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ZeroEffect

Cornering in a rear-wheel drive car

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I''m currently working on the simulating a car with real-world physics. The articles on the site have helped a great deal but I''m stuck on one issue... Assuming that a car is rear-wheel drive, and the driver has begun to take a corner by turning the front wheels, how can I calculate the sideways force on the car being generated by the front wheels based on the current angle of the tires and the current velocity of the car (assuming that slipping isn''t occuring)? Chris Z. ZeroFX Interactive

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It''s not exactly the front wheels moving that is causing the lateral force, it is the inertia of the entire body and its sudden change in direction. The car wants to keep going in the way that it has been, that accounts for body roll and other factors like that, if you are making this to be representitive of real world physics, you will have a degree of tire slip when cornering hard, if you are programming this with realistic handling but not modeling the tire action in real world then there would be no lateral slippage of the tires, i''m not really sure if i''ve helped, sorry i don''t know a calculation to figure out lateral movement

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The simple answer is you calculate it from the friction of the wheel contact. The wheels will roll without fricion in their forward direction. If they are turned while the car is travelling forward they cannot roll in that direction and they exert friction. Providing they are not turned too quickly they are able to exert enough friction to point the car in the direction they are pointing, so they keep on rolling. But if the wheels are turned too quickly/the car is travelling too fast the wheels cannot provide enough sideways friction and slip.

The sideways force is then the frictional force supplied by the wheels. It is different for the wheel rolling and slipping, and also depends on the road surface, the downward force on the wheel (which varies as the weight shifts in the car due to cornering, accleration, braking etc), tyre condition and temperature.

The other main factor is slip angle, which makes a small adjustment to the geometry due to tyre distortion, It applies at all times, not just when cornering, but is important when conrnering as it explains such phenomena as oversteer/understeer when braking & accelerating.

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