How do you make realistic car power transmission system? Engine is rotating at certain speed and causes torque that goes through clutch, gearbox, differential and brake to the tyre. I don''t know how to make this realistic way, how to get the tyre angular velocity, drifting, braking, engine braking and all this. I have rigid body oly for the car body. Do I need a rigid body for tyres too? And engine too? For all rotating parts that transfers power between engine and tyre? To achieve realistic result. It could be done with simpler angular-only rigid-body. But is there ''simpler'' ways?

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RacingTREME updated.

The angular velocity of the tire is simply: engine_rpm (rev/minute) / current_gear_ratio / differential_gear_ratio * (2*Pi/60) (units->radians/second). To compute edge velocity of
the tire simply multiply the number you just computed by the radius of the tire to get units in meters/second. You can simulate braking by applying a friction multiplier to the tire''s velocity.

Yes, that's the easy way.
But I do it the hard way

The problem is currently:
For each tyre I know the torque that came from engine, and the angular velocity of that tyre. I just can't get together the equitation to apply acceleration for car and for each tyre. Also brake torques should be applied somewhere. Also what is the feedback torque to send back to engine.
edit: Also need to know, what is the angular velocity of each tyre after the operation. There can be calculated the final engine rpm.

I'v got to think, think more...

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RacingTREME updated.



[edited by - stefu on January 12, 2003 5:35:53 AM]

Well, if you want the acceleration at each tire from the angular velocity of the tire it is easy enough to figure out as á = dù/dt. That is if you take the first time derivative of your angular velocity equation at the time for which you want to know the angular acceleration you will get the angular acceleration. To find linear acceleration from angular acceleration you simply multiply the angular acceleration by the radius of the tire. To incorporate braking torque is fairly easy because ô[total] = Óô so you simply add the brake torque (which should be in the opposite direction from the drive torque) to the drive torque and get total torque. Getting the torque applied on the driveshaft by the tire is slightly more complicated but can be found using the relationship: ô = F*r. To get the force applied onto the tire by the driveshaft you simply divide the applied torque by the radius of the tire. Now, because of Newton’s third law this same force is applied equally (with an opposite sign) to the driveshaft. You then take the force applied to the driveshaft and multiply that by the radius of the driveshaft to the the torque that is applied from the tires on the driveshaft. You can do this all the way back until you get to the engine if you want using the same principle.

Ok, I think I'v been thinking two days something too complex for me. I tried to get everything interacting realistic way, but couldn't match all things to work properly.

I know the basic pricniples, and got it working now with your rules. The only drawback is that I have to make it look like tyres behaving realistically (drifting, lockbraking, releasing, etc.). But I already have idea how to do this

Thanks for your time.

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RacingTREME updated.


[edited by - stefu on January 12, 2003 4:34:23 PM]