rec.autos.simulators

  Great timing, Gregor.  I just had this happen last night for the first time.
The car stopped, and the wheels went nuts.  It happened after I changed the cut
off speed for the low speed tire model and lowered the tire inertia by a factor
of four...  Will have to check it out, I knew this would happen.....

  BTW, you guys are handling limited slip diffs by keeping the differential
locked until the specified torque bias and preload are exceeded, then letting
the wheels accelerate away from each other according to the "clutch" torque
indicated by the ratio in torques across the diff, right?  This works really
well, it keeps the torque bias right on all the time.

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

currently I only have an open type differential implemented with a
viscous coupling. But if I did the proper locking, I would approach it
exactly the same way as you do.

-Gregor

Stupid thing of me; ofcourse acceleration is directly related to
torque through inertia. Was away for work when I realised it, duh, as
Gregor pointed out.
Anyway, I'll rethink the wheel locking thing. Real work is beginning
to swamp me again, and weather is getting nicer again; time for some
time off and enjoy the sun. :)

If I'm correct then though, keeping the braking torque as it is now
might get me incorrect accelerations using Gregor's original diff
eq's. But what for nearly locked wheels? This will be nearly equal to
a locked wheel, right? I'll have to look for overshooting the torques
and getting bad results when braking hard. Might be another fat bug to
squash.

...

On the C64, everything sounded cool as well, but only now do I realise
that most people could plainly hate it. ;-)
But ANY engine sound is cool, as long as it pitches. :)

...

Check out the source docs from Racer on my site; find
QLib/qsample.cpp; there's a piece of Wave loading down below. You'll
need WINMM.LIB I guess for some functions.

Try not to do it this way; it's a RIFF format (much like Apple's IFF);
very flexible.

Now on to real work, things are getting tight next week. Too tight for
fun. And at times like these, it's my phone that's crashed (well, the
central operation one, but that one won't reset), and my MS-Word and
printer makes my computer crash. Great! :(
Back to the Unix machine, ahhh. :)

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Free car sim  : http://www.marketgraph.nl/gallery/racer/

Can I ask which company that is?

this

And what class of car are you using: 1/10th, 1/8th, on-road foam, on-road
***, off-road?

Just curious!
Jonny

  Not just yet, I'd rather wait until it's released.  (Sorry :-))  

  It's on-road, but I forget exactly which scale and tire the 8:1 ratio was for
and can't find the blasted email that told me this!  

  No problem, wish I could give more info :-)

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

  Great.  It's nice when I finally do something right!

  Thanks,

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

  Well, it was quite a revelation to me when I discovered it could be done
directly this way rather than trying to calculate the actual driving torque at
each wheel independently, then derive acceleration from that afterwords, so I
know what you meant.  Not stupid at all :-)  As far as the weather goes, I
suppose if I had any sort of life at all, I'd be out enjoying it now too ;-)

  >If I'm correct then though, keeping the braking torque as it is now

  I haven't seen his diff equations and haven't tried a viscous differential
yet, so I really don't know what to say for that.  I do know that I'll need to
take another look at how I'm locking the wheels across the differential though.
 I plan on still using either totally locked or unlocked states and checking to
see if torque from slip ratio is enough to overpower the brakes before they are
allowed to unlock again.  This works really well so far, but it does need
another close look to make sure it's really right.  When the car's stopped, the
wheels may want to rotate in opposite directions.

  I figure you might as well stick to how you're doing it now since the tire
data isn't going to be spot on with a locked wheel anyway.  I suppose this does
let the slip ratio equations work, since the wheel velocity never actually hits
zero.  Now, I check for this with an IF statement set which probably isn't as
fast as your method.

 >Check out the source docs from Racer on my site; find

  Ok, I'll do that, thanks.

  I'll have to check on the RIFF thing too.  Unix?  What's that? ;-)

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