OpenBot TANK! by Spektyr

Last crawled date: 3 years, 3 months ago

Turn your open-source autonomous robot car into an autonomous TANK!
I decided a while back I wanted to build an OpenBot - https://www.openbot.org/
So originally I'm building this thing and I think "hey, this thing turns like a tank. If I ran some flexible rubber around these wheels it'd be even more like a tank."
Many hours later, I was on around version 8 of some home-cooked tank treads and many more hours later, I actually had something that worked. Even better, almost everything prints without supports.
Building the treads: it should take 34 treads per side (68 total). I had issues with them lifting off the bed as I printed due to it starting out as six small squares that build up. So I have two versions of the tread - one without a brim and one with. The manually-added brim serves to keep actual brim out of the hard-to-clean gaps, while still keeping everything stuck down nicely.
Once you have your treads, run a small drill bit through the pin hole on the "middle" part. What size? I don't remember. It's whatever will ream them out just enough that a piece of filament will slide through and turn freely. Then take some filament and shove it through two links of tread and cut it flush on both sides. Yeah, it takes a while, but we're building a tank that drives around by itself so it's worth it.
The road wheels print in two parts mainly just so you don't have to mess around with supports. Glue them together. Three per side, 6 total.
Drive wheels should print with supports with the "outside" down. You only need supports around that outer edge that hangs out. Two per side, 4 total.
Print your inner and outer frames (2 of each).
Then using basically any M3 screw (doesn't matter how long, as long as it's long enough to go into the wheels a bit, but not crazy-long) attach three road wheels to one inner frame and then attach an outer frame the same way. Snug enough it's not wobbly, but everything still spins freely.
The drive wheels fit inside the inner frame and are screwed in to the outer frame (same as the road wheels are, except no inner bolt). Tread goes around it all, and then the whole assembly presses into the drive shafts of the OpenBot the same way the original (lame) wheels do.
You can also use two optional tread deflectors to prevent the tread from riding across the middle body-bolt of the OpenBot (not pictured). They're designed to slide on/off easily and keep the top (return) leg of the treads from rubbing noisily along that bump.
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