Quote:
Originally Posted by Bruceb
Well we are considering using a lead screw as well and I for one don't think there is a weight penalty. The conundrum I have is trying to figure out much power I need to turn the thing.
The JVN calculator is not usable for this as far as I can tell.
Can someone provide some math for this or a lead screw power calculator?
Thanks
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https://www.youtube.com/watch?v=FUNFcvnKQ-Q
Right at the beginning of this video, you can see our lead screw-controlled claw (something I wouldn't recommend for a variety of reasons--it was far too slow for that application, and complete overkill on torque--but we considered it for a lift this year). The motor and planetary gearbox are attached directly to the non-mobile part of the robot, and the nut is attached to (and able to pivot on) the "elbow". As the screw turns, the nut rides up and down on the screw, forcing the distance to change and thus pivoting the claw.
For a forklift, you'd have a simpler setup: The motor would mount in line with the carriage motion, at one end. The carriage would contain the nut, and as you turned the screw you'd lift the carriage up and down.
Calculating the torque/speed at any given power requires treating the lead screw like an inclined plane to calculate the mechanical advantage. (So if a single rotation of the screw has a circumference of 1 inch, but the nut moves .5", you have a 2:1 reduction.)
Efficiency really matters, though--they tend to be resistant to backdrive, but slower than you expect them to be, especially under load or if the screw bends.