Bellicopter

Bell Brawls is the school's annual combat-robotics tournament. Bellicopter was the three-pound entry built by four classmates, fighting in a sealed arena against other student teams.

Four brushed motors drive the robot and a 1100 KV brushless motor spins the weapon, each through its own speed controller, all running off a single 850 mAh battery. An RC receiver handles driving and spinning up the weapon from a handset.

The overhead weapon was drawn in Fusion 360 and cut from AR500 steel by R/E Combat Robotics.

Across a team of four I drew the master sketch the robot was built around, then modelled a good deal of what hangs off it — the wheel motor jigs and parts of the chassis. Teammates did most of the manufacturing: laser cutting, 3D printing and casting. I soldered most of the electronics, and drove the robot at competitions.

The weapon does not sit on the motor shaft. It runs on a pulley-driven stack instead, so the shock of an impact is not delivered straight into the motor — the belt absorbs some of what would otherwise go through the bearings.

The robot kept ending up on its back, and once over it could not right itself — which in a timed match is as good as losing. The fix used what the robot already had: a jig on top that spins with the blade, so the weapon's own momentum pushes the robot back onto its wheels.

Thirty seconds from the maker portfolio film: the robot in CAD, the electronics laid out, and match footage from the tournament.

The final design reaches roughly 12,210 rpm and delivers about 4,500 N at an ideal impact — calculated figures for the design rather than measurements taken from a match.