I have spent a while trying to work out a simple equation to give me the driving force of the engine in a car using the inputs: Power, wheel radius and rpm but when I put in real numbers from a production car, I get low values of 2197N. The equation I have derived is:(adsbygoogle = window.adsbygoogle || []).push({});

Driving force = 30*P/(rpm*r*pi) where P is the power of the engine in Watts, rpm is the rpm of the wheel after it is geared down, and r is the radius of the wheel.

Assuming there are no passengers or even a driver and the effects of friction and drag etc. are neglected, by my calculation of the maximum acceleration in first gear, given a car mass of 1420kg, is 1.5ms-2 which seems to me to be too low even for a slow car.

To derive the equation I just used, the equations P=Tw, Torque= Force*wheel radius and w = (rpm*pi)/30, where w is the angular velocity, T torque and P power.

Can anyone verify if this equation is right and whether I have done something wrong?

Many thanks

Regards

Paul Harris

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# Calculating driving force from wheel rpm, wheel radius and engine power

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