Ball Screws and torque

[seventofour]

I have a set of 4 ball screws, 2 inch diameter by 0.50", one in each corner to lift up a 12,000lb transformer. Each side will have one motor driving a right angle worm gearbox in the center that will power the two other right angle gearboxes that turn the ball screws.
I was given that the torque for each ball screw will be 1800in-lbs. But I am curious on how they came up with that value. I don't have much experience working with ball screws usually we do all Acme threads, or is the calculation similar?

Any help in double checking their calculated torque would be greatly appreciated, as I feel it is a bit low.

Thanks in advance to those who reply.

 

[tygerdawg]

Torque is determined by load, ball screw pitch, lifting (turning) speed, how fast to accelerate to speed, efficiencies, & safety factors. The difference between ball screws & ACME screws is efficiency, load carrying capability, and precision. Load involves all linear & rotational inertias. Review the Engineering Guides of almost any ballscrew manufacturer and they should explain this. Or websearch & download The Smart Motion Cheat Sheet for guidance.

If lifting slowly (as they should) then 1800 lbf-in does not seem unreasonable.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com