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May 30, 2023Life in the constellation 12 min

The adventures of Henry and Team Halfway

By John Turpish

What is combat robotics?

Like everyone, Little Bears have hobbies, interests, and fandoms. And we like to share - it’s quite fun to see what others are into! The avocation I’ve come to be known for around the virtual office is combat robotics[1]: people build machines and have them fight each other in an arena.

If you’re unclear what I’m talking about, and you happen to be in the US, there are a handful of names that might be familiar:

  • BattleBots: The longest-running (in multiple incarnations) major TV show about combat robotics, and now the only one still active
  • NHRL: The premiere competition series
  • SPARC: The only major association of combat robots tournament organizers in the US. Even if your club doesn’t participate in the committee that writes these rules, they nonetheless almost certainly follow these rules or only deviate slightly
  • RoboGames: The biggest competition on the West Coast, the only competition with a weight class that has the same building rules as BattleBots, and the only major US competition with the dubious distinction of having had an arena breach
  • RobotRuckus: A super cool tournament

If none of this sounds familiar to you, just imagine bolting power tools to RC cars and having them tear each other up.

In just about any other fighting competition I can think of, the entrants are about as similar as possible physically. With most bot competitions, though, the intentional mismatch is part of the charm. Sure, there’s weight limits and various other rules, but restrictions breed creativity. I love the variety of different designs and approaches people take - and figuring out what works well against what, and under which circumstances.

It’s also the only spectator competitive hobby[2] I can think of that has a real audience and for which most of the “stars” are world-class engineers in their day jobs. One could do worse for heroes, if you ask me.

Dipping our toes in

But I’m not just a BattleBots superfan. I’m also a member of Team Halfway.

You see, my eldest child, Susy, and I got it into our heads that we’d like to try our hand at building and competing ourselves. Neither of us has any real background in this stuff, so we agreed to build from a kit. And not just any kit; we went with the most popular one, Viper, for which I knew Team Witch Doctor had published a series of tutorial videos. And we did it in its simplest configuration (as a wedge).

Thus was born…

Building in progress…


Here’s Henry!

If you’re wondering why it’s named Henry, you’re in good company - I also wonder this.

We did some limited testing at home.

Building it is half the fun, as they say (or they should say, anyhow).

Team Halfway hits the road

Once you have a combat robot, it’s not long before the arena beckons. So last spring, Susy and I took Henry on the road to get into the ring for the first time at the “Delta Nine Delivery: State of Franklin Robot Rumble.”

It was a long drive to northern Tennessee, but rather pleasant. Susy couldn’t remember having been in the Appalachians before, so that was a nice side experience.

Appalachian vista

On a side note, because it took place on April 1st, my wife let some people know I “took her child across state lines” to enter them into “a fight-to-the-death tournament operated by a drug ring.” Technically the only factual error is that the (legal) dispensary was the main sponsor but not operating the event, but you can see why the claim was nonetheless quite misleading.

A long drive

The big show

We arrived at the site at exactly the moment registration was to begin. We talked to an organizer, claimed a table, and got set up. We triple-checked that Henry was working in the testbox, charged the battery, etc.

Ready to do battle

But it turns out we weren’t just a rookie team; we were at a tournament run by rookie organizers. So then began a period of unclear length waiting for them to be fully set up.

The arena set-up

That did give us plenty of time to scope out the competition.

Competitors at the ready

And chat up our neighbors.

Meeting some friendly little bots


Let the battle begin

Eventually things got rolling with the Fairyweights: bots so small (150g max) that they’re generally seen as having a higher barrier to entry than the Antweights like Henry. I particularly enjoyed the very cute flippers having to fight each other. Flip. Flop. Flip, flip, flop. It doesn’t quite translate to video very well.

Eventually, Henry’s first match was at hand. Henry was up against Carbon Monoxide, a pretty nasty undercutter with control issues. You can see the sections of the event most closely related to Henry here. But here’s a behind-the-scenes summary.

