pic: 2010 window motor winch

[Tom Line]

Originally Posted by Joe Johnson

And equally important, how long will it take to lift you?

The window motors are basically 20W motors. This is pretty good but not with respect to the FP (almost 200W) and CIM (just shy of 340W).

Watts matter because speed and torque are just accidents of birth -- you can trade one for the other. Not fast enough, trade away some torque, get more speed. Need more torque, gear it down, give up speed, get some torque.

BUT... POWER is what it is. The peak power of a motor only goes DOWN when you gear up or down, it never gets MORE powerful.

If you are trying to lift a 120lbs motor 3ft in 10 seconds -- that means you need 54 Watts. If you only have 40Watts (the best you can do with 2 window motors at 12V) then you are not going to do that much work (lifting the robot that high) in that amount of time... ...no matter how you gear things...

For what it is worth.

Joe J.

Joe, that is the singularly best expression I've ever heard about how to pick a motor. I never thought about the torque vs. speed being an accident (not really an "accident" because you know what type of rotational inertia etc you'll end up with, but I know exactly what you mean).

I also never thought about looking at a motor from the energy side of things. I've always been more statically oriented, so I looked at torque - can I do it at that speed.... but the energy calculations make it a whole lot easier.

A light bulb just went on. Don't you love it when that happens?