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[DPRG] I bought the wrong gearmotors

Subject: [DPRG] I bought the wrong gearmotors
From: Rick Mann rmann at latencyzero.com
Date: Sat Feb 26 01:17:59 CST 2005

I have two shiny new Pittman GM8724S021-R1 60.5:1 12V gearmotors with 
500 CPR encoders. I bought them for a project similar to DPA's nBot. On 
his website, he mentioned how he used similar 19.1 V motors. For a long 
time I put off buying motors because of the price ($195 each), but I 
finally decided to go for it.

Unfortunately, I didn't check the specs carefully enough, and my output 
shaft no-load speed is about 75 RPM, whereas nBot has more like 128.

The worst part is that the distributor wants a 50% restocking fee.

So, what are my options? A) I can sell them at a small discount to 
someone on the list, and buy new ones. B) I was going to drive my 'bots 
wheels with a timing belt & pulleys, so I can put a larger pulley on 
the shaft and recover some of the speed (not sure what this does to the 
efficiency). C) I can drive the motors at a higher voltage, but part of 
the reason I wanted 12 V motors was to not have to have a higher source 
of voltage, and I don't know what overdriving these will do.

Any ideas? Anyone want a beautiful pair of motors (they're really quite 



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