Landracing Forum
Bonneville Salt Flats Discussion => Build Diaries => Topic started by: robfrey on November 28, 2009, 06:24:45 PM
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Well, you gotta start somewhere.
(http://i436.photobucket.com/albums/qq89/robfreyvogel/Streamliner%20stuff/streamliner33.jpg)
(http://i436.photobucket.com/albums/qq89/robfreyvogel/Streamliner%20stuff/streamliner32.jpg)
(http://i436.photobucket.com/albums/qq89/robfreyvogel/Streamliner%20stuff/streamliner34.jpg)
(http://i436.photobucket.com/albums/qq89/robfreyvogel/Streamliner%20stuff/streamliner35.jpg)
(http://i436.photobucket.com/albums/qq89/robfreyvogel/Streamliner%20stuff/streamliner36.jpg)
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Goodluck with your project :cheers:
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We will be water jetting many of the parts including the bulkheads.
Got a local guy here that is very reasonable and gives quick service.
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I see your using Ashlar.... my favorite cad is cobalt.
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I see your using Ashlar.... my favorite cad is cobalt.
Wow, i thought i was the last person left on the planet to still be using this stuff.
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I would recommend a rounded lower section (not a flat bottom) for safety and to loose the the low pressure area (and drag) generated by attempting to keep air from going under the vehicle.
I would also suggest inline front wheels. In the event of a tire failure inline front wheels will allow for some degree of stability and the ability to control the vehicle where a side by side arrangement would cause the vehicle to pitch to one side.
-also-
The cheese wedge nose is only efficient at speed over 700 mph (check out the term "wetted surface area"). A more rounded nose will lower Cd and increase speed for the potential speeds achievable. My personal recommendation is to look at the D.Vesco nose on the 'nator or the nose on the BUB MC liner and take design aspect from these examples.
Good luck
~JH
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Good luck guys :cheers:
Just wondering why did you decide on a flat bottom
Robbie
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down force :?
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Looks like you and Brandon have been really busy. Stay in touch my friend and good luck with the build.
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front end reminds me of the Brant and Wright liner, They are trying
to reach there goal of 200mph, Im not sure what your goal with the
car is, being an A/BG I would (GUESS) 300mph.
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Sparky,
This is just the first draft of the solid model to get into the virtual wind tunnel. We have about 40 days left on testing and design, once we start getting data we can determine if/what we need for down force modifiers.
Ivsalt,
Somewhere in the 300's would make me smile, somewhere in the 400's would make me happy! :-D
Dave,
This is all Rob's fault! If he would have never invited me over to "look" at the lakester, I wouldn't be doing this. Salt really effects people doesn't it, this must be what crack is like to a junkie.
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Good luck guys :cheers:
Just wondering why did you decide on a flat bottom
Robbie
Trying to get under the air and through it. Nebulous Theorem?
From what I understand, if you can't get a lot of air between bottom and the ground, it is best to none or almost none.
Please challenge me on this as all this aero stuff is new to me.
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down force :?
Are you saying that it will make a lot of down force or are you asking me if it will and how much?
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I was responding to the person who asked why you had a flat bottom---two reasons in my knowlege range---ease of construction and some down fore --- I am not second guessing you guys by any means --I am no aero eng,---just a southern country boy who sold trucks :-D!!!!!!!!!!!
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As far as the Flat bottom thing goes, I certainly don't know myself. I was thinking that we try a couple of shapes in the virtual wind tunnel and see what works and what we could construct.
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Robfrey,
I was questioning you just trying to learn myself.
Robbie
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I can see this thread turning into another of wild speculation, guesswork etc. as to what works correctly for a 400 mph wheel-driven device.
I'd suggest buying SAE paper 649B from SAE International since it describes the methods used to sucessfully acheive an FIA interntionl record over that speed and, if it fits your packaging requirements, purchasing one of Kent Riches bodies.
The various examples of Lynn Yaekel's designs have gone closer to 500 mph than anyone and seem to have no bad aero vices.
Getting the absolute optimum slippery shape may not be any more important than assuring yourself of driveline durability and getting the power to the ground.
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I can see this thread turning into another of wild speculation, guesswork etc. as to what works correctly for a 400 mph wheel-driven device.
I'd suggest buying SAE paper 649B from SAE International since it describes the methods used to sucessfully acheive an FIA interntionl record over that speed and, if it fits your packaging requirements, purchasing one of Kent Riches bodies.
The various examples of Lynn Yaekel's designs have gone closer to 500 mph than anyone and seem to have no bad aero vices.
Getting the absolute optimum slippery shape may not be any more important than assuring yourself of driveline durability and getting the power to the ground.
IB, do you have any pics of Lynn's cars? I did a quick search and didn't find anything, I would be very interested to see some of his design ideas. We are interested in gathering as much information/data as we can.
I'm in your camp with your second paragraph, hook-up enough power and aero becomes a bit less of an issue. Although, it's hard to ignore the efficiency tax of bad aero design.
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Yaekel designs?
