Re: gearmotors,encoders

--- In CAD_CAM_EDM_DRO@egroups.com, dave engvall <dengvall@n...>
wrote:

> > Hi,
> >
> > Just did a little experiment, I like to have data backing up what

I

> > say, otherwise my mouth (or fingers in this case) gets me into
> > trouble.
> >
> > I took a 36" length of steel tubing (1" OD, 3/4" ID, uncertain
> > parentage regarding alloy) and clamped it in a vise at the far

end. I

> > superglued a mirror sliver at the other end and trained a HeNe

laser

> > on it. I put a torque wrench to the same end and cranked it until

the

> > reflected laser beam on the wall indicated a torsional angle of

0.1

> > degree (equal to about 1 count on a 1,000 line encoder). The

wrench

> > indicated 47 to 50 in/lbs torque, or about 800 in/oz.
>
> Right out of Machinery's Hdbk. pg. 265 24th ed.
>
> alpha = 584*T*l/D^4*G
>
> alpha = 584*50*48/0.586*11.5E6
>
> ie torsional deflection in degrees. Using 7/8" dia ....probably a

good avg for 1" ball screw....800 oz-in torque and 4 ft length

> gives 0.2 degree or 1 count for an 1800 ct. encoder. This should at

least give a ball-park figure (no pun intended).

>
> Dave

Hi, it's always sweet when theory and experiment agree (within
experimental tolerance).

Mariss