Landracing Forum
Tech Information => Technical Discussion => Topic started by: Blue on June 17, 2008, 05:35:34 PM
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Just had an interesting read in ESPN magazine on human powered vehicles. The land class record holders are, of course, recumbent bicycles with ridiculously low drag. I was a little stunned at how far they have come since I last saw some of these in 1990.
The current record is 81 MPH! (200m trap, running start).
The current 1 hour record is 53.5 MPH.
Taking it from where I remember this, a fit human racer can sprint at about 2 HP and sustain about 1 for any length of time. The numbers above work perfectly for .9 HP=53.5 MPH and 2.1 HP for 81 MPH.
Anyone for 200 MPH on 13 HP?!!!!!!!!! :-o :-o :-o :-o :-o :-o :-o :-o :-o
The current record holder is a small guy riding a vehicle where they clearly traded off some wetted area for his small size. This reduced the total surface area. They seem to be running about 70% laminar flow on the vehicle sides and have stuck the canopy at the far back to reduce wetted area vs. having a longer laminar run like their nearest competitor.
The obvious advantages of these designs vs. common LSR are IN ORDER:
1. Absolute minimum separation: No blunt rear ends, minimal wheel openings, fairings in front and behind the tires.
2. Ground clearance: "ground effects" may sound sexy, but they are high drag. If we need downforce, we should use a low drag wing, high up in clean air like Teague did.
3. Absolute minimum wetted area: They are SHORT! Shorter means more aggressive pressure recovery, the first trade-off.
4. Significant percentage of laminar flow: Up to 60% of the record holder's wetted area is in laminar flow with favorable pressure gradients and no joints, hatches, vents, or other BS to trip the layer to turbulent.
Sites to check out are:
www.ihpva.org
and pictures of the best of the best:
http://www.speedbikebgl.de/eng/sbc2004e.html
And the open motorcycle guys could use some of these tail section ideas:
http://www.speedbikebgl.de/eng/galeriee.htm
A lurker on this site who's a race HPV builder contacted me on the side, I think there's still some speed to be had in these things... :-D
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81 mph with nothing but spandex shorts, a foam bike helmet, and a few layers of carbon fiber shell to protect you? NO THANKS! :-D
Not to mention bike tires with what speed rating?
But it does make you think.
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Dick Keller, a co-designer of The Blue Flame, is closely involved these days with human powered vehicles.
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Just had an interesting read in ESPN magazine on human powered vehicles. The land class record holders are, of course, recumbent bicycles with ridiculously low drag. I was a little stunned at how far they have come since I last saw some of these in 1990.
The current record is 81 MPH! (200m trap, running start).
The current 1 hour record is 53.5 MPH.
Taking it from where I remember this, a fit human racer can sprint at about 2 HP and sustain about 1 for any length of time. The numbers above work perfectly for .9 HP=53.5 MPH and 2.1 HP for 81 MPH.
Anyone for 200 MPH on 13 HP?!!!!!!!!! :-o :-o :-o :-o :-o :-o :-o :-o :-o
The current record holder is a small guy riding a vehicle where they clearly traded off some wetted area for his small size. This reduced the total surface area. They seem to be running about 70% laminar flow on the vehicle sides and have stuck the canopy at the far back to reduce wetted area vs. having a longer laminar run like their nearest competitor.
The obvious advantages of these designs vs. common LSR are IN ORDER:
1. Absolute minimum separation: No blunt rear ends, minimal wheel openings, fairings in front and behind the tires.
2. Ground clearance: "ground effects" may sound sexy, but they are high drag. If we need downforce, we should use a low drag wing, high up in clean air like Teague did.
3. Absolute minimum wetted area: They are SHORT! Shorter means more aggressive pressure recovery, the first trade-off.
4. Significant percentage of laminar flow: Up to 60% of the record holder's wetted area is in laminar flow with favorable pressure gradients and no joints, hatches, vents, or other BS to trip the layer to turbulent.
Sites to check out are:
www.ihpva.org
and pictures of the best of the best:
http://www.speedbikebgl.de/eng/sbc2004e.html
And the open motorcycle guys could use some of these tail section ideas:
http://www.speedbikebgl.de/eng/galeriee.htm
A lurker on this site who's a race HPV builder contacted me on the side, I think there's still some speed to be had in these things... :-D
Combine a powerplant like the one in this bike...
http://www.landracing.com/forum/index.php/topic,4010.0.html
...with those shapes and the results could get real interesting real quick.
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...But it does make you think.
Ahhhh, that is the idea.
Yeah, they are a little shy on safety features that we would be comfortable with (not to mention compliance with the rules). OTOH, the numbers are so much better than what we expect in LSR that it's worth taking a closer look at it.
Let's say we doubled the size of the current HPV record holder to put real tires on it (note that the design allows for decent diameter wheels!), a real person in a fire suit (I'm not fat, that's insulation!), roll cage, real helmet, ice vest, breathing bottle, and an actual engine. If we did all of this without adding drag beyond the size change ( :roll: bear with me here...) we'd need 24 HP for 200 MPH and 74 HP to match BUB-7's current speed. 100 HP would break through the 400 MPH barrier.
WOW.
I'll design it, I've even got shop space; anyone want to build it?
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Hard to keep that laminar flow percentage as the speed increases.
Jim
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Fascinating subject - wonder if Mr Reynolds and his number enters into projecting the bike's performance into 440plus mph?
Remarkably, the record holding Varna bicycle bears a more than passing resemblance to the eforts by NSU with motorcycles in the '50s.
Taking things a step farther, does this skateboard racer attached ready to race DOWN Shell Hill @ Signal Hill (Long Beach, Ca) in '78resemble Jack costella's latest two wheel efforts?
Nothing new under the sun!
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...But it does make you think.
Ahhhh, that is the idea.
Yeah, they are a little shy on safety features that we would be comfortable with (not to mention compliance with the rules). OTOH, the numbers are so much better than what we expect in LSR that it's worth taking a closer look at it.
Let's say we doubled the size of the current HPV record holder to put real tires on it (note that the design allows for decent diameter wheels!), a real person in a fire suit (I'm not fat, that's insulation!), roll cage, real helmet, ice vest, breathing bottle, and an actual engine. If we did all of this without adding drag beyond the size change ( :roll: bear with me here...) we'd need 24 HP for 200 MPH and 74 HP to match BUB-7's current speed. 100 HP would break through the 400 MPH barrier.
WOW.
I'll design it, I've even got shop space; anyone want to build it?
I would ride it... :mrgreen: even if it only ran 400 mph.. :wink:
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Blue,
I would like your opinion on doing a flat bottom lakester that is a NACA 66012 section in plan view with a flat bottom that runs about 1 inch off the ground and the top of the car would also be the 66012 shape in side view. I would not try to produce down force with the flat bottom, i.e. no rake and no diffuser, flat,straight and parallel to the ground plane and with pretty small area. I am think that using a 22 inch width the body would be around 180 inches long. Is this to much wetted area?
Thanks in advance for your comments.
Rex
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Blue,
I would like your opinion on doing a flat bottom lakester that is a NACA 66012 section in plan view with a flat bottom that runs about 1 inch off the ground and the top of the car would also be the 66012 shape in side view. I would not try to produce down force with the flat bottom, i.e. no rake and no diffuser, flat,straight and parallel to the ground plane and with pretty small area. I am think that using a 22 inch width the body would be around 180 inches long. Is this to much wetted area?