Where do you start?
Probably in the Bonneville record book.
Vesco, Nish, Ferguson are names that come to mind on that list. Maybe Hedrich too (not sure).
See the pictures of the last SCTA meet for the new streamliner Mr Riches has the molds for.
Good luck!
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Yaekel designs?
Where do you start?
Probably in the Bonneville record book.
Vesco, Nish, Ferguson are names that come to mind on that list. Maybe Hedrich too (not sure).
See the pictures of the last SCTA meet for the new streamliner Mr Riches has the molds for.
Good luck!
Got it, I didn't make the association of Yaekel with those cars/teams, I'm new to this and still learning names.
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Bbarn,
"I'm in your camp with your second paragraph, hook-up enough power and aero becomes a bit less of an issue. Although, it's hard to ignore the efficiency tax of bad aero design."
This is your quote. You may want to reconsider the cost of bad aero at the speeds you are talking about. If you have 3000 hp and go 400 mph you will need 4270 hp to go 450! Probably more than you can get by just screwing in the boost knob on your big block.
IB's comment regarding looking at Lynn Yeakel designs has alot of merit you may also look at the Burkland's car which has gone 454 and also the Poteet/Main car and the Spirit of Ret all 400 mph cars. Looking at your concepts it is the back of the car that is most important and if you look at any of the above mentioned cars and also Jack Costella's cars none of them have the type of rear end treatment that you are proposing. The idea is to split the air let it pass around your car and then blend it back together with the lest turbulance, the configuration of the rear of your car will not do this.
Again I would recommend contacting "Blue" on this site and see if you could get him to assist.
Rex
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Good aero probably won't add significantly to our overall cost. Lets get it right or at least as close as the computer says we can within the given design criteria.
It's always been my approach to racing to not copy what has been done before. If you only copy, how could it be better than what's already been done. That's what I like so much about LSR. It seems that everybody has their own idea on what works. No cookie cutter cars like Nascar or NHRA.
All that being said, there something to using a well tested body and installing the biggest hammer we can. LOL. I think that the biggest problem will be that there is probably not a body available that will hold all the crap we got to put in there. We need a lot of ice water on board. Also intercooler, pumps, electronics, etc.
I think what we have already designed would work but now is the time to optimize or make major changes.
Now, what is the easiest way to get this model into a simulator and start tweaking. We know the air intakes are way too big so I will have to fix those first.
Should I route the air intakes out the side of the body where I expect the exhaust to exit for more accurate simulation? Ex volume is actually three times intake volume but it might be better than doing nothing.
Of course who does this simulation work and how much does it cost? What format should it be in? What kind of accuracy can we expect?
Should we buy a copy of the program itself? How much is it? Might be worth it's weight in gold?
Thanks for all the input so far, we do appeciate!
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lets run at night :evil:
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It's always been my approach to racing to not copy what has been done before. If you only copy, how could it be better than what's already been done. That's what I like so much about LSR. It seems that everybody has their own idea on what works.
If I had a dollar for every one of them and a debt for everyone who had proof I'd build my own top end contender........ :-D
It's not copying per se Robfrey it's about refining ...the hard part about that is knowing why some things worked and others didn't ....there's a lot to get through.......
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Rex, I wasn't discounting aero as a whole, I'm just thinking that we are on at least decent footing with our basic design. Aero is a factor, if it weren't, bricks would go as far as arrows. I'm sure that some WT time will shed light on what we think will happen vs what will happen. Trust me, from a pilot's perspective, aero is a BIG deal. :wink:
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lets run at night :evil:
I'll install the headlights, that's item 3,246 on the task list!!!
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I am having trouble with NA- :-(---- now you want me to BOOST so the sun will shine on the SALT :?
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I am having trouble with NA- :-(---- now you want me to BOOST so the sun will shine on the SALT :?
Just saying once you've had boost, it's hard to go back (to NA)!
To quote Jake Blues- "I have seen the light!"
I understand it's not about copying but refining. Everything we do in LSR is refining to some point. Correct? EFI is just a refinement on the carb. Still adding fuel to our air, correct? To me, how much do vary from the beaten trail is the real question.
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Alright Sparky,
I changed my signature not to offend any of you NA guys.
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:? offended ----not offended just a warped sense of humor lol :-D :-D we are working on getting the parts to gether for a BOOSTED truck!!!!!!!
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I'm recalling a conversation with an experienced racer at Bonneville about his construction of his first streamliner. He had to have these tanks, those tanks, more tanks and such. He got the car almost done and discovered it was 35 feet long. Started over and built a much better version. Had teething problems, so no cigar.
Stan,
the roadster man.
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Yep, we're not done fine tuning the design yet, but that 35' isn't far off from our rough calculations. I think the images that are up at the top of this thread are 37' but we already know we can trim some out of the middle.
Based on what we did with the lakester, so far, we have had the engine coolant water to between 180-200F and have yet to make a full out run. It has 35-40 gallons of capacity which starts off with 95% ice 5% water, which may not be enough for a WOT 5 mile run. So for this project, we are assuming a lot more capacity for engine cooling reservoir.
One question we keep tossing around and maybe someone can shed some light on it for us. If the engine compartment is sealed, what kind of heat can we expect? or how much ventilation should we provide into the engine compartment to prevent any issues?
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A BUNCH---look at the sides of Burklands car----you may be going farther---but will not take as long!!!!!!!!!!!!!! I would bet almost the same coolant maybe just a little more you should be able to lean on it sooner
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I think we can calculate the ice water to last through the sustained pull, we have room in both volume and weight.
How much engine compartment ventilation do you think we should have? - airflow - Some, none, lots, doesn't matter... I would like to duct some amount of air into the front of the engine compartment and vent it out the rear either trough louvers on the side (at the mid-plate) or clear out the rear of the car.
I know standing beside the lakester at idle for about a minute without header wrap, you get plenty of heat. I have to assume that running 1,800F EGT at WOT it's going to be substantially more. On the lakester we didn't care as the engine compartment is open to the outside world. On the streamliner, we will be closing the engine compartment in, I would have to assume that we are going to need some amount of airflow through the compartment. :?
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FYI the Vesco Turbinator is 31 feet long with a 228 in wheel base. I think the longest streamline running is Skip Higgenbothems with a 300 in wheel base and a lot of over hang front and rear
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The original design on Page 1 looked goofy at first, but I thought about it for a few days, and it looks like it might work if it is low enough to keep a lot of air out from under the car. Just for fun, try it in your tests. Rounding the corners at the rear of the cheese head might help.
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agreed, we are going to redesign the nose a bit as our inlets are much bigger than we need.
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Design consideration #2. - Let the comments fly...
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Side-2.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Angled-Bottom.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_LeftSide.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Top-2.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_AngledTop.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_LeftSide.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_Top-1.jpg)
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Where are you thinking about putting the driver?
I like the concept. :cheers:
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Where are you thinking about putting the driver?
I like the concept. :cheers:
Driver? Crap, I knew I forgot something!
Seriously, still working out some of the details, but probably just forward of the front wheels in a semi-reclined position. There are still some additional mechanical elements to squeeze in, and we may have to lengthen the fuselage just a bit. Hopefully we can sort the last remaining items out in the next couple of weeks.
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How about using one of these Ebay #290381841916 drop tanks as your body .
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Curious to know what the reasoning for the outboard lanyard positioning of the rear wheels outside the body lines. It is true that this wheel positioning will provide a higher lateral stability the increased surface area will also add to the overall frontal area potentially higher coefficient of drag.
The truth is that in this design it would not matter (much) if the front wheels were also at this width and covered in the same fashion. THe surface area as viewed from the front would be the same. The frontal area is the second (other being Cd) of the 2 issues that detrimental to making the vehicle the most efficient that it can possibly be (the constraints of the engine and driver position dictate that the vehicle will have some frontal surface area).
One thing that the most successful designers did was take the widest necessary internal components (engine and driver) and made everything else as close to this size as possible and no more. Without naming names (rhymes with costella) is a prime example of why a 1300cc vehicle goes as fast as it does. Many people feel it’s the shape of the Nebs that make them fast….I happen to feel it is the unbelievably small frontal area that is the biggest factor for their success (open for debate, but whatever the case they are proven).
-ALSO
(I am not sure about this so take it with a grain of salt……)
With the rear drive wheels being so close together (and therefore dispersing the localized weight between the 4 wheels, unlike a 4 wheel drive vehicle where the front wheels are driven that support 50% or more of the vehicle weight) I feel to get a traction benefit it would be necessary to have a considerably higher amount of weight over these wheels. A weight this much higher to utilizes the traction potential could push the overall COG rearward making the vehicle unstable. A secondary rear end, drive and other components will increase the drive losses and lower whp. (this is just my back yard thinking…..may be waaaaay of base with all of this).
Please don’t think that I am talking poop about things, I surely don’t mean too.
I really like the changes done to the front end. Everything I say is just based on my personal speculation and I am often wrong.
~JH
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I also was interested in the twin screw configuration. I guessed the advantage was in contact patch being doubled. But that could be much more easily accomplished by running tandame wheels in a car with such wide track. But then perhaps frontal area would grow to much. Can you tell me why you are going with the twin rear ends? Have you considered a Gilmer belt drive for the trailing axle? I am going to go back and reread this from the beginning. I just don't understand it.
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No problem JHN, I am expecting lots of input, as a matter of fact, its the challenging of my ideas and assumptions that will help refine the design.
The reason that not all of the internal components are installed is because I am still working out the CG. I am trying to engineer the CG into a forward location so that the vehicle remains stable without having to add weight or come up with some other post-build fix. I think it is worth the extra time up front to plan on having the car set-up with CG and CP where they are optimum, that way we aren't forced to put some inefficient aerodynamic band-aide on or load lead into the car to correct some issue.
