Hello. As many others here, I am starting a project that involves some engineering and will at some point, if I go ahead with it, require an engineer to design and certify. But for now I'd like to understand the principals involved and dust off some of my 1st year physics and see how much of it I can solve with some help from experts. The details so far: -hoist controlled by a microprocessor that can vertically position the payload with 1/2"-1" accuracy -payload of 24 kg max -wire rope hoist line, 1/4" diameter (my calculations indicate this gives a safety factor of 30 or so and electric hoist applications require SF of only 7) -hoist line length is 100 m and mass of that length of 1/4" wire rope is 16 kg -desired lifting/lowering speed is 1 m/s -desired acceleration is .5 m/s/s, when lifting that works out to net acceleration of 10.3 m/s/s -winch drum diameter is .254 m when drum is loaded with wire rope So the force required to hit that acceleration during lifting: F = ma, F = 40*10.3 = 412 N The torque I'll need from the motor to achieve that force when the drum is fully loaded: T = Fd, T = 412*.254*.5 = 52.3 Nm I also have these formulas for selecting a motor: Ts = stall torque Wn = no load speed so T = Ts – (Ts/Wn)*W and W = (Ts – T) (Wn/Ts) That's as far as I am now and I'm now running into the issue of which type of motor is best for this application. I spoke with a supplier of motion control equipment who advised using a servo. That's all fine with me since they are made to keep track of position. However, because the velocity of the payload will vary as the amount of wire rope left on the drum changes I am considering having a sheave with an encoder, remote from the motor and drum that the wire rope would run over. This way the actual velocity of the wire rope could be read. What I'm not sure of is whether a servo can use info from an encoder that isn't attached directly to the motor. Can anyone provide some insight here? And since I wouldn't be using the servo's inherent position tracking ability, would I be better off using a regular motor with VFD?