NHRL Combat Robot “Abyss”

An image of the CAD model of a robot. The outer shell is hidden, revealing the motors and electronics inside.

An image of the CAD model of the same robot. The outer shell is shown, revealing metal armor on the top and bottom, and plastic armor around the sides.

A photograph of the finished robot. It has the same metal and plastic armor.

I started building a combat robot at the end of my sophomore year of high school. I worked with my friend Mtnash to design and build it. I did all of the CAD work while she helped with the fabrication, assembly, and brainstorming.

A photograph of an early robot test. There are three motors with wheels spaced evenly in a circle on a plywood frame. Each wheel has small rollers around the edge, which allows it to roll in any directon.

A photograph of a later version of the same test. The frame is more robust, with plastic and plywood. The motors have gears attached between them and the wheels, which are the same as the last version.

When we first started building the robot, we wanted to use Kiwi drive: 3 omni-wheels that would let us move in any direction. While we were able to get a prototype drivetrain mostly working, it proved to be quite tricky to drive well, and we decided that it would be best to shelve that idea for the time being and try a different approach.

Our next idea was a two wheeled robot with a very large centered spinning weapon. We didn’t use this idea either, as even the initial CAD model was several pounds over the weight limit. However, you can see the resemblance to our final robot design.

A CAD render of an later robot test. I has a long, thin, body with a large spinner that runs from end-to-end. It has normal wheels, and metal armor on the top and bottom.

A fun side note about this design is that the concept of a robot with a large spinner slightly ahead of two wheels is very similar to one of the robots that we ended up fighting - Chris Griffin 2. They ended up soundly defeating our robot, so this might be an interesting design to come back to.

Our final design is a “clamshell.” All of the electronics are housed in a TPU shell, which has cutouts for mounting plates and armor. The TPU pieces are held together with bolts that also attach aluminum top and bottom plates. I designed the whole robot with OnShape, which lets me share the whole design with you. You can find it online here:
https://cad.onshape.com/documents/7b9e0380ea9a5bf7b2ecf193/w/0419c64438c575769c294494/e/4f67d6fe28c8eec2e034a99d

A photograph of the robot during construction. All of the electronics components are tightly packed into a 3D printed plastic shell.

This body design proved to be very robust. Apart from one time when we got hit so hard that it unplugged our battery, none of our electronics were ever damaged from a hit. We learned to always glue our connectors together.

Unfortunately, our weapon mounting was not so robust. Our weapon was cut from AR500 steel, and was mounted on two pulleys turned from mild steel. These were mounted in bearings that sat in the aluminum plates. Unfortunately, an undersized dimension caused the pulleys to sometimes rub on the aluminum. The rubbing created enough friction to prevent the weapon from always spinning at full speed. Even worse, every time our weapon was hit, the bearings would crack and need to be replaced. Thankfully, I brought a lot of extra bearings to the competition.

A CAD render of the final robot weapon system. The weapon has a steel pulley bolted to each face, which is in turn sandwiched between two aluminum plates.

In order to make this robot, I had to machine several custom parts. All of the aluminum parts I was able to manufacture in my shop. However, the steel components were manufactured by SendCutSend and RapidDirect.

A photograph of 12 wheel hubs that I machined. They are small aluminum blocks with a large hole through the top face and a small hole for a set screw drilled into an edge.

A photograph of an aluminum plate which has been CNC machined to make the top and bottom armor plates.

A photograph of the finished robot showing its very shiny CNC machined aluminum armor plates.

A photograph of parts layed out on a workbench. There are six batteries, eight weapon motors, two weapons, 12 wheels, and probably hundreds of extra parts. — *Above:* Arranging almost all of the parts (and spares) that I brought to the competition.

A photograph of the robot fully dissasembled. Each component has been fully removed, and they are layed out geometrically. — *Center:* Knolling all 95 components for Abyss.

A photograph from a fight with the robot. Both robots are driving toward each other.