I am a little less concerned with the frontal area than I am with the wetted area and the ability to retain a highly laminar flow. You are spot on in your statements, the driver and the engine dictate that it must be a certain size. I've thought about everything from an in-line 8 and having the driver lay on his side to reduce the width, but none of it seems safe or practical. Oddly enough, you only hear about frontal area in automotive circles. I've seen some pretty large frontal areas on many aircraft that zip right along at some rather high speeds (see reference photo). (I've also seen what their gas bill is to accomplish it, of course, weighing 1.3M pounds has a pretty big effect on fuel consumption too.) I think it is more important to use highly efficient overall shapes and limit any disturbance of the air. Any air that is disturbed, needs to be controlled or shaped as much as possible to eliminate drag.
(Ref pic 1.0)
(http://www.wingweb.co.uk/wingweb/img/Antonov_An-124_Condor.jpg)
The outboard position of the rear wheels came from trying to add stability to the design and to incorporate a wing for down force. Theoretically, we haven't added twice as much drag (x2 wheel fairings), but rather only one. I was going to blade the aft portion of the fuselage, but I don't think we need to. The whole idea of putting a blade tail on the rear is to provide stability in yaw, much like the vertical stabilizer on aircraft, and it moves the CP aft. In this proposed configuration, we have the mechanical stability of a wider stance and the aero stability of two vertical stabilizers. One of the questions this raises for me is what happens when the CP is in the same plane as the CG in the z-axis? When a vertical stabilizer is used, it moves the CP aft, it also raises the CP higher than the CG, I am sure that has some effect I just don't know how much yet.
Down force - flat vs round bottom: This debate will probably rage forever, I haven't yet pitched my tent in a camp, but I am leaning a bit. I get the aero advantage of preventing airflow under a car. There are all kinds of proven examples out there from street cars to Indy cars and even LSR cars. The problem that I see with it is that you really have to be diligent to maintain a lack of flow under the car to maintain down force. Any change in the flow under the vehicle will affect its ability to generate down force. I also get concerned about cross winds and heaven forbid the car get a little sideways. The flow under the car from being sideways (not even 90 degrees, but some amount of sideways) will negate it's ability to generate down force. Expect to not have flow under the car and maintain that, and then what do you do when the unexpected happens?
My approach is that rather than control the variables, just eliminate or reduce the number of variables. I know that a wing works to generate lift, we've all seen it many times. I also know that you can introduce some really wild angle of incidence and still maintain good lift, so if the car gets a bit sideways, a wing is still effective. The other benefit to a wing for down force vs. flat bottom generated down force is that it is easier to control. Let's say that a flat bottom generates 5,000 pounds of down force at 400 mph and I have a wing that can generate the same down force at 400. Now, lets assume that I only need 2,000 pounds of down force to prevent wheel slip, any more than 2,000# is just generating useless drag. How do you control dumping the excess down force from a flat bottom? With a wing, you either decrease the angle of attack or retract the flaps and you can easily lower the down force in a controlled and precise manner.
I am not planning on using just physical weight to provide traction to the rear wheels, but rather aerodynamically generated down force to control traction. I want to put the CG where it needs to be for stability, then use aero to push the tires into the Earth. This will give us the benefit of having a lighter vehicle, a more stable vehicle because we have the CG where it should be and controllable traction for the rear wheels.
I would love to see 1/4 mile speeds in the 350+ range. To accomplish this, I would like to build a light car, very light. A light car can accelerate much quicker than a heavy one (I know, that was obvious), lack of weight obviously reduces the traction as well. There is going to be fine line that needs followed as aero down force can only be generated at certain speeds whereas weight is weight (for traction purposes). I would rather make the car light and use the aero to provide down force over the rear axles rather than move the CG aft to provide traction. I don't yet have enough data available to provide definitive proof of this concept, once we get more finalized in the design, I can determine the accuracy of this assumption.
Don't hesitate to challenge the concepts, I look forward to defending my ideas. Just remember, I have the right to disagree with others as much as they disagree with me! Challenges don't have to be adversarial, hurtful or mean, they can be spirited and respectful and at the same time very beneficial to a successful outcome.
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I also was interested in the twin screw configuration. I guessed the advantage was in contact patch being doubled. But that could be much more easily accomplished by running tandame wheels in a car with such wide track. But then perhaps frontal area would grow to much. Can you tell me why you are going with the twin rear ends? Have you considered a Gilmer belt drive for the trailing axle? I am going to go back and reread this from the beginning. I just don't understand it.
There are a couple of advantages: First, we are cutting the torque forces in half, let's assume we are generating 1800# of torque. If we put that through a single diff, that diff has to be capable of handling 1800fp. If we run that same through two diffs, each one needs to be capable of handling 900fp, thereby reducing the stress on the components. As well, we are doubling the contact area for traction, one of the unknowns here is how much traction loss will there be on the aft wheels from loose salt thrown up from the front drive wheels. Using tandem axles reduces the radial loads on the tires and provides some redundancy. I suspect that if a forward tire were to give out, it would more than likely take the aft one with it (depending on how it failed), so redundancy is a little less of a benefit. Also, see my other post about the axle fairing and down force generation.
