Servo - January 2012

FIGURE 4. Fleaweight bot Hedgehog.

pounded each other until only one survived. It was an incredible collection of bots and a great competition.

The opening match pitted my horizontal spinner “Hedgehog” (Figure 4) against Team Busted Nuts’ Melty Brain full body spinner “Berserker” (Figure 5). The match went the full three minutes, with both bots delivering and taking some awesome hits. The bots were literally flying around the arena like hockey pucks. Ultimately, the judges gave Berserker a well-deserved decision. It was the best Flea match I’ve ever had and a great way to start the competition. Berserker went on to the final match in the Flea competition.

Hedgehog eliminated Chris Olin’s fan favorite “Lefty” — the only Flea lifter — when he cut off one of Lefty’s “legs” (Figure 6). Chris continued to fight yelling, “It’s only a flesh wound,” but Lefty was finished for the day. Ultimately, Hedgehog had to tap out in a later match due to mechanical problems.

My vertical spinner “Tomahawk” (Figure 7) worked its way through the loser’s bracket to get to the final match. Along the way, Tomahawk defeated “Invertigo” by ripping out one of its speed controllers (Figure 8) and “Chairman Meow” by doing pretty much the same thing to its RC receiver and battery (Figure 9). In the semi-final match, Tomahawk avenged a second round loss to “Dirty Sanchez” (Figure 10), when Dirty Sanchez got bludgeoned by one of the arena hammers and

FIGURE 5. Fleaweight bot Berserker.

tapped out.

The championship match was another back and forth ordeal until a vicious hit from Berserker snapped the weapon motor shaft on Tomahawk sending the spinning blade flying. Although the match went the distance, Berserker was the clear winner of not only the match, but of the Flea competition.

Following the match, I asked Berserker builder Michael Gellatly to pop the top on the bot (Figure 11) and talk about the technology and design. The Melty Brain concept has been around for a few years and information is readily available on the Web. The concept is to spin the entire robot with one or more drive wheels so the entire bot becomes a weapon, and to use a computer and accelerometer to pulse the drive motor(s) at precise points to provide directional movement. An LED on top of the bot is pulsed to indicate the front of the bot and the forward direction of travel. The on-board computer is connected to a standard RC receiver to provide driver remote control.

Michael’s bot uses a Pololu Baby Orangutan controller, an accelerometer, and open source code. I saw my first Melty Brain a few years ago at RoboGames. That bot was a larger design and drove very nicely outside the arena, but it did not do well in combat — a problem that has historically plagued the Melty Brain bots. It’s obvious that Michael has cracked that nut (no team name pun intended) as his Berserker was unstoppable and clearly the best