Can't determine source of slight binding in one of our WCP SS gearboxes

We bought two new West coast products single speed gear boxes and have installed them on our West coast drive chassis. One side has a slight binding when you start rotating by hand. Sort of a catch when you first turn the wheel, but then it moves pretty smooth. The other side has no binding and rolls smoothly at all times. One direction seems a little worse than the other on the binding side. We have taken it apart and put it back together. Motors work smoothly when not connected. Everything seems in place and symmetrical. We are wondering if this binding is normal in some of these gearboxes when you first use them, but wanted to ask before we power it up and run it. It is definitely not the snowman holes as they are correct. We are using a 13 tooth pinion.

Some times gears have a burr on them, or a flat tooth. Check for those as well. Usually it can be resolved with a light touch using a small metal file on either side of that tooth.


I had this issue on my base with VexPro ball shifters, where the left side would have a binding problem. I later found out the issue was that the holes weren’t perfectly aligned/tightened, so the bind at the start would be to force the shaft/gearbox into place to be concentric with the rest of the base and then from there it would spin properly.

WCP SS gearboxes have “snowman” holes for mounting the motors with 12t or 14t pinions. If the motor is installed in the wrong hole, it can cause binding like that. Sometimes the motor will even “jump” fro the right hole to the wrong one from vibrations.

Have you tried turning it with the chains off? Just the gearbox and the direct driven wheel. Want to make sure the problem is where you think it is, as there could be something with the chain or sprockets that cause the slight binding - I’ve seen that before.

Binding issues with gearboxes are often cyclical - if you rotate at a constant speed, it’ll binding at a constant interval. Make a small sharpie mark on each gear, and note the positions of each when it binds. The gear that is always in the same position when it binds is the one you want to look more closely at!

If the binding is not cyclical, look at alignment for everything. Start rotating it very slowly through the binding period, and look closely to see what moves. You might have something that isn’t aligned quite right and “pops” into place once it starts moving, but when stationary can be pushed out of place (by the weight of the robot on the main shaft, possibly).

Also, I hate the snowman holes. I’ve seen them move from inboard to outboard by themselves way too often to ever trust them on a robot. The only way I’ll use those gearboxes is in an outboard configuration.


You have to either use some kind of clamp (inboard) or spacer (outboard) for the snowman holes to be reliable. No idea why this product has been out for years without some solution coming in the box with the parts. shrug

We had taken the chains off and the problem persisted so we were pretty certain it was in the gearbox. We checked the snowman holes several times and they were good although we did not fill them. We were using the outer holes which seemed less likely to be a problem. I thought the problem was something was misaligned but we could not find anything that looked out of place. However, like many problems, we took it completely apart one more time and when we reassembled it, everything worked fine. I’m glad we did not run it when it was catching although I’m guessing it would have slipped into place. Problem solved, solution unknown…

I know the standoffs recess into the plate. Iirc, occassionally during assembly the standoffs wouldnt seat right into the plate, causing slight misalignment.

1 Like

An issue I’ve seen several times (most recently about a month ago, when mounting four brand-new CIMs which had been shipped shaft-down and three of them wound up breaking out of their boxes) is a slightly out-of-line shaft on one of the CIMs which pushes the pinion into its mating gear too tightly; when this happens, it is usually more of an issue one direction than the other. The workaround/test is to remove the motor, rotate it 180 degrees around its axis, and re-mount.

We tap the snowman holes and put a piece of a #6 (or maybe #4, can’t remember) screw loctited into the hole we aren’t using.

1 Like

1712 has used this product for 5 seasons, and only once have we had to install a spacer, filler, or clamp to avoid snowman hole issues (and that was with the new 10t pinions). So long as teams take some proper QA when assembling these gearboxes, it doesn’t tend to be a huge issue. The griping about the snowman holes tends to be pretty overblown on CD.

I used them once in 2016. Both sides of the drivetrain had intense binding caused by snowman holes. Spacers are a must to fill the unused snowman side.
Also, a 20% failure rate is pretty bad for a drivetrain gearbox. Spacers should be included with them.

It’s not a 20% failrate. It’s experiencing an issue once in the five seasons and 14 total gearboxes we’ve purchased in that span, and even then it was before any competition was easily corrected. It’s a 0% failrate for snowman holes on the field for 1712.

1 Like

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.