Re: [CAD_CAM_EDM_DRO] Force versus torque for ballscrews was Re:BentNookballscrews ?????

On Tue, 2003-08-12 at 23:36, Jon Elson wrote:

> >By my calcs, it would take 500 lbs/31 inlb per lb = 16 in lb. The ratio
> >of force to torque for a 5 TPI ball screw is about 31 lbs / in lb.
> >
> >
> >
> This would make your ballscrews have a 50% power transmission efficiency,
> which is actually WORSE than an Acme screw! Regular 60 degree screw threads
> are supposed to be 40% efficient, I think. Acme is about 70%, ballscrews
> run at 90% or better. When lightly lubed, a high-quality ballscrew (even
> preloaded) is far better than your calculation above.
>
> Jon

How do you figure that, John ?

The constant of 31 is actually at 100% efficiency.

Here is the formula:

Force = Torque x 2 x pi x TPI x eff

With eff = 100%, you get Force = Torque x 31.4 where torque is in inlbs.
with eff = 90%, you get Force = Torque x 28.3
With eff = 50%, you get Force = Torque x 15.7

To get a constant for oz inches, divide by 16.

> --
> Kim Lux <lux@...>