas. (continue with your research and be aware you may need to make design changes along the way. I think you understand this.) But, make time to come to Bonneville, Speedweek, Cook shootout if there is one, World of Speed, World finals etc. Look at the cars. Talk to the owners, builders, drivers. Generally all will be willing to chat. Look at the packaging and how crowded it gets in there. Continue with your aero studies but consider you may need to give up some frontal area for space and stability. I think your project sounds exciting. A big leap in technology and maybe doesn't come to fruition but that is no reason not to try to come up with a workable design and then build it. Looking forward to follow your progress. Although it may be that it won't fit a SCTA or other class (FIA rules are different) or maybe no class or rules but safety is paramount. Get a SCTA rule book and study it. A Lot! There is a lot of information about construction and safety issues that can be applied to help you even if you don't run the car at an SCTA meet. JMHO
If the chutes fail and the brakes fail you will be in SLC pretty quick and your crew will be waaaayyyyy back there as you disappear over the horizon. :evil: :-)
-
Recognizing the preliminary stages of your project I will make a couple of suggestions that are common when someone comes to the forum with ideas. (continue with your research and be aware you may need to make design changes along the way. I think you understand this.) But, make time to come to Bonneville, Speedweek, Cook shootout if there is one, World of Speed, World finals etc. Look at the cars. Talk to the owners, builders, drivers. Generally all will be willing to chat. Look at the packaging and how crowded it gets in there. Continue with your aero studies but consider you may need to give up some frontal area for space and stability. I think your project sounds exciting. A big leap in technology and maybe doesn't come to fruition but that is no reason not to try to come up with a workable design and then build it. Looking forward to follow your progress. Although it may be that it won't fit a SCTA or other class (FIA rules are different) or maybe no class or rules but safety is paramount. Get a SCTA rule book and study it. A Lot! There is a lot of information about construction and safety issues that can be applied to help you even if you don't run the car at an SCTA meet. JMHO
If the chutes fail and the brakes fail you will be in SLC pretty quick and your crew will be waaaayyyyy back there as you disappear over the horizon. :evil: :-)
-
Rob and Jacksoni....great advise from you both...thanks. I recognize that ice water works and the majority of records over the years were set using it. I'd probably use it too if I could because its the least expensive, highly effect solution. Unfortunately I'm committed design wise to a small cross section/low Cd to take advantage of the Rotary IC/Gen-motors streamline packaging which I believe offers the best aerodynamic opportunity to push the wheel driven record to 600 or above. If what I'm proposing in my design turns out to be nothing more than a wishful exercise then that's ok....moving the goal post forward takes new ideas and group thinking on how to make those ideas work for some capable team. Thanks to everyone... :cheers:
-
Years ago, Don Vesco converted his motorcycle liner to a car. Offy powered. A wider track than you are thinking, as I recall about 10 to 12 inches.
The wreckage was over a mile...
I quick FYI .. To go 500 or even 600...in 5 or even 7 miles, you will never get to terminal velocity.
traction will be the limiting factor..
Build a car that you can survive a 400, 500 or 600 mph crash.. you can die slower also..
oh yea.... if you are looking for min CD.. then splitters wont work, as they need frontal high pressure to work, the opposite to what you are designing.
good luck
start cutting tubing..
salt is leaving quickly..
bob dalton
-
Here's a thought right out of left field and you can treat it as such if you want but it could simplify the whole process.
Why not start by building a relatively simple lakester using your proposed powertrain and maybe even the body shape and dimensions. It could be done using a single closer to stock engine. This would allow you to try out different packaging and cooling theories as well as other challenges that might arise without adding stability issues and the complexity that arises with multiple power sources.
People who have lots of experience on the salt often find a lot of issues when they try highly complex projects. A little experience with a more simple project may be valuable and might get someone else interested in the long term goal with deeper pockets. A little extra financial help never hurts for most of us. :-D :-D :-D
Good luck with the project. As you have intimated it keeps us all thinking and I believe that is a good thing. :cheers: :cheers: :cheers:
Pete
-
Hey Bob and Pete...thanks for the input. I may well have to rethink the track width or find a different way of vertically stabilizing the car. I like your idea Pete starting small and building up is sound advise for all the reasons you gave. Moving forward may eventually require that approach.
In terms of traction what's the thinking on total tires and placement? This project is aimed at setting the fastest wheel driven speed so record class rules aren't a limiting factor so long as we're allowed to run for time at event opportunities. Could we run 3 or 4 rear drive wheels and 1 lead steering wheel for example? From a packaging standpoint a wheel combination like that would fit my desired envelop with better traction opportunity. Is there a limit on total wheels for an unlimited liner?
What about retractable outriggers that spring out should the car begin to tip over left or right. I've seen the bike liners use something similar during launch. Thanks...
-
Simspeed , a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .
If the tail fin is tall enough a high speed yaw doesn't necessarily mean a roll .
-
Make a cockpit out of pvc tubing.. get a firesuit, hans, and current helmet on, and see if you fit...
My car 'was" (lol) 20.5" inside and if you ever saw me get in, it was tight. Not impossible, but tight.. 24 outside, body was 27" there to allow line clearance, total 30" at valve cover.
bob
That is tight Bob..I may have to let the shape scale up some to find room for everything. For now though I'll continue with the present cross section since it cost nothing but time to draw something different. Thanks...
-
Simspeed , a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .
If the tail fin is tall enough a high speed yaw doesn't necessarily mean a roll .
Well I like the idea of increasing the tail fin area to help out with the stability. Not much frontal area to a 1" fin. I've emailed Woody hoping to hear back from him before long. Thanks.
-
I’m liking the idea of a lakester as it is a great place to develop your power package. After you have worked out all the bugs, you will have a much better idea on what you can get away with after you have a season or so running it in the lakester.
You may be able to find one used, do your development work, then sell it for close to what you paid for it.
Do not underestimate the power of actual salt testing your power supply. It will show issues that are not experienced in any other forms of racing.
I know this sounds crazy but designing the body is one of the last things you want to do (in my opinion). It is of course great to have an actual design in mind the whole time but making wise choices about what engine, transmission, third member, turbos, cooling, intercooling, tires and all the other stuff that is not going to be fabbed needs to locked in first.
The body and tanks will then will just need elegantly wrapped around what cannot be changed.
I do like the way you dream big though! Now you just have to figure out which is the wisest way to get there and decide whether or not it is actually worth the time and expense to get there.
Yeah I know, that last one is a doosy!
Rob Freyvogel
#496
AA/BFS
-
Well I like the idea of increasing the tail fin area to help out with the stability. Not much frontal area to a 1" fin.
a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .
-
There are very few that have gone really fast,, you have several here chiming in. There are those that theorize and those that do, take advantage of those that have!
-
Good advice Eddie. I'm sorry if I don't give proper recognition to those that have done it, its because I just don't know who most of you are relative to your accomplishments. Hoping to learn more about you all. :-)
-
There are very few that have gone really fast,, you have several here chiming in. There are those that theorize and those that do, take advantage of those that have!
:cheers: :cheers: :cheers: :cheers: 8-)
Sid.
-
There are very few that have gone really fast,, you have several here chiming in. There are those that theorize and those that do, take advantage of those that have!
:cheers: :cheers: :cheers: :cheers: 8-)
Sid.
That is what I'm hoping to do Sid...thanks :-)
-
"Well I like the idea of increasing the tail fin area to help out with the stability. Not much frontal area to a 1" fin. I've emailed Woody hoping to hear back from him before long. Thanks."
I didn't phrase it well enough . I meant physically tall like 18" long and 5 ft tall so in a yaw when tire friction tries to roll the car outward the air pressure on the tail fin won't let it . I remember tall tail fin on Joe Law's lakester allowed a spin instead of a crash at Elmo .
-
I didn't phrase it well enough . I meant physically tall like 18" long and 5 ft tall so in a yaw when tire friction tries to roll the car outward the air pressure on the tail fin won't let it . I remember tall tail fin on Joe Law's lakester allowed a spin instead of a crash at Elmo .
5' on a 30" high car looks pretty tall John. But whatever works is good with me. At least we have something to move the Cp around with. Woody got back with me and fortunately for him he's got a lot of work going on. I will likely get these concept body analysis done elsewhere and hopefully work with Woody later down the road for a more detailed look at the car as a whole. Drawing up another body and chassis with a drooped nose for a CFD comparison of the two. Frontal area is almost identical for both so Cd is what I'm looking to compare. Thanks...
-
It almost always boils down to TIME-TREASURE-TALENT
-
Don’t forget about “Passion “ Sparky.
Key motivating factor.
Rob Freyvogel
#496
AA/BFS
-
It almost always boils down to TIME-TREASURE-TALENT
Don’t forget about “Passion “ Sparky.
Key motivating factor.
And you both missed the one we rely on the most.... Dumb Luck :roll: :cheers:
-
It almost always boils down to TIME-TREASURE-TALENT
Don’t forget about “Passion “ Sparky.
Key motivating factor.
And you both missed the one we rely on the most.... Dumb Luck :roll: :cheers:
We shouldn't be relying much on Dumb Luck -- at least regarding safety. My 2 cents' worth: use suspension, and have each steering wheel
pivot about its own pin. Build economically, and work gradually toward higher speeds, over many years. Good luck.
-
I've studied everyone's comments and suggestions and determined I had no ability to optimize Cg and Cp with the previous design. So I decided to take a different approach and repackage everything into a front engine layout as shown in the attachments. I've moved the drive wheels to the rear and designed single wheel suspension steering using a hub center mechanism with dual shocks and hydraulic steering control.
I designed a 50 lb refrigerant intercooler for the intake charge, oil and methanol at the front, and a 30 lb intercooler system for the drive motors and electric controllers at the rear. Those systems will use digital thermostatic expansion valves to meter refrigerant delivery through control channels in the engine management system. Low pressure heated refrigerant will bleed off from the expansion lines after passing through the connected intercooler tanks.
-
I was able to get 20° of steering lock to lock with the single front wheel vs. 6° for the dual front wheel chassis layout...big improvement. Do you know anyone else that's using manual hydraulic steering? Boats use it well, I'm figuring it should work well here too. Any thoughts?
-
More attachments
-
This new body design actually has a smaller frontal area than my previous one. Lots of detail missing such as the canopy bracing and tin work but this is just an exercise to see if I can get everything to fit. Any observations? Thanks...
-
Perspectives
-
I'm impressed!
Listening in to a bunch of folks that've been there and done that.
We don't get that all the time here.
(I'm way out of comprehending all of this, but I sure can see and respect a lot of guys who have been there – and someone's listening!)
-
You have mad Solidworks skills sir!
Rob Freyvogel
#496
AA/BFS
-
Also, you might want to reach out to Stand 21 to see if they will give you either a solid model or some good dimensions on the new helmets that are coming out. I think they are a bit bigger.
Rob Freyvogel
#496
AA/BFS
-
My original design also had four drive wheels in the rear like yours.
Great minds think alike! Lol
Rob Freyvogel
#496
AA/BFS
-
Note that vision out of this canopy design will probably be very distorted.
It is probably too shallow of an angle.
I would not worry too much about aero advantage of the extreme shallow angle. It is probably not worth the trade off of being more complex to manufacture and figuring how to latch / unlatch that behemoth.
Looks great though!
Rob Freyvogel
#496
AA/BFS
-
Note that vision out of this canopy design will probably be very distorted.
It is probably too shallow of an angle.
I would not worry too much about aero advantage of the extreme shallow angle. It is probably not worth the trade off of being more complex to manufacture and figuring how to latch / unlatch that behemoth.
Looks great though!
Rob Freyvogel
#496
AA/BFS
Thanks Rob...the canopy wouldn't open all the way to the front; just the conventional distance to the steering column support. There's no need trying to draw all that detail into a conceptual model. Not having driven a low angle profile like this I honestly didn't consider the distorted view which is certainly a concern. I still believe however the aerodynamic benefit of a low Cd and extremely small frontal area that is to be had from this power train combo for an unlimited liner should not be wasted. When the potential speed approaches 600 mph, which I believe is within range of this design, I think aero advantage becomes exponentially important all things considered. One option for the distorted view would be to have the forward most section of the canopy where the driver's line of site is concentrated to be optically ground to remove the distortion. One of my first designs used a metal canopy with a glass portal in the line of sight at the very nose, but I figured that would be too big of a driving/safety challenge. Thanks...
-
I'm impressed!
Listening in to a bunch of folks that've been there and done that.
We don't get that all the time here.
(I'm way out of comprehending all of this, but I sure can see and respect a lot of guys who have been there – and someone's listening!)
Thanks Stan...best to be respectful and listen to those who have and build from their experience I believe. At my age I don't have time to think I can figure this stuff out on my own...I'm old enough to know better. :wink: Thanks...
-
Also, you might want to reach out to Stand 21 to see if they will give you either a solid model or some good dimensions on the new helmets that are coming out. I think they are a bit bigger.
Rob Freyvogel
#496
AA/BFS
That's a great idea Rob...I'll dig into that. Thanks...
-
My original design also had four drive wheels in the rear like yours.
Great minds think alike! Lol
Rob Freyvogel
#496
AA/BFS
I didn't know that Rob. I'm just trying to look at limitations inherent in the sport and see if there are any advantages to my design that may offer a way to mitigate some of those problems. Fortunately, because there's no mechanical drive train issues to overcome I have a lot of freedom in putting components where I think they can return the greatest benefit. Although it looks like there's a lot of mass behind the dimensional center point of the car, all the mechanical components are relatively lightweight. The 8 motor controllers for example only weight 120lbs combined according to the mfg. specs. Each gen motor wheel combo should weigh 120 lbs for two motors (60 lbs each) and 54 lbs by volume for the machined aluminum wheel. That's roughly 816 lbs for the running gear and controllers. I seen the Cg being well forward of the car center line which is why I changed the design to this configuration. What does your aluminum front wheel weigh Rob?
