> I should have added that if neither wheel is slipping, there is torque
> at both wheels.
>
> But you're saying that the following is a misunderstanding on my part.
> It is not correct. I thought sure I experienced this with cars stuck in
> the snow... maybe my imagination.
>
> ======================================
> Seems to me that in most cars there is a drive wheel and a non-drive
> wheel. If the drive wheel slips, you have no torque at either wheel, but
> if the non-drive wheel slips, you still have torque at the drive wheel.
> ======================================
Well, as Doc Nugent has already mentioned, it's frequently the same wheel
that loses traction first. Because of the gears involved, there is a torque
reaction at the rear that tends to lift one wheel. But, whichever wheel
slips first, the other wheel can no longer supply torque unless you have
some form of limited-slip differential. This is easiest to see with the car
up on jack stands, where with the engine running and in gear, you can stop
either rear wheel and watch the other one spin. Don't stop the spinning
wheel with your hand of course, but once it's stopped, you can easily hold
it stopped with your bare hand. In effect, the torque applied to each wheel
remains the same, regardless of their relative speed.
BTW, one technique for getting unstuck with one wheel on ice is to apply the
handbrake. If you're lucky, the brake on the spinning side will warm up &
grab better than the cold one, leaving a little bit of torque left to move
the car. Doesn't always work, but I've done it twice that I can think of.
Also BTW, a good junk yard test for a car with a limited slip diff is to
turn one drive wheel by hand. If the other wheel turns the same direction,
it has a limited slip. With an 'open' diff, the other wheel will turn the
opposite direction.
Randall
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