I picked up at a ham swap, two low speed Servo Motors that controlled a tape reel,
used in an old 9 track 2400 ft reel-to-reel .5 inch wide computer tape drive. They say
"permanent magnetic servo motor" and have two wires coming out of each motor.
The way to check the efficiency and whether these things are still operational is to electrically hook them together. Hook the black wire on one unit to the black on the other unit and the red to the red. Then, if one turns by hand back and forth one shaft on one unit, the shaft on the other unit will rotate and do the same motion at the same time. What this is saying is the one unit being turned by hand is generating enough current, as a generator, to turn the other one as a DC motor. One can then do this motion slower until slippage occurs due to not being able to overcome the friction of the bearings. In this way one can get a pretty good idea of the efficiency of these units as a slow speed generator and motor. These passed the test.
The units are extremely sturdily built being 5.75" long and 4" in diameter and have a .65" diameter shaft with ball bearings each end. They have 4 separate brushes in each unit. They have a heavy duty flange with 4 holes for mounting. They came with the hub that clamps onto a reel-to-reel type tape still on the shaft. This is not the capstan motor, this is the one that drives the tape reels. I plan to use the inside aluminum ring out of an old tape reel to clamp-mount it on the hub, then mount this hub-ring unit in contact with an exercise bicycle wheel. The result will charge one 12 Volt battery or possibly two in series. I was told they were designed to be operated at 28 volts. At this time I am not sure how much power can be generated without causing a problem. My cost was $15 for both.
If the plan was to use these units outside in a small windmill then the housing and ball bearings would need to be made water proofed in some fashion. The model and company that made them are:
1600 Second St. So.
Hopkins, MN 55343
I think other reel-to-reel tape drive hub servo motors independent of brand should also
work. Just check them out as noted above before you purchase.
Offered by Mike.