Landracing Forum
Bonneville Salt Flats Discussion => Build Diaries => Topic started by: Larry Forstall on January 25, 2007, 04:56:37 PM
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Building for Maxton Mile. Ridden by Steve & Mark. Busa frame rescued from underwater burial during Katrina. Raked five degrees, Shortened 1000 Forks, 60" WB. Stock bore and stroke engine with the usual mods. Intercooled plenum (Tank and up pipe yet to be made). Hope to be ready this Spring but it is too cold to work on it. :roll: (http://www.imagestation.com/picture/sraid223/pf502ad8aed69efa33fcc119d027c75a6/eaee0969.jpg)
(http://www.imagestation.com/picture/sraid223/p56eefe5317314767eac6103e9b8d4721/eaee0963.jpg)
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Looks great Larry.......PLEASE, don't hang a 3rd wheel on it and call it a sidecar..............................!!!!
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The bike looks great . Are you gonna leave it naked or run it with the fairings.
Todd B. :-D
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Todd, no matter what class you choose to ride your bike in -- I know you just well enough to request that maybe the visual you're supplying isn't what I'd like to have just before lunchtime. Would you be so kind as to find another handle? I mean, watching you dance after qualifying was enough -- and you were weaering leathers then. I hesitate to allow myself to imagine. . .
Regards from way up north. It's good to have you onboard this forum, even if your name isn't what we'd prefer.
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Mark DeLuca came over today with the tank and seat from the N/A Busa. This is how the bike will be raced Todd. If Scott and others take all our old 1350 faired turbo records we might return to that battle but the current plan is to try to get a record above 220. Steve was the first to go 220 at Maxton (and 235) so it would be neat if he could be the first to go 220 naked. (No comments Slim!!). Notice the Kamm effect tail section as mandated by the "old" SCTA rules. (http://www.imagestation.com/picture/sraid223/peef5cb18d4386c67b686ff342f886342/eae5a10e.jpg)
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Very nice Larry :-). Tell Steve to be careful as I can't imagine 220 on that. Good thing I'm an old man and don't have to consider doing anything like that anymore :wink:.
Will you be bringing the bike like that to either Speed Week or BUB??
c ya,
Sum
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very impressive Larry ,I always look forward to your creations :-D 8-)
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It would seem the "OLD SCTA" rule had some thought in it beyond the obvious hazards of too long an extension of bodywork behind the rider.
Kamm was a pretty sharp cookie.
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It would seem the "OLD SCTA" rule had some thought in it beyond the obvious hazards of too long an extension of bodywork behind the rider.
Kamm was a pretty sharp cookie.
Hi Larry,
Very cool looking machine!
Larry and JackD,
I am a newbie who will going to El Mirage and Bonneville for the first time this year to experience some Land Speed Racing and get into the 200MPH Club. I have a +6" over catalyst street tail on my Busa that I planned on running. How far can the tail extend behind the rear tire before it becomes dangerous?
Thanks, Scott
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Scott
To begin do a Google search on Kamm aerodynamics.
It mostly talks about cars but handling exit air is common to bikes also.
The limitation of the area behind the rider is a product of an attempt to reduce the bad effect a cross wind might have of the ability of a bike to handle well.
To take it to an extreme and help to understand it, imagine a full sheet of plywood on edge and sticking out behind a rider.
It is no problem until the side winds turn up or you encounter the turbulence that surrounding objects like traffic might present.
It is more of a safety rule than anything else and effective handling the air within those boundaries can be very effective.
There is always a temptation to try to improve on it with a longer section with more area but always with a bad result.
Can AM Motorcycles did a very extensive testing project in the mid 70s that if available sheds quite a light on the variables.
In short, they went with the smaller limit.
Read up on it and let us know what you think.
"I feel it is better to point than hold your hand."
I can't speak for Larry. LOL
Jack
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That article on Can Am tunnel testing was in CYCLE Magazine a long time ago. At the time it was published, it was the most expensive article they had ever published. The result of their testing was the Can Am 125 that Bob Barker rode to a record of 137 MPH, as I recall. They had a fairing with a long tail. The idea was great but they ran the shorter version on their record runs. There was a foto of the bike in CYCLE.
FREUD
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I knew that would stir Freud. LOL
Legitimate mentions of safety are taken from experience and should willingly be shared.
