All participants build and operate robots at their own risk. Combat robotics is inherently dangerous. There is no amount of regulation that can encompass all the dangers involved. Please take care to not hurt yourself or others when building, testing and competing.

If you have a robot or weapon design that does not fit within the categories set forth in these rules or is in some way ambiguous or borderline, please contact the event organizer. Safe innovation is always encouraged, but surprising the event staff with your brilliant exploitation of a loophole may cause your robot to be disqualified before it ever competes.

Each event has safety inspections. It is at their sole discretion that your robot is allowed to compete. As a builder, you are obligated to disclose all operating principles and potential dangers to the inspection staff.

Cardinal Safety Rules
Failure to comply with any of the following rules could result in expulsion or, worse, injury and death.

Radios that do not operate using spread spectrum technology may not be turned on at or near events for any purpose without obtaining the appropriate frequency clip or explicit permission from the event.

Proper activation and deactivation of robots is critical. Robots must only be activated in the arena, testing areas, or with expressed consent of the event and its safety officials.

All robots must be able to be FULLY deactivated, which includes power to drive and weaponry, in under 60 seconds by a manual disconnect.

Locking devices
Moving weapons that can cause damage or injury must have a clearly visible locking device in place at all times when not in the arena.  It is strongly recommended that locking devices are painted in neon orange or another high-visibility color.  Locking devices must be clearly capable of stopping, arresting or otherwise preventing harmful motion of the weapon.

Weapon locking pins must be in place when weapon power is applied during a robot’s power-on procedure. The pin must securely affix in place so it cannot easily come loose.  This includes all powered weapons regardless of the power source.

It is expected that all builders will follow basic safety practices during work on the robot at your pit station. Please be alert and aware of your pit neighbors and people passing by.

Weight and size

This ruleset has been modified and written to apply only to Antweight and Beetleweight combat robots.

The MRCA finals cannot have any size limit, but qualifier events may implement a size limit based upon the event organizer’s discretion. Any size limit must be stated in the event details on the registration site, and any other place full details are listed.

Some MRCA qualifier events have steel floors. Robots cannot use magnets for additional downforce , permanent or electromagnets. The finals will not have steel floors, so this ruling is only relevant to certain qualifiers.

Weight Limits
To better facilitate the growth of Combat robotics in the Midwest there will be no Beetleweight weight bonuses in the year 2024.
The following bonuses are for Antweights only.

Wheeled Robots: Robots that use rolling motion must weigh less than or equal to 1lb (454g) for Ants and 3lbs (1361g) for beetles.

Shufflers and other forms of non-wheeled locomotion not covered in 3.1.2 must weigh less than or equal to 1.5lbs (680g).

Almost Walking Robots: Robots that use non-wheeled motion but do not qualify as a walking robot must weigh less than or equal to 1.75lb (794.5g). See 3.1.2 for a definition of a non-wheeled robot.

Walking Robots: Robots that walk must weigh less than or equal to 2.00lb (907g). See 3.1.3 for a definition of a Walking robot.

Robots with an electrical or mechanical sensor that activates a function on the robot that will affect the outcome of a match are entitled to an Autonomous Bonus equal to .25lbs (113.5g). See 3.1.6 for a further definition of the Autonomous Bonus.

Multiple robots can be run together under one name if their combined weight is under the standard weight limit for their movement type. These are commonly referred to as “clusters.”

The combined weight of clusters where all robots employ rolling motion must weigh less than or equal to 1lb (454g). The combined weight of clusters where all robots employ shuffling motion or other non-wheeled locomotion not covered in 3.1.2 must weigh less than or equal to 1.5lb (680g). The combined weight of cluster where all robots employ locomotion as described in section 3.1.2 must weigh less than or equal to 1.75lbs (794g). The combined weight of clusters where all robots employ non-wheeled motion must weigh less than or equal to 2lb (907g).

All robots in a cluster bot must be of the same drive type to receive any weight bonus. This does not include the Autonomous bonus which is applied to a maximum benefit of .25lbs as long as one bot in the cluster conforms to the guidelines listed in part 2.4.5.


All robots must have easily visible and controlled mobility in order to compete. Methods of mobility include but are not limited to:

Rolling (wheels, tracks or the whole robot)

Almost Walking Robot: Almost walking robots have no rolling elements in contact with the floor and no continuous rolling or cam operated motion in contact with the floor either directly or via a linkage. Motion is “continuous” if continuous operation of the drive motor(s) produces continuous motion of the robot. “Gyro walkers” fall under this criteria. “Bristle bots” also fall under this criteria. If you are intending to enter a non-wheeled robot in any event, contact the event as soon as possible to determine what (if any) weight bonus you will qualify for.

