Front wheel drive and two wheel drive on bikes?

[kiwi]

Is this allowed for Special construction motorcycles? I couldn't see anything in the rule book, though I may of missed it.
I haven't got any particular design in mind yet. Thought it would be best to see if it was legal before giving it some consideration.

[Glen]

NO, front steer and rear wheel drive.

[sheribuchta]

Glen, could you point out in the rule book where it says that  for special construction .



thanks  Sheri Buchta

[Glen]

Sheri
It's under streamliner, (also special construction) PG.113 - 7.H. This question has been asked before and as I remember it's for all motrorcycles. Best to verify with Tom, or Van.

[sheribuchta]

7.H is for streamliner only .



    Sheri Buchta

[kiwi]

Any idea of what the reasoning behind this rule is?
I know a rear wheel steer bike is difficult, maybe even impossible to achieve. But if someone could come up with a steering geometry that worked, and proved to control the bike well, why not?
I can't think of any safety issues with driving the front wheel if engineered well. I was thinking it might improve stability by being able to build a bike with a more forward weight bias. You could get the traction you want and the C of G would be moved further ahead of the C of P.
This being said I have never ridden a front wheel drive bike so I don't know what controlability would be like with wheelspin. 

[Milwaukee Midget]

Would you really want the front wheel applying power to a loose surface and controlling direction, too?  While the handle bars only turn the front fork, the whole bike is involved in the action of steering.

The penny farthing bicycle drives the front wheel and steers, too, but that's a tad bit slower than the speeds we'd be talking.

Forklifts use the rear wheels to steer.  It's been my observation that directional stability decreases with speed with such an arrangement.  Over steer is notorious.  I'd have a tough time imagining a geometry that would improve that situation, especially with only 2 wheels.

[saltwheels262]

i agree with mm .it's not safe.
too much steer at speed would upset bike and rider.(easy to do w/rear steer)
wouldn't it be easier to get weight bias and better traction with ballast placement?
or a custom frame? 

franey

[1212FBGS]

Not a new concept been done and failed before... pretty sure that's what killed Rokon motorcycles... Yamaha tried it a few years ago as a concept on a dirt bike, hasn't come into production...  You can try it under 7.A.4... but im pretty sure the SCTA would evoke 7.B.14....
Ya see an inherently unstable vehicle like a motorcycle requires gyroscopic force and coefficient of friction to stay upright... a lean angle to make a turn requires a slip angle of coefficient in order to initiate a counter steer on the contact patch.... In other words you need firm contact patch on the ground with the front tire... now if you happen to loose that contact because of power delivery... "Boom" glen rolls the crash truck ...  Not a dumb idea, I just think a smart person wouldn't try it....
Kent

[Dean Los Angeles]

Glen's reply is pretty typical.

A rule book either specifically includes or specifically excludes items. If it isn't mentioned, it's legal. Not even close with SCTA.

Front drive or rear steer for a motorcycle are technically legal because they are neither included or excluded. Neither one are safe and that is where Glen's reply comes from.

And safety isn't the only area. Interpretation over what is allowed for streamlining is as wild and wooley as the old west.

Just because it's not in the rule book don't plan on building unless you have something in writing. There is a ton of things that are not in the rule book that won't ever pass tech inspection. Or pass tech inspection and fail impound.

Don't ever take what anyone says verbally. Get it in writing in the log book. Because interpretation swings wildly from one guy to the next, what might be ok with one inspector, or all of the inspectors, this year, at this place, doesn't mean the next guy or a different place won't get you in trouble.

And if the inspectors are happy, your competitor can always protest.

If you feel that interpretation is wrong, you can always take it to the next level. Fight for what you think is right.

Don't you just LOVE racing?

[McRat]

I think the instant you start to lose traction from acceleration, it will be a bear to keep balance.  Normally, the tire will climb under the CG point to correct balance, but if the tire is spinning, it will actually accelerate the fall by applying even more load on the contact patch.  Ever ride too fast on wet leaves or ice?  You go down the instant the front tire slips.  If the rear slips, no biggy if you don't highside.  But the front is not forgiving.

If you had a very effective traction control system that would not permit slip, you might keep upright.

[Glen]

In the 2003 rule book it stated rear wheel drive only in special construction. I don't know when or if it was removed from the rule book. I have asked Dan Warner to address this and give us the answer.

[sheribuchta]

I went out to the shop and asked Willie about rear steer and front wheel drive. He said he thought that it was a great idea if you could find a transmission with 5 gears in reverse and some rear view mirrors for your helmet and a good medical insurance   
I can still hear him laughing as I type this letter.

Do they make a transmission that has five speeds in reverse?

Sheri Buchta

[Stainless1]

Kiwi, are you thinking of building a sidecar with front and rear wheel drive?  I see someone else injected the rear wheel steering idea  :|  we all know that is a bad one.  If you were thinking sidecar, then most of the arguments of steering safety are out the window and it could work.  Ask the question officially and be sure to let us know the answer.

[sheribuchta]

Sidecar, front wheel steering rear wheel driving only. Sidecar wheel can't steer or drive.
Sheri Buchta