NHRL Open Rules - 2025

The Spirit of The Rules

NHRL Open is a competitor-centric event that prioritizes creativity, safety, and entertainment. Our rules are designed to foster innovation while ensuring a safe and enjoyable event for all participants and spectators, and are written with our core principles in mind. As the rules have been substantially modified for the 2025 season, we have created a separate page elaborating on the intent and spirit of some of the changes here: Introduction to the NHRL Open 2025 Ruleset

Core Principles

• Safety: Our paramount concern is the well-being of competitors, audience, and crew. While we aim for minimal restrictions, safety measures are non-negotiable.
• Fun: We strive to create exciting and enjoyable events for competitors and spectators.
• Competitive Integrity: We require competitors to uphold principles of fair play and sportsmanship to ensure that victories are earned through honest effort, skill, and ingenuity, rather than exploitation or non adherence to the rules.
• Innovation: We encourage and celebrate novel, interesting, and unconventional ideas in robot design and strategy. We encourage competitors to push the limits of robotic combat, provided it's done safely and enhances the enjoyment of the event.
• Inclusivity: NHRL is meant for builders of all experience levels, from newcomers to seasoned veterans. We strive to welcome and celebrate builders of all backgrounds,  providing a platform for learning and high-level competition.

Expectations for Competitors

Hosting an event in accordance with the principles above is only possible with the cooperation of an immense community of amazing competitors who are willing to help. In pursuit of hosting the best possible events, we ask the following of every member of the NHRL competitor community:

• Be excellent to fellow builders, NHRL staff, and members of the audience.
• Come to events prepared to compete in accordance with the rules.
• Take a proactive approach to safety - model safe behavior and best practices and encourage it in others. Communicate any safety concerns with NHRL staff.
• Express your passion, personality, and creativity freely, but maintain enough decorum to keep the events family-friendly and welcoming to all.
• Design and compete in good faith, with the Spirit of the Rules in mind. We encourage competitiveness and innovation in robot design and strategy, but discourage the exploitation of rule loopholes or ambiguities.
• Ask proactive questions! If you are uncertain of how something works, unsure of the intent of a rule, have suggestions on how to improve an event, or if you want to do something fun that doesn’t fit within our normal competition, reach out to NHRL as early as possible by sending your questions and ideas to hello@nhrl.io

Builder Conduct Policy

It is a privilege to be part of the Havoc Robotics and National Havoc Robot League (collectively, “NHRL”) community. Everyone who is associated with NHRL must refrain from illegal, violent, dangerous, or irresponsible conduct that is detrimental to the integrity of and public confidence in the league. We must show respect for others inside and outside our community and we must strive to conduct ourselves in ways that favorably reflect on ourselves, our sport, our teams, the communities we represent, and NHRL. As such, NHRL has established this Builder Conduct Policy (BCP), which applies to existing and former builders, builders who have registered to compete, prospective builders, and members of our social media community (collectively, “Builders”).

The BCP is intended to address and sanction conduct detrimental to the league and sport. In order to uphold our high standards, when violations of this BCP do occur, appropriate disciplinary action must follow.

Expectations and Standards of Conduct

Builders must conduct themselves in a way that is responsible, promotes the values of NHRL, and is lawful. Builders that NHRL determines have engaged in conduct that violates these rules or the values of NHRL including, but not limited to, any of the following (“Prohibited Conduct) will be subject to discipline.

• Actual or threatened physical violence against another person, including dating violence, domestic violence, child abuse, and other forms of family violence;
• Assault and/or battery, including sexual assault or other sex offenses;
• Violent or threatening behavior toward any person in any NHRL setting;
• Stalking, harassment, or similar forms of intimidation;
• Illegal possession of a gun or other weapon (such as explosives, toxic substances, and the like) in any NHRL setting;
• Illegal possession, use, or distribution of alcohol or drugs;
• Crimes involving cruelty to animals as defined by state or federal law;
• Crimes of dishonesty such as blackmail, extortion, fraud, money laundering, or racketeering;
• Theft-related crimes such as burglary, robbery, or larceny;
• Disorderly conduct;
• Crimes against law enforcement, such as obstruction, resisting arrest, or harming a police officer or other law enforcement officer;
• Conduct that poses a genuine danger to the safety and well-being of another person; and conduct that undermines or puts at risk the integrity of NHRL, its facilities, or its personnel.
• Conduct that undermines the integrity of NHRL events and competitions or violates the letter or intent of the BCP.