-
... to be optically ground to remove the distortion...
Is that even possible? Isn't the shallow-angle distortion an inherent result of refraction of light entering/exiting the screen's surfaces?
-
... to be optically ground to remove the distortion...
Is that even possible? Isn't the shallow-angle distortion an inherent result of refraction of light entering/exiting the screen's surfaces?
That's a good question Jack. I may have assumed incorrectly that optical grinding and polishing could be brought to bear to correct the problem much as is done on modern fighter jet canopies. I can see your point that higher angle refraction is not something that can necessarily be corrected. So let's consider an alternative solution involving cameras and video optics systems that show crystal clear color imagery in real time. I wouldn't be against using such a system to supplement what might otherwise be distorted vision due to light refraction issues through a high angle canopy. Thanks for point this out...
-
Maybe you could cfd both conventional and your design to see what you are actually gaining.
Time to get philosophical.
I can speak with confidence when I say you have many, many battles ahead of you. It is wisest to choose the battles that make the most difference.
What you don’t want to end up with is a vehicle with everything being experimental. Time goes by fast and Bonneville has such a short season (limited run and test time).
I have learned to choose components based on “What is going to give me the least amount of issues and still get the job done” vs “the fastest components”.
Otherwise you will probably be chasing “new build” gremlins for many, many years and not getting to your goal before “life” happens such as health issues or personal problems.
I can tell that you are very ambitious guy which only speeds rate at which these problems come at you.
We haven’t even started to talk about corrosion issues and how much maintenance is involved from year to year on keeping up with that stuff.
IE, the stuff that you have finished is never really finished.
Rob Freyvogel
#496
AA/BFS
-
The new Bullet trains have a nose that is shaped like a Loon-- the only diving bird that leaves virtually no splash you may need to change your nose shape to make it less sensative to yaw
-
The new Bullet trains have a nose that is shaped like a Loon-- the only diving bird that leaves virtually no splash you may need to change your nose shape to make it less sensative to yaw
The nose is definitely a work in progress Sparky. I checked out the loon...I don't think that's a look I'm going for. :-D
-
Maybe you could cfd both conventional and your design to see what you are actually gaining.
IE, the stuff that you have finished is never really finished.
Rob Freyvogel
#496
AA/BFS
Sound advice Rob...thanks. I do plan a CFD study once I've arrived at what I consider the most likely shape based on the chassis parameters I've identified. I think I'm about there with what's physically possible to stuff in this frontal envelope. Things I'm discussing like refrigerant intercoolers, hydraulic steering, single wheel hub center steering, visibility issues, and electrical drive are all necessitated by the cross section profile I believe is critical to achieving unlimited wheel driven record speed. I think there are so many quality efforts underway in the conventional sense of mechanical drive trains that taking that approach for me is just a wasted effort. I'll never have the experience you guys have or the time to develop it in a conventional sense.
Yea, I hope to get down the track too one day, but only if the design concept I use has what I consider a substantial advantage over all the rest. What I'm coming to love about LSR is the idea that to set unlimited speed records one has to be on the cutting edge of ideas about how to go faster than the best that's come before. Whether I can make any of that happen remains to be seen...but in the arena of ideas I think I can bring a thing or two to the table. Leastwise, I'm enjoying letting my imagination roam with the possibilities. Thanks for helping to keep me in touch with reality Rob... :)
-
Like I said. I like the way you think BIG!
I also like your approach about designing the whole car, then deciding if you will actually build it. Not many people think this way.
You are certainly welcome to hang out in our pits this year. After seeing more closely on how the game is played, it will probably influence your design a bit even if it is witnessing what we do wrong. You can just as much from that.
Tom Burkland influenced our design quite a bit just from his emails about what he was experiencing driving down the salt. It was invaluable.
Rob Freyvogel
#496
AA/BFS
-
Like I said. I like the way you think BIG!
I also like your approach about designing the whole car, then deciding if you will actually build it. Not many people think this way.
You are certainly welcome to hang out in our pits this year. After seeing more closely on how the game is played, it will probably influence your design a bit even if it is witnessing what we do wrong. You can just as much from that.
Tom Burkland influenced our design quite a bit just from his emails about what he was experiencing driving down the salt. It was invaluable.
Rob Freyvogel
#496
AA/BFS
Thanks Rob...thanks also for the pit invitation; I'd be honored to visit with you just as I will be with others like Stainless who have offered the same during Speed Week. I'm anxious to see first hand what it takes to be competitive on the salt. I'm sorry if what I said in any way infers that I think you or anyone else is doing it wrong, I don't believe that for a minute. I only have fanciful ideas about going fast based on my limited understanding of aerodynamic theory and time spent behind the welding mask...which admittedly was many years ago. I believe what I believe but in no way do I mean to be disrespectful to those who know what they know and have proven it through the years. Thanks...
-
Here's a body redesign using the contemporary drooped nose look. I like Sparky's take on yaw effect from the taller slab sided nose. This is a proven design that when molded out of carbon fiber should be structurally sound hanging off the nose of the chassis. I think tubing hung out to the nose will flex too much under load in this application.
-
However enamored you are with flashed refrigerant cooling systems, to avoid designing into a dead end corner it would be good to verify that the system will remove the required amount of heat and do so at the required rate.
-
However enamored you are with flashed refrigerant cooling systems, to avoid designing into a dead end corner it would be good to verify that the system will remove the required amount of heat and do so at the required rate.
Right you are IO...start with a design and test before committing it to steel and aluminum. Thanks...
-
I think there are a lot of possible improvements here. I think you know most of those here are Bonneville /SCTA racers and think in terms of SCTA rules for running in venues governed by them. FIA/FIM may well be way different and allow other formats of construction. A streamliner in the former setting requires minimum 4 wheels (can have more) but they do not need to be in rectangular configuration. Your vehicle is looking more like a motorcycle streamliner. As has been stated if your eventual goal is just a wheel driven vehicle run somewhere for the ultimate wheel driven record, you are not bound by SCTA rules. Bolivia comes to mind.
-
I think there are a lot of possible improvements here. I think you know most of those here are Bonneville /SCTA racers and think in terms of SCTA rules for running in venues governed by them. FIA/FIM may well be way different and allow other formats of construction. A streamliner in the former setting requires minimum 4 wheels (can have more) but they do not need to be in rectangular configuration. Your vehicle is looking more like a motorcycle streamliner. As has been stated if your eventual goal is just a wheel driven vehicle run somewhere for the ultimate wheel driven record, you are not bound by SCTA rules. Bolivia comes to mind.
I watched the video series of the Ack Attack in Bolivia and that track is something else for sure. Most likely that's where new ultimate records will be set. Logistically it's a nightmare. The team sponsor better have deep pockets because it's going to cost a ton to race there.
Your point about non standard wheel locations Jacksoni crossed my mind too when I considered the design for V.4.0. I toyed with a four wheel diamond pattern which worked well with the body restrictions but the chassis layout for that just didn't work out for the small cross section. Stretching the current design allows for a third pair of drive wheels which would give a 3000 hp Kw equivalent requiring 4 more generators and probably a third 4 rotor IC. Far fetched stuff but doable with a big enough bankroll. Thanks...
-
I'm just speculating here (That seems fair game in this particular thread! :-D) but I would think that the more drive axles you put adjacent to one another you're going to run into ever diminishing returns unless you can add significant weight so there is no loss of tractive force. The more weight you have, the more difficult it becomes to accelerate. It's just another thing to think about. Drive at both ends is probably a better approach but it's difficult with the shape you're attempting to maintain.
Keep thinking! :-D :-D :-D
Pete
-
How efficient can electric motors and generators be made in comparison with conventional mechanical driveline components? I really like the idea of rotary engines as long as I have a really good hearing protection system if I'm around the vehicle. :-o :-o :-D
Pete
-
Now you've got my mind working, and that's dangerous. I would think this vehicle might benefit from a very limited travel suspension system such as elastomer donuts to aid with traction. Just another comment from the peanut gallery.
Keep everyone thinking. It's good for the mind!
Pete
-
How efficient can electric motors and generators be made in comparison with conventional mechanical driveline components? I really like the idea of rotary engines as long as I have a really good hearing protection system if I'm around the vehicle. :-o :-o :-D
Pete
From what I've read of mfg. specs 97 to 98% efficiency is top of the line Peter. That's pretty amazing really in my opinion. When we consider gear losses and the like for mechanical drive systems I'd think there's not much difference really. If anything the electrical drive systems may be more efficient all things considered.
Yes, I wanted to drive from either end but like you say its tough to do with this envelop. As with anything there are diminishing returns in adding more drive wheels. Tracking wheels one behind the other will also lead to traction issues I'm sure. That's why I wanted to stagger them in a diamond pattern but I couldn't figure out how to make that work in this application. Thanks...
-
With research input from Don (Raceengineer) I've studied the angular diffusion issue with the long canopy. I've come to the conclusion the canopy shown previously is infeasible so another solution is needed. The images below show a shielded cockpit where a real time camera system is used to show forward vision during a run.
I found a company (https://www.orlaco.com/ (https://www.orlaco.com/))that manufactures HD vision systems for all types of real time commercial applications including forward and rear view cameras. MirrorEye is used in the trucking industry and forward vision systems are designed for earth movers and forklifts. There are lots of other mfgs of course but this company has component systems available that could work in this application.
This is also the body geometry that I'm having a CFD analysis done on. I'm going test the CFD with and without the lower skirts to see what the difference is. Any thoughts?
-
The world record holding streamlined bicycle [Aerovelo - 89.59 mph] uses a video screen like you're thinking of. Another fast bike does the same, and also positions the rider facing backwards.
-
I might be mistaken but I don't think the camera idea would ever fly with SCTA/BNI. Now I realize you aren't going to set an international record at their meets but you might need all the time you can get on the salt to prep for an international record. George has sure used those meets to his advantage. I'd at least consider an alternative that would meet SCTA requirements even if it slowed the car at those meets,
Sumner
-
Ah, new and better technology (good cameras and video) causing trouble again. I am pretty sure SCTA had outlawed periscopes. A TV screen instead of a canopy to see out is likely not far behind. I agree with Sumner. The practice time etc could be invaluable. See all the issues all the fast cars have keeping things together before the big numbers happen (Target 550 and even George seem to wring stuff off pretty regularly)
What happens when the lights go out...….
-
The world record holding streamlined bicycle [Aerovelo - 89.59 mph] uses a video screen like you're thinking of. Another fast bike does the same, and also positions the rider facing backwards.
Facing backwards, wow...that's interesting. Not applicable here but I'd like to see that arrangement. I'll see what I can find on it. Thanks...
-
I might be mistaken but I don't think the camera idea would ever fly with SCTA/BNI. Now I realize you aren't going to set an international record at their meets but you might need all the time you can get on the salt to prep for an international record. George has sure used those meets to his advantage. I'd at least consider an alternative that would meet SCTA requirements even if it slowed the car at those meets,
Sumner
Well that's a excellent point Sumner. I figured the SCTA wouldn't allow it but didn't consider the practical need to use their events to get track time for the car and driver. Creating removable top section for the body that allowed use of a conventional canopy for SCTA events would solve that problem. I'll design a SCTA version of the body and use CFD to compare the two configurations. Thanks...
-
Ah, new and better technology (good cameras and video) causing trouble again. I am pretty sure SCTA had outlawed periscopes. A TV screen instead of a canopy to see out is likely not far behind. I agree with Sumner. The practice time etc could be invaluable. See all the issues all the fast cars have keeping things together before the big numbers happen (Target 550 and even George seem to wring stuff off pretty regularly)
What happens when the lights go out...….
Agreed jacksoni... As with any critical system, using proven componentry and back up circuitry helps protect against unintended consequences. It's safe to say the run would be aborted and parachutes deployed to bring the car to a safe stop. Anything can go wrong of course but that true regardless the circumstances or systems used. Given a proper design I wouldn't be afraid of the technology in this application. Thanks...
-
Facing backwards, wow...that's interesting.
You inspired me to refresh my memory on this. The backwards HPV is the invention of Damjan Zabovnik, and he actually does not use a camera, but a mirror. You can google him.
-
Facing backwards, wow...that's interesting.
You inspired me to refresh my memory on this. The backwards HPV is the invention of Damjan Zabovnik, and he actually does not use a camera, but a mirror. You can google him.
I looked him up...that's pretty amazing. Real innovation!! Thanks for sharing tortoise.
-
Ok, so I did a quick body section to change the top panels and canopy to more conventional geometry to run SCTA events for testing. The frontal area will remain the same as before but the Cd will obviously change somewhat. It'll be interesting to see how much difference in Cd there is between the two geometries. If the difference is inconsequential then no sense going to the time and expense to build both configurations. Any guesses on the two Cds before we run the numbers? I've added a rear view to show how the skirts run the full length of the body. The intent is to apply downforce for traction which I think will be need more than the added drag will penalize.
