pic: ARJ-101 full view



I was browsing through some old folders when suddenly - ballshifters inside the shaft of a CIM! I’m not 100% sure why I once thought this was workable but I thought I should post it here.

I definitely made some interesting engineering decisions on this.The overall module shape isn’t bad, but the versawheel is connected to the ring gear via standoffs (not shown) that would attach to a 1/16" plastic flange on the versawheel. I think the gear ratios were 3:1 and 7.7:1 on a 4" wheel, for free speeds of something like 30+fps high and 12fps low.

On the actual shifter, apart from being super small, the overall design of it didn’t look that bad. Except the balls could be completely stuck inside the shaft and not engage the gear, and required a 3/32" hole to be drilled 2" deep or so into a CIM shaft.

Overall I’m simultaneously repelled and attracted to this thing. It’s interesting to look at old designs like this one and wonder how to make it workable. Shifting inside of a CIM-in-wheel swerve is an interesting concept and if the CIM shaft were larger I might try something like this seriously. Who knows, maybe there’s a way to make it work out there.

This looks really cool! I would very much like to see the CAD for it so I can get a closer look.

Awfully difficult to tell from this view how possible it would be, but you could introduce more reduction using a planetary gearbox, which would also give you a larger shaft to work with for the ball shifting. Of course, that would increase the footprint substantially.

Cool stuff. Sometimes ideas that you decide are not feasible later get you thinking about other ways to do what you want. Our in wheel swerve design from 2014 got more attention than our coaxial from 2015, but was heavier, only a single speed, made speed feedback difficult but still everyone liked it better because it was different from the norm. I am now on the coaxial bandwagon since sensing wheel speed and shifting are very difficult with distributed swerve designs. Getting the motor power wires and the pneumatic lines for the shifter cylinder through the steering pivot without requiring steering limit stops would be an issue. Your designs have come a long way and its been fun watching them progress. Keep going and show us something revolutionary!!!

If you use a planitary you could shift like they do in hand drils by engaging or disengaging some of the ring gear.

CAD is in the 2015 offseason release: https://workbench.grabcad.com/workbench/projects/gcBvYbFAI7TQYHiKMOq7jiSQVQxuTYPyTAXwhy5IZUFIGK#/space/gcvLTQUiZ-c9-szjJsPH3WvpxdeKOB9B1Z2b-tQWAq3gUh
Look under CIMshift -> 101 to find this assembly.

This is a planetary shifter, actually. You shift between just a 72:25 (?) reduction and a 72:25 x (60:20 + 1) double reduction, by tying the second planetary to the first one.

I can totally see that. Personally I did like your CIM-in-wheel, but aftermaking some of my own decided the weight and space weren’t worth it.
Thank you!

See above. However, if I were to just disengage one set, the spread will be very low; I’ll be moving from a ratio of 4:1 to 5:1, or 3:1 to 4:1 just because of the way planetaries work.

Would the shifter built into the cim shaft not be considered modification of the motor? I suppose you could argue that if you can put a flat on a shaft, machining a few extra holes in it wouldn’t be much different.

[quote=] R30 A. The mounting brackets and/or output shaft/interface may be modified to facilitate the physical
connection of the motor to the ROBOT and actuated part. [/quote]

If the output shaft can be cut down to a stub, to inteface with a Versa-planetary, a few holes isn’t an issue.

If would be quite interested to see how something like this would hold up under operation, it is a relatively thin shaft, and drilling holes is going to weaken it considerably

Basically this whole design was based off R30 A. :stuck_out_tongue:
I doubt this would hold up as I’m removing most of the material in the CIM shaft, but given that each CIM is only driving one relatively small wheel, it might not be too bad. I didn’t bother to do the calculations before because the radial holes for the balls screw up traditional torsion calcs.