Bringing an Arena Out of Retirement

Posted in Uncategorized by Near Chaos Robotics on April 27, 2015 No Comments yet

This weeks post is going to take a bit of a different direction from the last few. Instead of talking about broad topics and skill building it will be on a recent project. In this case, it’s on the repairs and upgrades I’ve been making to an insect class combat arena.

The arena itself was originally used for Robot Battles events and was retired after Dragon Con in 2011. After that, it sat in a garage for a few years until the owner offered it up free of charge to whoever was willing to give him a bit of space back. I took him up on the offer and we got the arena moved from his garage to mine.

After a dusting and de-cobwebing the arena was ready for work to being. First up was a lot of patching on the floor:

A few hours of wood filler and sanding and the floor was relatively flat and ready for paint. I decided to go with a basic white paint as that’ll help the robots show up well on video and it’s going to get battered eventually and white will make for easy touch-ups.

With the painting done it was time for a test fit of a few critical components, namely the legs and lexan. A bit of wrestling with it and the arena was set up and ready for a bit of testing. I tossed Algos into the box and took it for a test drive. Overall, it worked quite well. Traction seemed decent and the wedge on Algos wasn’t finding any places to dig in.

The final bit of painting was up next. I was able to get an acrylic template for the starting squares cut at Freeside Atlanta. (

Some masking tape, paper, and a bit of time with the spray paint and the new starting circles were added. I decided to keep with the red/blue scheme the arena started with.

The observant reader will notice a large hole to one side of the floor. That hole is for the arena hazard. Obviously I couldn’t leave the hole open for combat, so the next order of business was to figure out why the arena hazard wasn’t working properly. Some experimentation in the shop revealed that the main problem was that the solenoids used to power the flipping plate could overextend themselves and jam, preventing the hazard from firing properly. To solve this I 3D printed four stop-blocks that were then glued into place using Goop.

A bit of testing later and I was convinced that the flipper was working well enough. With the hazard reasonably fixed it got a quick orange and black paint job to match the arena walls.

If you’re wondering how it works, there’s a contact switch in the flipper plate itself that’ll trigger the solenoids when it’s depressed. The solenoids are installed backwards and slam their rams into an angle bracket that pushes the flipper plate up, hopefully sending the offending robot into the air. In testing it was capable of sending a 1lb bot from the wall to the middle of the arena.

This left one major detail that still needed to be addressed, the pushouts. The openings in the wall are meant to allow robots to be eliminated by their opponent shoving them off of the combat surface. I wanted to create a pit that would be reasonably light, durable, and securely attached to the arena frame. After a bit of messing around with ideas I settled on steel framed baskets with an expanded metal skin and a thick foam lining.

The whole thing is made from steel that has been cut, bent, and welded into shape. The main structure is 1/4″ steel rod which slots into a pair of holes at the edges of each pushout. This attachment method allows the pits to be quickly dropped into place for easy setup and minimal risk of a robot escapee.

As with many things, the final detail was the paint. Each pit was hand made to match hand drilled holes, and because of that, they’re not identical. The pits were color coded to match the side of the arena that they fit to make things easier during events.

The last bit of work wasn’t much in the way of actual work. One of the two halogen bulbs had been destroyed at an event and was never replaced. I spent a bit of time looking around and found an LED replacement bulb and swapped in a set of them in the hopes that they’ll be more durable and be less of a safety risk since they should run a fair bit cooler.

At this point the arena’s in good enough shape for its first event, which is a good thing as it’ll be getting used May 9th at Freeside Atlanta for the first Freeside Robot Street Fight. (

There is more work planned for the arena. The next major addition will be the creation of another hazard that can be used at events.

Thanks for reading, if you’ve got questions or requests for future articles send me an email at or post it over here: