# Trying to Calculate The Minimum Force For Skateboard.

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1. Sep 19, 2015

### chuttney1

I'm building an electric skateboard. I am trying to calculate the bare minimum force and torque to move a 180 lb object on 4 polyurethane wheels from standstill for motor selection. I got lost in finding the coefficient of friction for polyurethane wheels and whether I am using the equation for rolling friction or the standard model used in schools of a big block with mass moving across a floor with no wheels.

Things I know I have to take into account are gravity, normal force, total weight of the whole system, force on each wheel, coefficient of friction and wheel size to find force and torque. Wind resistance is negligible.

Much help appreciated.

2. Sep 19, 2015

### Staff: Mentor

Rolling friction is the important quantity, together with friction at the wheel axle. Plus motor losses, those won't be negligible.

Don't forget a conservative safety factor as friction can increase, the ground can have some slope, wind might be relevant, and so on.