Re: Physics is...

[Orin Eman <orin@wolfenet.com>]

> >------------------------------
> >
> >Date: Tue, 10 Mar 1998 10:42:44 -0800 (PST)
> >From: Orin Eman <orin@wolfenet.com>
> >
> >> >Given this, I think we can remove any quantitative treatment of
> >> >speed differential and say if there is any speed differential,
> >> >max torque is going to the slower turning shaft.
> >
> >> The torsen is not a binary switch. The amount of torque shift 
> >> depends upon how much the two driveshafts resist turning, and 
> >> the difference between the two.
> >
> >Quite true, it is not a binary switch, what you say is absolutely
> >correct _if the shafts are turning at the same speed_.
> >
> >I said 'if there is any speed differential'... for there
> >to be a speed differential, all the friction surfaces must in
> >the torsen must be slipping, therefore all frictional forces must
> >be at their maximums, therefore torque split is at the maximum.
> >

> no orin, this is not what the torsen paper describes the torsen as doing
> (despite the 'weasel words' in section 5.2).  reference the figure on page 3
> and this show a *linear* relationship between speed differential and torque
> transmitted.

The version on http://www.mindspring.com/~audidudi/Torsen.htm
doesn't seem to have this figure, nor page numbers, so I'm afraid
I don't know what you are refering to.

> >If then max torque split is more than one shaft can take, it spins of course
> >and speeds up to the speed of the faster axle.  Once it reaches that
> >speed, then torque will probably go to the other axle.
> >

> no again, rotational speed has nothing to do with it, rather the torque
> reaction of each axle to the torque being distributed.  on decreasig torque
> reaction, torque is transmitted to the other axle, governed by the bias ratio,
> until both axles exceed their torque reaction limits...

OK, you are right, I went a bit too far with the 'spin up', though I
wouldn't go as far as to say that speed has nothing to do with it...
The weasel clause is beginning to make a lot of sense...
Torque will shift to the slower rotating wheel, up to the maximum
of that wheel's traction or the bias ratio, whichever gives a smaller
torque.  If conditions change such that the slower turning wheel
cannot support that torque, it will slip a tiny bit, enough to
unload those fancy gears, hence transfering torque to the faster wheel.

So, we have the initial condition of rear wheels turning slower,
getting max torque, then later torque shifting to the front as
conditions change - the oversteer then understeer that Scott
has described.

Orin.