-
Here is a scaled size comparison between Simspeed 4.4 and the Challenger 2 and Turbonator II. All three cars are scaled in inches based on info on respective websites. The standing man model next to D. Thompson is scaled to 6'2 which looks correct compared to the Challenger II crew members. All 3 cars are set equally at ground height. The biggest difference (frontal area) would be most noticeable from and head on view but I couldn't find correct perspective photos of the other cars to make that comparison. I didn't find any dimension info on the Speed Demon in order to scale that car for comparison so i left it out.
-
The trick is to get everything within that envelope.
Regards, Neil Tucson, AZ
-
This car is beginning to look more and more conventional.
DW
-
Yes it is, but the "conventional" vehicles it is being compared with took many years to get "conventional" as well. Design without experience is dangerous. There still may be some packaging advantages that will allow some improvement in cd. As you know the faster you go the more important that becomes with limited traction. The CFD drag predictions will be interesting. Hopefully reduced surface area (skin drag) and shape will show some improvement. If the front skirts are effective at creating some down force the drag will be higher than the skirtless design but final weight distribution and rear drive only may make the shirts unnecessary.
Regards, Don
-
The trick is to get everything within that envelope.
Regards, Neil Tucson, AZ
Hi Neil...yes that's true. I believe I've been able to scale all the major systems within the envelop. The wiring and plumbing I've taken into consideration and space is allocated for that routing. The power cables running from the generators to the controllers runs between the raised tubing in the chassis floor and the flat floor pan running the length of the chassis. The short run of cables from the controllers to the wheel motors snakes within the tubing entering the motors behind the wheels. Oil, methanol, glycerin, and dielectic fluid to cool the controllers are contained in the combo tank/intercoolers. Dry sump components for the IC engines are mounted adjacent to the generators and central oil tank/intercooler. The fuel system will be fed by a Waterman pump running off the nose of the forward 4 rotor. The engine control modules will ride in the flat space above the drivers foot well. There are no radiators or mechanical brakes. Cooling is via the chilled fuel and oil, and braking is via the chutes and measured reversal of the electromagnetic field driving the wheel motors. Thanks Neil...
-
This car is beginning to look more and more conventional.
DW
Hi DW...The look is a function of the application using feedback I've received from forum members. This latest version is designed to meet SCTA rules so that testing can be done at their events as Sumner and jacksoni wisely suggested. We may learn that "conventional" body geometry is sufficient to achieve record speed with the power train as designed so the added costs of the encapsulated driver and video system may not be needed for the first effort should we get that far. The Cd results should tell us if that's true or not. Thanks...
-
Yes it is, but the "conventional" vehicles it is being compared with took many years to get "conventional" as well. Design without experience is dangerous. There still may be some packaging advantages that will allow some improvement in cd. As you know the faster you go the more important that becomes with limited traction. The CFD drag predictions will be interesting. Hopefully reduced surface area (skin drag) and shape will show some improvement. If the front skirts are effective at creating some down force the drag will be higher than the skirtless design but final weight distribution and rear drive only may make the shirts unnecessary.
Regards, Don
Hi Don...valid points, thanks for stating them. The skirts are just a design exercise for CFD analysis to see if there is any potential benefit to be had. Cd, Cp, and Cg will all factor into those results. Thanks again Don for your research on the light refraction issue and aluminum wheel design. I very much appreciate your input. :cheers:
-
Sim Speed,
I highly recommend that you get a hold of Bruce Carmichael’s book “personal aircraft drag reduction”.
This will no doubt of fully influence design.
Let’s not forget this is rocket science not rocket art.
Also, why settle for eight rotors when you can have 12.
(https://uploads.tapatalk-cdn.com/20190524/5a33de05daf9190ddef439378589b3d8.jpg)
Rob Freyvogel
#496
AA/BFS
-
Yes it is, but the "conventional" vehicles it is being compared with took many years to get "conventional" as well. Design without experience is dangerous. There still may be some packaging advantages that will allow some improvement in cd. As you know the faster you go the more important that becomes with limited traction. The CFD drag predictions will be interesting. Hopefully reduced surface area (skin drag) and shape will show some improvement. If the front skirts are effective at creating some down force the drag will be higher than the skirtless design but final weight distribution and rear drive only may make the shirts unnecessary.
Regards, Don
Hi Don...valid points, thanks for stating them. The skirts are just a design exercise for CFD analysis to see if there is any potential benefit to be had. Cd, Cp, and Cg will all factor into those results. Thanks again Don for your research on the light refraction issue and aluminum wheel design. I very much appreciate your input. :cheers:
I might have missed it if you covered before, but rather than adding skirts, have you looked more into ground effect under the vehicle for downforce? Lots of benefits there.
-
Are the current unlimited wheel driven vehicles more traction-limited at lower speeds or more aero-limited at higher speeds?
To put down a monster number at the 5 mile you have to put down a monster number at the 2 and a quarter mile as well. Which is the tougher nut to crack right now?
-
I think Sim Speed is thinking more on the lines of Bolivia where there is this unlimited run up distance.
We know that Bonneville is good training for Bolivia but he will probably not set the world on fire at bonneville as far as numbers go.
Then again, he may surprise us!!!!!!
I think we should discuss whether a flat bottom car is more efficient than getting the car up away from the running surface and minimizing ground effect downforce.
Flat bottom car will make some down force at higher speeds but then again do you need that downforce at higher speeds and what price are you paying for that downforce.
Cfd does not do a good job of modeling this drag as far as I have witnessed so far.
What Woody and I have concluded is that if I were to build another car, it would be further from the ground.
That being said-
Flat bottom cars are way easier to build and maintain.
Rob Freyvogel
#496
AA/BFS
-
I might have missed it if you covered before, but rather than adding skirts, have you looked more into ground effect under the vehicle for downforce? Lots of benefits there.
My first design effort included a tunnel floor with IC exhaust dumping into the space to speed airflow exiting at the rear. I soon realized we'd need that space to run power cables from the generators to the controllers. So in an effort to add downforce to the nose and drive wheels I added the skirts for CFD testing. I'm hoping we won't need them but it will be good to know to what theoretical degree they may help or hurt. Thanks...
-
Are the current unlimited wheel driven vehicles more traction-limited at lower speeds or more aero-limited at higher speeds?
To put down a monster number at the 5 mile you have to put down a monster number at the 2 and a quarter mile as well. Which is the tougher nut to crack right now?
You need to be going between 370 to 400 at the 2 1/4 to go 500... 4wd is the probably the best way to get there. .. So a monster 2 is the 1st "Nut".
bob
-
Sim Speed,
I highly recommend that you get a hold of Bruce Carmichael’s book “personal aircraft drag reduction”.
This will no doubt of fully influence design.
Let’s not forget this is rocket science not rocket art.
Rob Freyvogel
#496
AA/BFS
Hi Rob...others also recommended Carmichael's book but I was unable to find a copy to purchase. If anyone has a PDF copy to share I'd appreciate it. Thanks...
-
I think we should discuss whether a flat bottom car is more efficient than getting the car up away from the running surface and minimizing ground effect downforce.
Flat bottom car will make some down force at higher speeds but then again do you need that downforce at higher speeds and what price are you paying for that downforce.
Cfd does not do a good job of modeling this drag as far as I have witnessed so far.
What Woody and I have concluded is that if I were to build another car, it would be further from the ground.
That being said-
Flat bottom cars are way easier to build and maintain.
Rob Freyvogel
#496
AA/BFS
Motorcycle streamliners appear to be good examples of geometry that minimizes ground effect downforce. Your design of the Carbinite LSR car minics that approach in an innovative way that I've appreciated since I first viewed it Rob. The active aero you employed to add downforce then transition to minimal drag at high speed is a nice feature of your design. It would be interesting to combine your approach with mine and split off a pair of the drive wheels to outriggers such as yours so that each of the four drive wheels are running in their own track on the salt. Without the need to provide mechanical linkage to power the wheels it would appear to be relatively easy to configure that layout and take advantage of the active aero flaps you designed. I'm wondering what the drag penalty would be for outriggers such as yours. What are your thoughts Rob?
-
You need to be going between 370 to 400 at the 2 1/4 to go 500... 4wd is the probably the best way to get there. .. So a monster 2 is the 1st "Nut".
bob
Thanks for that info Bob. Getting power to the ground early is apparently more important than one might assume.
-
Been watchin this topic as it has transpired. Many credible and knowledgeable people have been giving you solid advice.
Finally someone posted IMHOP the most important thing.
Looking at all the + 400 mph cars and how speed was approached -obsolete and current generations of dragster type motors and Reher and Morrison pro stock style, WW 1 aircraft engines, high tech, high turbo boosted mills, Gas turbines, etc, shapes from the sublime to the ridiculous, all needed TRACTION!
Hope you turn theory into reality. GOOD LUCK
-
Summers brothers went 425 mph 50 years years ago. We’re all pikers.
We have made little progress with all our technology.
Rob Freyvogel
#496
AA/BFS
-
I mention the Summers brothers and our lack of progress just to indicate that if you use conventional technology and do it everybody else is doing you’re pretty much get what everybody else has.
For some that’s enough, for me and Sim speed it is not.
-
I mention the Summers brothers and our lack of progress just to indicate that if you use conventional technology and do it everybody else is doing you’re pretty much get what everybody else has.
For some that’s enough, for me and Sim speed it is not.
I live by this as well (engine wise anyway). march on guys. :cheers: :cheers:
-
Been watchin this topic as it has transpired. Many credible and knowledgeable people have been giving you solid advice.
Finally someone posted IMHOP the most important thing.
Looking at all the + 400 mph cars and how speed was approached -obsolete and current generations of dragster type motors and Reher and Morrison pro stock style, WW 1 aircraft engines, high tech, high turbo boosted mills, Gas turbines, etc, shapes from the sublime to the ridiculous, all needed TRACTION!
Hope you turn theory into reality. GOOD LUCK
Thanks IB...I hope so too.
-
Summers brothers went 425 mph 50 years years ago. We’re all pikers.
We have made little progress with all our technology.
Rob Freyvogel
#496
AA/BFS
It's amazing isn't it. 50 years and the 500 mph has just been broken. As IB said traction is the common denominator and we've made virtually zero progress in that area. I don't know what it will take more than anyone else but there has to be new ground broken in how to put power to the salt. Several people are working on aluminum traction wheels and I for one believe that's the most promising opportunity on the horizon.
-
I mention the Summers brothers and our lack of progress just to indicate that if you use conventional technology and do it everybody else is doing you’re pretty much get what everybody else has.
For some that’s enough, for me and Sim speed it is not.
Looking back at the Summers brother what did they have that gave them the record and put them ahead of the field for so long? It wasn't HP; we can make more today with one engine than they did with four. Tires...not really; we're using virtually the same tire technology today. Aerodynamics...most likely that was their advantage because their body geometry is probably still as good as most everything running today. They put a package together that optimized the technology they had then and put it to the ground on salt that is most likely much better than what we have today according to many veteran Bonneville racers.
To get higher speeds increased traction and better aerodynamic body design is the key in my rookie opinion. I like Rob's use of active aero to increase downforce where traction is most needed, that's something I may well incorporate in my design. Smaller frontal area with clean geometry will allow higher speeds all else being equal, and that becomes exponentially more important as speeds increase. I believe my current design offers the best opportunity to reach record speeds because we can put competitive HP in what may be the smallest profile body of any that's come before. Like everyone else we need traction to reach the full potential of our design and that's going to take innovative ideas and borrowing the best of what's been proven to work. I'll be pitching ideas and asking those who are interested to help sort out the best design possible. Thanks for everyone's continued input and guidance... Terry
-
you just might be dealing with salt to salt traction
-
... there has to be new ground broken in how to put power to the salt...
By whose decree "the salt"? If no satisfactory stretch of pavement can be found, lay some asphalt- doesn't need to be durable (as highways are). On flat/level/desolate/cheap land, safely wide (60'?), whatever length (10 mile? 13 mile?). Other 'Unlimited' landspeed competitors will gladly share the costs.
-
you just might be dealing with salt to salt traction
How so Sparky?
-
... there has to be new ground broken in how to put power to the salt...
By whose decree "the salt"? If no satisfactory stretch of pavement can be found, lay some asphalt- doesn't need to be durable (as highways are). On flat/level/desolate/cheap land, safely wide (60'?), whatever length (10 mile? 13 mile?). Other 'Unlimited' landspeed competitors will gladly share the costs.
I agree if suitable land was available then a durable surface with a high traction coefficient would be idea wouldn't it Jack. Frankly I don't see that happening but it's something to consider. We need a generous billionaire to step up and make it happen...anyone out there know a generous billionaire? :wink:
-
Here is my take on 4 wheel drive using two inboard wheel motors and two outboard wheels with inboard motors using Rob's Carbinite design ideas. Active aero flaps for increased downforce traction is one big advantage, the second advantage is putting each drive wheel in it's own track on the salt. Vertical stability is also enhanced with the outriggers giving a much wider track at the rear which Rob and others (the rocket cars come to mind) have proven works to keep the car stable at speed. The big disadvantage of course is increase drag. I have no idea at this stage if the trade offs are worthwhile for my design. The wheel pods would need to be structurally sound and molded carbon fiber should be adequate with brace tubing as shown there to maintain position. I'm unsure how Rob controls the flaps on his car but I think a electro-mechanical actuators in each airfoil section would work best here with the available electrical power we have on hand.
This arrangement also allows the use of disc brakes on the outboard wheels as back up to the electromotive braking. Like with the Carbinite liner full floating axles would be use for the outboard wheels.
-
I too have been curious if salt one foot thick offered more traction than salt one inch thick.
Sent from my SM-T380 using Tapatalk
-
Sim,
With this design, you can make fuselage much thinner that you have drawn.