Walking Robot: Robots that require back and forth motion to translate in one direction without the use of any continuously spinning motion. Servo or linear-actuated legs and novel non-wheeled drive systems may qualify for this bonus.

Shuffling (rotational cam operated legs)

Flying (airfoil using, helium balloons, ornithopters, etc.) and ground effect air cushions (hovercrafts) are eligible for the “Almost Walking Bonus” weight bonus.

The Autonomous Bonus is given to robots that have added an extra sensory package to the robot that detects another robot or wall and performs a fight altering function in response. This can be electrical or mechanical. (An example of a mechanical autonomy system would be an automatic flipper that activates when it comes into contact with the opponent and then resets. An example of an electrical autonomy would be a hammer bot that auto fires its weapon in response to a robot entering an ideal area in front of the robot.) A true melty brain that uses sensors to determine its position/orientation auto qualifies for this bonus. FAILURE TO USE AN AUTONOMOUS SYSTEM WHILE TAKING ADVANTAGE OF THE BONUS WILL RESULT IN A -2 MODIFIER TO ANY JUDGES’ DECISION.  IF IT BREAKS MID TOURNAMENT AND SOMEONE DECIDES TO DO A WEIGHT CHECK, YOU WILL NOT BE GIVEN THE BONUS FOR THE RE-WEIGH.

Robot control requirements

Tele-operated robots must be radio controlled, or use an approved custom system.  Radio controlled robots must use approved ground frequencies, typically 27/49/50/53/75/900/2400 for the United States.

Tethered control is not allowed.

Pre 1991 non-narrow band radio systems are not allowed.

Radio system restrictions for this event with corresponding weight and or weapon restrictions:

Radio systems that stop all motion in the robot (drive and weapons), when the transmitter loses power or signal, are required for all robots with active weapons. This may be inherent in the robot's electrical system or be part of programmed fail-safes in the radio.

All robot radio systems must have a way to change frequencies or coded channels to prevent radio conflicts. Having at least two frequencies or coded channels available is required. Lack of extra frequencies may result in a forfeit.  Digital spread-spectrum radios that use frequency hopping or automatic channel selection qualify under this rule.

If you are using a home built control system, or a control system not covered here, you must first clear it with the event you plan to attend.

Toy radio systems are allowed, but the robot must failsafe or have no active weapon(s).

RC systems on the AM band are allowed at events for robots with no active weapons.

Autonomous/Semi-Autonomous Robots
Any robot that moves, seeks a target, or activates weapons without human control is considered autonomous. If your robot is autonomous you are required to contact the event before registration.

Autonomous robots must have a clearly visible light for each autonomous subsystem that indicates whether or not it is in autonomous mode, e.g. if your robot has two autonomous weapons it should have two “autonomous mode” lights (this is separate from any power or radio indicator lights used). Make sure the Judges are aware of your autonomous system, what it does, and where the indicator lights are located. As a competitor, this is your responsibility.

For autonomous robots, safe operation, arming, and disarming must be demonstrated in safety inspections.

Batteries and Power

The only permitted batteries are ones that cannot spill or spray any of their contents when damaged or inverted. This means that standard automotive and motorcycle wet cell batteries are prohibited. Examples of batteries that are permitted: gel cells, Hawkers, NiCads, NiMh, dry cells, AGM, LIon, LiFe, LiPoly, etc. If your design uses a new type of battery, or one you are not sure about, please contact the event you’re planning to attend.

All onboard voltages above 48 Volts require prior approval from this event. (It is understood that a charged battery's initial voltage state is above their nominal rated value)

All electrical power to weapons and drive systems (systems that could cause potential human bodily injury) must have a manual disconnect that can be activated within 15 seconds without endangering the person turning it off. (E.g. No body parts in the way of weapons or pinch points.)  Shut down must include a manually operated mechanical method of disconnecting the main battery power, such as a switch (Fingertech, Betz Botz, etc.) or removable link. Relays may be used to control power, but there must also be a mechanical disconnect.

All efforts must be made to protect battery terminals from a direct short and causing a battery fire.

If your robot uses a grounded chassis, you must have a switch capable of disconnecting this ground. ICE robots are excepted from this rule if there is no practical way to isolate their grounding components. You must contact this event for this exception.

All robots with active weapons must have a light easily visible from the outside of the robot that shows its main power is activated. It is still highly recommended for robots without active weapons.


Pneumatic systems on board the robot must only employ non-flammable, non-reactive gasses (CO2, Nitrogen and air are most common). It is not permissible to use fiber wound pressure vessels with liquefied gasses like CO2 due to extreme temperature cycling.

You must have a safe and secure method of refilling your pneumatic system.