“NHRL setting” means any physical or virtual location or conveyance used in connection with NHRL activities, including but not limited to event facilities, offices, private or off-site events, workshops, and social media platforms.

Reporting Misconduct

If you have witnessed Prohibited Conduct by a Builder, or are aware of any incident which, if the allegations were true, would constitute a violation of the BCP, you are obligated to promptly submit a report to NHRL’s Commission.

Reports must be sent via email to complaints@nhrl.io, and must contain:

• Your full name
• Your phone number
• Date(s) and time(s) of the incident(s), as applicable
• Any relevant information or context about the nature of the incident, identity of any all parties involved (including the legal first and last name of any individual(s) and contact information, as known or available)
• Any supporting evidence, like photographs, social media activity, emails, complete and unedited screenshots or transcripts, a news article, a police report, or other materials as applicable

Upon receipt of an incident report, the Commission will review it in a timely manner, and open an investigation. The investigation may include conducting interviews with the complainant, the accused, witnesses, and/or may include contacting the authorities if the Commission deems it necessary. The timing and scope of any investigation will be based upon the particular circumstances of the matter. In conducting investigations, the Commission will make reasonable efforts to safeguard requests for confidentiality from complainants or others with information. In addition, the Commission will not tolerate, and will discipline, any retaliation, threats of retaliation, intimidation, harassment, or any other adverse action against anyone who in good faith reports a possible violation or provides truthful information during an investigation.

In certain cases when further investigation is warranted, the Commission may choose to temporarily ban or restrict any individuals who are subject to said investigation until it has concluded, at which time the temporary ban may be lifted or extended or augmented with additional discipline.

Discipline

In the event where a Builder has been found in violation of the BCP, either by being formally charged with a crime or through the course of the Commission’s investigation, the Commission will determine what, if any, disciplinary action will be taken, and communicate its decision with the necessary parties involved. This decision is final and cannot be appealed.

Depending on the nature of the violation and other circumstances, discipline may be a suspension for a fixed or an indefinite period of time, or banishment from the league and/or its digital platforms. Discipline may also include a probationary period and conditions that must be met for reinstatement and to remain eligible to participate in the league. Repeat offenders will be subject to enhanced and/or expedited discipline.

Bot Design Rules

Overview and General Requirements

In order to compete at NHRL, all robots must:

• Meet weight limits for their class
• Meet the functional requirements for movement and weaponry
• Possess the required safety features
• Obtain approval for restricted systems before competing at an event
• Be free of forbidden features

Weight Requirements

NHRL offers 3 different weight classes to compete in: 3lb, 12lb and 30lb. All robots must be at or below the maximum weight listed for their respective weight class at the start of the fight. In any given class, additional weight bonuses and exemptions may be allotted to entrants that meet certain criteria set out in this section of the rules. Competitors may not stack weight bonuses, although a single robot may qualify for both a weight bonus and one or more weight exemptions.

If a builder elects to make use of a weight bonus, they must do so before an event begins. Their robot will be locked into that weight bonus for the duration of the event.

Locomotion Based Weight Bonuses

Robots fall within one of three locomotion type categories: Traditional Locomotion, Non-Traditional Locomotion, and True Walker Locomotion. Non-Traditional Locomotion and True Walker Locomotion are given weight bonuses summarized in the following table.