Thanks in advance for your comments.
Rex
Jim and IB: Cd(wet) decreases with increasing Rn faster than laminar run decreases. Yes, the laminar to turbulent transition moves forward with Rn, but any decent favorable gradient can keep the layer laminar up to millions of Rn. Beyond that, the Cd(wet) is so low it doesn't matter.
Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail. Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides. Get the whole thing up off the ground and fair the wheels. A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.
The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester). Remember, the 66xxx series were designed as wing sections. Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.
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And the open motorcycle guys could use some of these tail section ideas:
http://www.speedbikebgl.de/eng/galeriee.htm
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sadly the partial streamlining rules preclude the use of most if not all those tail sections , any further benificial streamlining is frowned upon for our own personal safety in the event of an unexpected sidewind,which may or may not upset the apple cart :x, brute horsepower has flirted for to long with marginal traction and is on a loosing bet , fiddling around the edges with frontal area is all thats left ,unless the rules regarding partial streamlining change ,sad but true :cry:
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Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail. Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides. Get the whole thing up off the ground and fair the wheels. A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.
The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester). Remember, the 66xxx series were designed as wing sections. Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.
Blue, when you fair the wheels, you are no longer a lakester...
Don't lakester bodies need to be designed with the rotating open wheels considered? And will the placement of those wheels effect the outcome?
And sorry, I like flat bottommed lakesters... :roll:
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Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail. Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides. Get the whole thing up off the ground and fair the wheels. A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.
The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester). Remember, the 66xxx series were designed as wing sections. Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.
Blue, when you fair the wheels, you are no longer a lakester...
Don't lakester bodies need to be designed with the rotating open wheels considered? And will the placement of those wheels effect the outcome?
And sorry, I like flat bottommed lakesters... :roll:
I suppose wind tunnel tests or side by side runs with otherwise identical cars would be required (or maybe the same car with different rear axles), but I have often wondered about the differences in aerodynamic effects of the wheels being at a distance from the body as opposed to being flush against the body. According to a paper published by Dr. T.P. Torda (chief aerodynamicist on The Blue Flame), The Blue Flame despite its struts and open rear wheels had only about a .22 subsonic drag coefficient.
The 1921 Tropfenwagen (see link below), despite its ungainly appearance, when wind tunnel tested by Volkswagen a few years ago had only a .28 drag coefficient!
http://en.wikipedia.org/wiki/Rumpler
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Blue, Just curious why then does all of Jack Costella's cars with their flat bottoms are so fast? Is it because of the top shape? Or?
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OK Blue time for some definition of terms. Fines ratio: If I make my body as a body of revolution as you said does "being more agressive with the "fines ratio" mean that I can shorten the length and still have good attachment and low aero drag? As I said the plan is for a lakester so I will have expose wheels but my plan is to have them at least 20 inches away from the car and all of the axles and connections covered by wing section shape fairings. I also plan to have both the inside and outside wheel coverings on the front wheels be non rotating and on the rear the inside wheel cover would not rotate. Is this worth the effort?
I have attached, I think, a picture of the Nissan gravity racer which does have faired wheels but I would of course not have the wheel fairings, but is this what you are describing?
Blue, I really appericate all of your input, and you will find on this site we are all greatful for any kind of aero info from an expert. Trouble is that we will use you like a "rented mule" to keep getting your ideas!!
Rex
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OK Blue time for some definition of terms. Fines ratio: If I make my body as a body of revolution as you said does "being more agressive with the "fines ratio" mean that I can shorten the length and still have good attachment and low aero drag? As I said the plan is for a lakester so I will have expose wheels but my plan is to have them at least 20 inches away from the car and all of the axles and connections covered by wing section shape fairings. I also plan to have both the inside and outside wheel coverings on the front wheels be non rotating and on the rear the inside wheel cover would not rotate. Is this worth the effort?
I have attached, I think, a picture of the Nissan gravity racer which does have faired wheels but I would of course not have the wheel fairings, but is this what you are describing?
Blue, I really appericate all of your input, and you will find on this site we are all greatful for any kind of aero info from an expert. Trouble is that we will use you like a "rented mule" to keep getting your ideas!!
Rex
I think that .28 Cd on the Tropfenwagen already shows you're on to something with your wing as body lakester concept.
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Blue, Just curious why then does all of Jack Costella's cars with their flat bottoms are so fast? Is it because of the top shape? Or?
The flat bottom of the Costella creation is so low to the ground that it eliminante the airflow effect which Eric explained.
But this is only possible if you run without suspension and you use the frame for the necessary twist during the run.
By the way - Eric - can you explain me the word "blunt" - sorry, for this word my English is too short.
And other thing - Al used a wing in August 2002 and slowed his speed down by 20 mph (5 percent).....using a wing, means to use the right shape...otherwise it works like a air brake
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"and you use the frame for the necessary twist during the run."
Can you explain this a little better? Does this mean that the frame is made to twist to take the load like a shock?
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NT3 has urathane blocks built into the frame structure to allow some give in the frame. I don't know abiut the others.
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Jack used a very interested combination for the frame design.
some parts are built to Cremona - which means a very stiff (strong) frame design - in the other part he used a standard frame design - which is only half so stiff.
the result is, that this frame works like a shock absorber.......
in other words - when one of the wheels moved up...by rough salt....the whole bottom makes the same move and stays so parallel to the ground.....(the most of the time)
very strange....but not strange for Jack Costella Innovator.....
This frame design and the now possible low bottom is one of the secrets why - especially the NT II - his racers are so damn fast.
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http://www.landracing.com/forum/index.php/topic,3999.0.html
In these photos of the Bruce Crower streamliner, it can be seen how Crower combined full suspension with side skirts.
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Forget 81 mph. What if aero was unimportant?
How about 167 mph on a bicycle!
(http://www.fredrompelberg.com/upload/Fred%20Rompelberg/Fred_zoutvlakte_tijdens_record_achter_auto_klein.jpg)
http://www.fredrompelberg.com/en/html/algemeen/fredrompelberg/record.asp (http://www.fredrompelberg.com/en/html/algemeen/fredrompelberg/record.asp)
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And the open motorcycle guys could use some of these tail section ideas:
http://www.speedbikebgl.de/eng/galeriee.htm
sadly the partial streamlining rules preclude the use of most if not all those tail sections , any further benificial streamlining is frowned upon for our own personal safety in the event of an unexpected sidewind,which may or may not upset the apple cart :x, brute horsepower has flirted for to long with marginal traction and is on a loosing bet , fiddling around the edges with frontal area is all thats left ,unless the rules regarding partial streamlining change ,sad but true :cry:
[/quote]
http://www.motorcycleshows.com/motorcycleshows/data/articlestandard/motorcycleshows/342007/451724/HistoryofSpeed_300.gif
Checkout the tail section (above) on Joe Petrali's world record Harley.
Below is a good photo of one of the Moto Guzzi dustbin fairing bikes. According to the plaque I saw at a museum, these bikes would do 180 mph on 75 horsepower.
http://www.webbikeworld.com/Moto-Guzzi-motorcycles/guzzi-photos/oldGuzzi.jpg
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i think you guys are mistaken jacks car is 23 feet long (salt snake) any flex in the frame would allow the bottom to drag not a good thing --i will see jack at el mirage this week end and will ask him and let you know willie buchta
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Blue
I am with you on the flat bottom and my reasoning is that I see the area around the streamliner that is closest to the ground is similar to a root section of a wing where it attaches to the fuselage. Imagine that being a sharp corner and the turbulence that would be created...
