[Looking for feedback] First Custom Aluminum Gearboxes

Hello there!

I’m looking for some feedback about this design for my team’s drive gearbox for this year. We normally build structures out of laser-cut plywood, but we decided we needed something sturdier this year. This one is planned to be made out of laser-cut 0.25in aluminum (we have a sponsor with a stronger laser that wants to fabricate parts for us). It’s a single-speed gearbox with 3 MiniCIMs and a reduction of 9:1. We were kinda inspired by the shape of 254’s gearbox last year when making this.

If you want some more information or other screenshot angles just ask.
This is also my first post, so correct me if I’ve done something wrong.

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Not a gearbox expert, but it looks solid to me. Three questions:

  • Why not just do an EVO slim 3 CIM?
  • Why are the plates so far apart? They look like there’s almost enough room in there for a three stage reduction or shifter.
  • Why isn’t it symmetrical? In particular, I would expect a strut directly connecting the left cluster shaft and output shaft in the first render, rather than that strangely angled one.
  • OK, four - I now see that there’s no connection between the “right” cluster shaft and the output gear. This double-loads the center CIM pinion. I’d prefer to put a gear there and spread the load out further.

I’d definitely beef up those standoffs. They seem pretty slim for a drivetrain gearbox, maybe double the diameter of the outer ones where they won’t intersect with the gears.

The middle motor pinion will see enough stress to flex it upwards. If the MiniCIMs were in a straight line when mounted, it wouldn’t be ideal but it would probably be fine. Make sure they’re steel.

Can you post a picture of this gearbox mounted onto its rail?

Here’s the picture of the gearbox mounted on its rail:

When you say make sure they’re steel, you’re talking about the motor pinions, right?

I recommend if you are going to be double loading a motor to add some sort of bearing support on the end of the shaft. I know somebody from 4587 (can’t remember their name off the top of my head) made a knockoff gearbox this summer based on 254 and would be a good place to reference when designing for a flat gearbox like this. Overall, good start! But I definitely suggest adding some sort to the middle shaft.

The lightening on that rail looks overly aggressive. Unless you really need the weight, I’d probably recommend not doing the lightening on it. The drivetrain is the most critical part of your robot.