Dave, I understand you wrote the physics engine for Viper Racing and Nascar
Heat if I remember correctly? Do these or any other sims you (or anyone else
for that matter) are aware of use dynamic roll centers and jacking effect due
to lateral/longitudinal tire forces?
Thanks,
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://www.racesimcentral.net/
| Hello,
|
| Dave, I understand you wrote the physics engine for Viper Racing and
Nascar
| Heat if I remember correctly? Do these or any other sims you (or anyone
else
| for that matter) are aware of use dynamic roll centers and jacking effect
due
| to lateral/longitudinal tire forces?
|
| Thanks,
|
| Todd Wasson
| ---
| Performance Simulations
| Drag Racing and Top Speed Prediction
| Software
| http://PerformanceSimulations.Com
I don't. ;-)
Have enough trouble figuring out realistic values for a static roll
center already. But it has been said here I think that GPL uses static
roll centers.
I don't know btw, but as my body rolls, the wheels roll along a bit
too, so maybe I could consider that as a sort of jacking effect (as it
moves laterally when the body rolls).
Ruud van Gaal, GPL Rank +53.25
Pencil art : http://www.marketgraph.nl/gallery/
Free car sim : http://www.marketgraph.nl/gallery/racer/
Cheers,
Steve Blankenship
Thanks. They're probably stuck in one spot then throughout the race.
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com
Yes, I recall that here about GPL as well. The jacking effect you're talking
about here should be a seperate force. If I remember right, you were
multiplying lateral force by the distance from the roll axis to the sprung
center of mass to get torque and wind up with load transfer. This is only
partially correct though, so check into it when you get a chance. The weight
transfer will not be correct if this is all that's done. The part you were
calculating gives the torque on the body, which eventually causes weight
transfer due to spring compression, however, the remainder of the weight
transfer is reacted directly through the linkages. This will make a big
difference in your sim because you're handling load sensitivity in your tire
model.
From messing around on paper, I figured that the jacking force exactly equals
the load transfer sent through the suspension linkages, but also lifts up the
center of mass. This is convenient, because you kill two birds with one stone.
I thought they would be seperate somehow, but they don't appear to be.
Anyway, I got a good chunk of my double wishbone system working yesterday. The
track width and camber change with wheel travel correctly as hoped, so now I
can move onto roll center calculations on the fly :-) Was hoping I might be
among the first to do it outside of the high priced engineering package area (I
think Gregor's been doing it awhile, and I'm pretty sure Chris does it.) :-)
Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com
