Building invincible shaft collars

[Dan]

Friends, here’s the situation: https://i.imgur.com/v3jejcY.jpg

I have the C rod (7/32″) turning the Tuning Fork part of the robot arm.

I have the A shaft collar holding the gear on an 8/32″ tube.

I have the B shaft collar holding a gear on a 9/32″ tube.

ABC all turn independently.

At the other end I have three similar gears: https://i.imgur.com/PP2UN9u.jpg

*Big picture*

I’m trying to make the gears stay on the tubes. Making plastic stick to metal is hard. A test with a set screw crushed the tube against the stuff inside the tube – bad. cutting a slot in the end of the tube is hard (burring, crushing).

Currently the shaft collars crack and then slip: https://www.instagram.com/p/BsOibIfn6Yc/

I haven’t given up yet on making a good shaft collar.
I’m looking for help to make shaft collars that don’t slip.
If there’s a better way, please show me!
I figure you have a 3D printer. Using our parametric shaft collar tool (https://www.thingiverse.com/thing:3234501) some M2x12 screws. M2 nuts, and our torque handle (https://www.thingiverse.com/thing:3343197) the idea is to print two slightly different shaft collars. test until one fails, evolve the failure, repeat until you have two invincible shaft collars. Share your results below!

*more on the tubes*
I have tube 9/32″ outside tube 8/32″ outside rod 7/32″. the difference between one item and the next is 1/32″ (0.79375mm). The tube wall thickness is 0.014″. That leaves a gap of 0.01725″ (0.43815mm) total. Each of these three items rotates at different times and speeds and they can’t rub on each other.

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