Could I tap your skills one more time as I am building a motorcycle streamliner and although I am in the gathering and design stage right now I would hope I am going in the right direction..I have two sheets of aluminum bent up like a taco shell and the plan is to make it look like a diamond looking from the front. The wing profile I was planning on is NLF-0414F although I now think that tangency with any profile will suffice.. What say you?/
Thanks in advance
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"1. Absolute minimum separation: No blunt rear ends, minimal wheel openings, fairings in front and behind the tires.
2. Ground clearance: "ground effects" may sound sexy, but they are high drag. If we need downforce, we should use a low drag wing, high up in clean air like Teague did.
3. Absolute minimum wetted area: They are SHORT! Shorter means more aggressive pressure recovery, the first trade-off."?
Hmmm.
Line drawing of Frank Lockhart's Stutz Blackhawk.
200+ mph on three liters in 1927!
http://www.jalopyjournal.com/forum/attachment.php?attachmentid=288047&d=1174003168
Here's a link to great photos of Bob Rufi's car with and without wheel fairings.
http://www.jalopyjournal.com/forum/showthread.php?t=149631
The aft section of a streamliner Breedlove built for the wheel driven record, and later converted into a rocket car, had some similarities to Lockhart's car.
http://www.landracing.com/forum/index.php/topic,3900.15.html
The Pumpkin Seed was another example of a successful high ground clearance design.
http://69.10.163.89/PUMKINSEED.JPG
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Just FYI - that Breedlove car Ratliff mentioned is in a private collection here in Wichita, KS.
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i think you guys are mistaken jacks car is 23 feet long (salt snake) any flex in the frame would allow the bottom to drag not a good thing --i will see jack at el mirage this week end and will ask him and let you know willie buchta
Willie, this "flex" concept for the frame is only used for the II and III - both bikes - the Yellow Submarine and the Salt Snake (Cliff Gullett) got a frame built to Cremona - means very stiff. If Jack used this flex for the bikes the racer would be all over the place...but not straight going.
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http://en.wikipedia.org/wiki/Reynolds_number
Explanation of Reynolds number
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Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail. Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides. Get the whole thing up off the ground and fair the wheels. A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.
The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester). Remember, the 66xxx series were designed as wing sections. Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.
Blue, when you fair the wheels, you are no longer a lakester...
Don't lakester bodies need to be designed with the rotating open wheels considered? And will the placement of those wheels effect the outcome?
And sorry, I like flat bottommed lakesters... :roll:
http://www.mulsannescorner.com/diffuser.htm
Some further insight into flat bottom aerodynamics.
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On the Salt Snake and the 5050 bike they are so close to the ground and a single track vechile I don't see how the bottom can't be scraping at any time any correction is being made. Lean the bike it scrapes. Seems to work anyway.
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Discussions of vortices and use of vortex generators to reduce drag/increase lift
http://www.mulsannescorner.com/vortexlift.html
http://www.b737.org.uk/fuselage.htm#AFT_BODY_VORTEX_GENERATORS
http://www.aerospaceweb.org/question/aerodynamics/q0255.shtml
http://www.aerospaceweb.org/question/planes/q0176.shtml
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I want to apologize to the bike racers who have reminded me to read the rules on tail sections. I had no idea they were so restrictive on the tail and allow so much up front. This is bad from a stability side: front fairings move the aerodynamic center forward and cause the bike to be more susceptible to crosswinds than a longer tail. Tails help point the vehicle into the wind and counteract the side force blowing the bike off course.
There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load. The top people in LSR that I have asked haven't seen that, if fact, just the opposite. The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.
Pork Pie: "Blunt" refers to the chopped off rear ends that we see at the back of parachute tubes and the back of most cars. Getting rid of that on a streamliner means doing movable cover doors like BUB or Burkland.
Rex: Yes, that's getting close; for a lakester, just take the wheel fairings off. As for airfoil sections, a body of revolution up in clean air can have a fineness ratio (length over max diameter) of as little as 3 or 4. Beyond 7 is a lot of drag, but could still be a good "liner" if there's minimal separation. A fineness ratio of 4 would mean a 66-025, a 66-020 = 5, and so on.
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I want to apologize to the bike racers who have reminded me to read the rules on tail sections. I had no idea they were so restrictive on the tail and allow so much up front. This is bad from a stability side: front fairings move the aerodynamic center forward and cause the bike to be more susceptible to crosswinds than a longer tail. Tails help point the vehicle into the wind and counteract the side force blowing the bike off course.
There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load. The top people in LSR that I have asked haven't seen that, if fact, just the opposite. The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.
Pork Pie: "Blunt" refers to the chopped off rear ends that we see at the back of parachute tubes and the back of most cars. Getting rid of that on a streamliner means doing movable cover doors like BUB or Burkland.
Rex: Yes, that's getting close; for a lakester, just take the wheel fairings off. As for airfoil sections, a body of revolution up in clean air can have a fineness ratio (length over max diameter) of as little as 3 or 4. Beyond 7 is a lot of drag, but could still be a good "liner" if there's minimal separation. A fineness ratio of 4 would mean a 66-025, a 66-020 = 5, and so on.
A fineness ratio of 3 is about what Bob Rufi had on his body of revolution liner back in 1939.
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On the Salt Snake and the 5050 bike they are so close to the ground and a single track vechile I don't see how the bottom can't be scraping at any time any correction is being made. Lean the bike it scrapes. Seems to work anyway.
I spoke to 5050's driver on the salt last year and he described a run where scraping in a sidewind slowed the bike 30mph.
Porkpie has described how when Costella's bikes are steered the front wheel displaces sideways to the right when the bike is steered left (and vice versa), providing a sort of "virtual lean".
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There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load. The top people in LSR that I have asked haven't seen that, if fact, just the opposite. The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.
I read a paper somewhere recently, focussed on sit-on bikes, purporting to demonstrate that the center of pressure on a bike needs to be a bit ahead of the center of gravity for safe handling. With the center of pressure behind, a wind from the left leans the bike to the right and steers it to the left; not the best situation, seems to me. Perhaps this is the source of the problems which led to banning extended tails on sit-on bikes.
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the person that wrote that article has never ridden a motorcycle in the wind before willie buchta
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O.K.......O.K. all these numbers impress
me..........but I like to believe in FACTS..................
the Can-AM wind-tunnel tests back in the early 1970's showed that a tail (not unlike the ones shown on the push-bikes) made a very big improvement in the Aero of the 125c.c. bike
tested...................but the FACT is that the bike
could not be riden safely above approx. 80mph.
.................with a very lite cross-wind..........FACTS
..............not theory on paper or wind-tunnel......
FACTS...............................FACT....a Dustbin fairing
makes for better Aero........return record run
of our sidecar at last years BUB.........approx. 5 to 8 mph cross-wind (in addition to bad traction)
the outfit got completely sideways in the speed- trap....only the sidecar driving skill of Larry Coleman saved the day.......FACTS............................
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the person that wrote that article has never ridden a motorcycle in the wind before willie buchta
I bow to your practical knowledge, but do you know where the center of pressure is on the bikes you've ridden?
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http://www.youtube.com/watch?v=gg6UOLiHD3o
http://www.competitionplus.com/02_18_2004/photos/wsid_04.jpg
Jay Upton, 230 mph fully enclosed sit on Top Fuel bike.
