I think I scored on motors & ? how to measure rpms

[hyp7]

Hey guys I think I scored on a few motors from a salavage yard--- no they arnt the amtetek 99 but they are from an old computer tapedrive system 2 of the motors are indiana general stamped 24 volts at 800rpms the other 2 are ink stamped 36v so not real sure on the last 2. When I tried them with my drill they would get 14 volts with slow rpms of the drill. And also when you short the two leads together it is very very hard to turn the motor.

Also what is a good way to get rpms on motors,& rotor speed?

Thanks Gene

[ghurd]

Get the cheap bike speedometer.

(Google search the board for "http://www.dealextreme.com/details.dx/sku.2682")

A better search will tell how to set the computer to read RPM from the K/H reading.

Searching "Cateye mighty8 mity8 enduro8" may get some better hits too.

Those have certainly been sitting for a while.  Run the motor on a 12V battery for an hour or 4 to get the bearing grease and brushes a little smoother.

Put a magnet on the motor shaft.

Connect a motor to a fully charged battery at 12.7V or so.

See what RPM the motor is turning.  Add about 10% to get an idea of the cut in if used as a generator.

G-

[Bayesoft]

You'll need 475rpm to generate 14.25vdc of voltage with the first two.  Minus efficiency losses brings you down to 12.113vdc.  What is the rated rpm of the other two?  Amps?