With DragonCon just over a month away and Battlebots far enough in the past, its time to get my CAD hustle back on and build a new robot. I decided to go the slightly expensive (but not impossible) 30-lb route. A sportsman 30, to be exact. I figure there are more competitions a year (DragonCon, Franklin, Motorama, silly Mass Destruction demos, etc) to really hone in on a design versus the competition or two max a year the 12-lb class are (so RIP, for now, Tough Love, you unbroken heart, you).
The goals I had with Skuld were the following:
Produce a hammerbot so you can understand the challenges and limits (Blacksmith is one of my favorite robots in Battlebots, to date).
Design a drivetrain that uses belts. In all of my many years of roboting and automotive design, I have never played with timing belts
Make an adorable hammer head from DragonCon seeing its a shoving match. I’m out to win the hearts of the fans, not the competition. Competitive robots tend to look boring.
See what all of these crazy kids are so hyped on brushless drive for.
Version 1 was finished after a week of all-nighters between my incubator and makerspace in Somerville, MA. I used 1/4” and 1/2” aluminum for the frame, base plate, and hammer module structure. I found I had a few challenges I wasn’t expecting, besides the unfamiliarity of developing a chain-not-for-drive system that had physical limits and seeing how belts want to behave/tension/wrap.
I decided to go with a brushless setup across the drivetrain and weapon motor for a few reasons:
I’ve been living the brushless life since high school
I honestly don’t know what controllers to get for a 30-60lb robot
Relying on a physical end stop for my hammer module means I want a forgiving motor if slammed to a stop
I’m grateful I have access to some of the waterjets around Cambridge or else this wouldn’t have been done on time. I likely also wouldn’t have been able to finish if I didn’t have so many Markforged resources nearby as well (thanks again for being our Battlebots sponsor…!). The cost of this robot was noticeable, but WAY cheaper than it should have been due to local resources and stubbornly making everything myself.
Night before Dragon Con, everything looked good to go! I burned out one of my Hobbyking Red Brick 100A ESCs, but had one 200A lying around that I swapped it out with. The gears in my gearbox were too tightly packed because i was off by ~0.7mm of clearance between levels and my inrunner. I also used WAY TOO POWERFUL of an inrunner for how I had my SimonK settings on my ESC. They always say the easiest way to learn is the painful way… especially as an engineer.
Competition day! And first fight… that remaining Red Brick 100A ESC burst into flames when I was shoving the kiddo in lime green behind me (he took a picture with me after… I yucked it up. Kid’s first fight and I gave him a story!). When I realized the drive was acting pesky, I tried to just continue forward throttle and waggled the hammer around for good measure and then… fire. The First at DragonCon in years! Thank you Randy (one of the many wonderful folk on CHAOS Corps) for hustling Skuld into the street. I still have the toasty bits as a reminder to ask for more help/understanding when flashing/doing anything with controllers that I’m not confident in.