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never bow to anything --i know of what i speak from practial experience because im a long distance motorcycle rider ive ridden in every kind of weather --if i were to guess i would say ive ridden well over 500,000 miles my best year was when i was 61 i rode 41,620 and i dont comute to work my shop is 25 feet from my house --i can tell you this if you are traveling east and the wind is blowing south the wind will move you to the south --if you want to keep going south you will have to lean your bike over to the left --im talking about a street bike --the bike i race is a sidecar bike 2 wheel rules dont apply its like driveing a car with 3 wheels just some thoughts willie buchta
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partial streamlined aerodynamics and rules ,its like a wheel it goes round and round , from the ban bikes or at least wrap them in cotton wool ,to the allow anything and be danmed with the consequenses ,to every thing in between ,its one of those we all agree to disagree subjects ,by the way Im in the anything and be damned camp :-D
cheers
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facts......the canam ordeal was ONE incidence......
NOT a real impressive study to base others on.....
impressive effort, but one teams results.......with one bike
and no systematic rework.....
now i know there have been other applications with
tails that seem to cause issues ie one of the HD bikes
many moons ago.....
BUT.....i for one am not going to make the ASSumption
that because team A had a handling issue with x tail that
tails are bad...for example....for my bike with cg horizontal of B, and cg vertical
of C, and center of pressure D......etc
its the total system that i would be much more interested in studying....
because sidecar E going 160-180 with a dustbin doesnt imply that sidecar
F that already goes 210+ without dustbin, will fail miserably with appropriately
applied aero resembling a quote dustbin fairing.......
it troubles me to see blanket comments......without due system analysis.....
it was OUTLAWED for decades to have a front fairing that had the nose beyond a vertical
line through the front axle...........THEN production bikes did this with higher stock speeds
than many bonneville records..........
additionally we were OUTLAWED to have tailsections extend beyond rear edge of rear wheel....
THEN stock bikes began coming out with tail sections beyond this illegal point....with fine
success, speeds and stability.......
THEN the scta rules makers MANDATED that any tail beyond rear wheel must be above
the top of rear tire....thereby requiring that extra surface area be high on the rear of the bike....
no we have bikes with MONSTER hp, hanging significant wt off swingarms trying to increase speeds.....
whats worse, incrementally refining a design to higher speeds, or having blanket beliefs relegate rules
to the point of potentially riskier practices
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bravo ,well said Joe :-D
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well its 5:51 friday morning and im leaving for el mirage in about 15 minutes and i was just wondering of all the members- guests-lurkers and experts how many i will see there going down the lake WFO hopefully everyone willie buchta
its going as fast as you can go --its not rocket science
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going as fast as you can may not entail rocket science......
but going as fast as you "could" may very well entail rocket science.....!!!!
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180 mph on 75 horsepower.
I think that, combined with the brake technology of the time, is the real reason dustbin fairings were banned.
Maybe if Moto Guzzi had the kind of brakes available today it might have been a different story.
Put a dustbin on one of those 260 mph Hayabusas and you'd be looking at a 300 mph bike.
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Hi Eric,
so, I can understand "blunt" as a try of a Kamm rear end
but so as a lot of racers are built - the side panels are a "try" of Kamm, but between the left and right side panels from the rear end are the chute tubes and "wholes"...means a open rear end without a closing sheet metal....which can create a vacuum behind the car....and with this bad turbulences...
To this a information - we are using a Kamm rear end at our streamliner - and we also get under the chute tube a open space.....but we need this to get the air out of the streamliner which goes thru the radiator....otherwise we would get a overheating problem....and if the Kamm end is done properly it's not too bad in a so configuration
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Hi Eric,
so, I can understand "blunt" as a try of a Kamm rear end
but so as a lot of racers are built - the side panels are a "try" of Kamm, but between the left and right side panels from the rear end are the chute tubes and "wholes"...means a open rear end without a closing sheet metal....which can create a vacuum behind the car....and with this bad turbulences...
To this a information - we are using a Kamm rear end at our streamliner - and we also get under the chute tube a open space.....but we need this to get the air out of the streamliner which goes thru the radiator....otherwise we would get a overheating problem....and if the Kamm end is done properly it's not too bad in a so configuration
In the links belows you can see how the chute cans were housed on Fred Larsen's car and The Blue Flame. Lynn Yakel would have preferred a longer taper on Larsen's car, but Larsen didn't have a long enough garage.
http://www.landracing.com/forum/index.php/topic,3900.30.html
http://www.landspeed.com/classroom/classbluelfame.html
Since you've mentioned using a radiator, you may also want to take a look at how the intercooler was mounted in the tail of the Honda Hawk.
http://www.landracing.com/forum/index.php/topic,3996.0.html
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I have to agree with Bakker, results are the key. It's one thing to have a low CD , but the execution is just as important. BUB Seven has a Cd of .08 both calculated and tested full scale at the wind tunnel. While this is superb, the whole package makes it happen.
This year we toured with the Cycle World show circuit featuring the Joe Petrali bike. The tail of the bike was tapered and appeared to have a low CD, but for his the record run Petrali removed tail bodywork. It looked right, but didn't perform in reality.
So what it really boils down to is the time ticket, that is the only way to validate any of these designs. Theory is great, but application is essential- Eric
CycleWorld Shows
http://www.motorcycleshows.com/motorcycleshows/Atlanta+Features/Worlds-Fastest-Motorcycles/ArticleStandard/Article/detail/451724
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In the sixties, when he was chief steward for USAC, Joe Petrali in the absence of any specific rules governing construction had to tech inspect cars such Breedlove's first and second jets, Walt Arfons' rocket, and Art Arfons' J-79 jet then decide whether they were safe to run.
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Mr. Ratliff.............brake technology had NOTHING to do with the banning of Dustbin Fairings in FIM roadracing back in the late 1950"s..................
You appear to have all the important
information at hand...................we will all give you a BIG atta-boy if you get the answer right............
(hint... the answer is noted much earlier on this forum)
O.K. people no fair helping Mr. Ratliff.....................
P.S. However, you are right on, regarding a Dustbin on one of the 260mph. solo bikes..........
but the conditions would have to be almost perfect.............................................................................
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Here are 2 photos (if I can add them properly) of a motorcycle with a streamlined shell which has a "dustbin" type front and a "Kamm" type rear. The bike went well in crosswinds when loaded with about 90lb of fuel loaded down low and got sensitive when the fuel was used up. It seems that a low CG helps the sidewind stability even with a large side area. The bike ran 81+mph at El Mirage in 1982 or 1983 with about 10 hp from a detuned Suzuki GN125 motor. It was designed for a High Mileage contest, so the rules were wide open. One way to test a theory is to build and test, that is why Bonneville is so much fun!
(http://i5.photobucket.com/albums/y176/bubbamatt/01SUZUKI-rear-view.jpg)
(http://i5.photobucket.com/albums/y176/bubbamatt/star.jpg)
Glad to see the forum active again.
Matt G.
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Mr. Ratliff.............brake technology had NOTHING to do with the banning of Dustbin Fairings in FIM roadracing back in the late 1950"s..................
You appear to have all the important
information at hand...................we will all give you a BIG atta-boy if you get the answer right............
(hint... the answer is noted much earlier on this forum)
O.K. people no fair helping Mr. Ratliff.....................
P.S. However, you are right on, regarding a Dustbin on one of the 260mph. solo bikes..........
but the conditions would have to be almost perfect.............................................................................
