Check out this fight in BattleBots World Championship VII (marked “Season 8” on most platforms), Episode 19.

When we last left off, HUGE was coming off of a razor-thin Round-of-16 victory over MadCatter. With the help of the irreplaceable Martin Mason, we had totally overhauled the weapon bearings halfway through the playoffs, taking a risk to swap out what we had been using, and pursue a more reliable approach for the remaining fights. In summary, here is how we described that process in our MadCatter blog post:

“…but we learned that the “High-Load” style (chosen newly for 2022) are particularly prone to this style of galling when they fail. While the normal-style Oilite bushing is less hard and less robust, it can ultimately survive damage without galling the axle and locking up. Whenever possible, we want to choose parts that will fail without causing an entire system failure, so we knew that the change must be made for future fight(s) against similar vertical spinners. From here on out, this will be an every-fight consumable, but hopefully something that won’t stop the blade turning!”

Hmmmmm…

“While the normal-style Oilite bushing is less hard and less robust, it can ultimately survive damage without galling the axle and locking up.”

Hmmmmmmmmmmm…

“…without…locking up.”

Hmmmmmmmmmmmmmmmmmmmmmmm………

So what the heck happened? The key, is to start at the beginning.

Witch Doctor is a legendary opponent, having competed in every prior season of Battlebots. They’ve been to the Round of 8 four times, overall Runner-Up twice, 2021 Golden Bolt Runner-Up, won two Bounty tournaments, won Re:Mars 2019, and in general cemented their place as one of the faces of the modern era of Battlebots. All of this adds up to the fact that the frame and construction of Witch Doctor is well-dialed, and much more solid than most robots that we have fought with the brushless iteration of HUGE (2020 and onwards). Witch Doctor was one of the most solid objects that HUGE had ever struck, and this shock causes damage inside of robots.

Also in the spirit of “starting at the beginning”, HUGE was at-this-point on its seventh fight of the season. In previous seasons, HUGE had fought in five (2018) or six (2019, 2020, 2021) total fights per season. Unlike many teams, we do not keep more than one fully-assembled HUGE in our pit. While we bring plenty of spares, all efforts go into preparing the main robot for each fight, and we feel that it’s better for keeping the focus on fielding the best possible robot. So to have a fight against such a sturdy opponent, along with being so late in the season, meant that HUGE’s internals were susceptible to the shock damage.

During the fight, we expected that the bushing had failed once again, and began spinning HUGE’s weapon slightly slower to try to prevent further damage. Given that prior damage was caused by overheating, slower = cooler, right? Surprisingly enough, the bushing had no issues, ending the fight a little loose but otherwise clean, smooth, and free of galling! So what caused the issues then?

HUGE’s weapon motors, stressed by all of these big hits (as well as the hits from every prior fight since the beginning of the season) decided that this very important moment was the right time to fail in a new way, bend their axles internally, and therefore eat many of the magnets inside. This happened to multiple motors at once. SO, rather than freeing up a stuck bushing, our aggressive thwacking was actually moving chunks of magnets out of the way, and into gaps in the motor, thereby allowing HUGE to spin back up again and go for more hits. Bench testing confirmed that these motors would spin freely before intermittently locking, and damage to the internals supports the idea that some of these magnet chunks were impacting things at speed. Moments like these are why it’s so important to have speed controllers that can deal with a situation where the blade is suddenly locked up, and can continue onward without exploding into a fireball.

For fighting Witch Doctor, we had decided on a strategy of trying to disable Witch Doctor’s weapon as fast as possible. With their experience, we expected that they would be able to adapt strategies quickly, and that we may not get many chances to hit critical parts more than once. Because of this, we ran with our longest “S-blade”, to focus on aggressive and highly-damaging hits. We owe our success to the S-blade, as we were able to build enough of a lead during the early portions of the fight that we could survive once we took the weapon system damage. Witch Doctor’s weapon was disabled in a single hit near the weapon area, and they were left on the defensive for the rest of the match. Being on the offensive and controlling the fight is the position you want to be fighting from!

Moving forwards, we were left preparing for extremely uncharted territory: the prospect of fighting twice in a single day. In the real world, the Battlebots Semi-Finals take place in the morning of the second-to-last day, and the Finals themselves take place later in the evening that same day. It’s important to never overlook an opponent, and take every fight one at a time, but we knew that we would be best served to take a few small steps to help prepare for the possible day ahead in the event that we made it to the finals.

With no time available to re-engineer HUGE at this point, we swapped in a set of all-new weapon motors for the final day. We also began to prepare some spare motors, in-case the failures came back again. Otherwise, we charged two full sets of batteries to be ready for a quick turnaround between matches, prepared a full second blade hub (to enable a quick swap), did regular maintenance (like replacing the bushings), and got to work developing a strategy for Copperhead.

The tense moments pre-fight are a lot more tense when you’re in the Round of 8.

When the blade catches an edge *just* right.

Cracked magnets in one of the weapon motors - 3 of the 4 motors looked like this.

Note the damage to the stator near the face of the motor. The motor shafts bent at the rear of the stator (left side of the photo), meaning that the top side of the rotor (which would normally be at the right side of the photo, just under the faceplate) was essentially traveling in an oval pattern.
This shifted the motor’s rotating outer can inwards enough, on big hits, to strike the stator, causing the magnets to crack. Given the damage here, it was definitely striking with some force. Without the epoxy hardening, this likely would have pinched, grabbed, or otherwise cut the internal wires - thereby disabling the motor. This motor, and all the others, still worked!

Ultimately, the damage that won the fight happened here within the first 10 seconds. Broken weapon rails, ears, pullies, bearings, etc. Most robots don’t last long enough to get hit this many times!

Slight damage to each wheel, and a close look at the ribcage piece that got ejected. You can see also that the chain to the self-righter broke when the ribcage flew off.

Damage to the chainguard (but it did it’s job).

The hit that removed the ribcage also went clean through the front wedge, and scraped up the side behind the wheel. Crazy!

An amazing trophy from the Witch Doctor team.

A large group of excellent people, all staring directly at the sun.

Be sure to check out the Witch Doctor Pit Pass episode about this fight for a behind-the-scenes look!

Thanks to HUGE’s sponsors, Mouser Electronics and TTI, Inc. Whenever you need electronic components next, either for hobby or professionally, remember that Mouser and TTI make it possible for HUGE to compete at Battlebots. We couldn’t do it without them!

If you’re interested, also check out our merch store to pick up HUGE gear, or your own pair of angry eyes!

Photo Credits: Dan Longmire, JCRB Photography