I am not familiar with the Gilmer belt drive, is it capable of 7,000-9,000 rpm?
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I doubt a Gilmer belt would live for as long as it would need to in your application, after further thought. They get some pretty good Feet per second going driving a blower in A/D class cars but lots of failures after 4 or 5 seconds. Some of the twin drive trucks I worked on years ago had two driveshafts leading aft from the transfer case and some had a drop in double reduction single shaft drive. Leaving out the double reduction, which will you be thinking about? I have no opinion. Just curious.
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I doubt a Gilmer belt would live for as long as it would need to in your application, after further thought. They get some pretty good Feet per second going driving a blower in A/D class cars but lots of failures after 4 or 5 seconds. Some of the twin drive trucks I worked on years ago had two driveshafts leading aft from the transfer case and some had a drop in double reduction single shaft drive. Leaving out the double reduction, which will you be thinking about? I have no opinion. Just curious.
Not my baileywick, I'll have to defer to Rob on this one. He is the expert on HP and getting it out and down to the ground. Hopefully by the end of this project, I'll be in a better position to answer these types of questions.
Rob, correct me if I am wrong, but there will be a single output from the transmission to the front diff and a single output from the front diff to the rear. Each diff will have it's own quick change gearing and neither will be aware of the other...unless we use dissimilar gearing in each :-o which would probably be bad. Also, there is no transfer case.
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Eye no nuttin about arrows (Street Roadster owner).
But I would sure like to see the twin-tank idea ressurected (with or without wing on rear axle). Seems like it would have some of the features you desire and they could be made equal weights with alloy engine and/or tank locations.
Besides, it just looks cool!
Stan
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There are a couple of advantages: First, we are cutting the torque forces in half, let's assume we are generating 1800# of torque. If we put that through a single diff, that diff has to be capable of handling 1800fp. If we run that same through two diffs, each one needs to be capable of handling 900fp, thereby reducing the stress on the components. As well, we are doubling the contact area for traction, one of the unknowns here is how much traction loss will there be on the aft wheels from loose salt thrown up from the front drive wheels. Using tandem axles reduces the radial loads on the tires and provides some redundancy. I suspect that if a forward tire were to give out, it would more than likely take the aft one with it (depending on how it failed), so redundancy is a little less of a benefit. Also, see my other post about the axle fairing and down force generation.
I am not familiar with the Gilmer belt drive, is it capable of 7,000-9,000 rpm?
[/quote]
One thing I see that you need to take a good long look at as far as splitting the torque loads in dual rear axles. I work as a heavy truck tech. Twin screw drive is the norm in the field. We regularly see shattered u-joints, differentials, axles, and pinions. Every component in the drive train is rated to safely take all the torque that the engine can deliver under normal circumstances.
The problem comes when a wheel looses traction for an instant and then grabs again. The resulting shock load through the drive train can amount to several times the nominal torque being applied, and the weakest part is immediately identified. Sometimes multiple parts fail at the same instant.
You may be tempted to think that since the salt doesn't provide the same traction as pavement, this can't be a problem. In fact, this type of failure is far more common in the winter, because the limited traction makes it more likely for a wheel to slip and grab. We've had 3 towed in so far this week.
I'm not saying that your set up would be doomed to failure and won't work, just pointing out a potential failure mode. :cheers:
One other thing to look at is the method of coupling the rear ends. In the pics of these set ups that I've looked at I only see 2 differentials. In the trucks there are 3, one in each rear end and one separating the input power between the two (called the power divider). The power divider is essential to proper operation because it allows the axle differentials to spin a slightly different speeds without binding up the drive train. Another relatively common failure that we see in the shop is when a driver locks in the power divider and takes off down the road. It usually burns up the diff or overheats and shatters the power divider in about 50-100 miles at highway speeds. I'd hate to think what 400MPH would do. This is because any time that you have 2 diffs they will be spinning at slightly different speeds unless the gears and tires are absolutely identical. I find it very hard to believe that you can find 4 tires that are absolutely identical in rollout diameter at all speeds. Normal manufacturing tolerances will inevitably produce some differences, which will translate into a very slight but significant difference in speeds between the axles, resulting in binding of the gears and excess drag, at best, catastrophic failure at worst without a power divider installed.
If you already have one in the design, forget that last paragraph. :-D
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"...In the trucks there are 3, one in each rear end and one separating the input power between the two (called the power divider). The power divider is essential to proper operation because it allows the axle differentials to spin a slightly different speeds without binding up the drive train. Another relatively common failure that we see in the shop is when a driver locks in the power divider and takes off down the road. It usually burns up the diff or overheats and shatters the power divider in about 50-100 miles at highway speeds..."
Now I know what happened to our semi tractor. Our lamebrain driver no doubt left the power divider locked when he drove down the road (on a 400-mile each way) trip -- and that's why the only way the truck will move now is when locked "in" -- otherwise the drive shaft just spins happily, all content because it's not delivering any power to a drive wheel. Yep - your analysis of what might happen -- happens.