I've seen one of the Moto Guzzi dustbin bikes up close in person. It's so low if you were standing on one side of a Hayabusa and it was on the other you might not even know it was there.
I also have a 1974 SCTA rulebook. There were no rules banning anything on a sit on bike. All the rules say regarding bodywork is "any streamlining apparatus is permitted that is consistent with the safety rules and good design practice." There were exactly twelve classes for bikes, six fuel and six gas, based entirely on engine displacement. Whether you had a race frame or a production frame didn't matter.
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P.S. However, you are right on, regarding a Dustbin on one of the 260mph. solo bikes..........
but the conditions would have to be almost perfect.............................................................................
Just curious, I have not witnessed a 260mph bike run, are we talking stock bodywork Hayabusa's, or something else?
I did a quick calculation (ok, I plugged it in an online calculator) shows a stock body work Hayabusa would need just over 400 horsepower, so that seems reasonable to achieve. Not easy, but there are many claiming much more power than that.
To go 300mph on the same horsepower would need to reduce the stock Cd to around 0.36 (from the claimed 0.561) This seems like a bit of a stretch to me, but maybe I'm missing something. Tires would be a BIG issue as well.
Back to the original topic, there is a classic photo of Burt Munroe's Indian, and beside it a much earlier design Indian. The latter design, and most of the "modern" motorcycle streamliners are low and long (The only exception I can think of is Dan Hanbrink's liner, but not really modern and had some different design goals in mind). I think the design process evolved for good reason.
The HPV designs have to position the rider to make good power, and weight is critical due to the short amount of time that a person can generate high power.
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P.S. However, you are right on, regarding a Dustbin on one of the 260mph. solo bikes..........
but the conditions would have to be almost perfect.............................................................................
Just curious, I have not witnessed a 260mph bike run, are we talking stock bodywork Hayabusa's, or something else?
I did a quick calculation (ok, I plugged it in an online calculator) shows a stock body work Hayabusa would need just over 400 horsepower, so that seems reasonable to achieve. Not easy, but there are many claiming much more power than that.
To go 300mph on the same horsepower would need to reduce the stock Cd to around 0.36 (from the claimed 0.561) This seems like a bit of a stretch to me, but maybe I'm missing something. Tires would be a BIG issue as well.
Back to the original topic, there is a classic photo of Burt Munroe's Indian, and beside it a much earlier design Indian. The latter design, and most of the "modern" motorcycle streamliners are low and long (The only exception I can think of is Dan Hanbrink's liner, but not really modern and had some different design goals in mind). I think the design process evolved for good reason.
The HPV designs have to position the rider to make good power, and weight is critical due to the short amount of time that a person can generate high power.
The exposed front wheel on a conventional motorcycle generates A LOT of drag. A well designed dustbin fairing might be enough to turn a 260 mph Hayabusa into a 300 mph Hayabusa.
In any case, a pair of canard wings like the ones Arvil Porter installed on Larry Welch's rocket bike (the first 200 mph drag bike) might be a wise precaution.
The motorcycle streamliner as we have known it for the past 50 years was created by Stormy Mangham back in the late fifties.
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Thanks Matt G. that is very cool of you to post that information...ie real world execution........
and feedback........first hand....:)
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We have had long discussions regarding Dustbin fairings on this forum in the past...........................
As we now know a Dustbin is legal at the BUB..... racing under AMA/FIM rules on solo bikes....however, as per the rules the fairing has to be mounted above the axcle still leaving a good part of the front wheel exposed.................
Running a Dustbin on a sidecar allows us to bring the fairing down to approx. 3 inches off the ground covering the front wheel completly except for the tire........this is where one gets full benefit of the fairing. Our sidecar as a whole
has a long way to go regarding good Aero, partly due to the fact we use a passenger in the sidecar, but the Dustbin fairing gives us approx.
20 to 23mph. over running"naked".........................
But it can be a hand-full in a cross-wind..........
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I think comments made by Sir Malcolm Campbell in 1946 when he wrote regarding his upcoming attempt with the first turbojet boat are applicable to the question of dustbin fairings and enclosed tails. "Well, it goes rather deeper than the mere desire to set up a new record. Standing by themselves, these speed records may mean much or little, as the case may be. Of course, there is a great sense of personal satisfaction in setting a figure which challenges the opposition but, if that were all, I should without much hesitation say that the effort was scarcely worth the time, trouble and expense involving in building a world-beating car or boat or aeroplane. It certainly would not be worth while if the achievement did not constitute a landmark on the road of progress. Every time we set up a new record of speed, either on land or water or in the air, we have learned something which can be applied to development and have travelled another distance towards that relative perfection of the machine which is the goal of human endeavor."
So if a Haybusa goes 260 mph does that by itself constitute a "landmark on the road of progress"? (Assuming such ideals are still remembered today). Have we "learned something which can be applied to development and have travelled another distance towards that relative perfection of the machine"?
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going as fast as you can may not entail rocket science......
but going as fast as you "could" may very well entail rocket science.....!!!!
bak149 has it right, if anyone thinks for a second that I am a cubicle engineer they need to read the signature under my avatar.
I believe that we need both theory and testing. From the practical side, guys like Willie are the best since they are unwilling to put up with theory that contradicts their experience while at the same time they are willing to accept theory that explains what they have felt and seen in real life. We have to test. If theory doesn't match reality, it is the theory that has to change.
BUT! Incomplete theory or messy interpretation of that theory often leads to messy data that only confuses the issue. We have to have clean data. That means a clean interpretation of the theory and a clean test vs. a contrary theory. There are some on this board who want to just keep pointing at history and old theory without adapting to modern experience. I don't accept any combination of theory and data without some explanation of why they explain each other.
On the ALSR, I had many, many people shoving theories at us. One of the best examples of what I spit at was one graduate student who said he had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number...
(if you're an aerodynamicist, you're laughing right now...)
His application to work on our program was accompanied by a statement that he had completed his doctoral thesis and was going to conduct experiments that proved his theory.
My dad would've boxed his ears for that.
Experiment tests theory, and nothing is completed or proven until it stands up to contrary (or "devil's advocate") testing. That's what Bonneville is for.
Let's just remember that the salt is a dirty experimental environment. Soft salt, wet salt, bumpy salt, hot, cold, wind, engine conditions, chassis tuning, got-to-make-a-run-now-because-if-I-don't-it's-next-year-itis, etc. etc. etc. all pollute the data. There's a lot going on out there that pollutes the aero data. Lots of people have read my posts here and believe that I can help them. I'm flattered, and I even want to help as long as it doesn't cost me anything.
So tape some yarn to your lakester and send me the pictures. You only have to go 60 MPH on a country road for most separation effects and causes to become apparent. Blunt aft vehicle depend on organized separation and are a little harder to troubleshoot, but there are some good, simple rules to follow and some easy test methods to create stable recirculation behind a "Kamm" rear end.
Remember my motto: Don't guess, TEST!
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going as fast as you can may not entail rocket science......
but going as fast as you "could" may very well entail rocket science.....!!!!
bak149 has it right, if anyone thinks for a second that I am a cubicle engineer they need to read the signature under my avatar.
I believe that we need both theory and testing. From the practical side, guys like Willie are the best since they are unwilling to put up with theory that contradicts their experience while at the same time they are willing to accept theory that explains what they have felt and seen in real life. We have to test. If theory doesn't match reality, it is the theory that has to change.
