JosuéBalcárcel

First combat robot design, and the first time I ever opened a CAD package. Fusion 360's interface was intuitive enough to self-teach the fundamentals (sketches, constraints, basic assemblies) while building this. Never manufactured: I didn't have the shop access or know-how yet to take it from screen to metal. But turning sketches into a working 3D model was the moment that confirmed mechanical engineering was the right call. The image is a screenshot straight from the working file, construction geometry, stray 55° dimension callout and all.

First iteration to actually reach competition. Drive came from two Fingertech Mega Spark brushless motors (2300kV); the weapon, a spinning drum inspired by BattleBots' Minotaur, ran off a 1200kV brushless motor. Every motor, ESC, and the battery connected through bullet connectors for fast field repairs. Final weigh-in: 2 lb 15.9 oz, under the 3lb cap after trimming the weapon and bottom plate.

DESIGN PROCESS

• Aluminum sheet chassis: light, and easy to cut on my high school's laser CNC
• Simple rectangular chassis, prioritizing assembly speed over optimization
• All components sketched and modeled in Fusion 360

Chassis panels were cut the same way as before, on the plasma CNC, but the side panels ran longer so they could be bent around the redesigned bearing holders. Same drum weapon, trimmed to fit on a bandsaw. Complete and ready for competition with no pre-battle issues.

WHAT WENT WRONG

On weapon spin-up and first contact, both 3D-printed bearing holders cracked, loosening the weapon and taking it out of the fight. The aluminum chassis picked up bends and dents too, a clear signal that the material and design margin weren't enough for what combat actually demands.

The headline change: wheels were gone entirely, replaced by a shuffler locomotion system. NHRL awards a weight bonus for non-traditional locomotion, and Melvin cashed it in on thicker AR500 steel weapon blades with more strike surface, cut by SendCutSend and mounted on a timing pulley between the two blades.

The chassis kept V4's proven approach, printed as a single piece in 95A High-Speed TPU, with the inner back corners re-engineered so the shufflers slide in as self-contained modules. With no clear shuffler reference designs online, the mechanism went through numerous designed-built-tested variations, prototyped in PLA, with the final shuffler feet printed in TPU for traction in the arena.

AN UNPLANNED WIN

The TPU chassis took multiple hits with only minimal damage, and a print imperfection did the rest. The outer walls came out with a stringy, "spaghetti" texture; mid-fight, an opponent struck Melvin's side and their weapon snagged on the loose strands, which wound into their weapon motor, overheated it, and set it on fire. Sometimes the defect is the feature.

The current build, and the first clean-sheet redesign since the original. Instead of another patch on the existing architecture, V6 is built around a brand-new modular system: subsystems designed to be swapped independently, so a damaged section means replacing a module between matches instead of rebuilding the robot. The same idea changes strategy, since one chassis can run different configurations depending on the opponent: wheels when a matchup calls for speed, shufflers when the weight bonus buys more armor or blade, weapon swaps to counter whatever is across the arena. Every previous rev's lesson feeds into the platform, from V3's cracked bearing holders to V4's energy-absorbing TPU. The result is a single platform that adapts match to match.