Spinning Drive Unit

Really like the design of the back part. Beautiful :)

Looks great! Where'd you end up getting the internal ring gears, KHK? Any updates to your controller since your last thermal deep dive post a few years ago? I've been kicking the tires on the H7 series for my next rev. 520MHz (550 if you want to risk turning off ECC) is a lot of compute power to mess with.

No motor drive updates, I'm still working through my supply of mini cheetah drives I ordered in 2019. Would probably switch to an STM32G4 if I did a refresh. Smaller packages, cheaper, some nice motor control features like a CORDIC unit.

Hah, yup, it makes a good controller for sure! My current controller is (rather heavily :) based on your original PCB layout, but updated with FD CAN, Rust, and the G4 [1]. It's a solid little chip; you can wire up a frankly staggering amount of hardware triggers, to the point where you're pretty much just reading memory for values to feed into your control loop. [1] https://github.com/timblakely/pino-rs

Ring gear (and all the other gears) are from an off-the-shelf industrial servo planetary. There are some pics of post machining them a few posts back. Once I've got both drive units fully buttoned up I'll do a detailed blog post.

Really cool stuff. I look forward to seeing how you put this thing to work. How did you decide to lay out the internal cooling passages?

Stay tuned, working on a detailed writeup of the design/build.