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All good info Wizzbang, I too have spent much time around big rigs. Binding is definitely an issue, especially when the tires will not grow at consistent rates due to mfgr tolerances. I have it on very good authority, that the 25.5 inch tires we are planning to run will in fact be 30+ inches in diameter at 400, that's about a 15% growth!
Loss of traction and the shock loads that it produce will be huge, not unlike tire chatter on a 1/4 mile drag vehicle. Tire chatter will identify weak links in a hurry. As for locking in the splitter, drive a 4wd locked up on dry pavement, it only takes one good turn to realize the amount of stress you are putting on the drive line from binding.
It has become apparent through the design process, that 400+mph is hard. Not just from an aero standpoint, but from an equipment survivability standpoint as well. The forces involved are amazing, trying to use existing equipment is definitely going to be a challenge.
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"...In the trucks there are 3, one in each rear end and one separating the input power between the two (called the power divider). The power divider is essential to proper operation because it allows the axle differentials to spin a slightly different speeds without binding up the drive train. Another relatively common failure that we see in the shop is when a driver locks in the power divider and takes off down the road. It usually burns up the diff or overheats and shatters the power divider in about 50-100 miles at highway speeds..."
Now I know what happened to our semi tractor. Our lamebrain driver no doubt left the power divider locked when he drove down the road (on a 400-mile each way) trip -- and that's why the only way the truck will move now is when locked "in" -- otherwise the drive shaft just spins happily, all content because it's not delivering any power to a drive wheel. Yep - your analysis of what might happen -- happens.
SSS, I once planned on putting together a book based on driver responses when these things happen. It is amazing to ask a driver why they have done what they have, the responses can be funny if you can separate the financial loss from the situation. It is equally amazing to hear the reasons why they can't take a particular load, I've heard everything from my dog just had puppies to my truck is parked in front of my house and is on fire! Unfortunately, it was easy to verify that his truck was legitimately on fire...
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By the rest of the way -- it was the same driver that drove home on a trip with one of the drive tires gone flat and just flopping around on the rim. No call to me, no call to a service shop -- just drove on it. I was amazed that the DOT didn't stop and chat with him.
He doesn't work for me any longer, that's for sure.
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There you guys go---picking on the poor old driver---the next thing you know you will want to put a data logger in there so that you can in the words of DD, " RECORD what actualy went on not what the Monkey is telling you!!!!!!!!!!!!"
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Probably of no help, but I've done a lot of racing with a locked transfer case (both drive diffs get fed same RPM), and individually locked diffs, both on the asphalt and dirt, up to and past the limits of traction. Not at BV since it's forbidden, but dragstrips and dirt pulls, drags.
You can lock the transfer case (center) with no problems. Turning radius is affected, so it's best for straights, you might want to unlock it after the pass for easy manuevering, but you can still force it to turn. If you also lock both axles too, it is nearly impossible to turn on either dirt or asphalt, and you WILL need to unlock to move other than in a straight line. You can still steer enough to race that way on asphalt or dirt, it's getting back to the return road that will be nearly impossible.
Yes, you can run the 1/4mi with all four wheels locked. The car stays pointed straight even if all tires are spinning, but it's path looks like a bowling ball path. It hooks to the left and drifts back to center the faster you go.
If you have a tote trailer, no problem. If you are going to try and manuever it back to the pits, you will need a way to unlock. I'd certainly leave the front axle open, as it really doesn't improve traction significantly. Keep in mind that if both axles are "open", you still get the poor turning radius if you have a locked Tcase (center section?).
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The power divider is also called an inter axel differiental
TORSENs ??
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Looking at the other end of the concept you may find that the tandum front wheels are the wrong design. All the cars I am familiar with that had that setup have crashed, original Flatfire, Manual Torres flathead streamliner(put the driver in a wheelchair for the remainder of his life), etc.
You need to design the front with the wheels offset ala Costella Neb III, Teague, Main and others. The tandum layout will not give the Ackerman effect needed to make even small steering corrections. The tandum layout tends to lift the outside tire and by effect the chassis instead of turning as you would expect.
The driver in the extreme front in a lay down position may result in driveablity issues.
You need Ackerman, scrub and the driver's head above his/her hips to be successful.
DW
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Tandem?
DW are you refering to side by side or inline?
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Inline Sparky
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The drawing shows side by side. I think they should be in-line, slightly off set actually, not on the same center line.
For example check out Speed Demon, Neb III, Al Teague, etc.
DW
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Make two narrow fronts instead of one fat: http://www.landracing.com/forum/index.php/topic,2796.0.html (http://www.landracing.com/forum/index.php/topic,2796.0.html)
Mike
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It won't be a lay-down model for the driver, there are way too many issues with that. The closest I want to get to a lay down is about a 30 degree reclined position, not much more than that.
