RE: Dave E. - you're making the wrong assumptions (re-send)

[David Eaton <david.eaton@computerland.co.nz>]

now scott, we're really getting into the 'what ifs' now aren't we?

so, we're really overcooked the corner, so much that the rears have *no*
forward motion, only sidewards slip, and the fronts are still going
forward?  pretty radical cornering dude...

to your points...

>-----Original Message-----
>
>Date: Tue, 3 Mar 1998 11:54:32 EST
>From: QSHIPQ <QSHIPQ@aol.com>
>Subject: Dave E. - you're making the wrong assumptions.
>
>Dave you are missing the biggest point.  Look at it this way, take a car any
>car go into a turn at 50mph, lay it out sideways, steering with the skid,
>what
>happens?  The rear tires will stop ALL forward rotation, the fronts, since
>they have a lower slip angle, w
ill still have forward rotation.  REREAD this.
>Now, go at that same turn with your Torsen q.  The physical properties of
>that
>track and slip didn't change, YOU have to change them with power or lift
>throttle.
> 
>What does the torsen think of this disparity, accel on?  IT assumes the
>differential between the slower rear driveshaft and the faster front to mean
>that the faster front is spinning.  Takes Tshift and puts it to the rear, YOU
>don't have to lift a wheel for this to happen.  AND you haven't equalized T1
>to T2, because you haven't done anything to reduce forward traction (which
>reduces transmitted Trg).  As soon as Tshift goes forward, the rear wheel
>slows again due to track NOT traction, and you hunt Tshift again, btdt.  NO
>lifted wheel.

not it doesn't.  i accept that at the worst, in this scenario, the
torsen will supply t(min) to the front axle, and t(max) to the rear axle
(given *no* rear axle rotation).  in this case the torsen will pull you
through the
corner with t(min) to the front, progressively dialling in more torque
to the rear as the rears gain longitudional traction.  in reality, the
torsen will apportion as much torque to the rear axle as it will
support, the rest going
to the front axle.  this is what you want....

the generation 1 locker will do the same thing, except that t(min) will
be greater for the fronts (at 50%), than the 30% available to the
torsen.  a win to the generation 1 manually locked diff.

but then we've seen that the wheel lift scenario is a win to the torsen
over the gen 1 locked diff.

however, most oversteer that i've ever had experience of involves
sidewards slip due to the increase in longitudional traction being
demanded of the wheel (classic definiton), overcoming cornering and
traction adhesion.  in this case the effect of which you speak doesn't
occur due to the higher rotation of the rear drive shaft than the
fronts.  in this case torque is removed from the rear axle and sent to
the front, which is exactly what you want.

so where's the hunt?

>Dave, frustration is high, I understand.  FORGET wheel lift, you don't have
>it
>in my scenario, so Trg stays at maximum, so does the Tshift front to rear.
>Understand, you can have a rear wheel spinning, and not have Tshift OR a
>reduction in Trg.  By definition of the center torsen in a turn.  Reread page
>10, the unlikely has to do with a torsen on a common axle, NOT a Center.
>This
>is the physics of the bite.  You don't understand it, that is different from
>the reality of maximum traction in a straight line, and a torsen center in a
>turn.

no you can't scott.  thats not what it says on page 10.  you have a
wheel spinning and you have maximum t(shift) with the torsen and also
with the manually locked generation 1 diff (not shift in this case as
much as
modulation).  the determinant here with the torsen is t(min).  if t(min)
torque causes wheel spin on one virtual axle, then t(min) *stays* to the
axle (and disappears as wheel spin).  this is a *good* thing.  the
generation 1
manually locked centre diff will *also* do this.  torque will
'disappear' to the axle in this case (ie. 50% of  torque to the spinning
wheel).

so with the torsen you have maximum torque loss of t(min) (30% with
quattro), while the manually locked generation 1 cars have a maxiumum
t(min) loss of 50%.  win to the torsen.

dave
'95 rs2
'90 ur-q