Also, you can lose the vertical stabilizer as the wheel pants become the new vert stabilizers.
Wider is better as wing and flap will not need as much angle of attack to generate needed downforce.
Rob Freyvogel
#496
AA/BFS
-
Rob is right on. The vertical stab is now redundant as the wheel pants take care of stability and CP issues. The distance between the body and the inner surface of the wheel pant is important. If they are to close together you can get interference drag. All this can be refined w/CFD, testing, etc.
Thanks for sharing
Don
-
A couple things to consider:
Back in the day from what I can tell from old video, they for sure had longer salt. The interstate wasn't there and I think they started almost back near where the truck stop is now. Craig clipped the telephone poles that use to run about where the interstate is now and ended up in the pond past it. Even since I've been going they backed up the starting area for the fast cars when they use to run both ways. Mike has done this at his international meets to make the course longer. Only problem is that now the cars are starting on basically mud on both ends and can't always use the extra length due to the surface. Hence the need now to go outside the U.S. if one is really serious about setting a big record over 500. It is probably pointless to build a car with that capability if one can't also afford to make that happen.
A lot of the traction issues have to be solved with a better solution than one's right foot, unless your name is Bob :-), and/or tire technology. You basically have to bury your foot and let technology take care of the rest in the means of traction control and how the power comes on (easier with turbos). I think that has been the key to George's success, but that is a guess.
Running on either the SCTA courses or the International ones that have been laid out to this point is not land speed racing but drag racing as pointed out by the numbers Bob posted. At over 400 you are eating up a mile in under 9 seconds. Not much time to accelerate faster. Look at the Turbinator's in car camera and watch the numbers.
One other big factor with cars is also the one hour turnaround. Can you get the car turned around and serviced (intercooler needs is a factor here) in the one hour and back down the track. A lot harder to make those two back to back runs than one first imagines.
I think it is easy to visualize a smaller car than what has been run. I've done it and so have others but when the actually packaging of everything comes into play it just doesn't happen. Look at the fast cars and you will see that there isn't a lot of wasted space in them. Costella maybe has been best at this along with the Buddfab Streamliner (131 mph/50cc) along with most of the other really fast cars.
I'd look at the comparison of the aero of more frontal area and a shorter car vs. a smaller frontal area and a longer car as for as the total drag of both is concerned. When I say I'd look, I meant this is an area where you need someone very knowledgeable to do the calcs. Slimspeed (I'd like to use your real name but don't know it) I know you say you can package all the components in the car you've designed but I still am very skeptical of that having been down that road to some degree. In the side view of your car along side existing cars I can't see a roll bar over the drivers head along with padding and the helmets in use now and the driver still having a slight line out front. That is merely an guess at looking at the drawing. Also heat management, especially with turbos, can be a huge deal in a tight car. George was plagued with this for a while.
It is amazing how much time it takes to build these cars and to get the bugs out and then find that perfect track and weather window to actually pull out a big run regardless of the class one is running in. This also usually involves a lot of help from others and of course a big outlay of money even running in lower classes. I've come to realize that at my age (75) time has basically run out as far as ever finishing my car and running it on the salt and I'm still in good health. It is a huge commitment in time, energy and money.
Hopefully you wont' take any of the above as being critical of your work as I've seen you put a lot into it. Just rambling thoughts that came to mind. Good luck and keep working hard at your goal,
Sumner
-
Sum,
I’m 53 and I feel my time has run out.
Sim,
I sort of said this before but maybe in not do many words.
The rewards of success in this area of motorsports does not even come close to justify price we pay to do it.
Salt fever is a real illness.
Even if the Carbinitelsr goes 500+ this year (and this is a might big “if”), it was way too big a price to pay. I was way too optimistic on both financial and time projections. Call it “Buyer Remorse or whatever”.
We always think we are smarter and and can do things better or we would not bother trying.
The reality is that it is usually true on stuff like our major ideas but all the other factors such as just being “good racers” and handling logistics all come in to play.
The best advise that I got and give-
You don’t even know what you don’t know.
Now if you give it plenty of thought and still decide you want to do this, we will be here for you.
Rob Freyvogel
#496
AA/BFS
-
Summers brothers went 425 mph 50 years years ago. We’re all pikers.
We have made little progress with all our technology.
Rob Freyvogel
#496
AA/BFS
Rob, I am not being critical of your post as this is just my opinion on this subject of progress since the Summers Brothers. First, this is an amateur sport = NO MONEY, equates to slow progress. Second, you deal with Mother Nature and every year the conditions are different, sometimes no Speedweek. Third, Running SCTA you only have 5 miles. Forth, you only have a couple of times a year to run on the salt, unless you are a fortunate person who can pay for private time. Fifth, Salt Gremlins always pop up. Sixth, Tires for fast cars have not always been available over the years. We are lucky just recently Goodyear has gotten involved.
Like I said this is just my opinion on why it has been slow progress since the Summers Brothers.
Most of you know this but for those that don't, if you enter the Fifth mile at 400 mph you have about 9 seconds or less to achieve a higher speed, since you are traveling at 586.67 feet per second at 400 mph. At 450 mph you have 8 seconds or less to achieve a higher speed. Not much time to gain speed for a traction limited surface, and tires that have grown from centrifugal force and have less contact area.
Okay time to get back to this interesting topic.
Tom G.
PS. I took to long to write this and I see Sumner has posted in ahead of me, so excuse me if I am redundant.
-
... a durable surface...
... We need a generous billionaire...
How durable do you need? A year? 2 years?
Laying a strip of asphalt doesn't require a billionaire.
-
Sim,
With this design, you can make fuselage much thinner that you have drawn.
Also, you can lose the vertical stabilizer as the wheel pants become the new vert stabilizers.
Wider is better as wing and flap will not need as much angle of attack to generate needed downforce.
Rob Freyvogel
#496
AA/BFS
I don't believe I can get the fuselage any thinner than currently drawn Rob (see attachment). This cross section is equally representative of virtually every section of the car which is filled to the max with chassis, components, and the driver. I did widen the wing area to 24" between the body and fairing on each side.
I also did an area calculation with the outriggers in place and the total frontal area more than doubled from 3.60 to 7.655 sq. ft. All else being equal that would also double the HP needed to reach a given speed with a given Cd based on spreadsheets supplied on the landracing.com website. I'll analyze to determine the Cd with and without the outriggers to see what's feasible and what's not. The drag penalty for the outriggers appears to be significant. We'll see... Thanks Rob.
-
Sum,
I’m 53 and I feel my time has run out.
Sim,
I sort of said this before but maybe in not do many words.
The rewards of success in this area of motorsports does not even come close to justify price we pay to do it.
Salt fever is a real illness.
Even if the Carbinitelsr goes 500+ this year (and this is a might big “if”), it was way too big a price to pay. I was way too optimistic on both financial and time projections. Call it “Buyer Remorse or whatever”.
We always think we are smarter and and can do things better or we would not bother trying.
The reality is that it is usually true on stuff like our major ideas but all the other factors such as just being “good racers” and handling logistics all come in to play.
The best advise that I got and give-
You don’t even know what you don’t know.
Now if you give it plenty of thought and still decide you want to do this, we will be here for you.
Rob Freyvogel
#496
AA/BFS
Thanks for the heartfelt comments Rob. I recognize the benefits don't justify the cost for most forms of motor racing. I can see your point about how building such a car is so costly and time consuming as to never be worth the price we as individuals must pay to bring it to reality. For most of us its an impossibility to begin with unless we put a sponsorship package together that benefits the sponsor(s) beyond the dollar return of the venture's success. If a sponsor can't parlay a record breaking outcome into intrinsic value exponentially greater than the investment, then its highly unlikely they will gamble the company's fortune for what is at best a dubious uncertainty. IMHO its not enough to break a record to justify the investment, one must set a new milestone that will hold for years so a sponsor can capitalize long term on the marketing opportunity. Creating a brand around the success of the venture is an obvious investment goal. Component mfgs can benefit if their products are part of the mix that achieves record speeds. Name sponsors need to associate their investment with commercial brand value away from the track and apart from the inherent aspects of racing for record speed which is too esoteric even in the best scenario to be of much value to anyone but the people who put in the sweat and effort to make it happen. Setting a record(s) is the objective for racers, but it's not the story line that sells the project to a deep pocket sponsor and attracts media coverage that reaches the masses with a message they find appealing enough to find favor with the sponsor's brand. It's the story behind the effort that sells....the speed achieved serves only to justify and validate why the effort was undertaken in the first place. Thanks...Terry
-
... a durable surface...
... We need a generous billionaire...
How durable do you need? A year? 2 years?
Laying a strip of asphalt doesn't require a billionaire.
Hi Jack...the paving itself isn't the greatest obstacle to overcome. The land, it's availability, location, cost relative to alternate use scenarios, as well as regulatory approval are all more important in my opinion. Imagine the difficulty you would face getting approval to lay down 10 miles of 60' wide paving at the salt flats. The location is probably ideal and would be the least costly to make race ready but that's never going to happen. The need for a billionaire is influence and the money to fight everyone who will stand up to stop it. Crowd funding isn't the answer in my opinion. But I like the idea...a lot. Thanks :-)
-
A couple things to consider:
Back in the day from what I can tell from old video, they for sure had longer salt. The interstate wasn't there and I think they started almost back near where the truck stop is now. Craig clipped the telephone poles that use to run about where the interstate is now and ended up in the pond past it. Even since I've been going they backed up the starting area for the fast cars when they use to run both ways. Mike has done this at his international meets to make the course longer. Only problem is that now the cars are starting on basically mud on both ends and can't always use the extra length due to the surface. Hence the need now to go outside the U.S. if one is really serious about setting a big record over 500. It is probably pointless to build a car with that capability if one can't also afford to make that happen.
A lot of the traction issues have to be solved with a better solution than one's right foot, unless your name is Bob :-), and/or tire technology. You basically have to bury your foot and let technology take care of the rest in the means of traction control and how the power comes on (easier with turbos). I think that has been the key to George's success, but that is a guess.
Running on either the SCTA courses or the International ones that have been laid out to this point is not land speed racing but drag racing as pointed out by the numbers Bob posted. At over 400 you are eating up a mile in under 9 seconds. Not much time to accelerate faster. Look at the Turbinator's in car camera and watch the numbers.
One other big factor with cars is also the one hour turnaround. Can you get the car turned around and serviced (intercooler needs is a factor here) in the one hour and back down the track. A lot harder to make those two back to back runs than one first imagines.
I think it is easy to visualize a smaller car than what has been run. I've done it and so have others but when the actually packaging of everything comes into play it just doesn't happen. Look at the fast cars and you will see that there isn't a lot of wasted space in them. Costella maybe has been best at this along with the Buddfab Streamliner (131 mph/50cc) along with most of the other really fast cars.
I'd look at the comparison of the aero of more frontal area and a shorter car vs. a smaller frontal area and a longer car as for as the total drag of both is concerned. When I say I'd look, I meant this is an area where you need someone very knowledgeable to do the calcs. Slimspeed (I'd like to use your real name but don't know it) I know you say you can package all the components in the car you've designed but I still am very skeptical of that having been down that road to some degree. In the side view of your car along side existing cars I can't see a roll bar over the drivers head along with padding and the helmets in use now and the driver still having a slight line out front. That is merely an guess at looking at the drawing. Also heat management, especially with turbos, can be a huge deal in a tight car. George was plagued with this for a while.
It is amazing how much time it takes to build these cars and to get the bugs out and then find that perfect track and weather window to actually pull out a big run regardless of the class one is running in. This also usually involves a lot of help from others and of course a big outlay of money even running in lower classes. I've come to realize that at my age (75) time has basically run out as far as ever finishing my car and running it on the salt and I'm still in good health. It is a huge commitment in time, energy and money.
Hopefully you wont' take any of the above as being critical of your work as I've seen you put a lot into it. Just rambling thoughts that came to mind. Good luck and keep working hard at your goal,
Sumner
Thanks for your comments Sumner...points well thought out are always welcome. Terry Peterson is my name but Simspeed works just fine. I did establish a line of sight from the drive's eyes when I designed the car. First through a long canopy and then the more conventional canopy we see in v.4.4 and v.4.5. drawings. If you look at the chassis minus the body drawings you'll see a full roll cage surrounding the driver with everything properly triangulated and braced. I haven't shown helmet padding in the latest version but there's room for it. All the major systems have been scaled in inches to fit in the body shell. It's not absolute, just a model to work with to see if all the systems can be made to fit and work out design elements for the best potential performance. Thanks...Terry
-
Sim,
Are you familiar with “area ruling”?
Where you pick up the wings and out riggers, the fuselage needs thinned.
If you take and cut up the car into 4” thick slices cross wise, then measure those cross sections and graph them, the graph should be smooth. This is important. We could have done a better job with this on the Carbiliner.
Flat sides are always bad even if it adds to frontal area.
You will always be more slippery if shape is changed gradually. IE your wheel pants should be shaped like airfoils.
Eric “Blue” was right when he steered us to the NACA 66 series airfoil. It is extremely efficient in terms of volume vs drag.
The wetted area of car that is laminar flow is only 1/3 of the drag of the wetted area not in laminar flow.
Believe it or not, if you would swell the sides of the car and shorten it, the drag should go down even though frontal area is increased.
You should also be able to lose the supports for the wheel pants by increasing cross section of the wing.
Those supports will be extremely draggy.
With the downforce in the rear, you will not need rear suspension. At least that has been my experience.