Pros and Cons to the driver being forward of the front wheels
Pros:
- I have the space available (This may change, there is still design work going on)
- The canopy can be smaller / the head of the driver will not need to protrude much above the fuselage to get good visibility
- Good separation of the driver from hot surfaces and flammable materials - The entire forward section of the car can be completely isolated from everything.
Cons:
- Less reference for yaw movements
- Not as much distance between the bottom of your feet and the immovable object that just jumped up in front of you
Steering is not an issue, you'll have to wait and see what we have in mind for that. Whether the driver is fore or aft of the steering wheels is not relevant in terms of steering complexities.
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BBarn, like the shape, but was a little concerned about the disturbance of air flow when it hits the rear wheel fairings and body. Larger space between the body and wheel fairings or changing the surfaces to blend more decreasing disturbance. Think of water flowing in a stream around closely located rocks. Before this interruption the air flow has smoothed out eliminating surface drag. Also, tapering the body in the aft region ever so slightly might help with reducing drag.. not necessarily bringing body to a point at rear.
Sparky, thanks for the clarification of "power divider"... I know it as "diff lock" also.
The diff lock was intented to increase traction for a limited event... such as in icey conditions or the like.
Using it for long periods of time causes the problems as mentioned. The class is out in my mind as to lock up resistance or binding to wheel slip over the length of use. Some wheel slip is what makes this design work and survive for short distances.
Ducting bottom air up through the body can be used to pre load the rear axle(s) also. This can help to eliminate some bad air and unwanted lift.
Low speed wind tunnel testing with smoke will give a good look at air flow... a lot cheaper this way than on the white stuff.
Enjoying your thread... keep up the good work. This is what I like about this site..
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It won't be a lay-down model for the driver, there are way too many issues with that. The closest I want to get to a lay down is about a 30 degree reclined position, not much more than that.
Pros and Cons to the driver being forward of the front wheels
Pros:
- I have the space available (This may change, there is still design work going on)
- The canopy can be smaller / the head of the driver will not need to protrude much above the fuselage to get good visibility
- Good separation of the driver from hot surfaces and flammable materials - The entire forward section of the car can be completely isolated from everything.
Cons:
- Less reference for yaw movements
- Not as much distance between the bottom of your feet and the immovable object that just jumped up in front of you
Steering is not an issue, you'll have to wait and see what we have in mind for that. Whether the driver is fore or aft of the steering wheels is not relevant in terms of steering complexities.
Note that I was not referring to the "Akerman effect" when I stated "steering is not an issue", I was referring to how the steering movements will be actuated, not the relationship of the front wheels to one other. I will ponder the front wheel arrangement a bit more, I am not sold on the current front wheel layout and have not ruled out a tandem front wheel arrangement...yet.
Keep in mind it is still early in the dream phase of the process, there will be significant changes to come...
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Higginbotham, put new hubs with Zero scrub radius hubs in ROSE ( which has inline strg.) this year to eliminate some issues she had in the past. Made it much easier to drive it-- your way :-) instead of her way :-(
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I thought I had a better photo of the Speed Demon's front wheels -- but no -- so you'll have to inspect this carefully to determine if there's much offset.
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intresting looking frt tire :-o
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That's Ron Main asking Mike Cook if there's enough tire left for one more run.
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I'm not sure I'd drive through the pits on that tire, let alone down the track, that's a mighty rough looking skin on the front one. Especially the loose skin that is hanging over the side and the big split in the top of the hide!
Could be camera angle or bad lighting...
Couple of questions come to mind: what tire is that? I don't remember hearing or reading about a GY tire rated to 400+? Also, it doesn't look like there is much room for growth between the two tires, any idea how much clearance for tire growth there is between them? The info I have on the MT 25.5 is that they grow 15% at speed, does this hold true for these GY tires? Also, what size are they, they look to be a rather small diameter?
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I seem to remember Al Teague saying one of the reasons he staggered the tires on his car was to keep the leading tire from salt blasting the one behind it.
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Cons:
- Less reference for yaw movements
- Not as much distance between the bottom of your feet and the immovable object that just jumped up in front of you
I would also think that the increased vertical surface area of the cockpit ahead of the front wheels will adversely affect handling.
~JH
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I thought I had a better photo of the Speed Demon's front wheels -- but no -- so you'll have to inspect this carefully to determine if there's much offset.
It almost looks as if the two tyres grew into each other
Gray
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Is that al tape over the welds?
To keep the salt out of the weld??
John
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Sure looks like a bolt in panel.
Pete
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Is that al tape over the welds?
To keep the salt out of the weld??
John
If you're talking about the silver tape on the wheels I believe it's covering the balance weights...SCTA requirement.
Buzz
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hhhhhhhhhhuuuuuuuuuuuggggggghhhhhhhhh willie buchta
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The tape is to seal the gap between the bolt in panel and the chassis.
DW
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The tape is to seal the gap between the bolt in panel and the chassis.
DW
Like most streamliners they are attempting to keep the salt confined to the wheel well salt boxes. The metal tape is better than duct tape for the job.
