Scrappy — 1 lb Antweight Combat Robot
// ABSTRACT
Scrappy is a 1 lb antweight-class combat robot I designed, fabricated, and competed with as President of Duke Combat Robotics. Through six competition seasons and four major design revisions (V2 through V5), the robot evolved from a first prototype into a battle-tested machine with a 19-6 record. Each competition produced a new design brief — structural failures drove material changes, weapon inefficiencies became geometry revisions, and pit-side repairs under 20 minutes became a discipline of their own.
SKILLS
TOOLS
Background
Duke Combat Robotics designs and competes with robots at the 1 lb antweight class — one of the most constrained weight classes in combat robotics. Every gram is accounted for. The robot must survive direct weapon-on-weapon impacts, deliver reliable driving in a chaotic arena, and be field-repairable in under 20 minutes between rounds.
Scrappy started as my personal entry into internal Duke competitions and grew into the team's flagship robot through iterative competition-driven development.
Design Philosophy
Antweight combat robotics is a systems engineering problem: maximize weapon effectiveness and drivetrain reliability while surviving the worst your opponent can deliver — all within 453 grams.
Every version of Scrappy reflects a deliberate trade-off between aggression (weapon power and reach) and resilience (chassis stiffness, motor protection, wiring survivability).
Weapon System
Scrappy's weapon is a horizontal spinning bar, chosen for its wide strike zone and capacity to store significant rotational kinetic energy. The weapon motor is a high-kV brushless outrunner paired with an ESC tuned for rapid spin-up.
Key design iterations across versions:
- V2: Initial bar geometry, direct-drive weapon mount
- V3: Widened bar for increased reach, improved weapon motor mount to reduce flex on impact
- V5: Revised chassis geometry to lower center of mass; weapon mount reinforced with hardened steel bushings
Drivetrain
Four-wheel drive using brushed gear motors chosen for their torque-to-weight ratio and replaceable gearboxes. The drive system was designed for fast directional reversals — a critical competitive advantage in antweight matches where arena control is won on agility.
Electronics
The control stack was intentionally minimal and robust:
- Receiver directly driving motor controllers (no microcontroller in the signal path — less to fail)
- Custom wiring harness with heat-shrink strain relief at every connector
- LiPo pack oriented to protect leads from weapon hits
- All components secured with vibration-damping foam to survive weapon-on-weapon contact
Fabrication & Manufacturing
- Chassis: HDPE panels for the outer frame (high impact resistance, self-lubricating), steel inner structure for weapon system support
- CNC-milled aluminum motor mounts
- All electronics hand-soldered and continuity-checked before every event
Competition Record
Scrappy competed at 6 events (Duke internal and regional open competitions):
| Version | Season | Record | |---------|--------|--------| | V2 | Spring 2023 | — | | V3 | Fall 2023 | 1st Place — Duke Fall 2023 | | V5 | Fall 2024 | Top competitor |
Overall record: 19 wins — 6 losses
Pit Engineering
Between matches, robots must be inspected, repaired, and ready to compete again — often within 20 minutes. This forced a design constraint: every component must be accessible and replaceable quickly. Scrappy was designed with modular electronics mounting and tool-accessible motor screws specifically to enable fast pit turnaround.
Lessons Learned
Competing six times with the same robot, improving it each iteration, built a design instinct that no classroom project can replicate. Failures that cost matches became the specification for the next revision. The 19-6 record reflects both the wins and the losses that improved the design.