Baby Blue Huge

Shortly after arriving at WPI, I was told about an on-campus plastic antweight competition for bots built over a weekend. I thought it would be fun to make a mini huge for this event. 

I started with some wheels laser cut out of EVA foam mats. I just stuck a 1/2" bore on them because this was the first part I was making and I didn't have a full plan for the rest of the robot.

From there, I designed a 3d printed hub to hold the wheel directly onto a 3mm shaft. It used a #4 setscrew threaded into the plastic to stay on the shaft and had the essential self-righting sticks integrated into them. The two pieces are held together using 4 plastite screws going through the wheel and aligned with the 1/2" bore for the wheel.

With the wheels taken care of, I started designing the frame. I planned on having a hollow dead shaft connecting the two halves so that wires could be run between them. To prevent the shaft from rotating, a hole was put in each end of the shaft for a plastite screw to go through and pin it in place. 

From there, I just added a cavity to press-fit the 12mm motor into, an area to put electronics, and a mounting point for the feet that stop the body from rotating when the wheels spin. 

Since I didn't want to mess with multiple receivers in each half of the robot (and also didn't have a spare receiver), I decided to stick all of the electronics in one half of the robot and route the two motor wires to the other half. This left one side empty and the other side packed with electronics.

I decided to friction-drive the weapon because I haven't found belts to be reliable in insect classes and it would simplify the weapon assembly. I laser cut a foam friction-drive wheel out of the same EVA mat used for the drive wheels and glued it directly onto the can of the outrunner for the weapon. The outrunner was bolted onto the frame and the blade was designed with a flat section for the wheel to run on. The final speed of this weapon is theoretically about 10k RPM because there is a 1:1 ratio on the friction drive wheel and the weapon motor is 1000 kv at 3s.

For the first event, I 3d printed the center shaft to keep the build to one weekend.

After some assembly, baby blue huge was ready to compete.