Full-Metal Roving

A project log for "Tenacity": Yet-Another-Sawppy-Project

Inspired by Roger and others, I'm making a SAWPPY-Alike rover, adding my own tweaks and mods.

steveSteve 05/15/2021 at 03:280 Comments

I got these in the mail the other day:

Sawppy builders will recognize these as the triangular wheel hubs used to mount the wheels to the drive shafts of the motor pods. My buddy Ed "Steamboat" Haas and I have been collaborating on replacing the 3D-printed parts of the motor pods that have failed most often with metal equivalents.  We're about a 2-hour drive from each other and the pandemic hasn't made collaboration any easier, but we've both got 3D-printers and tools and Internet connectivity and the hacker mindset to do crazy things and this the result. A bunch of hand-machined, hand-tapped triangular wheel hubs that started life as a single piece of round Aluminum stock.

I had to do a bit of filing and Dremel-ing to get them to fit inside the wheels, but that didn't take long. The Aluminum is soft, almost butter-like in comparison to the steel axles.  

I also had to grind out the detents on the axles a bit deeper and make them lie a bit flatter because the metal hubs don't flex and deform at all, so any angles or nubs in the detents showed up in the new hubs tilting against the shaft which led to the wheels themselves visibly processing when driven.

For somebody like me who knows just enough about materials to be dangerous, this was a bit of an eye-opener. I knew there were divots and digs in the shaft detents, even if they appeared mostly flat, but the way the PETG conformed to these, even under the tension of the set screw biting into the shafts really masked these imperfections quite a bit.  Even after this additional filing, the wheels still process a bit when free-wheeling, but this is mostly damped out with the rover on the ground and the wheels come under weight. On a couple initial test drives, this doesn't seem to affect the way the rover drives. I kind of don't care for now because this rover is still such an experiment and the metal hubs should go quite a ways to solving my problems of having to do wheel maintenance and swap out PETG hubs after a day's worth of driving.

Ed has his own album up over on Flickr documenting how these were made.
He also has a lot of neat stuff over on his Thingiverse account