In years where we ran these gearboxes we epoxied the snowman holes and drilled out only the set we needed, worked great all season.
We just had our sponsor cut out a few plates with the snowman holes replaced with regular holes. I haven’t seen any aluminum glitter coming out of the gearboxes all season thus far.
Not having used those gearboxes before, I didn’t realize they had that feature. If a student proposed this to me as a gearbox design, I would suggest they go back to the drawing board.
The snowman holes are certainly not the issue here.
Firstly, this is your drivetrain gearbox. The motor bolts should have loctite on them. They should never get loose, and should start off torqued down.
In the ~6 years of my team using these on our final bots, practice bots, and off season bots, we have never had any issue relating to these.
We had issues with the snowman holes back when we used WCP SS gearboxes. Can confirm adding loctite (and a washer to help the screw not dig into the aluminum) worked.
Not specific to your question but this is a video (by @PatrickW of 2910 swerve fame) that I found really helpful for designing gearboxes and such. Check it out.
@pchild 401 has a pretty nice 3 neo drive train if they wanna share.
We also used 6 NEOs this year. We went with a 7.33:1 gear ratio and we didn’t have any gearbox problems. We played defense almost every single match today but it’s worth noting that our belt setup was prone to slipping and protected the gearbox from stalling and shocks.
Which gearbox did you use? We are nervous of pressing the pinion of the evo slim onto neo motors as the rotor is not mounted to the casing of the motor apart from the mounting plate so a arbor press will likely destroy it. Do you use the AM14U4?
We used the 3 motor Evo slim gearboxes.
Our calculations for expected speed are documented here:
Using the spreadsheet, you can experiment with the different available ratios - you can even create your own! (But you may not be able to realize your own ratio).
Has anyone made “crescent” fillers to work around the snowman holes problem? While they would make changing motors just a bit more painful, they would essentially eliminate the “walking” issue. These could be milled or 3-d printed, as appropriate for teams. Quite similar to the epoxy solution @Justin_Foss suggested, but re-usable in either position.
I was thinking along the same lines, but they’d be so small that manufacturing would be a bit painful.
We did exactly that in 2017. Small 3d printed crescents. Just make sure you print a lot more than you need as they were so small far more were lost on the shop floor than actually made it into the gearbox. They also worked all season without issue.
How did you press the pinions onto the motors without breaking the motors?
You can remove the can off the motor to support the back of the output shaft while pressing.
Stick a ball bearing in there with some high strength epoxy? As long as you can guarantee it doesn’t fall out, it might work well.
You need to take the can off the motor. Be careful when doing this because it is easy to strip the screws. REV has a guide on doing this
A quick trip to Ace for some new, sharp 1.5mm Allen keys was extremely worthwhile. One for electrical lead, one for our build lead, and one for the team leader’s apron pocket.
Also, steady pressure increasing slowly is the best way to break the screw free. A quick jerk can strip the hex socket, and it will be very difficult to get the screw out after that.
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