Rob Freyvogel
#496
AA/BFS
-
(https://uploads.tapatalk-cdn.com/20190527/6c14dd1a9ebc6e55b2358669b52fa97f.jpg)
This car is area ruled for Mach 1.5 and is a bit different than sub Mach.
(https://uploads.tapatalk-cdn.com/20190527/b6b81b026f2aed5bc82c570ceac4c789.jpg)
Note, shapes on everything are way different than sub Mach designing.
We would be fighting wave drag much more that aero drag at these speeds.
Rob Freyvogel
#496
AA/BFS
-
As much as we all love the idea of long paved track we all know there is no way it can happen... and 60 feet would be scary at speed.... I think the SCTA uses 80-100... the FIA / FIM track in Bolivia was 130 if I remember that right... and still a sign got clipped.
Thick salt does have better traction than thin salt... because it doesn't crumble as easily... there is mud under the salt... and when the salt it is as thin as it is now, racing surface is determined more on how the mud dried than how the salt dried.
-
Those of us who were around back in the good salt days will remember how the salt was always cool to the touch even on the hottest days. This is a big factor to the design & survivability of LSR tires that have minimal rubber thickness in the traction area. With the salt being so thin now the surface temperature is a lot warmer creating higher tire temps but nothing compared to what would happen on a blacktop surface. High speed LSR tires won't survive there.
Sid.
-
You always have someone that can’t stay on course no matter how wide they make it.
With a stable car and better traction, the course could be half the width.
A better question would be what would the run off surface be? Grass?
Rob Freyvogel
#496
AA/BFS
-
Did you say Grass? Maybe these would work -need up the speed rating by a factor of 10 but the engineers can do anything..... :-o 8-) :cheers: :cheers:
https://www.msn.com/en-us/autos/news/meet-the-tweel-the-tire-that-never-goes-flat/ar-AABWhoz?ocid=spartandhp
Doh- sorry it's not Friday is it? :evil:
-
I was thinking about running on a frozen lake. We could build spiked tires. No rubber.
Unlimited ice for intercooler and lower ambient temps to keep overheating issues in check.
Would it still be considered “land racing”? Hmmm?
Rob Freyvogel
#496
AA/BFS
-
I was thinking about running on a frozen lake. We could build spiked tires. No rubber.
Unlimited ice for intercooler and lower ambient temps to keep overheating issues in check.
Would it still be considered “land racing”? Hmmm?
Rob Freyvogel
#496
AA/BFS
Sucking cold dense air into that engine ought to make more horsepower too!!! :-D :-D :-D
Pete
-
I was thinking about running on a frozen lake. We could build spiked tires. No rubber.Unlimited ice for intercooler and lower ambient temps to keep overheating issues in check.
Yeah, but Imagine the poor guy who has to drive the Zamboni back and forth after each run.
-
Ah, he reminds me of my fantasy of building a Zamboni to work on the salt. Wouldn't that be the ticket? Kinda hard to keep enough supplies (water and salt to dispense) on board for a multi-mile course, though. . . :evil:
-
You wouldn't actually need to cut a perfect course on a frozen lake. Just blade a berm around it, pump lake water into it & let it freeze. It could even be refreshed every night. Lets go ice racing, I think Utah Lake freezes! :-D
Sid.
-
it is amazing how much salt sticks to the tires at speed when conditions are rightalso how fast it can
-
Sim,
Are you familiar with “area ruling”?
Where you pick up the wings and out riggers, the fuselage needs thinned.
If you take and cut up the car into 4” thick slices cross wise, then measure those cross sections and graph them, the graph should be smooth. This is important. We could have done a better job with this on the Carbiliner.
Flat sides are always bad even if it adds to frontal area.
You will always be more slippery if shape is changed gradually. IE your wheel pants should be shaped like airfoils.
Eric “Blue” was right when he steered us to the NACA 66 series airfoil. It is extremely efficient in terms of volume vs drag.
The wetted area of car that is laminar flow is only 1/3 of the drag of the wetted area not in laminar flow.
Believe it or not, if you would swell the sides of the car and shorten it, the drag should go down even though frontal area is increased.
You should also be able to lose the supports for the wheel pants by increasing cross section of the wing.
Those supports will be extremely draggy.
With the downforce in the rear, you will not need rear suspension. At least that has been my experience.
Rob Freyvogel
#496
AA/BFS
My original body based on the Sears Haack profile was a perfect spherical arch from nose to tail. The length of the design currently is largely dictated by the power train and component systems. Your point about the bracing is well taken and gave me an idea how to eliminate them all together as seen in the drawings below.
By moving the wheel motors outboard with the wheels we can eliminate the need for axles between the chassis and the wheels. The wheel pods and flat wing structure would be a one piece molded carbon composite that saddles across the chassis just like the wing on a sport plane. Access to the wheels would be through removable covers (not shown) on the outboard side of the pods. The wheel motors would bolt to the pod from the backside above the wing (black circle) with the wheels bolted conventionally to the motor faces.
The flaps would work the same as before but here they're mounted down on the deck. I think they would be just as effective for generating downforce in this position. Cp would be well back of center line and my guess is that Cd would be much lower as well even with the added frontal area. I have no doubt the structural integrity of the the design would be maintained using this outboard wheel/motor arrangement.
-
More drawings
-
(https://uploads.tapatalk-cdn.com/20190527/6c14dd1a9ebc6e55b2358669b52fa97f.jpg)
This car is area ruled for Mach 1.5 and is a bit different than sub Mach.
(https://uploads.tapatalk-cdn.com/20190527/b6b81b026f2aed5bc82c570ceac4c789.jpg)
Note, shapes on everything are way different than sub Mach designing.
We would be fighting wave drag much more that aero drag at these speeds.
Rob Freyvogel
#496
AA/BFS
Pretty wild design Rob...
-
... I was thinking about running on a frozen lake...
Henry Ford did that on Lake Michigan to set a speed record (93 MPH) with a stripped-down Ford model K (circa 1908?). They spread ashes for traction. There was no concern then for whether it would be labelled "land speed" or not. He was almost sideways a number of times during the run.
-
... the surface temperature is a lot warmer... what would happen on a blacktop surface. High speed LSR tires won't survive...
So now we are truly needing a billionaire- to include plumbing in the asphalt for liquid cooling. :roll:
-
Sim,
Your Solidworks skills are impressive!
I’m sending g you a PM.
Rob Freyvogel
#496
AA/BFS
-
I may have modeled that rocket car but it was designed by Eric (Blue).
It is a really design. I mean all tanks, engines, etc are in place and math is done. I believe it to be the most practical approach to 1000mph.
Rob Freyvogel
#496
AA/BFS
-
More drawings
If you are going to go the way of carbonite just copy their design more closely. Your flaps will not work the same in ground plane. Rob will argue with me about this, but I feel there is drag penalty to the wheel pods being a separate entity even if by ruler there is no more cross section at a given point with the body being so much smaller at that point. You have drawn big wheel pods without the requisite smaller cross section of body size to offset it in order to maintain frontal surface area. What you have drawn is the worst of both worlds.
I said it earlier in the thread. All streamliners should have good aero, the minor differences in drag are the least of the issues. More important is driveability and traction/acceleration. Now if you are talking about slower cars then its all about drag, but if your still accelerating decent at the 5 then the numbers say that even a moderate aero reduction is not as significant as non fast guys think.
-
All streamliners should have good aero, the minor differences in drag are the least of the issues. More important is driveability and traction/acceleration.
You went with 4wd with good result. Did you consider 2wd for better power/weight combined with aero downforce for traction?
-
All streamliners should have good aero, the minor differences in drag are the least of the issues. More important is driveability and traction/acceleration.
You went with 4wd with good result. Did you consider 2wd for better power/weight combined with aero downforce for traction?
I did, every way I ran the numbers the 4wd won out. This was with the intent of more power than I am currently running though. I am at the bare minimum hp to have the advantage swing towards 4wd. Any less power then the added weight/complexity etc wouldn't pay for itself as proven by speed demon, Jack Costellas car etc. But more power/less perfect salt and I think the 4wd wins. With speed demon running a bigger motor this year than they have it will be interesting to see their numbers. I don't see them picking up anything by the 2.25 so it will all be on the back end. At 400 plus it is less than 8 seconds to go a mile, it is a lot harder to make gains in less time.
-
More drawings
If you are going to go the way of carbonite just copy their design more closely. Your flaps will not work the same in ground plane. Rob will argue with me about this, but I feel there is drag penalty to the wheel pods being a separate entity even if by ruler there is no more cross section at a given point with the body being so much smaller at that point. You have drawn big wheel pods without the requisite smaller cross section of body size to offset it in order to maintain frontal surface area. What you have drawn is the worst of both worlds.
I said it earlier in the thread. All streamliners should have good aero, the minor differences in drag are the least of the issues. More important is driveability and traction/acceleration. Now if you are talking about slower cars then its all about drag, but if your still accelerating decent at the 5 then the numbers say that even a moderate aero reduction is not as significant as non fast guys think.
Hi Eddie... Yes I agree there will be a definite aero drag penalty with the wheel pods. I'm considering using them anyway for several reasons, added traction as I've stated being one, but more importantly my power train design allows very narrow body geometry which is inherently difficult to stabilize with inboard wheels. Center to center track width for the drive wheels is only 9". As Rob Freyvogel and others noted pencil rolling a car such as my inboard wheel design has deadly consequences. The outboard wheel pods should help greatly to minimize the danger.
The flaps are not designed to work the same as one might expect on an airplane wing. Here the point is to add downforce to the wing to place added weight onto the inboard and outboard drive wheels; the weight load being transferred through the surrounding structure. As Rob's design has shown added drag due to the raised flaps directly translates into added weight on the rear section of the chassis which is reduced at higher speeds as the flaps are lowered. I'm not concerned about airflow below the flap across the bottom of the wing as there will be an edge seal to prevent much of the air from going under the wing and body sections. Downward pressure on the wing itself is another component of the design where the leading edge is tapered down for air to deflect over the top creating downward pressure at speed with what is yet an unknown drag penalty. We'll see how much when I submit the final model for CFD analysis. Thanks for your input...
-
I'd really like to learn more about the cars and LSR history/experience of forum members. If you have personal LSR information and pictures somewhere on the internet please share links where we can find and study your cars and hopefully learn from your experiences. Thanks... Terry
-
More tires does not equal more traction. Its all about the percentage of vehicle weight that is on the drive tires regardless if its 2 or 4 tires. If you have a 5 wheel vehicle and one coaster is carrying 30% of the vehicle weight the 70% being used for traction will not care how many tires it is sitting on. I could even argue that with the compound used on land speed tires, having too much of a contact patch could reduce traction....
The new Zealand teams new car has had a 4 front wheel drive system proposed in the past with either one or two coasters in the rear. Their tires seemed to be in tandem which creates other problems as well having a drive tire running in the rut 2 feet behind another drive tire.. It will be interesting to see if this is the design they come out with. I can't see the point, but there are a lot of people smarter than me. I know I am not done learning and will be the first to admit I am not a real doctor I just play one on tv.
Long story short, I spent a lot of years thinking through various designs and trying to get "fancy". In the end I went with what maybe a more traditional approach but on limited budget and talent it seemed to be the best approach for me. I am happy with the result so far, with more potential still I think. I think I am on par with the best for dollar per mph.
The lack of large incremental increases in speeds was mentioned earlier in the thread. I look at it this way. The physics hasn't changed so why would we be able to continue to make leaps and bounds in speed? The low hanging fruit is all gone, its going to be harder to make small increments as time goes on. Does that make the Summers brothers geniuses? or us stupid? No, While technology has opened a lot of doors as a small racer, I now have to be an expert in several more fields including EFI computers etc. Through technology I have gone faster with less resources than most but I have made a significant investment in my own education to make me a better "racer" and my opinions and theories are constantly evolving.
-
More tires does not equal more traction. Its all about the percentage of vehicle weight that is on the drive tires regardless if its 2 or 4 tires. If you have a 5 wheel vehicle and one coaster is carrying 30% of the vehicle weight the 70% being used for traction will not care how many tires it is sitting on. I could even argue that with the compound used on land speed tires, having too much of a contact patch could reduce traction....
The new Zealand teams new car has had a 4 front wheel drive system proposed in the past with either one or two coasters in the rear. Their tires seemed to be in tandem which creates other problems as well having a drive tire running in the rut 2 feet behind another drive tire.. It will be interesting to see if this is the design they come out with. I can't see the point, but there are a lot of people smarter than me. I know I am not done learning and will be the first to admit I am not a real doctor I just play one on tv.
Great post Eddie...although I agree with your outlook on life and experiences I'm not sure I agree or even fully understand your comments on traction. Traction is a function of contact patch and distributed weight in my estimation. The greater the contact patch (one tire vs. multiple tires) the greater traction potential there is for a given amount of weight distributed evenly across all drive tires. Power should be looked at as a constant force that turns the wheel(s) to the limit of available traction without exceeding the friction coefficient where slippage is incurred. Application of power beyond that point is detrimental to reaching maximum speed.
Certainly there is a weight/contact patch limit where maximum traction is limited given fixed parameters of total weight, power, and available traction coefficient. My view is that spreading the weight across multiple drive tires of equal contact patch increases traction potential for a given weight. What has the better chance of greater traction and higher speed given equal surface conditions (traction coefficient)...one drive wheel/tire carrying 70% of total weight, or 4 tires of equal contact patch carrying 25% of the 70% each? 2 wheel drive vs 4 wheel drive...why is 4 wheel drive better given that using your theory weight per tire is decreased proportionally thereby reducing traction per tire?
