Re: Torsen theory for Gary

[Orin Eman <orin@wolfenet.com>]

> Now, this whole arguement depends on several factors:
> (1) Does the torsen in fact redistribute torque to the rear wheels
>     when powering through a turn?

True.  Since this hasn't been quoted yet, here is an extract from
the infamous SAE 885140:

[40m radius turn, acceleration of 4 m/s^2, high-grip (uG approx 0.9)]

"...the front wheels follow a wider radius than the rear wheels on the
circular course, so that 0.2% of forced slip occurs _between_ the
two axles, which reduces the wheel slip under traction at the front
wheels, and reduces the slip at the rear wheels.  This results in the
tractive forces being redistributed towards the rear wheels, so that
the tractive force distribution is 38/62%.  The extent of this
redistribution decreases with increasing cornering radii and road speeds.
With small cornering radii and low speeds the extent of torque
redistribution can increase to the torque split limit of 25/75%.
[Orin: that shudder from the rear you feel in parking lot turns.]
On a high grip surface, the torque limit split is reached at
a radius of about 15 meters."

So, yes, absolutely, you can get 75% torque rear due to cornering alone.

> (2) Assuming #1 is true, how much does the rearward torque shift 
>     affect the attitude of the car?  (i.e. large or only small affect)

Good question.  This is the question that needs addressing.
Phil says aligment is crucial.   Tires matter too.

What does happen when torque goes to the rear?
Weight transfers to the rear, reducing grip available and
increasing slip angle at the rear.  This would appear to
magnify the effect, but it all started when you turned
in and would have reached some balance, maybe at the 75% rear max.

In addition, the weight transfer has caused suspension movement,
changing both toe and camber.  Whatever the camber change,
it too is likely to reduce grip and increase slip angles
since maximum grip is at 0 deg camber and you are unlikely
to be moving towards 0 deg at this stage.

Toe is the unknown at the moment.  It directly affects slip
angle - what is the static toe setting but an initial slip angle?
Any toe change due to the suspension movement is going to add to
or subtract from the slip angle changes due to the weight transfer
and that I believe is where we should be looking.

Scott, what are the slip angles?  Is a 1/6 deg difference
significant?  The SAE paper claimed slip angles of 2 deg.
Initially I thought the static toe setting would be insignificant...
but 1/6 out of 2 is about 8%.

Just more questions...  let me know if I screwed up on the
grip analyses.

Orin.