pic: Team 2451 Pwnage Custom Bag Motor Slip Ring



A Pwnage alumni redesigned our custom slip ring design and repackaged it using Bag motor brush assemblies and designed all the components so they can be 3d printed. This is not currently COTS legal for use during the season but an engineering exercise. Hopefully First will revisit this rule and allow custom slip rings in the future.

Best thing about it is that it does not contain mercury. The bad thing about it is that it does not contain mercury.

With integrated encoder mount!
Very nice.

Edit: Nevermind I figured it out

These are my favorite COTS slip rings :wink:

That’s my type of slip ring.

Very sweet. Remember to keep in mind that a 0.002" clearance on a 3D printed object is akin to a “press fit” (true story) in metal.
What’s the final weight on that thing? I love the integrated encoder BTW. Is it for CIM speed or rotation?

.43LBS as shown with encoder, the previous design using CIM brush assemblies was .72LBS. This version would be able to handle the power of one CIM motor. Using a single Bag Motor brush assembly for each CIM cable, with both brushes wired in parallel, would have the same surface area as the single CIM brush internal in the motor. Current capacity should be exactly the same as the CIM itself.

Also note that (barring some ridiculous design) these will not be spinning nearly as fast as a motor has to. You may be dealing with <5 rotations per second pretty much always. Not the ~100rps of a motor

Here are some more images of the design to get a better view of what’s going on:

Sorry for the large images.

Imgur Album

One of our concerns at first was the fact that there could be full current load with no rotation. In a motor the rotation cleans the brushes and uniformly wears the commutator. In a slip ring for a swerve unit the rotation could be described as sporadic. We were concerned with arcing, pitting of the commutator ring, fusing of the brush to the ring, etc. This is why we used clear polycarb housings on the original prototype. But after running the slip ring for extended test cycles and after disassembly and inspection we found there was no reason for our concerns.

I think this is brilliant - really clever engineering using mostly commercial components, with a few 3D printed adaptors.

I hope you are able to deploy them! It would be a shame to have such carefully designed and tested components outlawed on safety grounds, while sketchy mechanical assemblies (some holding back serious stored energy) skate through no problem.