Hello, I'm in a design project of a cart. i want to decide a geared motor power and RPM. but I'm in a trouble with this because I'm unable to calculate the motor with radial friction.the cart is with steel wheel and drive on steel rails. place help. Total weight cart+carrying material - 4.5 Ton Radius of wheel - 80mm Required speed of cart -0.8m/s Thank you. Udaya.