Germanology

[QSHIPQ <QSHIPQ@aol.com>]

>Scott,
>I guess I still take issue with some of your terminology. 'Mechanics' would
be a 
>more accurate term than 'physics'. Torque shift is really a result of the 
>mechanics of the Torsen. Physics does play a part in all of this, because the
>operation of the gears, bearings and other mechanicals is governed by the
laws 
>of physics, i.e. friction, opposing forces, inertia etc. However, the Torsen 
>differential and its behavior was designed by mechanical engineers and
designers 
>using the mechanics of gear design and mechnical engineering design. -Just my
>engineering $0.02.
I argue physics applies more because friction is specifically absent to the
operation of the switch, as we would associate a clutch lsd, vc, or magnetic
plate switch.  Since there is not any "speed" in mechanical terms, only torque
in gear terms (worm or helix gears specifically), I believe a torsen to be a
more physical property alliance than a mechanical one.  I could take either
here, however, the model has enough variables, that computing friction loss in
a worm gear might overtax an overtaxed (pun intended Jeff) super cray.

>What I'd really like to know is, in your argument, are you stating that due
to 
>rear wheel slip angle alone, that maximum torque shift can occur?  I would
agree 
>maximum torque shift occurring in the middle of a turn could cause an 
>interesting scenario. However, from reading the Gleason white paper, my 
>impression is that it would take a significant loss in traction in either the
>front or back drivelines to cause a maximum torque shift.
No, understand, that paper is ONLY refering to fwd/rwd, and implies that awd
will have the same characteristics.  Except one huge thing changes with no
change in the Torsen design.  When you put it in the center, it is driveshaft
"traction" not specifically wheel traction that controls Tshift.  Front AND
Rear AND Relative slip angle becomes more variables.   In fwd and rwd, slip
angle is a constant and the opposing wheels 'angle' is insignificant to the
operation of the switch.  So, slip angle is constant to the driven wheels in
fwd/rwd, and a variable in a center torsen.  "Traction" is also redefined,
since in fwd/rwd, traction is the tires slipping.  In a center Torsen,
"traction" CAN be tires slipping, but "traction" can also be slip angle, since
in a center torsen, there is another set of diffs before the tires.  So a rear
tire sliding sideways is "seen" in by the torsen as the fronts spinning
faster, Tshift rear.  Remember, a torsen is ONLY a traction switch to ALL
inputs.  Including slip angle and relative slip angle variables.

>My understanding of 
>Torsen mechanics is that torque shift is essentially instantaneous, and is 
i>nfinitely proportional to the loss or gain of traction on a given output 
>driveline. In fact, the statement 'Since division of torque is automatically 
>achieved by the Torsen differential in proportion to available traction...'
from 
>the Gleason paper would seem to imply this. 
Yes, but 'available' traction in terms of slip angle also creates Tshift.
Think of traction as the FORWARD rotation of a wheel.  That's how the Torsen
senses it.  It can't compensate for any slip angle variables.  It doesn't have
to in a fwd/rwd application, cuz it's constant to the switch.

>I guess that given a type 44 (and possibly anything else) cornering near the 
>limits, it may not take that much torque shift to cause a variation in the 
>chassis dynamics. Whether the variations are good or bad is another question,
>and that could depend on the driver. One aspect that could be investigated is
>whether or not there is some resonant frequency or oscillatory mode of the 
>Torsen-drivetrain-chassis system which could cause problems. Since Urqs and
>type 44s have significant different dynamics, and different tires and
suspension 
>tweeks can have different dynamics, perhaps this could explain why some
people 
>experience the bite and others don't.
>If I'm just repeating stuff already discussed on this thread, my apologies to
>the list.
>Just being a curious observer...
Could explain it, tho I had it happen in a 90q.  Cf has a lot to do with the
significance of the bite.  Why?  Cuz in a wheel lift scenario (cornering hard
in dry pavement) the torsen reduces total Trg, center torsen acts a proper
traction device.  Hard to lift a wheel when it's wet or slick.  

I can easily explain the differences in the 44 and Urq with the following:
g = wheel thrust/weight
Weight transfer = (weight x cg height/wheelbase) x g 

So, no problem with Urq's not going so quickly as 44's.  But boy does lower cf
increase significance....  BTDT

HTH

Scott Justusson
QSHIPQ@aol.com