I'd like to learn more about you track experiences Eddie...and links you can share? Thanks for commenting... Terry.
-
Yes,
Good comments Eddie!
Btw, does anybody know how much distance the Summers Bros used to run the 425mph speed?
I bought the book but skimming through it, I did not see that info.
Have not read it cover to cover yet.
Rob Freyvogel
#496
AA/BFS
-
4wd is better in the sense that no matter what all your weight is available to be used for acceleration/traction. Any weight resting on a coasting wheel is pure penalty without any benefit. Weight bias is key for stability so a rear wheel drive car is always fighting this relationship of stability vs traction. A front wheel drive car will always be fighting its own weight transfer under hard acceleration. People don't talk about weight transfer much but it is still a factor.
Until this sport gets developed to the nth degree we will continue seeing a wide range of designs (which keeps it fun).
I don't have any facts readily explainable to back up my thoughts on multiple tires vs less given the same weight on said tires. Call it racers intuition. Again maybe I am wrong. Maybe its as simple as the nature of the surface, Bville racers have long said a narrow tire is better than a wide one. There is something to be said for a tire being planted and biting vs floating on the marbles.
If you are on facebook, you can look me up at Ed Umland or Eddie's chop shop. I don't really post too much technical specifics but am happy to answer most questions. I don't have a long storied history, just a low buck racer doing what I can. I have run several classes being what I consider successful in all of them. Since getting into LSR my goal was always to go as fast as I could on my own budget and talent so I ran a little in other classes to gain experience before building my streamliner. I left a lot of potential on the table in the other classes though since I didn't spend Years chasing either of them.
Rob brings up another good point about Summers distance used. This years speedweek saw the highest speeds ever and in less distance. Again physics, this would definitely qualify as big jump in accomplishment if you ask me.
-
Given the proposed hybrid-of-sorts propulsion system discussed in this thread, maybe one should look at what the big electric streamliners are doing for traction (and traction control), driveline motors (or wheel hubs), speeds obtained, vehicle weight and aerodynamics for some historical reference.
Also excuse the off-topic subject query: With rotary engines spinning axial permanent magnet generators -- are the rotary engines to be throttle actuated or set at a fixed RPM for maximum output? Will the electric wheel hubs be driven by the driver actuated throttle input and pulling "juice" as needed via a software (traction) control system -- or controlled by how? No black box (power management system) necessary between said both to make it work?
-
4wd is better in the sense that no matter what all your weight is available to be used for acceleration/traction. Any weight resting on a coasting wheel is pure penalty without any benefit. Weight bias is key for stability so a rear wheel drive car is always fighting this relationship of stability vs traction. A front wheel drive car will always be fighting its own weight transfer under hard acceleration. People don't talk about weight transfer much but it is still a factor.
Until this sport gets developed to the nth degree we will continue seeing a wide range of designs (which keeps it fun).
I don't have any facts readily explainable to back up my thoughts on multiple tires vs less given the same weight on said tires. Call it racers intuition. Again maybe I am wrong. Maybe its as simple as the nature of the surface, Bville racers have long said a narrow tire is better than a wide one. There is something to be said for a tire being planted and biting vs floating on the marbles.
If you are on facebook, you can look me up at Ed Umland or Eddie's chop shop. I don't really post too much technical specifics but am happy to answer most questions. I don't have a long storied history, just a low buck racer doing what I can. I have run several classes being what I consider successful in all of them. Since getting into LSR my goal was always to go as fast as I could on my own budget and talent so I ran a little in other classes to gain experience before building my streamliner. I left a lot of potential on the table in the other classes though since I didn't spend Years chasing either of them.
Rob brings up another good point about Summers distance used. This years speedweek saw the highest speeds ever and in less distance. Again physics, this would definitely qualify as big jump in accomplishment if you ask me.
Thanks for the links Eddie...great stuff. Look forward to following you adventures. :cheers:
-
Given the proposed hybrid-of-sorts propulsion system discussed in this thread, maybe one should look at what the big electric streamliners are doing for traction (and traction control), driveline motors (or wheel hubs), speeds obtained, vehicle weight and aerodynamics for some historical reference.
Also excuse the off-topic subject query: With rotary engines spinning axial permanent magnet generators -- are the rotary engines to be throttle actuated or set at a fixed RPM for maximum output? Will the electric wheel hubs be driven by the driver actuated throttle input and pulling "juice" as needed via a software (traction) control system -- or controlled by how? No black box (power management system) necessary between said both to make it work?
Hi SuperL...Traction control for this design should be easy to achieve. As I envision it, wheel speed sensors will allow the motor controllers to see which wheels are spinning relative to each other and automatically adjust power to each wheel as needed to maximize acceleration given available traction. We won't use a foot throttle because that too susceptible to driver nervousness. A hand throttle lever (like a boat) will allow the driver to feed in IC power to the generators at a fixed rate which will in turn supply high voltage current to the motor controllers. The controllers will direct current to the wheel motors based on programming fed by real time wheel sensor data. The controllers will attempt to maximize motor acceleration to whatever limit electrical current is being received from the generators. If for example the driver had the IC engines at full throttle wheel speed would ramp up progressively based on available traction to each wheel. There would be no need to try and throttle the IC engines up and down during a run as controller programming will compensate for wheel spin effectively acting as the acceleration throttle. Wouldn't want the IC engines to run at max output constantly, the driver's job is to push the IC throttle forward in tune with forward thrust and increase in speed. The driver would most likely use a bump and run approach to advancing IC power letting the car build speed progressively as traction allows. Pulling the hand throttle back would automatically kill power and slow the car when needed for whatever reason. The whole scenario could be programmed to maximize acceleration but that's something that will need to be evaluated with testing. Thanks...Terry
-
I've done some work for https://www.wrightspeed.com/ . Interesting comment by an engineer there, when they cut power, the truck rear tires would "lock up". Sliding to a stop...
So plan on a programmable "ramp down" .
FYI.. I don't believe anything is "easy" when you are dealing with electronics and a salt environment.
bob
-
I've done some work for https://www.wrightspeed.com/ . Interesting comment by an engineer there, when they cut power, the truck rear tires would "lock up". Sliding to a stop...
So plan on a programmable "ramp down" .
FYI.. I don't believe anything is "easy" when you are dealing with electronics and a salt environment.
bob
Great point Bob...negative torque is created when one backs off the throttle and could lead to the wheel motors locking up unless there are adequate programming controls to configure current routing between the generators and motors. Woldesemayat & Nam (2017) identified causes and solutions that can be applied to controller programming to either eliminate the problem allowing coasting, or more desirably in this application induce degrees of electromotive braking to begin slowing the car as soon as the IC power is cut. Braking rate can be programmed based on speed allowing the chutes to do their job initially and applying greater amounts of negative torque at lower speeds to bring the car to a stop. The great thing about EV propulsion is that almost everything is programmable. Thanks... Terry
References:
Lee, H., Woldesemayat, M. L., & Nam, K. (2017). Zero Torque Control for EV Coasting Considering Cross-Coupling Inductance. IEEE Transactions on Industrial Electronics, 64(8), 6096–6104. doi:10.1109/tie.2017.2681973
-
I would think a Vernier throttle more like small plane ( all I've flown were single engine) which can be "slammed" open or closed or twisted to gradually increase or decrease power would be better than just a "boat" like lever.
-
If you are using PM DC torque motor, the braking torque problem is fairly simple. Since the motor is now acting like a generator, controlling the electrical load on the "generator" will control its braking torque. Polyphase AC motor braking torque control is a much more difficult problem.
Regards, Neil Tucson, AZ
-
I would think a Vernier throttle more like small plane ( all I've flown were single engine) which can be "slammed" open or closed or twisted to gradually increase or decrease power would be better than just a "boat" like lever.
That may be just the ticket jacksoni; I've never flown an airplane so that throttle control is new to me. I'll study up on it...thanks. Terry
-
If you are using PM DC torque motor, the braking torque problem is fairly simple. Since the motor is now acting like a generator, controlling the electrical load on the "generator" will control its braking torque. Polyphase AC motor braking torque control is a much more difficult problem.
Regards, Neil Tucson, AZ
Hi Neil...yes the Yasa P400 RC gen/motors I'm designing around are 700v DC permanent magnet axial flux motors. The standard 80mm cartridge model falls a little short of my peak power goals but Yasa offers custom windings to get there. I'm confident stacked Yasa gen/motors and controllers can deliver what my power train design calls for. Thanks for the info... Terry
-
Very interesting discussion IMO, thanks for sharing it. :cheers:
If you are using PM DC torque motor, the braking torque problem is fairly simple. Since the motor is now acting like a generator, controlling the electrical load on the "generator" will control its braking torque. Polyphase AC motor braking torque control is a much more difficult problem.
Sorry if I missed it, but I don't think I've seen mention of where the energy recovered under braking goes. In a modern diesel-electric locomotive the generated power is dissipated as heat in the braking grid resistors mounted atop the car body. In a contemporary EV the generated power is used to recharge the battery.
Tim
-
I am way out of my realm here, but don't most racing organizations require a throttle with a return spring that forces the throttle to always return to idle position if control pressure is removed? I wonder if a throttle that can be set in position like a boat or aircraft throttle (I think that is what is being described here) would be allowed.
-
Very interesting discussion IMO, thanks for sharing it. :cheers:
If you are using PM DC torque motor, the braking torque problem is fairly simple. Since the motor is now acting like a generator, controlling the electrical load on the "generator" will control its braking torque. Polyphase AC motor braking torque control is a much more difficult problem.
Sorry if I missed it, but I don't think I've seen mention of where the energy recovered under braking goes. In a modern diesel-electric locomotive the generated power is dissipated as heat in the braking grid resistors mounted atop the car body. In a contemporary EV the generated power is used to recharge the battery.
Tim
Hi Tim...no we haven't discussed where the energy goes when power to the wheel motors is cut and they effectively become generators feeding electromotive force back into the circuit that drives them under IC power. Up front I'm not an engineer...mechanical, electrical, or otherwise. What I'm commenting on here is my understanding of how this circuit would work under the conditions described. I may be half wrong or entirely wrong but I don't think so unless or until shown otherwise.
If the electrical circuit between the generators and motors is broken or disconnected there will be voltage but no current flow so the gen/motor mechanism will free wheel to some theoretical maximum voltage the circuitry can withstand. All well and good for idling or coasting but contributes nothing to braking. When the circuit is closed however the gen/motors switch roles and electromotive force or EMF generated by the wheel motors is effectively driving the IC gen/motor connection. The degree of force the IC gen/motors sees is determined by voltage the controllers are programmed to power the now reversed circuitry.
In my vision of the design, when power to the IC engines is cut (throttle off switches off ignition spark and fuel injectors) the 8 rotors and spinning generators become an active flywheel. Reversed polarity EMF from the wheel motors attempts at low voltage to slow rpm of the flywheel and reverse rotation of both the generators and IR rotors. EMF Voltage is progressively increased as IC rotor rpm comes down to the point where the IC gen/rotors actually begin to rotate in the opposite direction and begin ramping up flywheel rpm absorbing braking energy generated by the wheel gen/motor EMF. During the spin down to IC flywheel reversal the aluminum rotor housings and separator plates become heat sinks acting as resistors to dissipate heat build up in the gen units. The oil and coolant pumps all being electric motor driven would continue to run in standard rotation to keep oil and coolants flowing until IC flywheel eventually stops.
In a rotatory engine there are no valves or cams to contend with; reverse rotation is possible where the engine acts as an air pump under compression load dumping compressed air back into the atmosphere through intake ports and turbo housing. When the car comes to a stop the IC flywheel is still spinning and can spool down under is own internal friction load. I'm open to correction or clarification on any of this if someone with better knowledge knows reasons why this wouldn't work. Thanks...Terry
-
I am way out of my realm here, but don't most racing organizations require a throttle with a return spring that forces the throttle to always return to idle position if control pressure is removed? I wonder if a throttle that can be set in position like a boat or aircraft throttle (I think that is what is being described here) would be allowed.
You may be right Doc... I'm not familiar with the rules on this. it shouldn't be a problem if this approach isn't allowed. We could work with a forced idle position spring by setting an EMF coast mode between between throttle up and full throttle off positions, where EMF braking would only be triggered in the throttle off/power off position. Thanks... Terry
-
I don’t see it just locking up the wheels when you lift your foot off the throttle.
There are many ways to skin this cat.
Rob Freyvogel
#496
AA/BFS
-
I don’t see it just locking up the wheels when you lift your foot off the throttle.
There are many ways to skin this cat.
Rob Freyvogel
#496
AA/BFS
I agree Rob.
-
I cleaned up the rear section of the car and shortened the chassis a couple of feet by removing the inboard support bracing for the outboard wheel motors. I also added the chute tube and support structure and designed the chute cone doors to open and close with an actuator when triggered. This design only needed 10° of movement to clear the chute path. Don't know if that's enough to keep the tether lines from whipping them apart at speed. We only have room for one 6" chute tube in this design, can we pack 2 chutes in that? Thanks...
-
More drawings
-
Looking better and better!
Rob Freyvogel
#496
AA/BFS
-
Even if you do not plan on running SCTA you will probably want to have a second chute.
Btw, chute tubes do not need to be round.
When you get closer, I will send you one of my spare chutes so you can experiment with how you can fold up shroud lines to fit in your tubes and adjust design if necessary to fit.