For pneumatic systems, the maximum actuation pressure is 250 PSI and Tank pressures above this must be regulated down to 250 PSI. Tank pressures above 250 PSI must also have a safety relief. Bots containing pressures above 250 PSI need to make the EO aware at least 2 weeks prior to the event All components must be used within the specifications provided by the manufacturer or supplier. If the specifications aren't available or reliable, then it will be up to the EO to decide if the component is being used in a sufficiently safe manner.


Hydraulic systems are allowed with pre-approval by Event Organizers. Event Organizers reserve the right to disqualify any hydraulic system deemed to be unsafe. Furthermore, You will also be expected to clean any hydraulic fluid that leaks into the arena.

It should also be noted that if the Finals are hosted by an EO that does not want a hydraulic system operated in their arena, the robot may not be permitted to participate in the Finals.

Internal Combustion Engines

Internal Combustion Engines (ICE) and liquid fuels need pre-event approval depending on the ventilation and safety procedures of the event.

Fuel and Fuel Lines
All commercially available grades of automobile or RC hobby fuel are allowed. Alcohol, Nitro-methane, jet fuel and other specialty grades of fuel require prior approval.

Fuel lines and tanks must be made of high quality materials and all ends must be clamped securely.

All fuel tanks and lines must be well protected and armored from all sides, including moving parts and heat sources inside the robot.

Fuel tank volume, on any robot, shall not be greater than the amount required to operate the engine for more than 1 minute longer than the match time at combat power plus a reasonable pre-match warm-up period. Total fuel volume, including fuel for both ICE and flame weapons (if allowed) may not exceed 20 oz unless prior approval is granted from this event.

The output of any engines connected to weapons or drive systems must be coupled through a clutch which will decouple the motor when it is at idle. (This does not include motors used for generators and hydraulic pumps.)

Any engine connected to a weapon must be capable of being started while the weapon locking pin is in place.

All engines must turn off or return to idle at loss of radio signal and turn off at loss of radio receiver power.

All engines must have a method of remotely shutting off.

Any robot with liquid fuel and oil must be designed not to leak when inverted. (Minor oil leakage may be tolerated, however you may be called if it affects the other robot or becomes a large cleanup issue and the leaking robot will forfeit.)

Use of engines other than standard piston engines (i.e. turbines etc.) require prior approval for any event.

Rotational weapons or full body spinning robots

Spinning weapons must come to a full stop within 60 seconds of the power being removed using a self-contained braking system.

Springs and flywheels

Springs and flywheels in the 1lb class do not have any additional restrictions beyond those that apply to all weapons, but contact the event with any questions about the implementation of springs or flywheels.

Forbidden Weapons and Materials
The following weapons and materials are absolutely forbidden from use.

Weapons designed to cause invisible damage to the other robot. This includes but is not limited to:

Electrical weapons

RF jamming equipment, etc.

RF noise generated by an ICE. (Please use shielding around sparking components.)

EMF fields from permanent or electro-magnets that affect another robot’s electronics.

Entangling Weapons or defenses:  these are weapons or defenses that can reasonably be expected to stop drivetrain and/or weapon motion by being wrapped around rotating parts. This includes nets, tapes, strings, and other entangling materials or devices.

Weapons or defenses that can reasonably be expected to stop combat completely of both (or more) robots.

Weapons that require significant cleanup, or in some way damage the arena to require repair for further matches. This includes but is not limited to:

Liquid weapons. Additionally, a robot may not have liquid that can spill out when the robot is superficially damaged.

Foams and liquefied gasses

Powders, sand, ball bearings and other dry chaff weapons

Un-tethered projectiles

Weapons with an open flame are not allowed.

Flammable liquids or gasses

Explosives or flammable solids such as:

DOT Class C Devices

Gunpowder / Cartridge Primers

Military Explosives, etc.

Light and smoke based weapons that impair the viewing of robots by an Entrant, Judge, Official or Viewer. (You are allowed to physically engulf your opponent with your robot however.) This includes, but is not limited to the following:

Lights such as external lasers above ‘class I’ and bright strobe lights which may blind the opponent.

Hazardous or dangerous materials are forbidden from use anywhere on a robot where they may contact humans, or by way of the robot being damaged (within reason) contact humans. Contact the event you plan to attend if you have a question.

Special weapon descriptions allowed within MRCA
Tethered Projectiles are allowed.

Tethered projectiles must have a tether or restraining device that stops the projectile and is no longer than 4 feet.

Heat based weapons are allowed.

Heat based weapons cannot be preheated before a match. They can only be powered during the duration of the match. The exception is a match pause that the heat based weapon robot was not responsible for.

At their maximum temperature, a heat based weapon has no limit but must be deemed safe by the EO and is still subject to rule 12.4

It is expected that the operator will do their best to keep heating elements off of and away from the polycarbonate or other vulnerable sections of the arena. This is to avoid expensive damage to the arena, as well as the potential of a dangerous arena breach.

MRCA Robot Construction Specifications v1.30