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 Any car-physics experts around?

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unfairlane

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Anzahl der Beiträge : 26
Anmeldedatum : 2010-08-01

PostSubject: Any car-physics experts around?   Fri 01 Oct 2010, 5:02 pm


I`m trying to make a league out of the many great musclecars that has been made lately but I find it a bit hard to make them compatible.

I do not know too much about how to modify the car-physics, all I can do is to uppgrade tyres, put in some equally tuned race-enegines, change gear-settings and (try to) adjust the carweight a bit closer to the real thing. Btw; some of the cars has wery strange weight-numbers in hdc & sp-files; shouldn`t these files correspond/show the same weight-values?

Now if there only was a car-physics tool to make all these numbers understandable.


Dyno 2003 is a good tool to make realistic enegine-files, free downoad here:

http://loco4fomoco.com/video.html

- just search up and add the needed head-flow and cam-files Wink
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unfairlane

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Anzahl der Beiträge : 26
Anmeldedatum : 2010-08-01

PostSubject: Re: Any car-physics experts around?   Mon 11 Oct 2010, 9:54 am


To follow up this; here`s one example of strange physics on big US-cars:

HDC-file:

Mass=1493.0 // all mass except fuel (1283kg car + 75kg driver weight)
Inertia=(2180.25,2443.82,426.88) // all inertia except fuel

Still the same car, now SP-file:

[BODY]
name=body mass=(1142.0) inertia=(1081.0,1210.0,177.0)
pos=(0.0,0.00,0.0) ori=(0.0,0.0,0.0)

Shouldn`t these files correspond?

Another car, same class:

HDC-file:

Mass=1565
Inertia=(1190.933,1558.327,367.543)

SP-file:

[BODY]
name=body mass=(1090.0) inertia=(1239.0,1387.0,170.0)
pos=(0.0,0.00,0.0) ori=(0.0,0.0,0.0)

And so on.

Since I have no references I`ve just putted in some deacent numbers to equal out a bit, like this:

HDC-file:

Mass=1540
Inertia=(1540.0,1560.0,360.0)


SP-file:

[BODY]
name=body mass=(1540.0) inertia=(1540.0,1560.0,360.0)
pos=(0.0,0.00,0.0) ori=(0.0,0.0,0.0)

Mybe a bit heavy for a car in race trim but at least corresponding values.
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streckensau
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Anzahl der Beiträge : 79
Anmeldedatum : 2010-06-23

PostSubject: Re: Any car-physics experts around?   Mon 11 Oct 2010, 3:54 pm

Hi unfairlane,

the values you mention look a bit like NFS??

the mass is as you stated the static weight of the car - e.g. the SCCA cars should have around 1100-1200 kgs w/o fuel or other liquids nor driver - which makes a total mass of around 1180-1300 kgs - the value needed in the .hdc

the inertia is calculated by means of a complex integrale formula with torque, mass, speed of objects and some more issues. For the sim cars I normally use experimental values - calcuted by rule of thumb. So for let´s say the Mustang I´d use with 1180 kg weight 1160 N in x-axis, 1400 N in y-axis and 300 N in z-axis. The Center of gravity will be due to a live axle at +260 mm from ground. You need to experiment a bit with because it corresponds with the tire grip levels and torsion values and the aerodynamic forces. The higher the aero forces, the higher the possible inertia can grow. Since the inertia is a dynamic force, the static values in the .hdc may not be as close to reality as we experience it while driving a real (race)car.

The values in the .sp file are valid only for a specific part of the car, the complete body or any hinges, wheels and so on. Thus the values are different from the .hdc

Maybe this will help you in finding the desired values

Cheers streckensau Cool
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