Halo Pt.1: A first adventure in combat robotics (Overview)

A friend of mine and I have been developing a battlebot over the past several months. I thought it was about time I started documenting the project.

This is the first attempt for both of us, so we aren't attempting to play with the 220lb monsters you see on TV. Luckily, there are non-televised events with weight classes all the way down to 150g. We settled on the 3lb beetleweight class as a compromise between cost and "kickass".

In any weight class, there's a general rock-paper-scissors relationship between three robot archetypes:


Simple rams on wheels. Most are designed to be as low and indestructible as possible. These tend to get beat by


These feature a large lifting element. They seek to toss their opponent out of the arena or simply on their back. Lifters are countered best by


The scariest of the lot. These bots store as much energy as possible in a spinning element, and then try to release it as fast as possible in their opponent. These are most often beat by wedges capable of withstanding the blows.

There are a few exceptions to these trends (see: blacksmith), but the best advice for newbies like us is to pick and archetype and try to design around its weaknesses. When narrowing down our bot designs, Pierce and I were weighing "awesome factor" pretty heavily.

So we picked spinner

Spinners are harder to build of course; poorly designed ones tend to destroy themselves more than their opponent. But They are also perfectly capable of launching both bots across the arena after a good hit (especially in the beetleweight class).

Spinners come in a wide variety, but the general types are:

Verticle Spinners

Can either be drum style (see minotaur) or disk style (see counter revolution). They generally try to knock their opponent into the air with an uppercut.

Horizontal Spinners

Since in this style the spinner is parallel to the floor, builders have more room to be creative. Most common is the spinning bar style, as popularized by the legendary Tombstone. After that, shells are fairly common, and then the occasional ring spinner.

And then there's Meltybrain

We chose meltybrain. Meltybrain is a style where the robot uses its drive wheels to spin in place. The result is that the entire robot frame becomes a horizontal spinner disc. This simplifies all aspects of the mechanical design, but with a catch: the robot still needs to be able to move laterally. But if it's spinning in place, how does it go forward? what even is forward anymore? The solution is to use a fast microcontroller, robust sensing, precise timing, and some math. This is quite a change from the dumb RC receivers most bots use, which is why most builders don't attempt this style. But if mastered, meltybrain can unlock massive damage potential while being tougher for it.