Hi, I am trying to solve a problem. I want to try to calculate the torque needed to make a crane move on rails. I attached simple drawing of a crane. i want to calculate torque needed for each one of the four wheels so i could try choose proper electromotors and reducers. I don't need exact calculations, i want some guidance at how it is calculated. P.S. sorry for my English, not native language but trying hard. P.P.S. dimensions in drawing are in mm.