Neo vs CIM pinion compatibility issue

Fun thing I just found out the hard way, vex 9T cim-bore pinions do not actually press-fit on neos. Instead, they just crack. Yay. You would think they do but according to the vex support people I emailed with, cims are actually 7.95mm, and they have already heard of teams having this problem. Their solution was to sand the motor shaft, but it sure doesn’t seem to sand down.

Would have been nice of them to note somewhere, given that vex’s cim drawing lists the shaft as 8mm no tolerance, but so it goes.

That’s interesting. We ran those pinions in 2020 with Neos, and they pressed on fine.

Sandpaper will probably work if you need to make it work…or switch to a minicim.

I ran into this a few years ago, throwing the motor in a vice and running some steel wool on the shaft with the motor on fixed things. Communicating with VEX support at the time, you need to remove a very small (0.0006”-0.001”) amount of material to make it work.

interesting! I tried sandpaper, but it seemed to just break the sand off the paper :persevere: What sort of steel wool did you use, coarse or fine? might have to give that a try next.

I’d be surprised if sandpaper didn’t work. You might be removing enough material as is without realizing it; I’d double check with a pair of calipers. We used steel wool simply because it was laying around and was less aggressive than sandpaper, given how little material you want to remove.

1 Like

Emery cloth might hold up better

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