pic: Possibly Useful Contraption

[Fred Sayre]

They use globe motors and have a high reduction. They were originally used for satellite dish positioning. They are pretty heavy, but we took one apart and were able to take the weight down. I apologize I don't have any exact figures for that.

They do provide really nice mounting options, and the decent sized through hole offers some unique possibilities

I remember finding them for cheaper, but a google search turned this site up:
http://www.skycraftsurplus.com/index...OD&ProdID=1016

[sanddrag]

So, the current BaneBots backorder got me thinking about this thing again. So, I went and picked one up today. This thing is really neat, and particularly easy on the wallet ($16 with 20% off coupon). Oddly, mine came pretty much ungreased, which was actually a good thing. I first opened it up and filled it with abrasive rubbing compound, and ran it for maybe 15 seconds each direction on high speed from a cordless drill to wear it in, and then I flushed it out with solvent, and packed it with EP wheel bearing grease with moly. It spins pretty nice and smooth now. I noticed the outputs shafts are rather sloppy in the bushings which is somewhat unfortunate. Maybe about 20 thou under size, but that didn't affect its operation much. I tested putting 50 ft-lbs back-driving into the output (with no additional support on the shaft) and it held fine. It seems to be just on the verge of being able to backdrive. With any sort of other gearing coupled to the input, I doubt it would backdrive. Anyhow, I mounted the thing in a bench vise, rigged up a pipe and mass which put about 25 ft-lbs on the output shaft (again, no additional support) and I coupled a Ryobi 18V a cordless drill to the input shaft. Worked fine in both high and low gears. I noticed when powering the motor for the arm to go down, the motion is a little bit jerky, but it still works just fine.

I personally wouldn't use this thing as the final stage of gearing in an arm, but it seems like you most certainly could.

If somebody is struggling to get a gear reduction for an arm and you're out of money, this thing may be worth a try if you have the machining capability to adapt to its square shafts. And the input shaft is not a standard 1/2" square, it is larger.