Glossary

This glossary explains common terms used in robot combat. If a term has its own page on this wiki, it's linked. Missing a term? Feel free to add it.

A

Ablative armor

Armor that's meant to be damaged or torn off, absorbing a hit so the robot underneath doesn't have to. Judges are told to ignore damage to purely ablative armor (see SPARC Judging Guidelines).

Active weapon

A weapon with its own power source and actuator, such as a spinner, flipper, hammer or lifter, as opposed to a passive wedge or plow.

Active wedge

A wedge that can be raised or lowered by its own actuator. The SPARC Sportsman rules allow any number of active wedges but only one passive wedge (see SPARC Restricted Class Regulations).

Antweight

In the USA, the 1 lb (454 g) weight class. In the UK, "antweight" usually means 150 g. See Robot Classes.

AR500

A hardened, abrasion-resistant steel plate often used for wedges and armor in larger robots. Very hard, but can crack under sharp impacts.

Arena hazard

A feature of the arena meant to affect the fight, such as a pit, saw, hammer, spike strip or push-out zone.

B

Bar spinner

A spinning weapon made from a single bar, usually with an impactor at each end. Can be horizontal or vertical. See Weapons.

BEC

Battery eliminator circuit – a voltage regulator that powers the receiver and servos from the main battery. See Battery eliminator circuit (BEC).

Beetleweight

The 3 lb (1.36 kg) weight class in the USA; 1.5 kg in the UK.

Bite

How deeply a spinning weapon's tooth can reach into the opponent on each hit. More bite means more of the weapon's energy is delivered. Bite depends on the robots' closing speed, the weapon's speed and the number of teeth.

Brushed motor

A simple DC motor with brushes, controlled by a basic speed controller. Common in drive systems of small robots. See Motors.

Brushless motor

A motor without brushes, controlled by a brushless ESC. Much more powerful for its weight than brushed motors, and the standard choice for spinning weapons. See Motors.

Bye

An automatic win when a scheduled opponent forfeits or doesn't show up.

C

C rating

A battery's rated maximum discharge current, as a multiple of its capacity. A 1000 mAh battery rated 50C can in theory supply 50 A. See Batteries.

Clamp / Clampbot

A robot that grabs its opponent with a clamping arm, often to carry it into a hazard. See Weapons.

Closing speed

How fast the two robots are approaching each other. Higher closing speed gives a spinning weapon more bite.

Control bot

A robot that wins by controlling its opponent (pushing, lifting, pinning, flipping) rather than causing damage.

Crusher

A weapon that squeezes or pierces the opponent with a powerful jaw or arm, often hydraulic or leadscrew driven in larger robots.

D

Disc spinner

A spinning weapon made from a disc, usually vertical.

Double elimination

A tournament format where a robot is eliminated after its second loss. The SPARC standard for classes of 6 or more robots (see SPARC Match Rules).

Drum spinner (drum)

A short, wide spinning cylinder with teeth, mounted horizontally at the front of the robot and spinning upward. Compact and very sturdy. See Weapons.

Dustpan

A wide, scoop-shaped wedge used to get under and control opponents.

E

Eggbeater

A vertical spinning weapon shaped like a looped bar or "eggbeater," usually with teeth at the top and bottom of the loop.

ESC

Electronic speed controller – the circuit that controls a motor's speed from the receiver's signal. See ESCs.

F

Failsafe

The behavior of a robot when it loses radio signal. Rules require all motion (drive and weapon) to stop. See Radios.

Fairyweight

The 150 g (0.33 lb) weight class (called "antweight" in the UK).

Featherweight

The 30 lb (13.6 kg) weight class.

Flipper

A weapon that launches the opponent into the air, usually powered by pneumatics in larger robots or a fast servo or brushless motor in smaller ones. See Weapons.

Forks

Several narrow wedges (wedgelets) side by side, used instead of a solid wedge to get under opponents. They can count as a single passive wedge under Sportsman rules.

Full-body spinner (FBS)

A robot whose whole outer shell or ring spins as the weapon. See Weapons.

G

Gyroscopic effect

The tendency of a fast-spinning weapon to resist changes in its orientation. It makes robots with big spinners turn sluggishly, and can lift one side of a robot off the ground when it turns. Some robots use it to self-right ("gyro dance").

H

Hammer / Axe

A weapon that swings an arm down onto the opponent. See Weapons.

Heavyweight

In SPARC rules, 242.5 lb (110 kg, "UK Heavyweight") or 250 lb (113.4 kg, "US Heavyweight"); some events use 220 lb.

Hobbyweight

The 12 lb (5.44 kg) weight class.

Horizontal spinner

A weapon spinning flat, parallel to the floor, such as a bar or disc. See Weapons.

Hub motor

A motor built into or directly driving a wheel, often a brushless outrunner. Saves space and weight in the drive system.

I

Insect classes

The small weight classes, usually 150 g, 1 lb and 3 lb (and sometimes 6 lb and 12 lb).

Invertible

A robot that can drive normally when flipped upside down, usually because its wheels stick out above and below the chassis.

J

Judges' decision

How a match is decided when neither robot is knocked out by the end of the match time. See SPARC Judging Guidelines and Judging Systems.

K

Kickplate

A strong plate or beam around the edge of the arena floor that takes direct weapon hits so the arena walls don't have to. See SPARC Arena Construction Best Practices.