BUT! Incomplete theory or messy interpretation of that theory often leads to messy data that only confuses the issue. We have to have clean data. That means a clean interpretation of the theory and a clean test vs. a contrary theory. There are some on this board who want to just keep pointing at history and old theory without adapting to modern experience. I don't accept any combination of theory and data without some explanation of why they explain each other.
On the ALSR, I had many, many people shoving theories at us. One of the best examples of what I spit at was one graduate student who said he had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number...
(if you're an aerodynamicist, you're laughing right now...)
His application to work on our program was accompanied by a statement that he had completed his doctoral thesis and was going to conduct experiments that proved his theory.
My dad would've boxed his ears for that.
Experiment tests theory, and nothing is completed or proven until it stands up to contrary (or "devil's advocate") testing. That's what Bonneville is for.
Let's just remember that the salt is a dirty experimental environment. Soft salt, wet salt, bumpy salt, hot, cold, wind, engine conditions, chassis tuning, got-to-make-a-run-now-because-if-I-don't-it's-next-year-itis, etc. etc. etc. all pollute the data. There's a lot going on out there that pollutes the aero data. Lots of people have read my posts here and believe that I can help them. I'm flattered, and I even want to help as long as it doesn't cost me anything.
So tape some yarn to your lakester and send me the pictures. You only have to go 60 MPH on a country road for most separation effects and causes to become apparent. Blunt aft vehicle depend on organized separation and are a little harder to troubleshoot, but there are some good, simple rules to follow and some easy test methods to create stable recirculation behind a "Kamm" rear end.
Remember my motto: Don't guess, TEST!
Some of that "history and old theory" is The Blue Flame got hit with a 40+ mph crosswind at over 600 mph and jumped sideways but didn't roll.
The modern experience is the Breedlove car rolled when hit by a 15 mph crosswind (although my hypothesis is a lot of that was due to Breedlove torquing the crap out of the car when he tried to regulate his acceleration by going in and out of burner).
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Here's a couple of machines that although fully enclosed were among the last otherwise conventional bikes to hold the outright record.
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As we now know a Dustbin is legal at the BUB..... racing under AMA/FIM rules on solo bikes....however, as per the rules the fairing has to be mounted above the axcle still leaving a good part of the front wheel exposed.................
Somebody correct me if I'm wrong, but their are also restrictions on the tail fairing (also discussed somewhere else on this forum), and that was what was required in addition to the dustbin to get to ~0.35 Cd. The dustbin alone I thought only got down to around 0.4 to 0.45 Cd (which isn't too shabby!)
I was really mostly curious about what bikes were running 260mph, but interesting thread for sure.
I don't doubt that somebody in APS could do that well or better in terms of Cd (and even frontal area), but stock bodied Hayabusa to 300mph seems like it would take a lot more than "just a dustbin fairing" to get to 300mph, but I wouldn't be surprised to be proven wrong either. There are certainly some impressive naked records getting set lately.
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As we now know a Dustbin is legal at the BUB..... racing under AMA/FIM rules on solo bikes....however, as per the rules the fairing has to be mounted above the axcle still leaving a good part of the front wheel exposed.................
Somebody correct me if I'm wrong, but their are also restrictions on the tail fairing (also discussed somewhere else on this forum), and that was what was required in addition to the dustbin to get to ~0.35 Cd. The dustbin alone I thought only got down to around 0.4 to 0.45 Cd (which isn't too shabby!)
I was really mostly curious about what bikes were running 260mph, but interesting thread for sure.
I don't doubt that somebody in APS could do that well or better in terms of Cd (and even frontal area), but stock bodied Hayabusa to 300mph seems like it would take a lot more than "just a dustbin fairing" to get to 300mph, but I wouldn't be surprised to be proven wrong either. There are certainly some impressive naked records getting set lately.
The fastest vehicles at the Texas Mile and Maxton pavement land speed events are bikes (turbo Hayabusas). It turns out a bike can run as fast on one mile of pavement as it can on three miles of salt.
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Blue I have always had the feeling that directing the engine exhaust to fill in the low pressure behind a vehicle hard to test in a wind tunnel as it would need to be a rolling road that also had a chassis dyno so you run the engine WOT and generate the exhaust flow. So my question is there some way to do some baseline calcs on a CFD model that matches wind tunnel testing and add in X lbs per minute of air at Y airspeed and show what effects there might be. I would think the aircraft folks have this sort of tool. Next is there a way to predict the center of pressure movement vs relative speed? My concern is to predict if the CP will move forward as speed goes up and possibly go from stable to unstable.
On the enclosed chute tubes.. they scare me to death.. when and if a run is going bad and you need to slow down asap you are adding door deployment time to chute deployment time to actually slowing the thing down..
Dave
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Hi all,
Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post. If I'm not, I'd love to talk to this guy whoever he is - sounds like he could really help me in my research, with his interesting theories!:
On the ALSR, I had many, many people shoving theories at us. One of the best examples of what I spit at was one graduate student who said he had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number...
(if you're an aerodynamicist, you're laughing right now...)
His application to work on our program was accompanied by a statement that he had completed his doctoral thesis and was going to conduct experiments that proved his theory.
My dad would've boxed his ears for that.
I have never spoken to Mr. Ahlstrom, or his dad for that matter. My only attempt to establish contact with him, with a simple request for more information through Steve Fossett's PR man in 2007, was ignored, though evidently I have provided fodder for him if I have become worthy of making an example of!
I did not state that I had finished my PhD. I have not. I'd imagine it'd be quite hard to finish your thesis if you hadn't done any experiments...
I did not apply to work on his program. I have not ever said I had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number.
I did say that I thought my work, some of which was on land speed record cars, including Breedlove's car, would be of interest to him, as it has been to a few others in the land speed racing community. Evidently it was not and I thought little more of it until now.
It is hard to know where Mr. Ahlstrom has been drawing his inferences from, then, although if you're anything like I apparently am, you could almost be tempted to come up with some more unproven theories: I wrote to Craig Breedlove around the same time, and in more detail about the early findings of my research, but once again a reply was not offered.
Perhaps Mr. Ahlstrom had also gotten his hands on a couple of presentations I gave at a symposium on shock waves, in Italy in 2006, in which I put forward some interesting undergraduate computational studies on the aerodynamics of Thrust SSC, as well as some of my own preliminary investigations into the aerodynamics of wings in transonic ground effect. This work preceded and informed an extensive wind tunnel program at the US Naval Academy in Annapolis, supported by the Royal Aeronautical Society.
Fortunately, neither of these fine institutions deemed it necessary to ‘box my ears’ at any stage.
Mind you, since then, much of my research has become publicly available in peer-reviewed journals - it'd surely have to be these formal results and discussions that caused Mr. Ahlstrom to scoff so decisively. The benefit of both reading and publishing in such journals is their insistence on rigorous validation of theories and models against reliable experimental results. In this way they ensure that they are not about to stake their reputation on substandard, unproven or incomplete work.
Given this, coupled with his adversity to personal contact, it would therefore make sense for Mr. Ahlstrom to address his issues with my research to the editors of these journals so that his criticisms can be properly put to a wider, interested and informed audience in an appropriate context :-)
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Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post.
