rec.autos.simulators

  It is already included.  When you calculated longitudinal force (Fx), that
was partly a function of load.  The wheel only cares how much force is
resisting acceleration, it doesn't care whether it's coming from grip or load,
or a combination of the two.

  I still don't understand how those formulas will let you directly calculate
the acceleration of the wheels and drivetrain if they are not in contact with
the road.  Aren't they giving you an "effective mass" to add to the vehicle
mass, causing the whole thing to lose acceleration directly, rather than
returning an "effective rotational inertia"?  Perhaps I need to look more
closely.. :0)
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://www.racesimcentral.net/

"effective mass" = "effective inertia" / (Tire radius)**2

that keeps the units correct as mass units.

If the tires aren't in ground contact, then the Tire radius isn't needed because
the force times radius term is no longer involved in the equation of motion.

So you can just use the "effective inertia" that has collected together
the effects of all the parts different rotational accelerations.

Be careful for the wheels not in contact application though.
I think that the gear ratio squared terms in the in contact equations
of motion come about through the combination of the accelerations
and also the ground force feeding back through.
For the wheels free case the useful effective inertia
may just have gear ratio to the first power:

torque = inertia * acceleration =  (i1 * a1) + (i2 * a2) + (i3 * a3)
          = ( i1 + G12  i2 + G12  G23  i3) * a1

for parts with inertias i1, i2, i3 geared together
such that  a2 = a1 G12,  a3 = a2 G23

- Matt

  Was I right about the list of equations in my other post?  I haven't tried
them yet, but did a little on paper.  Will take a closer look at what you just
posted when I have time.  (It's 1:45 am now, gotta get up in a few house :-))

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

...

I prefer to use them to get at a torque at the wheel, instead of
directly calculating the acceleration at the point of the formula.
It's then easier to separately include other forces; rolling
resistance, the road pushing back against the tire and ofcourse
braking.

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/

  Understandable.  I think I'll try it the other way first and see what happens
:0)  

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