Locomotion Weight Bonus Table

Weight Class	Non-Traditional Locomotion Bonus	True Walker Bonus
3 lb	1.5 lb	3 lb
12 lb	6 lb	12 lb
30 lb	15 lb	30 lb

If a robot qualifies for both a locomotion based weight bonus and a multibot bonus, the builder must choose one bonus or the other. In order for a multibot to qualify for a Non-Traditional Locomotion weight bonus, all of the segments must feature either Non-Traditional Locomotion or True Walker Locomotion. In order for a multibot to qualify for a True Walker Locomotion weight bonus, all segments qualify for True Walker segments for mobility.

NHRL has sole and final discretion on how Locomotion Based Weight Bonuses are awarded, and True Walker Locomotion weight bonuses must be approved before a robot is registered for an event.

Non-Traditional Locomotion Definition

Any robot that falls outside the definition of a “Traditional Motion System” qualifies for the Non-Traditional Locomotion Bonus. NHRL classifies Traditional Motion Systems as a robot that relies on rotational motion of a component in contact with the ground as its method of locomotion around or orientation within the arena. This includes all forms of wheels (round, non-circular, spoked, or offset axis) even if those wheels are parallel or near parallel to the arena floor. It also includes continuous tread, track or belt driven systems.

Non Traditional Locomotion Systems may not use unpowered rotating objects (wheels, drums, rollers, ball bearings, etc.) as a means of friction reduction with the ground. They are also forbidden from using powered or unpowered wheels or wheel-like design features to ease rotation or to orient their robot within the arena. This requirement applies even when a robot is inverted or in other orientations that differ from their default orientation.

Examples of Non Traditional Locomotion Include:

• Shuffling
• Bristle Bots
• Flying Systems
• Gyroscopic Precession
• Torque Reaction
• Jansen Linkages
• Hovercrafts

True Walker Definition

True Walkers are robots with one or more legs that allow the robot to move around the arena. Legs are defined as articulating design features which contact the arena floor, which can move with two or more degrees of freedom. In order to qualify as a True Walker, locomotion must not be possible solely through the continuous rotation of one of more motors. True Walkers must also meet all the requirements for Non-Traditional Locomotion.

The total weight of spinning weapon components of a True Walker bot cannot be more than 150% of the nominal weight of their weight class - i.e. 4.5lb for 3lb class, 18lb for 12lb class, and 45lb for the 30lb class.  

Competitors who wish to use the True Walker Bonus *must* have their design approved by NHRL staff before registering their robot for an event. NHRL reserves the right to approve or deny any robot the True Walker Bonus at its sole discretion at any point in the season.

Multibot Weight Bonuses

A single robot entry may be divided into up to 4 segments. Robots with multiple segments may qualify for the multibot bonus, which allows for the combined weight of all segments to exceed the normal weight class limit.

Each segment of a robot using the multi-bot bonus is allotted an equal portion of the increased combined maximum weight. Unused weight from one segment may not be applied to other segments of the multibot.

Alternatively, an entry may have multiple segments without making use of the multibot weight bonus system, in which case the robot’s weight may be distributed in any way between segments. With or without a multibot weight bonus, all segments of a multibot must individually meet the mobility and weapon function requirements for their base weight class.

While not strictly required, it is strongly encouraged that multibots have a cohesive visual theme. This helps referees, judges, and spectators alike in understanding and enjoying the match.

The weight allowances for multibots making use of the Multibot Weight Bonus are summarized in the following table:

Multibot Weight Bonus Table

Weight Class	2 Part Multibot Max Segment Weight	3 Part Multibot Max Segment Weight	4 Part Multibot Max Segment Weight
3 lb	2 lb	1.33 lb	1 lb
12 lb	8 lb	5.33 lb	4 lb
30 lb	20 lb	13.33 lb	10 lb

Note that segments receiving a multibot weight bonus cannot be further subdivided - e.g. you may not have a 30lb entry with one 20lb segment and two 10lb segments.

Multibots making use of a multibot weight bonus may not begin a match physically connected to one another.

Weight Exemptions

Any bots with flamethrowers, hydraulic, pneumatic, or ICE-powered systems will be weighed “dry” (without fuel or stored operating liquids). This extends to any approved system that makes use of stored liquids or gasses, including lighter-than-air robot systems such as chambers filled with low pressure helium.

