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Old 02-20-2003, 12:07 PM   #21
Grappelli
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Default Re: Yamaha's 2 Wheel Drive

It's been under development for 10 years, it's been on show for 5. I think you'll see it on one of the offroad bikes in the next 18 months.
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Old 02-20-2003, 04:04 PM   #22
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Default Re: Yamaha's 2 Wheel Drive

This could revolutionize road bikes too. It could allow 160 + HP bikes to use more of their power on the street. By reducing wheel spin and pushing back the "wheelie limit", motorcycles could accelerate much harder.
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Old 02-20-2003, 04:55 PM   #23
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Default Re: Yamaha's 2 Wheel Drive

The tire's tendency to "track" straight has nothing to do with tucking the front. Simply put, a tire slides when it's asked to give 100.0001% of it's available traction. If you aren't paying attention, this can lead to a slide. In the case of a front tire, this results in sudden understeer or "tuck" wich can easily result in low-side crash. Adding torque (either braking OR accelleration) to a tire that is already giving 100% of it's available grip, will result in that tire sliding, regardless of whether it is cornering, accellerating or braking.



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Old 02-20-2003, 04:59 PM   #24
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Default Re: Yamaha's 2 Wheel Drive

Damn man, I didn't realize you were a physicist as well as an investment banker.
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Old 02-20-2003, 05:02 PM   #25
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Default Re: Yamaha's 2 Wheel Drive

It would allow very long and very low bikes with wheelie bars that were already in contact with the ground, levering weight onto the front tire, to accellerate harder, but would have no effect on sportbikes. On a sportbike, traction is not the limiting factor to accelleration, because aside from power to weight ratio, center of mass is the biggest limiting factor to harder accelleration, due to the bike's tendency to wheelie under hard accelleration.
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Old 02-20-2003, 05:50 PM   #26
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Default Re: Yamaha's 2 Wheel Drive

But if the available torque is divided between the front and rear wheels than all of the motor's torque wouldn't be going to the rear which would lesson the likelyhood of a wheelie, right?



Isn't that why an all wheel drive car won't break the rear wheels loose and have better traction?
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Old 02-21-2003, 04:48 AM   #27
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Default No and no

Assuming tire radius of 1 foot (close enough for government work), thrust in pounds = torque in pounds-feet. Max torque at each wheel (before wheelspin) is then equal to the weight on that wheel. Max aceleration happens when the weight on the front wheel = 0 (wheely starts) or the torque applied to each wheel = the weight on that wheel. Since the sum of the weights = the weight of the bike the maximum total thrust = bike weight (if the coefficient of friction is 1).



Max thrust = bike weight x coefficient of friction whether 2wd or 1wd.



Since the weight on the front wheel when a wheely starts is 0, the front wheel motor will just spin the wheel.



AWD drives with enough horsepower break both wheels loose unless the CG is too high, in which case they wheelie.

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Old 02-21-2003, 05:00 AM   #28
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Default Re: No and no

That's what I was thinking (lol), but I just wanted to see how smart everyone else was.



Thanks.
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Old 02-21-2003, 05:05 AM   #29
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Default About counter-steering

Jean-Claude Olivier: "It makes riding much more relaxed when you don't need to counter steer... Since the rider does not need to counter steer and can avoid rear wheel slides, control of power becomes much easier. Unlike a conventional motorcycle where even an experienced rider will fight with a sliding tail end, the 2-Trac is much more controllable. All you need to do is lean into a curve, the bike will follow your command precisely and stays perfectly in the desired line."



Actually the 2-Trac has very effective power counter-steering. When the bike is leaned to the left the contact patch moves to the left of the fork pivot axis. Under power this produces a counter-steering torque to the right that induces more lean. With well designed electronics and geometry the bike produces just the right amount of counter-steer automatically and the rider just leans and steers left into the turn.
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Old 02-21-2003, 05:22 AM   #30
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Default Re: Yamaha's 2 Wheel Drive

On a sportbike, traction is not the limiting factor to accelleration



On the street, on street tires, with a light rider the CG and coefficient of friction can be low enough that traction can be the limiting factor.



On the track with CF around 1.3 you're definitely the expert, especially at your size.
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