Competitor #1: Carbon Monoxide

All those occasions of talking to the TV at home was decent preparation to offer advice as the coach-in-the-corner during the fight. One aspect I didn’t consider, though, is how very audibly close you are to the opposing team. I was able to hear their adviser’s commentary, which at one point gave me some awareness of what their plan was. I got very soft-spoken with my advice from then on.

In general, a floor-scraping wedge like Henry should do pretty well against an undercutter, as they can redirect the opposing weapon (horizontal motion to vertical), causing the opponent to lose control and damage themselves. And that did happen, kind of. However, Carbon Monoxide was prepared to be violently thrown around the arena repeatedly, and Henry’s simple plastic “armor” was unable to hold up to their weapon.

After the match, Henry’s wedge was completely gone. The top armor was cracked with a piece missing. There was damage to a wheel. The chassis itself (the aluminum holding the whole thing together) was bent and actually cut at one point. A wire was pulled. There was a decorative eye missing - though apparently the announcer got his hands on it and added it to his hat, much to Susy’s amusement.

When we got back to the our table in the pits, we had a very sober assessment of the damage. The tournament was, after all, double-elimination. Upon first look, I couldn’t envision how on earth we could fix this. We didn’t have spare parts. We didn’t have an awful lot in the way of tools beyond the stuff used to build it in the first place and a few tools I happened to have around the house for non-bot reasons. I hate to admit it, but I was tempted to suggest we drop out of the tournament.

But I kept that thought to myself. This was a decision for the team captain to make, and I would follow their lead. And Susy wanted to cobble something together. It was a struggle and a half, I’ll tell you. We sourced “parts” from other people’s trash. We borrowed tools and screws. We made trip after trip to the test box to see if maybe this time it would kind of work ok enough.

After a few hours of nearly non-stop motion on our team, we got Henry to a point that Susy was willing to call drivable, or at least as drivable as it was going to get. The new “wedge” was one kind of plastic, thoroughly covered in duct tape, then another kind of plastic, covered in several more layers of duct tape. We never did replace the eye; rather we dubbed it “Zombie Henry,” as it was clearly completely dead and had kinda-sorta come back to life, but in a hobbling sort of way.

We got the duct tape idea from our neighbors, who pointed out that it can blunt the force of a spinner, and by that point we were able to look up our next competitor and see it was another horizontal. I still had my doubts about this strategy, as it gives up on the ramp’s deflection capabilities. That said, one can’t really question much, much more experienced competitors, especially ones already lending tools, especially under such time pressure. And the team captain seemed to agree, so I wasn’t going to push the issue.

We did get a bye - we had a round without an opponent to match up against, which helped with the repair time.

Ready for round two

The next matchup was Henry versus Pluticorn’s Revenge.

Competitor #2: Pluticorn’s Revenge

This bot was a two-wheeled undercutter with its weapon axis rather close to its center of mass, which seems a little less fashionable these days, even if I still prefer it.

It didn’t take long to see how Henry was going to hold up this time around. Pluticorn’s Revenge was able to slice right through our makeshift front panel with ease. After only 26 seconds of a nominally two-minute fight, Henry was no longer able to move at all (we would later learn a wire had been sliced). Susy turned to me and said, “Oh, no!” as it was clear what was happening. At this point the question was really whether to allow the opposition to continue to beat on Henry and get counted out, or tap out early to salvage what was left of the bot. As this was our second loss, there was no longer any strategic point to tapping out, as I had discussed with Susy on the way in - it was really time to leave it all on the table. But, on the other hand, clearly there would be no conceivable way to win the match. Also, standing there not driving, and watching your bot get bashed, isn’t a ton of fun.

So I simply asked Susy, “Would you like to tap out?” The opponent heard our conversation and stopped driving to turn and listen in. Susy tapped out, and it was over.

All tapped out

As an aside: BattleBots doesn’t have tapouts. Sometimes the competitors will have a gentlemen’s agreement and the to-be-winner will simply wait for the count-out. Other times, Riptide feels the need to do nigh-irreparable damage to Shredderator, and there’s nothing anyone can do about it, because them’s the rules. It’s just one of the ways the TV show differs from typical competitions.

So yeah, we didn’t exactly tear up the world with a mind-blowing winning streak. But I think we put up a respectable effort, learned some, and had fun. And while the drive was longer than I would prefer, it did give us plenty of time to chat/bond/make memories, and that’s a win of its own.

What comes next?

Well, there’s two plans, which we may advance in parallel.

On one hand, there’s a pretty significant competition at DragonCon in September we may want to participate in. That’s enough time to do a somewhat significant build, but knowing that unforeseen failures come with breaking new ground, we’re reluctant to do the big ambitious thing. So for now, we plan to fix and upgrade Henry instead. In particular, the plan is to get the pre-packaged horizontal spinner add-on. On one hand, that’s kinda cool because Susy always liked Tombstone on the show. And on the other hand, it’s perhaps somewhat ironic/poetic if you look at the opponents we lost to in our first go-round.

The bigger plan hearkens back to the early days of Susy, Lily, and I watching classic BattleBots together. They both went through the mental exercise that lots of new fans do: “What would I build?” Without my prompting, they both sketched up their ideas, which I think is quite cool. What is perhaps even cooler: it sounds like Susy wants to make “This Side Up” a reality (but at one pound rather than 250 pounds). It’s going to take some time to do that right, especially since neither of us have the background for this.

Because mistakes are easier to fix in software than hardware… because custom parts are easier to order if you have a CAD drawing… and perhaps at least a little bit because I’m a software guy and find it less intimidating… I insisted we start the lengthy process of bringing This Side Up to life with a little CAD. We haven’t even finished that part, but here’s a sneak preview of the unfinished first draft:

The next bot takes shape…

Our next bot may be just a plan and a gif at the moment, but one thing I learned from this first foray into competition is that planning, building, and driving with my team captain is an adventure worth undertaking.


1. I feel the need to insert a minor note on terminology. I’m not in love with the term “combat robotics,” especially since search engines often think you’re asking about machines of war, but it’s the most accurate of the widely-used terms. For example, if you look it up on Wikipedia, you’ll see they call it Robot Combat. And that immediately begs the question over whether these machines are, in fact, robots.

Much ink has been spilled, and an entire podcast founded, over arguments about what does or does not count as a “robot.” On some level, it doesn’t matter. In my opinion, that podcast’s definition is ridiculously too narrow, but nonetheless most of the machines we’re talking about here aren’t robots, which is why I call them “bots.” Software “bots” are called that because they have some attributes of robots (in particular, automation), but lack other features needed to be robots (hardware). These machines are the exact inverse - they are extremely similar to robots physically, but in most cases lack automation.

You would be permitted to enter a true robot into a combat robotics competition, by the way, as long as you follow some safety precautions (see rule 7), but few people do. It might seem counterintuitive to refer to a non-robot activity as robotics. It actually works, though, as “robotics” means “The science and technology of robots, their design, manufacture, and application”, and there is no doubt that the technologies and techniques at play here certainly do transfer over to building true robots. 

2. I’ve also made a point to avoid the word “sport”, which to me is a game which is also an athletic competition. Soccer, basketball, tennis, and boxing are all clearly sports by this definition. Combat robotics isn’t particularly athletic - the question is similar to whether “e-sports” are sports, and I think not. As an illustration, I would claim discus throwing isn’t a sport for the opposite reason - it’s certainly an athletic competition but I wouldn’t consider it a game.

John Turpish
John TurpishSenior Backend Engineer, Little Bear LabsLinkedIn

John's a dev who likes to build to last; most known for his work in native-compiling languages like Rust & C++. Dive deep or collaborate: why not both?

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