Flamethrower bots will be weighed with an empty tank installed. Competitors should bring an empty tank for weigh-in purposes.

Pneumatic and ICE-powered robots will remove their tank(s) for weigh-in. Any pneumatic tanks must be commercially available.

Competitors who bring hydraulic systems must declare in advance how much hydraulic fluid is in their system and how much it weighs. The fluid weight will be subtracted from the robot’s scale weight. These bots may be subject to random inspections, where the hydraulic fluid will be removed and measured.

Electronic components such as computer systems and sensors dedicated solely to the function of discrete autonomous systems (weapon, drive, self righting) do not count towards a robot's weight. Systems such as stability control and meltybrain directional process do not qualify. These systems must be easily removable for weight and inspection, or a competitor must be able to show the presence of these components on the robot during inspection and bring identical spare components for weigh -in purposes. These components must be approved by NHRL before an event.

Any active cameras or recording equipment on the bot do not count towards the robot’s weight but must be approved during bot inspection by a Bot Inspector. Camera systems that appear to confer a competitive advantage via additional weight will not be approved, at NHRL’s sole discretion.

Functional Requirements

Movement

Robots must be able to demonstrate controlled movement at a sufficient speed.

Robot mobility will be demonstrated during the robot inspection process. In the 3lb class, robots must be able to move at a speed of at least 10 feet per minute. In the 12lb and 30lb classes, robots must be able to move at a speed of at least 20 feet per minute. They must also be able to navigate between corners of the test box or arena. Robots that do not appear to be sufficiently mobile or controlled may be asked to complete the "Movement" portion of the NHRL Functionality Test. Robots are only required to pass a mobility test at the beginning of an event.

In a multibot, each segment must independently meet the mobility requirements.

Drones and other flying robots can compete at NHRL as long as they adhere to all other design rules. Flying robots must be able to begin matches in contact with the arena floor while all moving systems are idle or deactivated. Any competitor that operates a drone must comply with local, state and federal regulations.

Weapon Systems

All robots must have an active weapon. An active weapon is defined as a weapon or mechanism that operates independently from the robot’s drive-train or means of locomotion and is clearly designed to negatively influence the opposing robot. In a multibot, all segments must include an active weapon.

Certain robot sub-types are exempt from the requirement that the weapon system operates separately from the drive train.

• “Meltybrains”, (bots that can show controlled movement while spinning at rapid speeds)
• “Gyro Walkers” and “Torque Walkers” (bots that use spinning masses or weapons to generate inertia to induce translational motion)
• "Bristle Bots" (bots that move in part or in whole based on vibrations caused by spinning masses)

Other inventive weapon systems may be approved on a case by case basis.

"Thwackbots,” (robots which use momentum created by the robot’s drive-train to ‘actuate’ an otherwise unpowered weapon) do not qualify as having an active weapon.

NHRL strongly encourages competitors designing a non-conventional active weapon to share their plans with NHRL in advance so confirmation can be given if the weapon is deemed active or not. In the event that a ruling on a weapon is required at a NHRL tournament, the robot in question will be required to complete the "Weapon" portion of the NHRL Functionality Test.

Competitors must approach the testing process in good faith. If a robot is able to pass the weapon test but it appears (through lack of use) that the weapon was never intended to be used as tested, Tournament Stewards will be notified. Builders will be warned that they appear to be intentionally skirting weapon functionality requirements, and the robot may be disqualified or not allowed to compete at subsequent events.

Modular Weapon Systems

Modular weapon systems are defined as component assemblies that drastically change a robot’s weapon type, and that are interchangeable between fights. For example, a modular weapon system may allow a competitor to choose between a horizontal spinner and a vertical spinner configuration between fights.

Modular weapons should be designed as modules, meaning they can be bolted or otherwise attached to a robot chassis as a unit. Builders may be asked to demonstrate that they can effectively swap between modules within the minimum repair time allotted to their weight class. A modular design may be required to complete the NHRL DUMMY Test with separately for each module.

