How to Build a Combat Robot

Combat robots are cool and you can build your own. Check out this 3-part video series on how to build one yourself!

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Relevant Public Service Announcement: The call for makers for NoCo Mini Maker Faire closes at the end of the day today, so get your applications in and we'll see you there next month!

Robots are cool. I tend to like robotics for the same reason LEDs are so popular; you get to see something happen when you power up your project. Sure, posting data to the Internet is cool and all the rage these days, but seeing something move under your control is really neat. Also, when you get to see your newest creation break stuff, that's REALLY fun.

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Casey posing with his 60-lb combat robot

Combat robots are more than just just mindless destruction though. One of the things I like about them is the design challenge. Everything has to work perfectly AND under extreme conditions. It's one thing to get something moving, but to do so while something is trying to destroy YOUR robot adds another level of complexity to the design. Additionally, when you show up to an event, you have no idea what you'll be going against. Sure, they'll be the same weight, but you have no idea what weapon they might have, how fast they'll be, or what crazy armor configuration they'll use. You need to design for the unknown.

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Last year, Casey tricked me into building a combat robot. I say 'tricked' because once I built one I got hooked. We even incorporated the competition at the last SparkFun AVC. After AVC, I decided to create a small series of videos showing the basics of building a small combat robot. I'd love to see more people building them and competing around the country. Starting small is the way to go; you learn a lot and you don't have to spend a ton of money doing so.

The first part of my video series is concerned with the design. I chose a spinning drum, mostly because that's what I had seen work with Casey's larger 60-lb robot (shown above). Start with what you know. The robot's name is Sgt. Cuddles and he just wants a hug. Cuddles competed at RoboGames 2015 in San Mateo.

When you build a robot, you have a big choice to make. You can go for offensive, or defensive. Weapon or wedge. This is the choice all combat robot builders make. Build a weapon, and you get to see parts fly. Build a wedge, and you most likely have a better chance of winning. I went with a weapon, because wedges aren't any fun. Part 2 focuses on the spinning drum.

Lastly, the electronics. This is the part everyone's probably most interested in. Before I built Cuddles, I hadn't really done much with RC before. I had never seen inside a combat robot and didn't really know what made them run. After doing a bit of research I found that it's actually pretty easy to piece one together. Having it do well in a competition is another story though...

Now that you're all amped up to build a robot, you might be wondering where you can compete! We have good news for you. The same arena that was at this year's AVC will be at NoCo Mini Maker Faire, October 10th and 11th. I will be building a new 3LB robot for the competition. Be sure to susbribe to my channel for more robot videos and other stuff. Also, if you have any questions, post a comment. Now get building!

Comments 15 comments

  • Mr. Ben / about 7 years ago / 1

    Just curious. What size was the combat arena at the Sparkfun AVC? It looked to be an approx 6ft x 6ft footprint. Thanks.

  • BeerCannon / about 7 years ago / 1

    Now you need theme music (sung to the tune of Sgt. Pepper's...) "Sgt. Cuddles Antweight Combat 'Bot"

  • SMTGuy / about 7 years ago / 1

    Great videos! One question, in the first video, you show Solidworks (or a plug-in) or something, running your CAM simulation. What software are you running there? I have Solidworks, I'm building a CNC, and having CAM output is the next hurdle.

    • that's HSMXpress. It's a FREE plugin for Solidworks for basic 2.5D CAM stuff. It's really nice. I've been using it for a couple years. You just click on the CAM tab and go. I highly recommend it. It also has export settings for most machines, including Mach3.

  • Mr. Ben / about 7 years ago / 1

    Robert, awesome video series!!! My son and I are working on a Battlebot with a sheet metal frame (it's simple & we don't have CNC access). We'd like to use a Redboard (& relays) instead of a bunch of speed controllers for driving the motors. Sound doable? I saw a post by Nick a few years back doing something like this.

    • Honestly, it's possible, but not recommended. You really want/need a speed controller instead since relays just aren't optimum for reversing quickly. A speed controller will be a simpler and easier way to go. You will need an RC transmitter (as per the rules), so you might as well go with standard speed controllers. You CAN use the ArduMoto shield and have the Arduino read in the PCM signal from the RC receiver. that's relatively easy to do. But you need a proper motor driver, relays won't cut it.

  • Sembazuru / about 7 years ago / 1

    Something that you didn't cover was exactly how heavy Sgt. Cuddles weighs and if you had to make any design changes to choose lighter (or were able to choose a heavier) part.

    Also, how much concern is there for damaging the batteries from all the impacts these robots expect to sustain? (I ask as I'm looking at an inflated LiPo flat-pack in a pocket charger that I've dropped on the ground once too often...)

    • Good questions.

      I did the design in solidworks and manually added the parts that I bought (added their weight with the models), and then used the materials tool to define the density of all the other materials. Once the design was done, it was within a gram or so of reality, so I came in 5% under weight, which is what I wanted. The scales at the events aren't necessarily calibrated. I also have a second set of screws for the weapon which were longer, so I could add a few grams that way.

      For the batteries, as long as they last a 3-minute match, you're fine. I'm still using the original battery, but with enough fights, it will probably swell up and need replacing. It's seen as a consumable, but it's only $10 or so. The armor plates and the chassis takes nearly all of the impact. With the internals floating around, a LOT of the impact gets dissipated and doesn't translate directly to the battery or electronics.

  • Member #2129 / about 7 years ago / 1


    So my son, age 6, and I watched Battlebots this summer and he is super excited by it. He wanted to start building a bot together and I am all for the Maker Spirit he has. I thought it might be the easiest to start with a kit per say so he can do some of it himself. Any suggestions? We are open to guidance and help on this.


    • M-Short / about 7 years ago / 1

      Also, if he's not wanting to battle at this point check out some of our kits. The Redbot Basic and Redbot SIK are the only all in one kits, but we do have a few different chassis and motor drivers.

    • Sure thing. Check out FingerTech Robotics. They have kits. I have zero idea what a 6-year old can and can't do, but that's as easy as it can possibly get for building a robot. They have instructions and will be a nice simple build without surprises.

  • BeerCannon / about 7 years ago / 1

    Thanks for the great videos, and the amazing "Beardtronics" logo.

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