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• # Help with Electric motor car calculations please.

Discussion in 'Calculations' started by arjg89, Apr 27, 2013.

1. ### arjg89New Member

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Hello,

I am new to this site and I would appreciate some help with some calculations. I am designing an electric car and need some answers to some of these calculations.

The car has to have a weight of 1.45kg, Including all components. And has to have a maximum speed of 2meters per second.

I need to calculate F
And if i know the radius of a wheel, how do i calculate the torque at the wheel driving along the ground?

Thanks.

2.
3. ### WmechMember

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Apr 2013
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what do you mean by F? Is it the normal force? or tractive force (friction force)? Once you have the friction force, you can find the torque by the multiple the radius of the wheel.

4. ### mhjones12Well-Known Member

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As Wmech said, the torque needed to have the wheel drive along the (flat) ground is the friction times the radius of the wheel. There is no way to calculate this friction. You may be able to make some very rough estimates, but you going to just have to build it and measure what the friction is.

5. ### WmechMember

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In any case, you have the speed of the car. you can simply do a conversion the car speed from meters per second to inch per minute. Then calculate your circumference based on your diameter or the radius of the wheel. Use the circumference and the speed in inch per minute to find your rpm.

As for the torque, there are two way to calculate that. One is to use the friction force and the other one is to use the rpm and the horsepower.

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