All modules must be declared during Bot Inspection at the beginning of an event. Alternative modules must be presented during robot inspection (although they do not need to be installed unless requested by an inspector).

No more than 50% of a robot’s weight may change between weapon modules.

Safety Requirements

Master Power Cut-Off Requirements

Bots must have one or more easily accessible power cutoffs that can remove power from all weapon and drive systems. Power cutoffs can be in the form of a switch or removable link. 3lb robots may use a battery connector as a removable link, but removable links on 12lb and 30lb entries must have a dedicated removable link with adequate strain relief on its wiring.

Power cut-offs must be able to be deactivated within 15 seconds. Power cut-offs must be accessible without disassembling the robot, with the exception of a small amount of tape to cover or help retain a removable link. The use of zip-ties to secure the removable portion of a removable link is not permitted.

Power cut-offs must be easily accessible. For 12lb and 30lb robots, power cut-offs must be located such that they are accessible when the robot is in its primary fighting orientation.

Power cut offs must be able to be accessed and actuated with one hand (although competitors are allowed to use both hands during the event).

Battery Limitations

Nominal battery voltage may not exceed 75 volts without explicit approval from NHRL. It is understood that a fully charged battery pack will have an initial voltage above its nominal voltage.

Any robot system that produces voltages above the robot’s battery voltage limit must be approved by NHRL prior to participating in any competition and may require additional inspection. Email safety@nhrl.io to discuss your design.

Robot Control Systems

Robot controls and communication systems must pass a failsafe test overseen by a Bot Inspector at Bot Inspection in order to compete. In the event of signal loss or transmitter power-down, the bot’s drive system must stop within 30 seconds and weapons must come to a complete stop within 60 seconds.

All robots and multibot components must have a dedicated receiver(s).

Autonomously controlled robots are allowed, but they must still retain a radio control module that can remotely activate and deactivate the robot.

Size Limitations

Robots must be able to easily fit within the NHRL fire safety cart in the event of a fire or other safety emergency. The approximate inside dimensions of the fire-safety cart are 23” x 23” x 44”. NHRL will be working to expand these dimensions during the 2025 season.

Larger robots may be approved if they can be easily and immediately modified to fit into the cart - e.g. a portion of the robot can immediately be bent or removed such that the robot easily fits within the cart. Approval should be obtained before an event, and is subject to change if NHRL staff feels the robot cannot be safely enclosed in the event of an emergency.

A robot’s size and design must not be used to interfere with the procession or filming of a match. For example, you may not release umbrellas into an arena that obstruct the view of the fight.

Weapon Locks

All weapon systems must have a lock that stops their actuation, extension, expansion, rotation, ignition, etc. Weapons that move or rotate must have a lock or be constrained such that movement is restricted in all directions. This includes designs such as CAM lifters.

Weapons that shoot projectiles must have a physical means to prevent the expulsion of the projectile.

Weapons that shoot gasses, such as flamethrowers, must have their safety lock system approved before an event. Flamethrowers and similar systems must also include covers for any exposed hot surface ignitors or spark gaps.

Weapon locks that force the competitor’s fingers to be in the path of the weapon for an extended period of time will not pass bot inspection.

Weapon locks MUST be marked by an easily visible and well marked tag. Tags must be marked with “Weapon Lock”, “Remove Before Fight”, or other similar language, and must be at least 1” x 4” in size. Tags must be sturdy in construction - they cannot be paper or cardboard.

Additional information on acceptable and unacceptable weapon locks is available in Appendix B.

Restricted Robot Systems

Restricted robot systems are design features that are permitted at NHRL, but require either extra care and may require pre-approval by NHRL staff before being allowed to compete.

Internal Combustion Engines

Robots may use internal combustion engines, including piston engines, jet turbines, and other designs. Combustion engines may be manually or electrically started during load in, provided they do not cause the weapon or robot to move.

Consumable fuels and their tanks do not count towards your overall robot weight. Fuel tanks will be removed for weigh-in.