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enlarging the pic i can see that the only tape in the pic is right below eag on the front wheel rim covering a wheel weight ---which i dont think is required by the scta---i think its done to keep salt from building up against the weight and causing a imbalance problem willie buchta
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What is metal tape? Where do you get it?
Following this build is interesting.
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McMaster Carr
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Nate Jones put aluminum tape over the weights when he shaved and balanced the tires on the lakester. I thought it was an extra precaution to keep the weights on.
Willie-- I like your thought on the tape keeping the salt from lumping up on the wheel weights.The aluminum tape looks like something that was made for sealing ducts. Maybe it's duct tape for a street rod.
Harv
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In airplanes we called it speed tape, it's good to about 600 MPH or so. It is also available at Home Depot, in a slightly thicker version that is duct tape. The HD version is only good to about 450....
go to the basement, look at the furnace, you will likely see some :-D
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The drawing shows side by side. I think they should be in-line, slightly off set actually, not on the same center line.
For example check out Speed Demon, Neb III, Al Teague, etc.
DW
I can certainly appreciate the history of some of these teams having success with the staggered arrangement, but I am very uncomfortable with it from an aero standpoint. The exposed sections of the tires will combine their respective flow fields and at some point this will become a significant aerodynamic rudder. Because they are staggered, the rudder effect would then have to be trimmed out with steering in the other direction.
I think they have not gone fast enough yet for this to be an issue. Dynamic force (and the resulting psuedo-rudder force) increases by almost 60% from 400 mph to 500 mph; so we'll see. Personally, I would not "design in" a potential failure mode like this. TSSC did and suffered yaw transients that required lock-to-lock corrections at over 500 mph. OK, we'd all love to get going that fast; but I still wouldn't install a pretty obvious handling mode like this.
The in-line salt-spray-into-trailing-tire issue must be solved for this design anyway: the rears require it. Whether this is a fixed or movable fairing (to account for tire growth) in front of the second tire requires data. I suggest someone run across some sand or dirt with the same amount of wheel spin as LSR (5 to 10%) and video the "spray". Do it with a street car, race car, AND your wife's FWD minivan! I have heard dozens of theories about this effect and IM<<<<HO, it's all speculation without data. Show me some close-up tire ejecta video at different speeds, with different surfaces, and different vehicles and let's design to the data. The video I've seen of Bonneville is simply not high enough resolution in this area to design a new car from.
Lots of "old salts" (much respect and no pun intended) have decades of experience on where the salt ejecta ends up on the wheel wells. Instead of assuming that this build up was caused by things we haven't video'd, let's get some video and corellate it to the salt build up. Better understanding and designs for all will result.
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Design consideration #2. - Let the comments fly...
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Side-2.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Angled-Bottom.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_LeftSide.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Solid_Top-2.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_AngledTop.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_LeftSide.jpg)
(http://i889.photobucket.com/albums/ac92/bbarnhart_photos/Streamliner/Version3/Trans_Top-1.jpg)
Put turbos at the back of the engine compartment by the tranny; there's more volume there. Put the radiator, fuel cell, and intercooler in front of the engine at the widest point. Cockpit between the front wheels and engine compartment; this, again, it is to keep the widest things in the middle like JHN says. Bump the cross section around the engine to include decent manifolds. Lots of power and reliability is lost in current designs from inadequate manifolds (especially in the 400 mph club. I apologize for this, we all need to look at other motorsports to see what optimized turbo intake and exhaust manifolds look like when people have spent millions of dollars on a few percent gain. Specifically look at Indy car.)
The "frontal area" does NOT matter. #1 is separation (no blunt tails), #2 is wetted area (smaller is better, look at Wheeler), #3 is laminar run. I hope I have time this year to write an article on this for the LSR community that explains these issues in terms that will help everyone design better cars. Everyone who posts here is more than intelligent enough and experienced enough to understand the truth about aero vs. the myths. But it's not intuitive, and there's a lot of bad information out there.
Yes, neck down the sides of the body just in front of the wheel fairings, then go straighter aft over the diff's, then taper to a point. Yes, a point. Any, and I mean ANY blunt tail will create more drag than the entire rest of the car. Tandem (side-by-side) fronts will be higher drag and harder to fair than in-line; solving the steering will be the other way around. I'm working on that.
Last, with all due respect to the records and speeds established by the Costella and Costella-type designs, drag build up calculations show all those flat bottoms and blunt tails are in fully separated flow. To go faster, we need to get back to what makes downforce with the least drag, not the most: i.e. wings, not ground effects. Good wings can produce 5 to 30X the downforce-to-drag ratios of any ground effects. They are less sensitive to ride height and do not cause lifting when the car gets out of shape. Good wings have a 5 to 30:1 L/D; ground effects are lucky to hit 1:1.
To any who wish to use ground effects, I urge you to read "Race Car Aerodynamics" Joseph Katz ISBN 0-8376-0142-8. Air going under the car is what creates downforce, not the other way around.