gearing problem. Help please!

We’re running very light on mentors this year, so if you guys could help us out with some advice it’d be much appreciated.

we stole the CIM motors from drive team (2) so that we could have the high torque motors to lift tetras at the end of a long arm. The CIM motors run at 5000 some odd RPM and we are trying to gear them down to about 10. We cant find transmissions that would fit our CIM motors. If anybody knows where to find transmissions that would work with the CIM motors, please let us know.

Does anybody know if we can still use the Van Door motors?

Thanks so much,
687 Articulation Team.

Yes you can still use the Van Door Motor from Taigene that is in the kit.

As to a 500 to 1 gearbox with the Chiaphuas as input, this is going to be tricky.

10 RPM is mighty slow.

But if you insist on such a high reduction, I recommend using some sort of Jack Screw for the last stage. You can get relatively effecient ones with ball nuts. If you try to go with a straight spur gear gearbox, you are really going to have to beef up the last several stages. 1000N-m (2000N-m if you use 2 Chiaphuas) is a LOT to deal with, requiring very strong gear teeth.

Joe J.

In My Humble Opinion:

CIMs are much more suitable as drive motors. Use all four of them! For your arm, use the window motors, which have worm gears inside so they won’t backdrive (easily). If you need a third pivot point, use the van door, but it’s worm gear is significantly easier to backdrive.

CAVEAT: I’m a programmer, and this is all regurgitated information from our chief gearhead.

I’d give those CIMs back to the drive sys (I did the drive sys for my team and i made sure that I had all 4, so i mght be slightly biased)… If you need a gear reduction that big- the easiest thing to do is a worm gear- they have one heck of a reduction and will not back-drive…good luck

You can definitely get the Andymark gearboxes to use which can be found under the product section of … if you feel the need of more help, feel free to send me a message and I would go over a few process that you would need to go through with you in order to make your own gearbox. Good luck.


Unless you are trying to pick up 2 or more tetras on a >5 ft arm, you wont need these motors. 2 Fisher price motors would actually give you more than enough power, and all you need is a 10:1 chain and sprocket reduction. You could also probably use van door… or maybe even Globe)

Moral of the story… give those CIMs back!

If you use 2 of the KOP gearboxes in tandem, they are designed to handle the load of 1 chip motor.

This “double stack” will give you a reduction of:
= 1:162ish

From here you are a simple #35 chain reduction away from 500:1
(10:30 in chain gives you 488:1 overall)

Disclaimer, this setup can handle ONE CHIP MOTOR ONLY. If you run 2, you are toeing the line. But… honestly… with one chip - the stall load on a 4 foot arm is 130 lbs. Do you really need any more torque?

For more information on the “double stack” transmission, refer to the “FIRST 2005 Transmission Manual-RevB” found here:

Good Luck – feel free to ask questions about this feedback,

Don’t forget about a worm gear reduction system. May use up some weight really quickly, but you are using a cim. My team’s rookie year we had to do something like that. used a 25:1 at max gear reduction. I was only told about it but it worked. My suggestion would be to use a window motor instead, it doesnt rotate as fast and gear reduction should be a snap.

worm reduction or harmonic drive

And for the kit gearboxes, don’t forget you may be able to use an AndyMark Planetary and a fisher price instead of the CIM. Your outpur speed will be a little higher.