Fuel tanks containing liquid fuel must be meaningfully protected, and robots are limited to carrying only enough fuel to last for 5 minutes of runtime.

Under no circumstances is a robot permitted to intentionally eject liquid fuel into the arena. In the event of large amounts of leaked fuel, a match may be halted and the robot may be disqualified if the leak cannot be quickly and safely addressed.

Any bot that uses internal-combustion engines must go through the NHRL Design Approval Process and be approved by NHRL staff no later than three weeks before an event. NHRL strongly encourages that new designs be reviewed with NHRL staff before a robot’s design is finalized and before a robot is registered for an event.

Flame-Based Systems

Robots with flame-based systems must be able to self-light and self-extinguish. In the case of signal/communication loss with the transmitter, flame and heat-based weapons must self-extinguish in 30 seconds.

Fuel tanks containing flame system fuel must be meaningfully protected. Air gaps can be used to enhance the protection of fuel tanks, but cannot be the only means of protection. A suggested starting point for meaningful protection is ¼ inch of PLA with 30% infill for 3lb robots, and ½” of the same for 12lb and 30lb systems.

NHRL allows the use of propane, butane and other fuel sources that are gaseous at STP (standard temperature and pressure). Fuels cannot be self-oxidizing and flame systems must not include additional oxidizing systems (e.g. oxy acetylene torches and similar). Robots may use compressed air, fans, or similar means to aid in combustion, but air and fuel cannot be mixed within sealed enclosures. Matches may be stopped and your robot disqualified if, at the discretion of NHRL Staff, cage equipment, cameras or safety gear, is being excessively damaged by fire.

NHRL currently approves the following fuels for flame based weapons, with the following fuel limits for each robot weight class:

Weight Class	Fuel Limit for Propane, Butane, Isobutane
3lb	6 Ounces
12lb	16 Ounces
30lb	16 Ounces

Additional fuel types may be approved with advance notice. Currently, MAP-Pro and Plaslode fuel are under review. All means of fuel storage must be designed to default to the closed position if removed from the robot.

Any bot that uses flame based systems must go through the NHRL Design Approval Process and be approved by NHRL staff no later than three weeks before an event. NHRL strongly encourages that new designs be reviewed with NHRL staff before a robot’s design is finalized and before a robot is registered for an event.

Heat Based Systems

Heat based systems such as heat guns and soldering iron lances are allowed. Electrically heated surfaces such as glow-plugs, nichrome wire, or hot surface igniters do not require special approval or inspection processes.

Combustion based heating systems must go through the NHRL Design Approval Process and be approved by NHRL staff no later than three weeks before an event.

Plasma based systems may be approved on a case by case basis, and must go through the NHRL Design Approval Process and be approved by NHRL staff before registering for an event.

Projectile Systems

A fired projectile’s maximum speed may not exceed 300 miles per hour. Additionally, a tethered projectile must not be designed in a way that is likely to become entangled with the opposing robot.

Projectile based systems may not use ramset charges, blanks, or similar devices in their design.

Inductive Systems

Inductive systems are allowed, but may not be used to directly attack opponents. For example, you may inductively heat the tip of your own hammer, but you may not attempt to attack your opponent by inducing magnetic fields in their robot’s armor or electrical components. Competitors may be asked to demonstrate that their inductive systems do not pose an EMF based risk to their opponent and do not pose an excessive risk to arena systems like cameras.

Magnetic Systems

Externally mounted permanent magnets intended to adhere to opponents are not permitted. Permanent magnets intended for other purposes (attachment of ablative armor for instance) are allowed as long as they do not introduce an excessive risk of entanglement.  

Electromagnetic systems are allowed, but must be approved by NHRL Safety Staff, and may be required to have protective Weapon Lock style covers for use outside of matches.

Other Restricted Systems

Robots with the following systems must go through the NHRL Design Approval Process and be approved by NHRL staff no later than three weeks before an event.

• Pneumatic Systems
• Hydraulic Systems
• Any robot with components (such as spinning weapons) with speeds over 300mph.

