rec.autos.simulators

  I'm testing/debugging a rudimentary four wheel drive system in my car sim.
Suppose there was a center, front, and rear differential, all of the open type,
on a car with the same size tires at all four corners, and the same gear ratios
front and rear, and equal rotational inertias everywhere.  If this car was
making a tight low speed corner, where all wheels are clearly turning at
different speeds, would the road reaction torques to the tires be the same at
all four corners?  

  With a 2WD rear wheel open differential running with no acceleration, the
wheel speeds and slip ratios arrive at a state where the road reaction torques
are equal at both rear wheels.  Shouldn't this also be true of four wheel drive
with open diffs all the way around?  After all, the front two wheels can
accelerate towards or away from each other to equalize themselves torque wise
across the axle, and so can the rears.  I'm wondering because currently when
negotiating a tight corner with no skidding or acceleration, I wind up with
more road reaction torque at the inside rear and outside front corners...
Surely that isn't right, is it?  

  Thanks for any input,

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://www.racesimcentral.net/

we have the same problem here, we try to simulate stuff precisely, but we miss
telemetry data , we worked with TEAM who had WRC and Super 1600 cars,
i talk with a pilote, but he did't really know how the cars worked and they can't
give us telemetry datas.Anyway, our game is on PS2 so we don't have to be precise
as a simulation.

I never drive a 4WD cars for racing so i can't have an idea myslef.

However, what's it's true for left/right must be true for front/rear.but it's only
an intuitiv answer.

The thing i miss, is if you take a low speed corner, you must have more load
on front outside and less load on rear inside.

  Thanks for replying, Sebastien.  I'm talking of taking a very low speed
corner, maybe only .2-.4g acceleration or so.  I'm sure the tire loads are
different as you said, but even with a rear "only" open differential 2WD, the
slip ratios adjust themselves to the loads so that the road reaction torques
wind up being equal at left/right sides.  Suddenly with 4WD though, it's not
happening at either end, much less all four corners.  The front ring gear spins
at a different speed than the rear, but I figured that across each axle, the
torques would equalize anyway left/right, even if the front/rear split was
different (I'm not concerned with the front/rear split just yet).  Hopefully
I'm wrong though and a real 4WD open setup really works this way :0)  

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com