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Pololu 20D motor part number decoder

I’ve been using your 20 D metal-geared motors for a while now, and wanted to use a motor from my spare parts bin in another project. Unfortunately I have forgotten the gear ratio for this motor, and I can’t figure it out from the part information printed on the motor body. The printed part information is:

FK-130SH-14225
DC/12V 170504

The ‘DC/12V’ is easy enough to figure out, but how do I decode the gear ratio from the rest of the information? I’ve looked through your information on the website, but I couldn’t find a part number decoder - can you help?

TIA,

Frank

Hello.

Unfortunately, the information on the 20D motor does not indicate the gearbox that is attached to it, but there are other ways we could potentially identify that. Can you measure the length of the gearbox? Checking that against the information in our 20D gearmotor dimension diagram should narrow down the possibilities.

From there, I recommend running your motor without any load attached, measuring its free run speed, and comparing that to our free run specs for each gear ratio. A tachometer would be the ideal tool if you have one, but you could probably just manually count the number of rotations the output shaft completes in a minute. If the output turns too fast for you to count, you can run it at a lower voltage and then scale it to determine the free run speed at the nominal voltage. For example, a motor that runs 600rpm at 12V should run 100rpm at 2V (12/2=600/100) , which should be much easier to count.

- Patrick

Patrick,

Thanks for the quick and informative reply. Hmm, I’m sure I can rig up a tachometer of some sort, but it’s a real PITA when I pull a 20D motor out of my parts bin and don’t have a clue regarding it’s gearbox ratio.

Have you guys ever considered labeling the gearbox? It sure would make things easier for us poor mortals ;-).

Thanks,

Frank

We do label our 20D and 25D gearboxes using permanent marker, but unfortunately that can rub off over time. Our 37D gearboxes have the gear ratio laser engraved, but we currently do not have that for our smaller motors.

- Patrick

Patrick,

Ah, now that you mention it, I do see some VERY light traces of red marking pen on several of my 20D motors. Might want to consider a more permanent system than ‘permanent’ marker pen, or at least put the marking on the shaft or rear end, where handling is less likely to rub it off. Now that I know this, I’ll be sure to label any further acquisitions using my trusty Brother P-touch label machine.

Frank