Gears for CIM

I am in charge of designing a swerve drive for my team. I am having touble finding a spur gear that has the bore size to direct connect to the CIM’s.

What i need it for is a CIM with a spur gear direct connect that goes to a .5" axle with another gear on it. I would like about a 6:1 gear ratio but if larger can be found that would be aswome. Note: the larger gear has to be smaller in diameter than a standard FIRST wheel.

So if anybody has a place to buy gears for a cim that would rock.

here is a gear that will fit a CIM shaft, you should be able to find some gears that will mate with it at the same web site.

not sure if you’ll find a 6:1 ratio though…that usually takes two stages of reduction to achieve

The Toughboxhas an optional output ratio of 5.95:1 with the 40 tooth output gearand the 24 tooth cluster gear. And what do you know, the output is a .5" shaft. AndyMark must have already thought of this application. :rolleyes:

Thanks for the quick answers

I know this doesn’t directly apply to your question, but when your designing the crab drive leave like .003" inbetween gears. If you plan for them to mesh perfectly, youll find they grind a bit and dont spin that well.

Matt the bore for the cim gear is 8mm with a 2mm key way.

Right-o. But that’s not just for swerve drive.

That distance, or looseness between gear teeth is called backlash.

ALL gears require some backlash to allow optimal function. Too much causes other problems. Normally, if you buy a set of small feeler gages you can set your backlash consistently. You always want some.

This occurs over two stages though, so it might not be what Mat is looking for. Keep in mind Mat that 14 teeth is probably the smallest CIM spur gear you’ll find, which means you’ll need an 84 tooth gear to mesh with it in order to get the ratio you want in one stage. A spur gear that size will have a radius of somewhere around 4.5 inches, which might be a problem for you depending on what wheel diameter you plan on using. If you are set on having a single reduction, Martin Sprocket’s pdf catalog list 20dp 14.5pa spur gears with sizes all the way up to 132 teeth. They even happen to carry an 84 tooth gear, what are the chances? :smiley: (By the way, the 84 tooth gear they carry has a 1/2 inch stock bore, so all you’ll need to do is broach a keyway into it. It also weighs 2 pounds, so be careful :rolleyes:)

Mike C.

It’s not a terribly significant difference, but AndyMark also sells 12 tooth CIM gears:

You probably won’t be able to accomplish this in one reduction with the CIM placed directly above the wheel. This would require having a final gear slightlly smaller than your wheel and a pinion slightly larger than the CIM Motor (>52 teeth), which will not accomplish the desired reduction. A pinion gear smaller than the CIM motor will cause the motor to intersect the wheel.

If you want to modify a gear yourself or have a shop do it for you, then any stock gear with a 5/16" bore will work.

5/16" bore will work with an 8mm reamer. Ream the gear with an 8mm reamer and broach with a 2mm keyway broach. Add a set screw over the keyway if you want or use the retaining ring as used by AndyMark.

Just to add to this, a Letter O size drill or reamer measures 0.316", and that will work just fine too.