Kinetic energy (KE)

The energy stored in a moving object, especially a spinning weapon. For a spinner it depends on the weapon's moment of inertia and the square of its speed, so doubling the speed gives four times the energy.

Knock-out (KO)

A win when the opponent can't move under control for a 10-second count. See SPARC Match Rules.

Kv

A brushless motor's speed constant: how many RPM it spins per volt with no load. A 1000 Kv motor on 11.1 V spins about 11,000 RPM unloaded.

L

Lifter

A weapon that lifts the opponent with a powered arm or wedge, usually to flip it over or carry it. See Weapons.

Lightweight

The 60 lb (27.2 kg) weight class.

LiPo

Lithium polymer battery – the most common battery type in combat robots. Powerful and light, but can catch fire if damaged, overcharged or over-discharged. See Batteries.

Locking pin / Weapon lock

A clearly marked pin or block that physically stops a weapon from moving whenever the robot is outside the arena. Required by the SPARC Robot Construction Specifications.

M

mAh

Milliamp-hours – a measure of battery capacity.

Mecanum wheel

A wheel with angled rollers around its edge that lets a robot drive sideways. See NameThatPart.

Melty brain (melty)

A full-body spinner that can also translate (drive in a chosen direction) while spinning, by pulsing its drive motors at the right point in each rotation. See Melty Brain.

Middleweight

The 120 lb (54.4 kg) weight class.

Mixing

Combining the throttle and steering signals so one stick can drive a tank-steered robot. See Radios/Mixing.

Moment of inertia (MOI)

How hard it is to spin something up or slow it down. A weapon with its mass far from the center has a higher MOI and stores more energy at the same speed.

Multibot

An entry made of two or more separate robots that together make the weight limit. See SPARC Match Rules for how knock-outs work for multibots.

N

N20 motor

A small, cheap brushed gearmotor (about 12 × 10 mm) used for drive in many 150 g and 1 lb robots. See Insect Class Motors.

O

Overhead spinner

A horizontal spinning weapon mounted on a tall post above the robot.

P

Passive wedge

A wedge that isn't moved by its own actuator.

Pin

Holding an opponent so it can't move. SPARC limits pins to 5 seconds when stationary and 10 seconds when active.

Pit (arena)

A hole in the arena floor; a robot that falls in loses. Also the area where teams work on their robots between matches.

Plastic antweight (plant)

A 1 lb class where the robot's custom parts must be 3D printed from specific plastics. See Plastic Antweights.

Plow

A blunt, wide wedge-like front, often used to push and control.

Polycarbonate (Lexan)

A tough, clear plastic used for arena walls and sometimes robot armor or covers.

Push-out

An opening in the arena wall; a robot pushed through it loses.

R

Rumble

A match with more than two robots at once. SPARC standard rumbles last 5 minutes.

Ring spinner

A full-body spinner whose spinning weapon is a ring around the outside of the robot.

Round robin

A format where each robot fights every other robot in its class. SPARC standard for classes of 5 or fewer.

S

S (cell count)

The number of LiPo cells in series in a battery: 2S is about 7.4 V, 3S about 11.1 V, 4S about 14.8 V. See Batteries.

Saw

A spinning blade with many fine teeth, designed to cut rather than hit.

Self-righting

The ability of a robot to get itself back onto its wheels after being flipped. A dedicated self-righting mechanism is often called a srimech.

Servo

A small motor with built-in position control, used for lifters and flippers in small robots. See Servos.

Shell spinner

A full-body spinner with a dome or shell spinning around the robot.

Shuffler

A robot that moves on rotating cam-operated legs instead of wheels. Gets a 1.25× weight bonus under SPARC rules (see Robot Classes).

Spinner

Any robot whose main weapon spins.

Sportsman class

A class with limits on weapon power and wedges, to make robots easier to build and contain. See Sportsman Classes.

Spin-up

The time it takes a spinning weapon to reach full speed.

Suplex

A control weapon that grabs the opponent and flips it over backward, over the top of the robot. See Weapons.

T

Tank steering (skid steering)

Steering by running the wheels on each side at different speeds, like a tank. The most common drive layout. See NameThatPart.

Tap out

When a driver concedes the match.

Test box

A small enclosed box for safely testing robots, especially spinners, outside the arena. See Test Boxes.

Thwackbot

A robot that spins its whole body in place, swinging a weapon on a long arm. See Weapons.

Tip speed

The speed of the outermost point of a spinning weapon. Sportsman rules limit it to 20 ft/s. Tip speed (ft/s) ≈ RPM × diameter in inches × 0.00436.

TPU

A tough, flexible 3D printing plastic widely used for small robot chassis and armor. See 3D Printing.

U

UHMW

Ultra-high-molecular-weight polyethylene – a tough, slippery plastic used for armor and chassis, especially in insect classes.

Undercutter

A horizontal spinner mounted very low, so it hits the opponent's wheels and lower body.

Un-stick

A pause in the match so the referee can free a robot that's stuck on the arena or on its opponent. See SPARC Match Rules.

V

Vertical spinner (vert)

A disc, bar or eggbeater weapon spinning upright, so it hits the opponent upward. See Weapons.

W

Walker

A robot that walks without any rolling or cam-driven parts touching the floor. Gets a 2× weight bonus under SPARC rules.

Wedge

A sloped front edge used to get under opponents, deflect weapons and control the fight. See Weapons.

Wedgelets

Small hinged wedges, often in a row, used to get under opponents.