My 1LB Combat Robot, Will Turner

I built a 1LB Combat Robot over the course of the past few months. It has been a lot more fun, and stressful than I ever thought it would end up being. I even managed to compete down in Texas on June 2, this year. The process to get there has been fun, and also a lot longer than I expected it to be.

It all started about eight months ago when I bought myself a 3D Printer, the Ender 3. 3D printing as a technology has always fascinated me, and when I say always, I mean for at least ten years now. It was only recently that strides have been made in the technology to allow it be much cheaper, as well as reliable enough to be used by the masses. I have also managed to find steady employment and time enough to work on my printer.

I was originally inspired to make my own combat robot by the /r/battlebots subreddit. It’s a mix of a TV show fan-base, as well as a community for amateur builders. I followed it because I am a fan of big robots destroying the crap out of each other, and was introduced to the hobby side of it.

This hobby side is what I am happy to talk about today. Battlebots as a genre is generally limited only by weight, and un-fun weapons. Things like nets and radio jamming aren’t fun to watch or fight, and so they are disallowed. The only other real limit to what can be built is your imagination. The battlebots TV show usually has robots that weigh between 60 pounds and 340 pounds. Its an awesome amount of destruction, and totally worth watching.

However, these huge bots are hard to start making, and expensive to maintain. Going all the way down to one and three pound robots is a lot easier, and also a lot less expensive. This is where my 3D printer comes in. It is not only viable, it is actually often done where a robot uses 3D printed materials as their robot body / base. And thus; the seed of my idea was planted. I have a 3D printer, why not make my own tiny robot to fight with?

Parts for my robot ended up being well, not cheap. I had no RC equipment when I started, and had to buy everything from scratch. I also had no real tools to work with besides the very basics, so I had to buy that as well. However, for the robot internals alone, with spares, it cost me about $200. I also had to buy a radio, and the aforementioned tools.

Plastic for my robot is actually really cheap, which is a good thing. I ended up making a LOT of prototypes. A roll of 1000g of plastic costs about 18$, and each body I made ended up weighing about 80g. So, doing the math, about a dollar each. I switched materials from PLA to PETG (easier to print and cheaper vs more impact resistant) when the prints changed color.

Printed protypes, left to right, oldest to newest. I switched materials once I was fairly confident that it would be put to use.

Far left, I was testing mounting sizes for the internals, as well as various layout options. Next left weight too much, and the gears I had set up for it would not be stable enough to work. Middle bot had support for two drills, but that one would never make weight limits. I have vague plans of two drills in the 3lb category. Far right where minor revisions and fitting adjustments.

I also broke my weapon motor in the middle of testing and fitting, about a week before the combat event started. Luckily, the local hobby shop had a replacement, even if it wasn’t cheap.

As for the design, well, someone on the internet told me that drills were a bad idea. I wanted to do something original badly enough that I decided to take that as a challenge, rather than a discouragement. So far, the guy has been right, but I’m not done exploring this concept yet.

My original idea was an underminder style bot, that would go around poking holes in the other robot. This idea had a lot flaws, so my goal was to mitigate or outright remove them as I found them. Ideas for shovels to push other bots into my drills where added then discarded for weight reasons, dual drill setups where added, then removed for weight reasons. Different wood drills where added, then removed last minute, for weight reasons.

The final design literally wasn’t finalized until I left for the competition, the morning of. Despite all this, I managed to tie for fourth place with my bot at the competition. Okay, due to the way the tournament operated, I lost before I could compete for third place. Regardless, I was very surprised with how well my robot ended up doing.

My brother, and totally awesome person, helped me with the whole process the weekend before, and I could not have done this without him. He also filmed the fights.

The first fight I did was vs another new builder, who had a saw on a moving hand. Since I had never been in a bot fight before, (much less practiced driving my bot) I was basically going in blind, and hoping for the best.

It turned out about as well as a grinder vs plastic could have gone. I also had issues moving, due to me not thinking about castors at all, and issues with the drill being, well, useless. I tapped out when all the power wires were cut. I spent a good half hour resoldering them all with my brother. If someone else hadn’t dropped out, this also would have been the end of my robot, because I didn’t have it all put together in time.

However, I did end up having enough time to resolder all the wires, (barely) and was able to continue fighting. I was still having issues with the movement at this point, and I also didn’t change the battery out, because it would take too long to do. A guy who was there suggested I tape over the screws I was using as castors, and that ended up working way better.

Strategy for this fight was honestly to try to make some scratches on the other bot, and maybe push them into the hazards. The lip on the edge discouraged the last half of my plan, but I think i might’ve succeeded on the first half of my plan.

The second fight went to a judges decision, and I ended up winning that fight, so the judges figured I did enough to get a win. I switched the batteries, and since I sustained no damage that round, I waited for the next fight.

This fight was actually rather sad to watch, as both of our weapons were having issues. Mine kept getting caught on the inside of my bot, and his, well, he just got completely destroyed by one of the top three bots in his previous match. I ended up winning because his bot stopped working, for whatever reason.

It was around this time that my brother noticed that I was continually switching my weapon on and off, with a knob. He was awesome enough to change that particular control to a switch, which made turning it on and off a lot easier. Since I didn’t sustain any damage from that fight, I charged my batteries and waited for the next fight.

My plan was to poke my drill in the hole left by previous fights in the other bot, then turn it on and wreak havoc.

Unfortunately, my drill got actually caught on the inside, and I wasn’t able to turn it on. Howe3ver, the other bot lost power to its wheels, and so I won anyways.

I spent some time playing with the drill after the fight, and it turned out that the inside of the bot was slightly too small, and the set screws were catching on the body of my bot. I turned the drill some, and hoped for the best in the next fight. I did also take a hit from the other bots spinner, but it didn’t stop my bot at all.

Next fight, my bot was running on hopes and prayers. The drill bit would catch regularly when it was turned on, and i had a lot of holes in my bot that I didn’t make for weight reasons.

And that was the end of my winning streak. It turns out, survivability is king when it comes to battle bots. If your bot can’t last the whole two minute round, then you have lost by default. My bot had a terrible weapon, but it was able to survive much longer than a lot of the other bots, and ended up placing much better because of it. However, as soon as I went up against a bot that had weapons that broke my survivability, I ended up losing.

Since my bot lasted acceptably long, my focus for the next competition will be to make the drill much more durable on the inside, as well as much more free spinning. I plan on competing July 6-7, so expect a new post around then.