Control bots & ground game
A control bot has no active weapon. It wins by getting under opponents, controlling their movement, exposing them to arena hazards, and surviving to a judges’ decision on damage, aggression, and control.
Ground game — whatever gets you under the opponent — decides most head-on engagements, so it matters on weapon robots too. Being underneath breaks the opponent’s traction, lifts their wheels, points your armor at their weapon, and disables most of their weapon types while enabling yours.1
Why getting under works
Section titled “Why getting under works”Sliding under the opponent:
- transfers their weight onto your driven wheels, raising your pushing force and lowering theirs,
- lifts their wheels off the floor so they can’t drive,
- presents your armored underside to their weapon instead of your vulnerable sides,
- feeds them into your weapon, if you have one.
Forks — the modern standard
Section titled “Forks — the modern standard”Long narrow prongs that ride on the floor ahead of the robot. Their small contact patch is easy to keep flush, so they get under almost anything — including wedges, which is why forks displaced wedges as the primary ground-game tool.1
- Sharp forks — short and pointy, mostly on vertical spinners. Guide the opponent into the weapon and stop wedges getting under; out-reached by longer forks, so paired with weapons that already counter long forks (drums, eggbeaters) or with fast flanking drive.
- Reach forks — long, optimised purely for getting under and controlling. On head-on hits they slide into the gaps between the opponent’s shorter forks and lift first. Heavy and vulnerable from the side; common on lifters and overhead bots.
- Corralling forks — long forks on the front corners, often soft plastic. Stop opponents escaping a pin or getting to your sides, and widen your footprint for stability.
Bring spare forks to every event — they wear and bend.1
Wedgelets
Section titled “Wedgelets”A middle ground: extra-wide forks or angled plates covering more of the front. More durable than forks and better against off-plane hits, but they struggle to get under real forks. Used like sharp forks.
Wedges
Section titled “Wedges”A full sloped front face. Simple and durable, but the large floor contact makes it hard to keep the whole edge flush, so narrower forks slide under it. Don’t rely on a plain wedge to get under a modern opponent.1
Wedges do have one strong modern use: anti-horizontal armor. A hard, flat, upward-angled face — usually bent titanium — deflects a horizontal spinner’s blade upward instead of taking the bite, and most horizontals carry no ground game to punish the wedge in return.1
Wedge / fork geometry
Section titled “Wedge / fork geometry”- Front-edge height: as low as the arena floor allows. Sub-millimetre gaps are normal on competitive forks. Arena floor seams and your own flex set the practical limit.
- Angle: shallow (10–30°) to get under; steeper resists being wedged in return.
- Coverage: watch the corners — gaps there are where opponents get a purchase.
- Rigidity: a fork or wedge that flexes up under load loses its gap. Back it with ribs, a stiffener plate, or a hardened edge.
- Surface: hard and smooth on top so the opponent slides up; well-supported underneath.
Downforce magnets
Section titled “Downforce magnets”On steel-floor arenas, neodymium magnets in the baseplate add normal force without adding weight the way ballast would — more traction for pushing and more resistance to being flipped. Common on control bots and wedges; set wheel hardness and ground clearance to suit the extra pull.1
Ground clearance and skids
Section titled “Ground clearance and skids”The front edge and hardened skids define ride height. Set it so:
- the front edge bites under opponents,
- the robot still drives when inverted,
- you don’t high-centre on floor seams or the kill-saw slots.
Materials
Section titled “Materials”AR steel or spring/tool steel for the working edge of forks; bent 6Al-4V (Grade 5) titanium for anti-horizontal wedges; UHMW, HDPE, or TPU for low-friction and soft corralling elements.21
References
Section titled “References”Footnotes
Section titled “Footnotes”-
Ping, L., with L. Skotiniotis, I. Talbert & D. Tran. Beetleweights for Dummies (Fall 2025 revision) — builder-maintained beginner guide distributed via the NHRL Discord. Sections: Ground Game (Wedges, Forks, Wedgelets); Robot Archetypes (Wedge Bots, Lifters). ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7
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Meggiolaro, M. A. RioBotz Combat Robot Tutorial, v2.0, PUC-Rio, 2009 (CC BY-NC-ND) — wedge geometry, ground clearance, and edge materials. ↩