The NHRL Design Approval Process

Any restricted feature listed in this section as requiring NHRL approval must be approved by NHRL Safety Staff.

To begin the process, competitors must email NHRL at safety@nhrl.io. Competitors should begin the process as early as possible, and no less than 3 weeks prior to the competition so that a review of the design can be conducted by NHRL Safety Staff. You will be asked to provide documentation of your design and a description of your safety processes, and NHRL staff will review the required safety procedures relevant to your design.

We cannot guarantee that any proposal sent less than 3 weeks before an event will be approved in time for the competition. Robots with unapproved designs will not be allowed to compete using their restricted systems and may not be allowed to remain in the competition venue.

Forbidden Robot Features

Rocket motors (also referred to as rocket engines), fireworks, and airbags are not allowed.

Electrical and weapons intended to directly destroy or interfere with electrical systems through electric currents or magnetic fields are not permitted. This includes EMPs, radio jammers, and tasers.

Weapons (or other robot systems) that primarily act by obstructing visibility are not permitted.

However, weapons that produce smoke or fog as a by-product of their attack are allowed.

Any system that directly targets or that may result in harm to those outside the cage is not permitted.

This includes, but is not limited to high intensity lasers, high luminosity or strobing lights, or excessively loud noises.

Entanglement devices are not permitted.

An entanglement device is defined as a component, subsystem or armor configuration that is designed to be entangled in the rotational or moving parts of an opponent.

Fabric, foam, and other ablative armor is allowed, but ablative armor must not be designed in such a way that it presents a likely entanglement risk. The decision of what is a likely entanglement risk is up to the discretion of NHRL Tournament Stewards. NHRL reserves the right during an event to require that design features be removed from a robot if those features unexpectedly prove to be major entanglement risk.

Liquids expelled from the robot are not permitted with the exception of bubbles made.

However, liquids expelled from a robot that become gaseous or solid shortly after leaving the robot and/or before hitting the opponent are permitted. Expelled liquids must be gaseous or solid at STP conditions.

Arena fouling systems are not permitted.

Arena fouling is defined as the release of items or materials that are excessively difficult to remove from the arena that would impede subsequent matches. The release of non-entangling materials that impede an opponent’s operation is not otherwise considered arena fouling.

Most hazardous materials are not permitted.

Hazardous materials are generally not allowed within the arena, aside from those outlined elsewhere in the rules. A non-exhaustive list of disallowed materials includes:

• Strong alkali metals such as metallic potassium or sodium
• Corrosive or noxious gases such as chlorine, fluorine, or hydrogen sulfide
• Meaningfully radioactive materials

Additional Design Rules

Spare Robots

Bringing multiple copies of your robot is allowed at NHRL. Spare robots must be as close to exact copies of the original as possible. If a robot design features interchangeable parts of modular systems, all of those parts must be compatible with all spare robots.

The identity of a spare robot is defined by its chassis - the structure around which a robot is built. Spare chassis must be presented during initial Bot Inspection and will be marked by a small colored sticker. Spare robots must complete Bot Inspection before being allowed to compete. Builders that wish to switch to a spare robot must notify the Pit Desk.

Robots that do not feature a central chassis must contact NHRL before an event to determine a reasonable alternative means of distinction between spare robots.

Passive Components

Competitors may place non-robot objects within the arena with their robot at the start of a match as passive components. The combined weight of the object(s) and the robot must be below the relevant class weight limit and the segment must not conflict with entanglement or safety rules. Robots with passive components are not eligible for multibot or NTL weight bonuses.  

Passive components can be intended to break apart from robot segments, or be intended to be dropped, launched, or otherwise ejected from a segment. These components cannot be designed to act as independently operating segments of a multibot.

Tournament Format

2025 Tournament Format Rules are still under development, but are directionaly similar to the 2024 rule-set. Until they are released, please see the NHRL Rules - 2024 for guidance and the Introduction to the NHRL Open 2025 Ruleset for notes on important changes that may influence your design and strategy for 2025.