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car physics (again)

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dapope    122
Hello Everyone, Let me start of by saying thanks for all the great info Ive got from searching around here the last few days. Ive implmented a little c# application that takes torque values for a given RPM and calculates the horsepower, and ft-lbs of force at the rear tires for a given RPM. Im afraid I may of approached this solution the wrong way. Im taking torque values from dyno readings and building a curve based on RPM. I see others using wheel speed as the basis for torque. Im also curious as to the best way to simulate RPM build up. I want to be able to calculate the RPM for a given throttle setting for x period of time. This is a little outline of my thoughts, any help would e appreciated. Supply a max_rpm value, torque mapping diff ratio, and gear ratios. From this derive HP and ft-lbs of force at rear tire. supply a weight and drag coefficent and apply the above calculated force to the object and calculate acceleration. How would one simulate the easy revving of a car in neutral vs one in gear? I know I asked alot of questions, but any help from a newbie is appreciated :) -=dapope=-

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oliii    2196
that's the problem with modeling a car driving system from the wheel or from the engine.

the old school way is to set the engine RPM to the wheel RPM, which is deducted from the car's forward velocity. It's highly innacurate, obviously (does not count wheel spin, clutch control, and idle engines).

throttle @ RPM -> engine torque -> ratios (gear + final drive) -> torque at wheel contact point -> force on car -> new car velocity -> wheel RPM -> ratios -> engine RPM.

To do proper car engine modelling is more complicated. Revving up a car at idle, you need to consider stuff like engine internal friction, internal drag, inertia, most of it would be guesses and approximations. Stuff like gear box and drive train, wheels, and even the engine can be modelled as free wheels, interconnected via either links, cogs, the clutch, or the contact patch (at the tyre).

That's my take on it. Some people on these forums made some pretty cool car demos.

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