RE:RE: A New Look at Torsens

[QSHIPQ@aol.com]

Chris Miller writes:
>OK, please clarify something for me.
>Take a track corner, assume a perfect surface, repeatable line, steering 
>angle, etc.
>As you go through the corner, the torsen will distribute torque at some 
ratio 
>between the front and rear axles.
Yes, any torque to the torsen is distributed.  Any turn with torque makes the 
torsen distribute other than 50f/50r 

>In a straight line, equal distribution front rear.
>while taking the corner, what will the ratio be?  

Depends on wheelbase, cf, rate of acceleration, weight of vehicle and radius 
of turn.

>Must it be either 50/50, or 25/75, or 75/25? or can it be in between?

Dave E's referenced paper would indicate that slip angle differences tend to 
make BR to the rear, up to the Bias Ratio of 75/25.  However, if a wheel 
starts to lose traction, then the BR changes again.  The exact BR rear 
depends on a bunch of factors, the biggest being wheelbase, cf and radius.

>Is it a three-state device (rear 75/25 front, or front 75/25 rear, or equal 
>50/50), or does it continuously vary the ratio?
Varies as you add slip angle, engine torque, weight transfer cf, etc.  As you 
unwind the steering wheel, the ratio varies again.  Think of it this way, a 
torsen with torque applied to it, ALWAYS varies the BR when you aren't in a 
straight line.

>  My understanding was that 
>the ratio would vary, and only on a full-lock turn would there be enough 
>difference between front and rear wheels to go to full bias ratio...

That's a relative slip angle argument.  When you lose traction, you lose the 
slip angle input to a traction input, indeed, the torsen can go to a full BR 
without full lock turning.  It can be either a relative slip angle argument, 
a traction argument, or a nasty case of both.

>If you take the same line at the same speed, same steering wheel angle, will 
>the ratio always be the same?

That's a lot of variables to control, I argue no one can consistently.  The 
next lap you take that turn, your effective cf has changed, just due to 
heating of the tires.  It's possible, get yourself Dave E's SAE reference 
paper for what conditions you need for that "claim".  Good luck.

HTH

Scott Justusson