re: torsens

[eliot <eliot@eskimo.com>]

just to clarify a few things:

a locked center diff is every bit torque distributing as a torsen, except
that ratios can range from 50/50 to 100/0 and 0/100.

if you are travelling in a perfect straight line with equal traction
on all 4 wheels, torque is split 50/50 with a locked center diff.

if you put one axle on a dolly, the locked center diff will redistribute
torque 100/0 to the axle that is not on the dolly.

those are the 2 extremes and torque distribution will vary between those
depending on conditions.

the torsen's worm gears could be cut to give the same kind of 100/0 split
but implementations limit things down to 75/25 because they want to
prevent wind up on tight turns. 

likewise the viscous coupling can be adjusted to give vary between 50/50
and 100/0 split but real world implementations always allow some slip due
to normal turning manouvers.

the only other major point to note is that the torsen is completely
freewheeling under braking, whereas the VC and locked center diff
will attempt to redistribute torque if one or more axles lockup
under braking.  this is bad for ABS but good for competitive
situations where ABS is not allowed by the rules.


eliot