Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders

> 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