Swerve Drive Assembly falling apart

Our team constructed a swerve drive base, and it was working perfectly with code and everything for some time, but inexplicably yesterday, the bolt that was securing the small gear in 2 different mk4i modules came out in the middle of driving. It appears that the bolts stripped the threads out of their holes as well, so we aren’t sure if we will have to replace the modules or not (luckily we have backups in case).

We used a good amount of Loctite on all the bolts in the modules, as well as the magnets (which we also suspect might be loosening, due to some wheels being off), so we aren’t really sure why this is happening, and any advice in how your team made sure that bolts are secured in the modules would be great.

If you can add a pic showing the bolts that you are having issues with that would be helpful.

Can you send pictures of what happened?

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We also had this issue despite copious amounts of loctite on the bolts. When ours backed out it got caught in between two of the gears and put a quite significant gash in both, and ripped the threads out of the shaft. We ended up re-tapping the hole and putting the bolt back in with even more loctite. As for the gears, they aren’t in stock currently so we’re just running them damaged. Not an ideal fix, but putting in a PO and waiting for parts would mean weeks without swerve, not to mention the parts in question aren’t in stock anyways.

Are these the gears your referring to? I believe this to be something team need to keep an eye on, over time, the bolt that holds that gear in place will eventually vibrate loose and back out (we used loctite).



Yikes that’s some bad wear.

Gonna have to keep an eye on situations of wear and tendency for stuff to get caught and run thru module gearing over the season.

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disclaimer: this happened near the end of our 2nd regional. Probably more a result of a lack of preventive maintenance. Our theory is that the screw backed out and the gear was able to ride up the shaft and wobble around.

We also had the issue with the screws in question backing out. The last time we also had the threads rip out.

Is there a reason why a half inch FHCS is used in a location with what appears to be a 3/4" tapped hole?

Here are pictures of what ours looks like. I hope they have a fix because we do not have spares.


Can you clean up and retap the threads (carefully to not cross thread)?

Blue loctite everywhere is the solution.

we actually red loctite in this situation and use heat and an impact whenever disassembly is req.
200 matches and ENDLESS hours of practice time on the chassis and had no issues such as this with the mk4i

We blue locktited and bought a new driveshaft from SDS. When that gets here we will use loctite 243 on that one corner. We caught it when it happened on only one corner so that is a benefit of testing a stripped down robot so we can see the drive systems realy well. It sounds like some people use the red loctite stuff. I guess you then have to store it as a unit because it will not come apart again but if it gives you multiyear service I guess its worth it.

Would these lock washers help/fit? McMaster-Carr

My Team had the exact same problem on all of our modules.



We noticed that there is more threads that aren’t used so we tried 5/8ths and 3/4in length replacements: McMaster-Carr

The 3/4in bolts fit in the shaft but they could not be installed without disassembling the module so we opted for the 5/8ths bolts.

We also switched to red loctite and haven’t had any problems.

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Akash,
blue loctite didnt work for us, as they still get loose.

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For loctite to work well, both sides have to be thoroughly decreased.

For what is worth the 12-24 screws that came with our modules are 1/2" long. The same as on the bill of material. The directions call for them to be 5/8" long. Normally a wouldn’t worry about a 1/8" difference.

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