New chassis

My balancing robot project has had a long hiatus, because my life in general has: I went on holiday, mostly to visit family, and broke my ankle, so it turned out I was away for 2 months.

I should have posted before I left. After getting the telemetry working, I started to converge on the correct settings for balancing, to the extent that the robot would often stand up for 10 seconds or so. Then one of the gearboxes started sticking.

I started off on another tack, buying two gear motors, rather than tinker with the arrangement I had, or embark on the rather complicated project of machining my own. What swung it was I finally found some more affordable ones: MFA Como Drills 950D. The link is to the 11:1 ratio version, which I choose. 50:1 just seemed like it would be too slow.

I think this should make things much easier: the slack in the gearbox is minimal, so the robot should be able to react faster, and require less damping. I'm doubting my choice of ratio now, but at least if I need to buy another set of motors, they will be drop in replacements.

Anyway, mounting these motors onto the maker beam frame was going to involve too many brackets, and too much weight. I've been building a chassis out of aluminium angle and channel. I've used my jigsaw table to do the cutting, and it's proved to have reasonable accuracy, although it makes hard work of the bigger sections. I've improvised some clamps using the maker beams and some threaded rods. Here's a picture of it ready to be drilled:
The idea being that if I now drill right through, having checked everything is square, etc. it should line up perfectly when I screw it together. The holes in the bottom are for the motor brackets, which I had to measure carefully.

I was originally going to glue the frame together using epoxy, and then drill and rivet it, but I wanted to be able to pull it all apart again, so I could drill more holes as needed. I'm going to drill holes at 20mm intervals on the front and back faces: you can probably see where I've punched them. That should be plenty. I can use these to attach maker beams to prototype new features: it's 100mm internal, as you can probably see, so 100mm beams can go inside or outside.

I've drilled some of the holes, but not finished yet. I need some machine screws to arrive before I can finish assembly anyway.

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