I hope someone could verify/help/alter/add on my design calculation of an electric vehicle (in my case is a powered wheel barrow,3wheel, 2front wheel,1 back wheel castor, dc electric motor powered 2 front wheel). The specifications are: Speed : 2m/s maximum Weight : 150 max kg Gearbox :step down gearbox (this is compulsory, so I don’t have a choice using a speed controller) I started off by calculating the torque requirements for this vehicle : The forces are rolling resistance, acceleration and slope requirement. Mass Force exerted on the wheels = 1500N I assume the coefficient of rolling friction to be 0.1 Rolling resistance,Fr = Cr*N = 0.1*1500 = 150N Slope requirement,Fs = 1 on 5 = 1500*0.2 = 300N Acceleration, 0 to 2 m/s in 2 seconds F = m*a =150* (2-0)/2 =150N Total force required (worst possible case) =150+150+300 =600N Total torque require at wheel end = 600*(wheel diameter,D) = 600*150mm =90Nm Before I start the motor selection, I am using a Step Down gearbox with a maximum rpm input from the motor of 2000rpm(assuming 100% transmission efficiency). The gear ratio varies from 17:1 to 68:1. I find the wheel diameter which I have use for calculating torque by using the relationship : Rpm = speed/phi*D I know the output rpm and by selecting different diameter of wheel the range of speed would vary accordingly. I have found out that a 150mm diameter wheel would give out a maximum speed of about 2m/s which is the max specification speed. I choose a bosch 24V 750Watt http://www.boschmotorsandcontrols.co.uk/elektromotoren/produkt/0130302001/index.htm Nominal voltage UN 24 V Nominal power PN 750 W Nominal current IN 40 A Nominal speed nN 3300 min–1 Continuous torque MN 2,2 Nm Breakaway torque MA 11 Nm Direction of rotation L Type of duty S 1 Degree of protection IP 10 Weight approx. 3,8 kg Part number 0 130 302 001 The motor will be gear down about half so that it can be use for the Step Down gearbox which have a maximum input rpm requirement of 2000rpm(I realize that this will make the max speed lower than 2m/s but it will almost double the torque). The total torque require to overcome is 90Nm.sice the breakaway/stall torque is 11Nm, the output torque is : Motor torque =11*(gear ratio to Step Down gearbox)*(lowest gear ratio of gearbox) =11*2*17 =374Nm>90Nm So I conclude that the motor is sufficient enough to perform the task. questions that i am trying to find out : a)Is the calculation for the total torque requirement ok? Do I need to include anything else(such as static friction, inertial body force)? b)Is my torque output calculation valid?