# [torsen] RE: differential/torque sensing

QSHIPQ at aol.com QSHIPQ at aol.com
Mon Mar 31 07:52:03 EST 2003

```Andre:
Let's back up a second here...  Back to your "bike" analogy:
turn the bike upside down, pedal it so that wheel accelerates to 20 miles per
hour.  First, that takes a lot of force to do so, even on an unloaded wheel
in first gear.  But as you accelerate faster, you reach the limit of how fast
you can turn your hands = redline.  Now, after you have reached that 20miles
per hour, stop pedalling, and have a friend put his hand on the wheel and
rotate around the circumference of the wheel opposite the direction of
travel.  The reverse force is now on the "other" side of the gear (torsen
basket).  At a certain point that negative force generates negative rotation.
Nothing has changed to do so in terms of load on the gear.  The more
negative force you place on the gear, the faster these events will occur, but
there isn't a different force in terms of braking vs reverse accelerating.

Over to the torsen, this reverse torque sends the helix gear to the "other
side of the basket", so that more torque is allocated to the faster spinning
axle.  If you actually put the car in reverse while you are coasting forward,
more reverse torque is applied.  Eventually the car will come to a stop, then
it will start to accelerate backwards.  From a standstill, this force will
follow inversely weight distribution.  So, from a resting 50/50 state, slip
increases at the rear wheels relative to the fronts backing up, and more
torque goes to the wheels with more slip, up to the maximum bias ratio of the
differential in reverse drive mode.

So, in the above "unlocking" scenario, we know that torque is going to the
unloaded axle.  When does that change when in "reverse drive" mode?  I argue
it doesn't.

Thoughts?

SJ

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