Yes, Graham, you are the graduate student I referred to. I did not use your name to avoid a public confrontation, and you are welcome to contact me at my e-mail address or by PM; both of which you have access to since you have registered on this site. I am only too happy to keep a dispute of technical theory private until someone challenges me in public. Having exposed me to public criticism, you are now vulnerable to the same. BTW, I publish too, am a guest lecturer, and write my own code; you could've found this out with a proper search. This doesn't make my work (or yours) any more valid, it just means that it passed technical review and is worthy of discussion.
You were far from the worst example of "help" that was offered to us. By far the worst was someone claiming to have the "secret" of using electromagnetic vehicle and exhaust plume charging to create a "gravity well" and an over-unity effect. Your work stays within the limits of the second law of thermodynamics and was worth consideration. I reviewed your e-mail to Craig, you never contacted me, so I do not understand where this "avoidance of contact" idea comes from. In your e-mail, you postulated that your research with un-validated CFD "proved" that "shock waves" lifted the back of Sonic Arrow and caused the 1996 roll. You were specific in your insistence that your TBD "test" would "prove" your theories.
This is the basis for my dismissal of your attitude and work.
Whether or not you have accurately modeled transonic and low-supersonic objects and vehicles in intimate ground effect of a porous and plastic surface is not apparent from your research. What is apparent is the following:
1. No known CFD solver has been validated for ground effect.
2. You are one of the few researchers exploring intimate the science of ground effect on transonic and low supersonic objects.
3. Your work does not account for decay of shock reflection via a variable density, variable porosity, and variable structure surface (welcome to playa, a VERY non-linear group of effects). In addition, the explosive disassembly of the surface by the shock requires the surface ejecta to be included as significant to the model.
4. Your work does not account for the detailed mechanical and aerodynamic features of TSSC and Sonic Arrow 96. For example, rolling tires, local surface alpha, suspension deflection, gross vehicle alpha (controlled vs. actual), louvers and negative Cmu on TSSC, aft separation and its effects on transition to terminal shock and stagnation, etc. These are major, not minor effects for shock formation and decay, as well as all pitching moment, stability and control effects. FYI, no models or drawings exist of SA-'96. The die cast model is ~95% accurate for SA-'97 and less than 60% accurate for Fossett LSR-'08.
5. At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature. The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8! Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground. This increased the strength of the the upper surface shock. Tehrefore, there is a downforce based roll component, but not a lifting force based roll component. Did you account for any of this?
6. Like many proponents of the flat-bottom cars (I'm not saying you're one), you made no distinction in your e-mail between blunt-fat vehicles like TSSC and high fineness ratio vehicles like Sonic Arrow. Strength of a compression wave is proportional to the first and second order of displacement: max cross section and fineness ratio. This is linear wave drag theory that I am sure you are familiar with.
It is for these and other reasons that Dr. Hal Ahlstrom and myself believe that CFD is not useful in this instance. In fact, it is detrimental, in that it will create a vast volume of questionable data that will probably lead in the wrong direction due to its volume. A better course would have been to ask us if we could add some aerodynamic sensing to our data collection along with detailed 3D vehicle coordinates so that you could validate your modeling with our data. As you embark on your career in aerodynamics, try to remember that it's not real until it's tested.
Don't guess, TEST!
and this doesn't mean CFD.
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Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post.
Yes, Graham, you are the graduate student I referred to. I did not use your name to avoid a public confrontation, and you are welcome to contact me at my e-mail address or by PM; both of which you have access to since you have registered on this site. I am only too happy to keep a dispute of technical theory private until someone challenges me in public. Having exposed me to public criticism, you are now vulnerable to the same. BTW, I publish too, am a guest lecturer, and write my own code; you could've found this out with a proper search. This doesn't make my work (or yours) any more valid, it just means that it passed technical review and is worthy of discussion.
You were far from the worst example of "help" that was offered to us. By far the worst was someone claiming to have the "secret" of using electromagnetic vehicle and exhaust plume charging to create a "gravity well" and an over-unity effect. Your work stays within the limits of the second law of thermodynamics and was worth consideration. I reviewed your e-mail to Craig, you never contacted me, so I do not understand where this "avoidance of contact" idea comes from. In your e-mail, you postulated that your research with un-validated CFD "proved" that "shock waves" lifted the back of Sonic Arrow and caused the 1996 roll. You were specific in your insistence that your TBD "test" would "prove" your theories.
This is the basis for my dismissal of your attitude and work.
Whether or not you have accurately modeled transonic and low-supersonic objects and vehicles in intimate ground effect of a porous and plastic surface is not apparent from your research. What is apparent is the following:
1. No known CFD solver has been validated for ground effect.
2. You are one of the few researchers exploring intimate the science of ground effect on transonic and low supersonic objects.
3. Your work does not account for decay of shock reflection via a variable density, variable porosity, and variable structure surface (welcome to playa, a VERY non-linear group of effects). In addition, the explosive disassembly of the surface by the shock requires the surface ejecta to be included as significant to the model.
4. Your work does not account for the detailed mechanical and aerodynamic features of TSSC and Sonic Arrow 96. For example, rolling tires, local surface alpha, suspension deflection, gross vehicle alpha (controlled vs. actual), louvers and negative Cmu on TSSC, aft separation and its effects on transition to terminal shock and stagnation, etc. These are major, not minor effects for shock formation and decay, as well as all pitching moment, stability and control effects. FYI, no models or drawings exist of SA-'96. The die cast model is ~95% accurate for SA-'97 and less than 60% accurate for Fossett LSR-'08.
5. At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature. The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8! Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground. This increased the strength of the the upper surface shock. Tehrefore, there is a downforce based roll component, but not a lifting force based roll component. Did you account for any of this?
6. Like many proponents of the flat-bottom cars (I'm not saying you're one), you made no distinction in your e-mail between blunt-fat vehicles like TSSC and high fineness ratio vehicles like Sonic Arrow. Strength of a compression wave is proportional to the first and second order of displacement: max cross section and fineness ratio. This is linear wave drag theory that I am sure you are familiar with.
It is for these and other reasons that Dr. Hal Ahlstrom and myself believe that CFD is not useful in this instance. In fact, it is detrimental, in that it will create a vast volume of questionable data that will probably lead in the wrong direction due to its volume. A better course would have been to ask us if we could add some aerodynamic sensing to our data collection along with detailed 3D vehicle coordinates so that you could validate your modeling with our data. As you embark on your career in aerodynamics, try to remember that it's not real until it's tested.
Don't guess, TEST!
and this doesn't mean CFD.
"At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature. The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8! Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground. This increased the strength of the the upper surface shock. Tehrefore, there is a downforce based roll component, but not a lifting force based roll component. Did you account for any of this?"
This does not conflict with my previously stated hypothesis that the car rolled because Breedlove going in and out of burner trying to regulate acceleration was torquing the crap out of it.
However, Dr. T. P. Torda changed The Blue Flame from stub wings to open struts not because the wind tunnel tests (performed at Ohio State under the direction of Dr. J.D. Lee) were indicating the stub wings generated compression waves, but because the tests indicated the interaction of vortices coming off the nose with the stub wings created rear end lift.
On the other hand, it is good to know my proposed use from 1983 of swept wings to support outboard jet engines on the front of a vehicle (see link below) could be correct in principle.
http://www.landracing.com/forum/index.php/topic,4108.0.html
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graham--i learned at a very early age never to snitch on anyone ESPECIALLY YOURSELF
willie buchta
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HAha, thanks Willie Buchta, but I don't feel like I "snitched" on myself. I'm not in hiding :-)
You will notice that I have not rubbished anything Mr Ahlstrom has said relating to his thoughts or findings as he has done with what he knows of my work, unproven or otherwise - despite the forum name, I did not come here for a technical discussion, much less some sort of flame-war. I took issue with his false statements regarding me personally, and I think I set those straight in my original post. Although I was not named publicly, I felt the need to address the numerous inaccurate statements that referred to me, lest we all have to read through the forum rules again.
I stand by what I wrote to Craig Breedlove, although I in no way sought to lecture him and had hoped for a proper discussion I could learn from, and I've definitely learned... my lesson about discussing work in its early stages. At the time it seemed more urgent in that the car looked like it was going to run again soon and I wanted to find out as much as possible. In the end I could find out no more about the wing profiles, and certainly did not know enough detail to make some results public. I do not believe one single other person has actually seen any of that work of mine, yet it appears to have generated a lot of discussion.
I didn't mean to step on anyone's toes by forwarding my own thoughts to Craig Breedlove based on my experience to that date. I do not wish to be involved in an argument on a web forum.
I did not then claim to be right or have all the "answers", and I never would. My research speaks for itself and I would again refer criticisms of my work to the journals which have reviewed it, and published it as reliable, so that those comments are subject to the same level of review as my work was. I am always interested to read about conflicting or supporting research.
Eric, Stuart Radnofsky assured me he had contacted you on my behalf. If he did not, then I apologise for assuming you didn't wish engage in a discussion at that time. If there was misunderstanding, please do not treat my letter to Craig as an application to join your project or a statement of completion of my thesis. I also have no interest in modeling your revised car, your work is your own and I have no intention of pestering you with my thoughts on the matter or creating, as you rightly put it, a vast volume of questionable data.
With regards to the presentations I gather you have seen - one was not my own work, although I by-and-large support the findings and certainly deemed them to be worthy of closer investigation. The other was an absolutely preliminary CFD study. The nature of the symposia was designed to allow researchers to discuss such work and recieve valuable feedback, which I did. If I had thought these results were in any way worth publishing, I would have done so. We do not watch the rough first cuts of movies, but sometimes our interest is piqued by the teaser trailers.
Many CFD solvers have very accurately modeled ground effect aerodynamics for a variety of applications, but you are more than entitled to your own opinions on their appropriate uses. I'm well aware of the limitations of computer models.
At any rate, I'm not designing or building jet cars and even then I'd just be clogging up a message board which is useful for many others, so I wish you all the best in your tests.
Graham
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As long as we're discussing supersonic cars, something I think would be worth revisiting is the issue of whether the results below represent the minimum size required for a supersonic steam rocket car or if it might be feasible to go smaller.
http://www.landracing.com/forum/index.php/topic,4008.0.html
Waldo Stakes ( www.sonicwind.com ) has long believed his tiny "Sonic Wind" rocket ice sled could go supersonic given perfect conditions.
A few weeks ago I got curious about how fast a 4 inch diameter turbocharger rotor would be going at 80,000 rpm if it were a wheel on a car. When I did the math it worked out to around 900 mph.
So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.
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So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.
With those very small wheels, you wouldn't, I would think, be able to run a lot of static downforce, so you'd need a body design which would have stable lift/downforce characteristics under varying conditions. No movable aerodynamic surfaces allowed, right?
Leave me off your list of potential drivers.
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So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.
With those very small wheels, you wouldn't, I would think, be able to run a lot of static downforce, so you'd need a body design which would have stable lift/downforce characteristics under varying conditions. No movable aerodynamic surfaces allowed, right?
Leave me off your list of potential drivers.
It's Formula One and the rest of those Euro wussies that started the trend of not allowing movable aero devices (although F1 is changing that either next season or the season thereafter).
However, movable aero has always been legal in land speed. In 1962, Art Arfons set an SCTA record of 338 mph with movable aero. In 1964 and 1965, Arfons set the FIA record three times with movable aero. Arfons also used movable aero on the land speed car he ran in 1990 and 1991.
Who says a car only need four wheels? For ultrasmall wheels on a land speed car, I envision modules like asphalt racing skis except with titanium wheels and brake calipers on the frames that use the wheels as brake disks. The wheel bearings would be lubricated with a pressure fed oil system like a turbocharger.
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Eric,
just a information to the SoA Sonic Arrow models.
From the 96 version was three very accurate models by Arthur Russell of LA. in 1:12 scale
One was given to a sponsor, one was modified (in the Rio Vista workshop) at first into the 97 and than into the 2000 version, which was never complete released into the real car. The modification was done by Decal Dave, a very talented artist - he was also in the team which built the original car and he done the alignment of the racer in 98/99, after they found out that the frame was bend in 96.
The third model is in parts still by Arthur Russell.
I got picture from the 96, 97 and 2000 version.
Craig Breedlove gave the 2000 version to Steve Fossett - it was on the plane when he was 2006 at Bonneville.
You be right when you write that the 1:43 scale model is not 100 % correct - but for a China model and a record breaker model it is not bad.
Also, Arthur Russell done a 1:43 scale model of the 96 version - but he done only the master, he never produced some models with this master. The "outrigger" would be very critical to do them in resin.
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Fascinating subject - wonder if Mr Reynolds and his number enters into projecting the bike's performance into 440plus mph?
Remarkably, the record holding Varna bicycle bears a more than passing resemblance to the eforts by NSU with motorcycles in the '50s.
Taking things a step farther, does this skateboard racer attached ready to race DOWN Shell Hill @ Signal Hill (Long Beach, Ca) in '78resemble Jack costella's latest two wheel efforts?
Nothing new under the sun!
Even that was not the first time.
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just a information to the SoA Sonic Arrow models.
I was aware of the Arthur Russell models, although I was given the impression that they were 1997 versions; thank you for correcting this.
The one of the three that stayed in Breedlove's possession was modified to the 1999 mod list and used for shows and sponsor solicitation in 2001 through 2006. Breedlove loaned it on a limited basis to Steve (not a gift), but insisted that it was not included in the program sale and specified its return.
Since 2006 we eliminated many features of the 1999 configuration and made many other changes. Without intimate knowledge of our work (i.e. being a member of our shop) it would be impossible to know the critical details of the vehicle that would pertain to a CFD model of significant accuracy.
Decal Dave was not a member of the original build team, in fact, none of the original build crew stayed on from 1993 to 1997. There were three complete turnovers of crew from 1993 through 2000. Absolutely no one person involved at any point has the entire story. This was a major impediment to our (Fossett LSR) investigation of what we had, what was good, and what needed work.
This is ridiculously off-topic. I was trying to encourage discussion of a minimum drag motorcycle based on HPV's.
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Graham,
Our opinions are our own, I do believe that you should re-read your email to Craig before making statements about what you did and did not say.
I do want to make two things clear:
1. You are one of only a few people looking at supersonic ground effect and this has never been adequately modeled to effect detailed vehicle design at ground distance to vehicle ratios under 10%. At full suspension compression, we are below 1%. It is an interesting and difficult field, I wish you the best and look forward to seeing more of your work.
2. I should have said that no code has been validated in ground effect for transonic and supersonic flow at detailed levels of vehicle and surface features comparable to LSR vehicles and playa. While this may seem like a small point to some, I trust you understand the significance of these effects vs. the fidelity of the model defeats the model's utility for design work.
We will be publishing multiple papers on the program (win, lose, or crash) in both SAE and AIAA after we have completed our tests and have validated data. You can then review our work along with everyone else in the technical community.