A legitimate question deserves more than yes or no answer and direction to the availble research is best. :wink:
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Thanks for the info guys. I first thought Kamm was the fab guy who made Larry's tail. :-D After a little Internet search, It's all much clearer now.
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Thanks for the info guys. I first thought Kamm was the fab guy who made Larry's tail. :-D After a little Internet search, It's all much clearer now.
Was that a better way to answer ?
"Leading one to arrive at a conclusion you might already have will serve both better and point up any misconceptions for both."
"When you see someone beating their head against a wall, it is important to find out if they are trying to make their feet feel better or knock down the wall.
All of that might be done with a hammer with a better result either way."
.
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The Can-Am record was set at 136.537 mph in 1973.....with a fast run just over 138 mph...with a 125c.c. Rotax engine with 22 hp on fuel....todate the record has not been beaten and still stands. Extensive wind-tunnel testing was done on the bike in Canada
It was run with a long tail (seat)...but at 80mph
it handled so bad it was not safe. The streamlining. of the bike was so good that on the return run the engine locked up.... and still coasted thru at 133+mph. This was a factory effort by Can-Am. For the last 6 years the name of the rider has been misspelled in the SCTA/BNI rule book. But he does not care....the record still stands
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Dem old guys is sumthin ain't they ?
They might just have a bit of experience to draw on.
"Learning from the experiences of others is a big part of getting old."
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In regards to the Can-Am wind-tunnel test......
a complete write-up was done showing the results of the various configuration tested on a rolling test-bed (with the rider on board) The final fairing that was used to set the record can be purchased from Airtech. (Kent has the mold).
In past years I have given copies of the test results to some of the Land Speed Racers that race the small displacement bikes. I am at the present time away from home, however, if interested sent me a PM and when I get back home after April 5..... I will be glad to send out a copy. It is very interesting reading.....as far as I know it is the only published study done on
partial streamlined motorcycles. AH, YES, the good old days!!!!!!!!!!!!
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There have been a number of studies by Universities, Subject Matter experts, OEMs, and Sanction Bodies.
All have reached pretty much the same conclusion.
A lot can be easily learned from the Gravity Powered Vehicle association for example.
The most readable and hopefully understood of all that I have seen is the Cycle article.
You should take BOB up on his generous offer. 8-)
(I fixed a spello)
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Thanks for the info guys. I first thought Kamm was the fab guy who made Larry's tail. :-D After a little Internet search, It's all much clearer now.
Was that a better way to answer ?
"Leading one to arrive at a conclusion you might already have will serve both better and point up any misconceptions for both."
"When you see someone beating their head against a wall, it is important to find out if they are trying to make their feet feel better or knock down the wall.
All of that might be done with a hammer with a better result either way."
.
Pointing the new guys in motor sports in the direction of pertinent public research is always a smart thing. A lot of peripheral questions will get answered this way. I think everyone should do their homework when they plan on sharing a potentially dangerous play field with others. :wink:
I've been searching for photos of the 125cc Can-Am body work. So far no luck. But I have found some very interesting body work used before 1950. Sorry Larry for hijacking your thread.
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It is about streamlining and Larry started it !!!!
I think those "OLD GUYS" are a gang. LOL
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In regards to the Can-Am wind-tunnel test......
a complete write-up was done showing the results of the various configuration tested on a rolling test-bed (with the rider on board) The final fairing that was used to set the record can be purchased from Airtech. (Kent has the mold).
In past years I have given copies of the test results to some of the Land Speed Racers that race the small displacement bikes. I am at the present time away from home, however, if interested sent me a PM and when I get back home after April 5..... I will be glad to send out a copy. It is very interesting reading.....as far as I know it is the only published study done on
partial streamlined motorcycles. AH, YES, the good old days!!!!!!!!!!!!
bak189, I would definitely like to read that study.
Thanks, Scott (smcleod007@msn.com)
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I'll see if I can locate the foto that I did for CYCLE. It looks like space age.
Wasn't it KAMM (a German man) that did the research that stated that the shortened tail section was the
practical compromise to the extended tail?
A fellow named Ritter, who worked with Vesco, rode a 250cc Yamaha above 160 MPH with a copy of the Can Am fairing.