Oh yeah, they grow a bit during a week at the salt even though you will rinse them after every use. Can’t explain it but it seems to consistently happen so leave yourself a little extra room.
Rob Freyvogel
#496
AA/BFS
-
Another thing I noticed about this design that uses a clamshell door is that the chute’s come out a little lazy. There is a giant low pressure area created on the backside of the clamshells. Naturally the chute does not want to go from low pressure to high pressure so you will need to get it forced out pretty good to get it into clean air and it will still probably bounce off the ground.
Were you planning on using a drogue chute?
Rob Freyvogel
#496
AA/BFS
-
When looking at the car from the top view, as the air comes between the fuselage and the wheel pants and gets towards the rear of those items, there will be a low pressure area created since it is opening up like a Venturi.
Low pressure area above your wing is not good.
The fix is to shorten up the wing cord wise.
You may want to extend the leading edge of the wing where it meets the fuselage to compensate for the shorter cord.
Rob Freyvogel
#496
AA/BFS
-
I definitely vote for a small pilot chute that can be shot into the slip stream up or side ways to pull the main chute out---bouncers are not fun and will get you written up for late chute
-
I am very happy about how we did our chutes by ejecting them straight up into clean air. I barely have to think about touching the lever and the chute is at full snatch.
Our design is sort of a jack-in-the-box approach and the entire chute package is thrown out of the box.
This system does not use a drogue.
Initially we had a drogue and not a sprung bottom. The problem that we were experiencing was that the cords were actually getting burned by friction when existing the radiused edge of box.
The only thing I would change is to make the chute door on the primary a two piece design that opened at the center. With the one piece design, the door is a little big and I am concerned about the air breaking it off at over 500. So far so good at 420 but we do have a couple of spare doors made just in case.
Rob Freyvogel
#496
AA/BFS
-
You might want to look at changing it to a soft flexible material to save damage to you or somebody else running over some of it.
Sid.
-
I had a great meet up with Stainless, John Boy and the crew yesterday in Denver...great bunch of guys. Stainless had his new chassis in tow for body work and I had a test fit which was definitely tight just in the bare chassis. I can see the need to rethink how best to design around the driver with helmet and driving suit as many here have stated. For now we'll continue with what we have dimension-wise for this concept stage but eventually we'll have to scale everything up for production drawings once the final concept is nailed down. Thanks again Stainless...fun day and highly educational. Best of luck to you and the crew with the new Bockscar 2.0 lakester...
-
:cheers: :cheers:
Mike
-
Yea we tried to lead Terry astray... but he is smarter than the average bear... errr racer...
I think the test fit was a good experience.... it will be a lot tighter in a SFI 20 and Snell 20 (future), than blue jeans and a shirt.
Enjoyed our talk... see you at the salt with any luck
-
Terry, It was nice to spend time bench racing. Thanks again for dinner. If you are coming to the city again it would be great to see you again. We dropped the Bockscar II off to get the aluminum panels fabricated.
John
-
Terry, It was nice to spend time bench racing. Thanks again for dinner. If you are coming to the city again it would be great to see you again. We dropped the Bockscar II off to get the aluminum panels fabricated.
John
Hey John Boy...I'm excited to see the body wrapped in tin with the nose cone in place. It's amazing the record speeds you guys have achieved with such small engines. Stainless is doing a great joy updating what has proven to be a well designed record setting machine. I look forward to our next get together. God bless...
-
Just caught up on this thread. Some seriously excellent work here!
I can assist with Aero testing should you choose. The subject is far too expansive to put into one post here, but if you ping me at abracabratby@yahoo.com and we can discuss. The type of testing is really going to be dependent on your budget and needs.
CFD is the most obvious choice, but not all CFD is created equal, everything from boundary conditions to the type of cores you run the solver on all have an effect on the results.
Windtunnels are tricky for streamliners because all the facilities that you would want to test at (i.e. full moving ground) are not capable of positioning the wheel pads at the narrow tracks and long wheelbases that you typically run. That leaves fixed ground facilities that can leave big question marks on the results.
Anyhow, message me if you like.
James
-
Just caught up on this thread. Some seriously excellent work here!
I can assist with Aero testing should you choose. The subject is far too expansive to put into one post here, but if you ping me at abracabratby@yahoo.com and we can discuss. The type of testing is really going to be dependent on your budget and needs.
CFD is the most obvious choice, but not all CFD is created equal, everything from boundary conditions to the type of cores you run the solver on all have an effect on the results.
Windtunnels are tricky for streamliners because all the facilities that you would want to test at (i.e. full moving ground) are not capable of positioning the wheel pads at the narrow tracks and long wheelbases that you typically run. That leaves fixed ground facilities that can leave big question marks on the results.
Anyhow, message me if you like.
James
Hi James...thanks for the offer. I'll get back to you when we've reached a consensus on the drive layout and body shape we think is best suited to the unique drive train I've introduced. Essentially we'll be looking to compare the best inboard and outboard drive wheel body geometry to see what the drag penalty is for receiving the added benefits of vertical stabilization, increased traction potential, and added downforce or weight loading of an active aero wing flap on the outboard wheel design. As I mentioned previously, the outboard design more than doubles frontal area but we're still less than 8 sq.ft. total. Not great when we consider the inboard wheel design is only 3.6 sq.ft. Thanks... Terry
-
When looking at the car from the top view, as the air comes between the fuselage and the wheel pants and gets towards the rear of those items, there will be a low pressure area created since it is opening up like a Venturi.
Low pressure area above your wing is not good.
The fix is to shorten up the wing cord wise.
You may want to extend the leading edge of the wing where it meets the fuselage to compensate for the shorter cord.
Rob Freyvogel
#496
AA/BFS
Hi Rob...I'm working on a redesign of the chutes, wing, flap and various chassis parts to compensate for adding two chute packs. Not sure just yet how best to get the chutes out into the air stream. I should have something to show in a few days. Thanks... Terry
-
Here is the redesign of the chute system allowing for two full size packs. The tail cone in this design is ejected and acts as the pilot chute to pull out the main chute using a short tether cord. The shroud lines run from inside the body fitted packing can back to a formed steel loop that's bolted to the frame rails for the anchor point. We'll probably use two bolts in shear rather than thread tension to retain the anchor loop.
The tail cone itself would be rotomolded high density plastic that sets into the tail stock with spring loaded trigger pins. The front edge of the tail cone would pop up into the air stream and be flipped backward away from the car pulling the chute out with it. The second chute could be pulled out by a second tether cord affixed to the shroud lines of the main chute near the end of its full extension. That would keep the main chute lines clear to full deployment before the second chute leaves the car for it's deployment. The second chute could always be independently ejectable if need be.
-
More details
-
you may be running afoul of the SCTA definitation of a car in that it has to have tow frt steering wheels
Rules 3 L and 4 D
-
you may be running afoul of the SCTA definitation of a car in that it has to have tow frt steering wheels
Rules 3 L and 4 D
Well then Sparky looks like I'll have to add back that second front wheel. Only this time I can duplicate the sprung center hub design for both steering wheels with a common tie rod to the hydraulic steering box. Thanks for identifying that requirement... Terry
-
Be aware that the frts have to have a measurable difference in their foot print to not be considered a Motorcycle I have heard. Higginbotham's was about 1/4"
-
you may be running afoul of the SCTA definitation of a car in that it has to have tow frt steering wheels
Rules 3 L and 4 D
Well then Sparky looks like I'll have to add back that second front wheel. Only this time I can duplicate the sprung center hub design for both steering wheels with a common tie rod to the hydraulic steering box. Thanks for identifying that requirement... Terry
While we are on the subject you might also consider Rule 1.N Course Damage. I'd run your idea of deploying the tail cone by them also. They might feel that could result in course damage.
I'd also reconsider the idea of the first chute deploying the second chute. What if the first didn't deploy? I personally feel they should be independent systems. Also you don't usually want the second chute to deploy immediately. They are different sizes and maybe types and you normally want the car to decelerate for a period of time on the first before deploying the second.
Sumner
-
you may be running afoul of the SCTA definitation of a car in that it has to have tow frt steering wheels
Rules 3 L and 4 D
Well then Sparky looks like I'll have to add back that second front wheel. Only this time I can duplicate the sprung center hub design for both steering wheels with a common tie rod to the hydraulic steering box. Thanks for identifying that requirement... Terry
While we are on the subject you might also consider Rule 1.N Course Damage. I'd run your idea of deploying the tail cone by them also. They might feel that could result in course damage.
I'd also reconsider the idea of the first chute deploying the second chute. What if the first didn't deploy? I personally feel they should be independent systems. Also you don't usually want the second chute to deploy immediately. They are different sizes and maybe types and you normally want the car to decelerate for a period of time on the first before deploying the second.
Sumner
Yes, good point Sumner. I'm still looking at different chute designs to find something I'm happy with. I have other issues to deal with on the gen/motor dimensions. I incorrectly drew the width of the motors to half of the 80.4 mm they should have been. Not sure how that happened but it will increase the width of the outboard wheel pods more than I'm willing to allow as an increase to total frontal area. I'll either have to delete the outboard wheels or go back to inboard motors and drive axles running out to the wheels to keep the pods thin as they are now. I'm working on the redesign now. Thanks... Terry.
-
Major design changes for Version 4.8. I've added the second front wheel to meet SCTA requirements. The hub center design works well for both front wheels giving a maximum of 16° turning radius lock to lock. I've had to rethink the IC/gen/motor combo because I used the wrong gen/motor width dimension in my previous drawings.
Breaking the 4 rotor IC engine down to two rotors paired to two gen/motors turned sideways then stacking that combo into 4 pairs back to back works better than the linear arrangement shown before. Here we can optimize intake runners and exhaust headers to maximize flow to and from the turbos. It also allows a better layout for the dry sump pumps, cooling lines, and electrical power lines back to the controllers. It also lowers the height of the engine for better driver visibility. This will necessitate custom rotor/gen/motor housings where one rotor and one gen/motor will be paired together in a single housing then mated to a second rotor/gen/motor housing to make up two rotor/gen sections. Rotors counter rotate in this design for opposing two rotor banks but that fine because the electrical polarity is switchable.
The bigger problem turned out to be the width of the outboard wheel pods due to the wider gen/motor housings. I came up with a better design that moves all four drive wheels back inboard but I'm staggering and overlapping the wheel placements to put each wheel in it's own track on the salt. This required flaring out the body behind the driver which increased frontal area from 3.6 to 5.23 but that's much better than the 7.93 sq.ft. of the outboard wheel design. The car has grown in length again to just over 37'.
I've decided to incorporate active aero into the chute tail cone section. The rear wing and tail cone will pivot at the front to raise the wing angle to increase downforce thus adding weight to the drive wheels as per Rob's Carbinite design. As speed increases the wing will lower to zero angle of attack producing zero drag and downforce. At the end of a run the wing will raise again opening the tail cone for chute deployment and adding drag to help slow the car. The chute packs will be ejected into the slipstream using mechanical or pneumatic ejectors.
Don (RaceEngineer) turned me on to the Szorenyi 3 rotor IC design out of Australia. I was aware of their earlier 4 rotor design but it didn't appear feasible to me. This new 3 rotor design has a number of advantages over the Wankel engine that Mazda manufactured. I'm going to follow up with the Szorenyi people to see where their prototype efforts stand. Any feed back from forum member on this latest design will be appreciated. Thanks... Terry.
-
More attachments
-
Still more
-
Repeating
-
Last ones
-
Very last ones...
-
What's going to be the effect of lifting the tail at maximum speed to initiate braking? It looks to me like there will be an instantaneous huge load increase well behind the rear wheels, thus unloading the front end. Would it not be better if only the center section was raised and the majority of the flat area keeps the aerodynamics stable?
Keep thinking, this is fun. :cheers: :cheers: :cheers:
Pete
-
The other thing you may want to keep in mind is that you have to handle this beast. You only have an hour to turn around, service and get back on track if you want to set an FIA record. You also have to load and unload the car. These requirements can seriously alter some of the other requirements you're trying to meet.
Good luck and keep us all thinking.
Pete
-
Quick turnaround: I sure wish I could find pictures of the Burkland's turntable thingie for speeding the turnaround. It was a slightly raised platform that Tom would coast the car onto after the down run. The car stopped on the top - a turntable!
While the crew attacked the car the table rotated 180 degrees, some people walking backwards while changing plugs and filling tanks, some walking frontwards (on the other side of the car) - and stopped with the car pointing at the start line. Finish the servicing, roll the car back to the surface, and viola, all ready.
It was quite the symphony in motion. Thanks for bringing back the memory. :cheers: :cheers:
-
I'm with PJ, not only will that upset the apple cart... I don't think you will be able to build anything strong enough to move that much aero load. Move the smallest amount of body that will get the chutes out. Something that mounts on a parallelogram disrupting the minimum amount of air.
-
I think Pete has a good point. You might want to consider air brakes like the ones used on the F-86 Saber Jet. They extended out laterally on both sides so there was no pitching or yawing moment.
Regards, Neil Tucson, AZ
-
..... As speed increases the wing will lower to zero angle of attack producing zero drag and downforce. . Terry.
As speed is increased you still need downforce in some form, either weight or aero. If it is aero you will need to adjust the angle of attack or it could be way too much at the same wing angle.
The 'aero wall'. I like to think that as the car has to overcome more and more aero drag to go faster it is like taking the car to a cement wall and putting the front bumper on it and burning the tires down. The air is that wall and since it takes eight times more HP to run twice as fast you have to get that HP to the ground. You need traction, one way or another, to get that done at top speed when you are against that 'aero wall' or the car is just going to spin the wheels/tire (if you have them) and go no faster. The problem just isn't accelerating at slower speeds but also at terminal speed.
In our case with Hooley's car the weight added (over 2000 lbs) wasn't there so much to prevent spinning the tires under acceleration but to keep from spinning the tires at maximum speed. The weight hurts when it comes to acceleration and I think that Rob is on the right track with the aero downforce but that can also be very tricky. We added a wing when that was finally allowed but decided against the first big one as we had no idea how much downforce it might create. So started with a small one that was pretty neutral and had plans to work up. A wind tunnel and someone who really knows what they are doing would be a much better alternative but also more expensive,
Sumner
-
Simspeed,
What is the distance from the aerodynamic center of the new rear spoiler/wing (will be close to the geometric center) to the rear wheels and the front wheels? This will determine the effect of the torsional moment (pitching torque) that will effect the load shift and possibly lift the front wheels off the ground. The aero loads on a high angle of attack wing are very high at the targeted speed. The Lateral air brake flaps as Neil suggests would be preferred and can be made strong enough to handle the load (it's done on airplanes primarily made of aluminum).
IMHO it would be safer after throttling down the engine/motors to deploy a relatively small chute first. Then flaps and second chute. Then carbon-carbon disc brakes.
As was pointed out, Traction is most needed at max velocity in order to continue accelerating the vehicle. Trading low drag for higher down force as speed and thrust increase is the technically preferred to adding weight but it is tricky and aero must be well sorted.
The turntable is mandatory if your going for a FIM record (turn around within an hour).
Feed back is always welcome!!!
Thanks
-
Sumner makes some good points.
The angle of attack of the plane here is going to create some pitch issues that will make handling difficult. Not to mention the required strength of the system will make it both heavy and expensive. Even if it doesn't cause the vehicle to flip, the change in balance will be big enough that it'll unnerve you driving it. Half the battle of going fast is giving the driver confidence in the machine.
Aero done right is expensive, but you'd be surprised at how many people don't do Aero to save money then blow 3 times that amount on trying to get more power out of the engine. The problem in our field is available correct facilities. Layne and Tom did a great job trying to help teams with the understanding and providing a local facility. But it's tough business model. In the end the facility the teams really needed was much bigger and more expensive than the market is willing to bear.
Think that Gene Haas spent 80 Million on his facility for Nascar/Indy etc. And that facility is about 250mph too slow for what guys on this forum are doing! And those teams are pouring every dime they have into engineering other aspects of the car that are throwing up problems that no-one ever expected. It's truly a monumental task. So big a problem that it's no-one wonder teams spend more on driveline, at least there they can see the end goal.
Anyway different conversation for a different time and place (beer at my camper during speed week).
Keep up the good work.
-
Hey Peter... your post went missing after the forum update but I did not look at the Target 550 air brake system. Pretty slick I'd say. Great use of space isn't it. Thanks... Terry
-
Sumner makes some good points.
The angle of attack of the plane here is going to create some pitch issues that will make handling difficult. Not to mention the required strength of the system will make it both heavy and expensive. Even if it doesn't cause the vehicle to flip, the change in balance will be big enough that it'll unnerve you driving it. Half the battle of going fast is giving the driver confidence in the machine.
Aero done right is expensive, but you'd be surprised at how many people don't do Aero to save money then blow 3 times that amount on trying to get more power out of the engine. The problem in our field is available correct facilities. Layne and Tom did a great job trying to help teams with the understanding and providing a local facility. But it's tough business model. In the end the facility the teams really needed was much bigger and more expensive than the market is willing to bear.
Think that Gene Haas spent 80 Million on his facility for Nascar/Indy etc. And that facility is about 250mph too slow for what guys on this forum are doing! And those teams are pouring every dime they have into engineering other aspects of the car that are throwing up problems that no-one ever expected. It's truly a monumental task. So big a problem that it's no-one wonder teams spend more on driveline, at least there they can see the end goal.
Anyway different conversation for a different time and place (beer at my camper during speed week).
Keep up the good work.
Hey James...thanks for the invite I hope to be there. Your points about money invested in support infrastructure of other motorsports versus LSR is spot on. There's just no where near the commercial appeal of LSR as there is almost any other form of auto racing, and I don't think there ever will be. It goes back to a previous post I made on telling the racer's story in such a way that drives public interests and backing of corporate sponsors who want to sell products and services to them. Until we develop a scenario that draws everyone to the table of common interests LSR will advance only incrementally for decades to come in my opinion. I'd sure like to see a breakthrough of some type that peaks the public consciousnesses. Thanks... Terry.
-
Considering everyone's thoughtful comments on the impracticality of placing an air brake wing behind the rear wheels I've shown here what mid mount active canard wings might look like just ahead of the quad drive wheels of the current design. In this scenario the elliptical wings would tilt down as shown at the start of a run to add downforce/aero weight to increase traction as needed to build speed. The wings would pivot back to reduce drag and downforce at higher speeds but could be electronically controlled to maintain just enough positive angle needed to pressure load wheel weight for optimum traction through control programming. As many have pointed out LSR cars hit a wall where aero drag can become greater than available traction and power limiting acceleration. It occurs to me that through programmable active aero, in conjunction with traction control, acceleration can be increased for a given combination up to a certain point that should in theory allow the car to obtain greater speeds than one without such a system. Your thoughts... Thanks.
-
more...
-
more
-
Terry,
I like the wing w/ dihedral, combines 3 things ---the roll stability of the fin, the downforce of an inverted wing and drag brake when rotated and it's in the right place. Detail is not real clear but the bottom surface of the horizontal wing should be convex (wing shaped) and the top should be flat and the near vertical "wing" should be convex on the interior surface and flat on the outer surface (left wing rolls body right and right wing rolls body left. Lift increases the more the body rolls (self righting or one wing counter acts the other hopefully to keep it shiny side up. Downside-- if one wing fails the other will cause the vehicle to roll. How will these act in a strong side wind? The near verticals should probably have a short chord length to minimize there area to cross wind?
Hydraulic control for the air brake function?
What is the current frontal area? (with the correct engine diameter?
Fewer comments, I guess folk are busy getting ready for SW!! I've been busy..
-
How will the wing affect your bailout procedure? In an emergency I'm sure there would be no hesitation to step onto the wing but how will you do during tech?
Keep going, I'm enjoying the evolution.
Pete
-
Pete,
Valid question. The final position of the wind (within the wheelbase) needs to be adjusted based on detailed aero work. When I said "it is in the right place I meant generally (ie: behind the rear wheels won't work). Final position may likely be more forward to balance downforce on front vs. rear wheels (for stability). Which is the linear ratio of position. The weight of the driver is a low load relative to the aero loads so the wing could be built robust enough to have a "step plate" area. Thanks for highlighting this detail. Lots of design considerations to balance.
Don
-
Terry,
I like the wing w/ dihedral, combines 3 things ---the roll stability of the fin, the downforce of an inverted wing and drag brake when rotated and it's in the right place. Detail is not real clear but the bottom surface of the horizontal wing should be convex (wing shaped) and the top should be flat and the near vertical "wing" should be convex on the interior surface and flat on the outer surface (left wing rolls body right and right wing rolls body left. Lift increases the more the body rolls (self righting or one wing counter acts the other hopefully to keep it shiny side up. Downside-- if one wing fails the other will cause the vehicle to roll. How will these act in a strong side wind? The near verticals should probably have a short chord length to minimize there area to cross wind?
Hydraulic control for the air brake function?
What is the current frontal area? (with the correct engine diameter?
Fewer comments, I guess folk are busy getting ready for SW!! I've been busy..
Hi Don...I appreciate your comments. I used a simple ellipse shape for the wing/fin cross section. I used the NASA FoilSim app to calculate downforce for the various parameters and angle of attack the wing would go through from a max of -14.5? forward pitch producing roughly 2500 lbs of downforce at 250 mph back to 0? angle producing zero lift and 19 lbs of drag at the same speed. 250 mph is the max speed setting for the app. An ellipse shape offered the best performance characteristics for this configuration based on the app's various settings.
At zero angle of attack the fins should produce neutral left/right loading acting like normal stabilizer fins. At negative pitch angles the fins would produce offsetting outward loading to hopefully help stabilize directional control. No doubt if one fin fails at speed the car will roll. Fin construction and support structure will need to be well engineered with safety factors. I think this design will respond well to side winds given that the body itself acts as a wind block for the low wing placement. Yes, I think electro-hydraulics is likely the best control system for this design. Total frontal area of V.4.8 with wings is 6.388 sq.ft. Thanks... Terry
-
How will the wing affect your bailout procedure? In an emergency I'm sure there would be no hesitation to step onto the wing but how will you do during tech?
Keep going, I'm enjoying the evolution.
Pete
Hey Pete...I think the wing structure will be strong enough to handle driver ingress and egress given the need to engineer it for high aero loading. Thanks... Terry.
-
Pete,
Valid question. The final position of the wind (within the wheelbase) needs to be adjusted based on detailed aero work. When I said "it is in the right place I meant generally (ie: behind the rear wheels won't work). Final position may likely be more forward to balance downforce on front vs. rear wheels (for stability). Which is the linear ratio of position. The weight of the driver is a low load relative to the aero loads so the wing could be built robust enough to have a "step plate" area. Thanks for highlighting this detail. Lots of design considerations to balance.
Don
Yes, I agree Don. For V.4.8 I've placed the wing as close to the traction wheels as practical for maximum effect. For V.5.0 I'm splitting the drive wheels fore and aft in a conventional 4 wheel drive configuration so the wing/fins would likely be more centrally placed for equal weight distribution. I'm designing V.5.0 as an experiment based on input I received from Tom Burkland. Hopefully we'll get a good discussion going on that design and how it compares to V.4.8. Thanks... Terry.
-
Terry,
I have never had the privilege of meeting or talking with Tom Burkland only know him by reputation (and advice he has given others on the forum). IMHO, your talking to an excellent resource.
So the V.5.0 will have drive wheels inline? (still 3?) Hopefully this will allow narrower cross section (smoother taper) at the rear.
My guess on wing placement would be 20% to 30% of w.b. ahead of the effective center line of the rear (drive) wheels, but the analysis will fine tune that. I would think, it not be 50/50 balanced, but biased to the drive wheels for "traction" with enough downforce on the front wheels for stability. A multi element wing, in the horizontal section, should increase the downforce and may be of net benefit (drag racers claim 6000 lbs downforce at ~300 mph with multi-element wings, but CFD should help refine). The body and the "vertical" wing section should act as spill plates making the inverted wing(s) more effective. The initial wing placement looks to be coincident with a reduced body cross section this is good and may be important if speeds above .80 mach are achieved (in deference to the area rule).
Looking forward to V.5.0.
Regards, Don
-
Attached are screenshots of the new V.5.0 design. This is a conventional 4x4 wheel drive layout with a sprung front suspension and solid mounted rear axle. The steering geometry pivots at the center of the wheel contact patch as suggested by Tom B. The body geometry began as a tear drop but ended up as shown in order to fit the drive system in place. Your thoughts are appreciated. Thanks... Terry
-
More
-
More
-
Last...
-
Motorcycle streamliner? It appears that you'd need to counter-steer to maintain balance, as with a motorcycle.
I'm not criticizing- just my knee-jerk reaction to the pictures.
-
I see a few problems with this design. Structurally take a look at your lower tube of the rear half of the chassis where it turns up and intersects the cage portion of the chassis. This will flex that cage tube and create a major flex point in the chassis. Just run that tube straight along the bottom of the car. People like to get too fancy with the bends most of the time just creating problems.
Stability wise I see some potential problems. Not knowing where the cg is for sure, it appears to be far behind the center of pressure. This thing will be twitchy. It may or may not straighten itself out. For this type of shape to work the cg has to be really far forward. Even then a tail fin will probably still be required. I had a similar plan with my car and while the aero would self straighten it had to get a certain amount of yaw before creating enough drag to straighten. This shape will have a similar problem.
-
New Wing
-
If this car, as illustrated, even gets the slightest amount side ways it will redefine the expression "pencil roll"!
Nice CAD work though.
Rex
-
It appears to me that with the flat side design of the car the power units could be moved to the inside of the wheels instead of the outside. While your steering would be limited, this is normal for most streamliners and the lateral stability would be much improved.
Pete
-
If this car, as illustrated, even gets the slightest amount side ways it will redefine the expression "pencil roll"!
Nice CAD work though.
Rex
It appears to me that with the flat side design of the car the power units could be moved to the inside of the wheels instead of the outside. While your steering would be limited, this is normal for most streamliners and the lateral stability would be much improved.
Pete
Thanks for your comments Rex and Pete. I didn't think I could fit the wheels in the body work if I ran the power units on the inside, but I've checked and it appears I can make everything fit for the front wheels and still keep 12 degrees lock to lock steering. The rears have to stay as mounted because the body tapers so much toward the back. I'll redraw for that configuration. Thanks... Terry
-
From an aero drag perspective you don?t want a rounded rear section. You want a sharp trailing edge to separate the flow cleanly.
-
Hi Everyone... I'm moving this topic to a new thread in the Build Diaries forum here http://www.landracing.com/forum/index.php?topic=17792.0 (http://www.landracing.com/forum/index.php?topic=17792.0). I won't be updating this thread any more so come see the latest update V.5.2 in the Simspeed UWD design project diary and help critique the project toward an optimum design. Thanks for contributing...