1. The problem statement, all variables and given/known data This is a final hurdle of a long question designing a simple gear train. That is done but now am not sure of my calculations for power in / out and torque in and out, so hopefully someone can help? OK - I have 4 spur gears inline, Gear A = 100 rpm 80 Teeth (input motor - unknown power?) Gear B = 160 rpm 50 Teeth (idler) Gear C = 160 rpm 50 Teeth (idler) Gear D = 400 rpm 20 Teeth (output against a load of 200 Nm) And ALL shafts carry a frictional resistance of 5 Nm 1/ What is the input power at shaft 1 (gear A)? 2/ What is the efficiency percentage? 2. Relevant equations P = TW T = P/W T1 x W1 = P input 3. The attempt at a solution I have done the following: (TA x WA) - (TB x WB) - (TC - WC) - (TD - WD) = ZERO And TA x WA = Power input Convert the rpm to rad s: Gear A = 100 rpm = 10.47197551 rad s Gears B and C = 160 rpm = 16.75516082 rad s Gear D = 400 rpm = 41.88790205 rad s Input Power (Pi) = (TB x WB) + (TC x WC) + (TD + WD) = (5 Nm x 16.75516082 rad s) + (5 Nm x 16.75516082 rad s) + (5 Nm + 200 Nm x 41.88790205 rad s) Input Power = 8.755 Kw Torque in = Input power / WA = 836 Nm Torque out = 205 Nm Power out = TW = 205 Nm x 41.88790205 rad s) = 8.587 Kw Efficiency = Output power / Input power = 98 % Does this look correctly tackled? Any advice very welcome!! I like the 205 Nm out as the gear ratio is 1 : 4 and the output is 1/4 input, which makes sense?