He stepped off at 160 when a crosswind caught him right at the final light on the return run of a USFRA meet.The fairing
was so narrow that he didn't have enough bar movement to compensate. Don asked him before he ran what he would do if the wind caught him. He told Don, "I guess I'll have to step off." At least he had a plan and it worked. He trhew his arms up into the wind and pushed off the pegs. His gloves weren't taped to his leathers. They rolled up and he had two small salt burns on the inside of his wrists and that was all.
He was uninjured and when we made it to the bike that was more than a mile on down the track, the front wheel was still spinning so fast that it burned a groove in my sneaker when I pushed on the tire to stop it from spinning.
The bike passed tech after it crashed.
FREUD
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As soon as I return home, Scott, I will get your address and send you a copy..............It should be kept in mind that this study was done in the early 1970's, and I am certain a lot more has been done since that time. Just one thing that I found very interesting in regards to seat-fairings.....
the sides of the seat (roadracing type) angle
showed best at 30 degrees...with the back of the seat open...and cut-off square. Very few seats that are being used these days reflect this thinking. But then again as I noted a lot more has been done since the 1970's. It's late and this "old" man is going to bed!!!!!!!!!!!!!!!!
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Part of what they learned beyond the performance gain was the cleaner the air stream behind the rider was made the less the next racer could keep up in the turbulent draft.
NASCAR on the other hand loves the draft and the related slingshot because it makes for better crowd entertainment.
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What I've gathered so far on the truncated Kamm tail section is, is that the amount of aerodynamic slipperiness gained by tapering out the rear of a vehicle to an aircraft style point or edge makes the vehicle less practical to use on the ground except in a smooth straight line with no wind changes. In a passenger car, storage capacity, ease of access and parking far out weigh a few miles per gallon. What Kamm found was that you don't need to make a long tapered surface to effectively recombine the air as it travels around an automobile. All it takes is that the rear of the vehicle needs to narrow the back end enough to get the recombination flow started smoothly.
Having read an Internet article on Kamm's findings and knowing some basic aerodynamics, this is how I would apply the information towards my safety on a motorcycle zipping around at very high speeds.
Adding a longer tapered tail section in most cases will smooth out the air flow in a straight line.
The safest and quickest way to find your optimum shape and size is to have free access to a 250mph wind tunnel.
Even after designing a perfect slippery tail section in a wind tunnel there's no guarantee Mother Nature is going to let me use it.
The farther the tail extends past the rear axle, the more leverage it will have to move the bike around during bad turbulence or cross winds.
In the air, a plane with a big tail section in bad turbulence or cross winds will pitch and yaw but its not that big a deal since you have 3 axis of control.
Momentary pitch and yaw on a motorcycle at speed is a very bad thing. :-o
That being said. It would seem that the small performance gain from using a long tail section is out weighed by the risk of "loss of control" on a motorcycle at speed.
Am I on the right path here?
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Seeing that we are now on aerodynamics (Sorry Larry)....as a "old guy" I would like to point that the old vintage type fairings that we ran in roadracing on bikes with only..........maybe 60hp
on the high side...... had very good aero....One fairing that comes to mind is the "Peel" fairing
developed for the Isle of Man races....this fairing really works. In today's Vintage Races this fairing is still being used with great success.........
the RC Barker Eng. 500c.c. Norton Manx runs a consistent mid 140mph in the Daytona Vintage Races using a Peel. I feel a lot of the outstanding
speeds we are seeing today is horsepower
and not aerodynamics.....this is is somwhat proven by the fact that in order to go really fast one needs around 250lbs over the rear wheel to get traction. Us "old" guys did not have much horsepower to work with.... so we worked on Aero....
Don Vesco understood this better than anyone....
and his many records and roadrace victories prove the point.
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NASCAR on the other hand loves the draft and the related slingshot because it makes for better crowd entertainment.
NASCAR loves anything that keeps cars bunched together and crashing. On the other hand NASCAR hates anything that resembles real racing. They're also making a big thing about cheating while any legal innovation that provides an advantage is penalized to make all cars equal again. This leaves cheating as the only innovation that gives you an advantage you can keep. At least until you get caught.
John N
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You guys are wonderful.
All of this from the faithful and not the leadership.
It kinda makes you wonder what lead the rulers are taking.
There is hope.
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Bob,
Give me the correct spelling and I'll fix it.
DW
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Dan, you were supposed to move your clock forward in the spring, not back, you are up and on the computer too early.... :roll: