Latest iteration of spinny boiii, with a custom CNC-machined weapon and bulky TPU armor
Internal electronics layout with motors, motor controllers, RC receiver, battery, and power distribution
Winning the face-to-face engagement with a shower of sparks!
Took some heavy damage but still eeked out the win
Powerful hit launches opponent "Action Surge" airborne at ARC Roborumble 2024
spinny boiii - 3lb Combat Robot
A competitive beetleweight combat robot with an egg-beater drum weapon and a powerful magnet-assisted drive system
Quick Facts
“spinny boiii” is my first competitive beetleweight (3-pound) combat robot. The design we settled on is a compact 2-wheel-drive (2WD) chassis with a wide beater bar drum spanning the front of the bot. I started building this robot in 2020 with my teammate, Benji Miller, while I was creating ASU’s student combat robotics program. Read more about each version of the robot below.
Design Iterations
Version 3 - spinny boiii gets competitive
Major redesign with an overhauled weapon system and updated materials
Quick Facts
Version 3 of spinny boiii (yes, we add an extra “i” for each major version) proved to be a major step forward in both performance and reliability. The previous version was reasonably durable against vertical spinners, but if it was hit hard by a horizontal spinner, the front side armor and weapon mounts would fail, often resulting in a fully ejected weapon. The biggest change in V3 was the addition of a dead shaft mounted to thick TPU side rails, preventing them from being pulled apart. The metal front side armor was replaced with thick TPU guards, which can have chunks torn free but don’t deform plastically. These guards take a lot of damage, but they are easy to replace and cheap to make.
This version also benefited from a lot of custom CNC-machined parts that I machined at work. These include a S7 tool steel beater bar weapon (which I hardened to 54HRC in my heat treat oven at home), aluminum timing pulleys, and a weapon motor mounting insert that doubles as a small heatsink. Since upgrading to machined pullies, we have yet to break a timing belt, even after 22 fights, and there is effectively zero pulley wear.
Just-machined drum, clamped in the mill's vise with soft jaws
The beater bar (right) was machined from a $10 offcut of S7 tool steel (left)
Finished drum with its needle bearings and dead shaft
CNC machined aluminum timing pulleys
Two drums in the heat treat oven
Drums air-quenching after the initial treatment
A heat-treated drum with its pulley. The white TPU insert helps reduce shock transfer to the weapon motor
One of the beater bars broke during its 5th fight, but it kept spinning and we won! Future versions will improve the drum durability
Major Improvements
Weapon System:
- New CNC-machined S7 tool steel drum (asymmetric egg-beater design)
- Hardened dead shaft mounts to thick TPU side rails, preventing them from pulling apart during side impacts
- Custom CNC aluminum timing pulleys, with TPU mounting insert to reduce shock transfer to the weapon motor
- No screw holes in the drum to prevent stress risers and cracking (pullies mount with driving dogs instead)
Drive System:
- Repeat Pro 2006 motors, for more power and tougher gearboxes / shafts
- High-quality magnets from K&J Magnetics, for better traction
- Clamping wheel hubs with D profile to prevent slippage
Frame and Armor:
- T700 carbon fiber top and bottom plates, joined with aluminum standoffs
- Thick TPU side rails help reduce shock transfer to the motors
- Bulky TPU front guards are strong enough for 1-3 matches, don't fail catastrophically, and are easy to replace
Electronics:
- Upgraded to BA2320-1860kv for higher tip speed
- Upgraded to ELRS receiver for better signal reliability
- Silicone foam wrapping for better shock absorption
- Conformal coating of electronic potting compound to protect against impact and debris
Fight Video Playlists
Version 2.1 - First taste of victory
Material overhaul with magnet-assisted drive and refined weapon system
Quick Facts
Version 2.0 - spinny boii's makeover
Complete redesign, converting to a 2WD drum spinner
Quick Facts
Version 1.0 - spinny boi's first steps
Barely drove, but we learned a lot
Quick Facts
