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There is no single “combat-robot weight class” or universal weapon list. The organizer, season, class, locomotion definition and event format determine what you may enter. SPARC Robot Construction Specifications v1.4, NHRL’s 2026 Open Rules and an event’s own inspection instructions use different limits and definitions. Treat the current rulebook as the authority, then ask the event inspector about any design the text does not clearly cover.
Why the same robot can be legal at one event and illegal at another
Combat-robot rules are not one international standard. A class name such as “3 lb” normally identifies a base mass limit, but the permitted mass can change for a shuffler or walker, and an event may not run every class listed in a general specification. Rules can also set a particular weigh-in configuration, registration deadline, inspection sequence and time at which the limit is measured.
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Compare events on five separate questions:
- What is the base class limit?
- How does the rulebook define a wheeled robot, rolling shuffler, walker or other non-wheeled machine?
- Does the event grant a locomotion bonus or an exemption, and what hardware qualifies?
- When and in what configuration is the robot weighed?
- Is that class actually running at the event you plan to enter?
Never transfer a bonus, weapon allowance or safety procedure from one league to another without checking the wording. A design that fits a published class table can still fail an event’s inspection if its configuration, module or operating procedure is different.
Published weight classes: SPARC and NHRL are different systems
SPARC Robot Construction Specifications v1.4
SPARC’s specification, dated 8 October 2023, lists these base classes. The figures are specification values, not proof that every current tournament offers every class.
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| SPARC class | Metric equivalent |
|---|---|
| 0.33 lb | 150 g |
| 1 lb | 454 g |
| 2.2 lb | 1 kg |
| 3 lb | 1.36 kg |
| 6 lb | 2.72 kg |
| 12 lb | 5.44 kg |
| 15 lb | 6.8 kg |
| 30 lb | 13.61 kg |
| 60 lb | 27.22 kg |
| 120 lb | 54.43 kg |
| 220 lb | 99.79 kg |
| 242.5 lb | 110 kg |
| 250 lb | 113.4 kg |
The same SPARC table gives higher limits for rolling shufflers and non-wheeled robots, but the amount depends on the class. In the 3 lb row, for example, the listed allowance is 4.5 lb for a rolling shuffler and 6 lb for a non-wheeled robot. That example is not a formula to apply elsewhere; use the row and definitions in the specification. SPARC’s footnotes say the 242.5 lb class was, when published, exclusive to Robot Wars and the 250 lb class exclusive to BattleBots.
NHRL’s 2026 Open Rules
NHRL’s 2026 Open Rules offer 3 lb, 12 lb and 30 lb classes. NHRL defines its own bonuses and exemptions, so a SPARC locomotion allowance cannot be imported into an NHRL entry. Read the NHRL class language together with its weigh-in and registration instructions.
For a practical comparison, write the two rulebooks side by side and record the base limit, qualifying locomotion, bonus or exemption test, weigh-in timing and whether the specific event is accepting that class. Keep the resulting notes with your build documentation; memory is a poor substitute for the current inspection checklist.
What weapons are allowed?
The answer depends on the class and event format. “Allowed” can mean mechanically permitted, within a speed limit, approved in advance, safe to operate outside the arena, and eligible for judging. Those are separate tests.
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SPARC Sportsman classes
SPARC gives Sportsman classes specific limits for rotating devices. A device rotating more than 360 degrees is limited to a tip speed at or below 20 feet per second, with additional stated treatment for certain saw and drilling mechanisms. A weapon that exceeds the ordinary limit requires organizer approval. The organizer may also restrict or reject a design considered excessively destructive, even if a numerical limit appears satisfied.
SPARC open-air combat
SPARC separately sets a 20 feet-per-second absolute maximum for slow spinners in open-air combat. Certain systems capable of tearing pieces from an opponent require organizer clearance. The open-air rule is not a blanket permission for every spinner; it is a format-specific example of why the venue and class matter.
NHRL active-weapon and module rules
NHRL’s 2026 rules require an active weapon. A mechanism that is merely present is not enough for scoring if the robot does not intentionally and effectively use it. NHRL explains that the weapon must cause harm and affect the state of the fight, but it does not have to be capable of destruction.
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Unusual or high-energy designs
The cited rules do not establish a universal ban or permission for flames, projectiles, entanglers or any other particular weapon type. Submit an unusual concept to the organizer well before registration closes, describe its energy source and failure modes, and obtain a written decision when possible. Do not wait until load-in: an inspector may require a redesign that cannot be completed at the venue.
Safety controls every competitor should prepare
Weapon locks
SPARC requires a clearly visible locking device on harmful moving weapons whenever the robot is outside the arena. Its specification calls for a high-visibility color and a secure fit, and it requires locking pins when weapon power is applied during a robot power-on procedure. Size the pin or bar for the actual weapon torque and make it impossible to miss during inspection.
SPARC’s blunt warning is: “Runaway bots are VERY dangerous.” The sentence appears in SPARC Robot Construction Specifications v1.4 and should be treated as an operating rule, not a slogan.
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NHRL requires cutoffs for both drive and weapon systems, with requirements for accessibility and operation. The exact switch location, labeling and test method are event-specific. Install controls that an official can reach quickly, label them clearly and verify that they remove the intended power rather than merely disabling a transmitter command.
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Physical separation and transport
- Keep the weapon locked whenever the robot is outside the arena, including in the pits, queue and inspection line.
- Carry a fitted lock, spare lock hardware and the tool needed to install it.
- Use a rigid cart or carrier so a dropped robot cannot contact a trigger, switch or exposed weapon.
- Separate batteries, fuel, pneumatic hardware and sharp spares until the event’s loading procedure allows installation.
Testing rules and workshop procedures
NHRL requires drive and weapon tests to occur in a test box, with a stated wheels-up exception for robots that have a second dedicated weapon switch. It prohibits driving around the pits or other venue areas. A wheels-up test is not permission to spin a weapon without the required lock, cutoff and supervision; it is a narrowly described exception to the drive-test arrangement.
Plan your test sequence before arriving:
- Install the required weapon lock and confirm that the lock cannot fall out under vibration.
- Place the robot in the event’s test box, or configure the documented wheels-up setup if your machine qualifies.
- Have the inspector or designated safety official verify the drive cutoff and weapon cutoff.
- Test drive, weapon arming and emergency shutdown separately at low risk, then perform the event-approved full test.
- Remove power before changing a module, adjusting a chain or reaching near a stored-energy part.
In the workshop, wear safety glasses and appropriate personal protective equipment when using power tools. NHRL limits spark- or dust-producing tools to designated areas and assigns fuel and pneumatic loading or unloading to its Robot Hazard Station. Follow the venue’s hazard-station process instead of filling a tank or handling fuel at the pit table.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Inspection, documentation and what to bring
NHRL requires inspection before a robot’s first fight and may ask you to demonstrate relevant safety features. Other events can impose different checkpoints, so build a portable inspection folder containing:
- the exact rulebook version and class entered;
- a mass worksheet for every legal configuration and module;
- photos or drawings showing weapon locks, power cutoffs and battery restraint;
- module declarations and any written organizer approval;
- radio-frequency, battery, pneumatic and fuel information requested by the event;
- a short shutdown procedure that a volunteer can follow.
At inspection, show the controls rather than describing them abstractly. Ask the official to identify the cutoff, observe the lock being installed and confirm which modules are recorded. If an inspector interprets a clause differently from your reading, follow the official ruling for that event and record the change before you enter the arena.
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A pre-event decision process for a new design
- Choose the event first. Download the current construction, tournament, battery and safety documents named by the organizer.
- Identify the base class. Record the limit in both pounds and kilograms and note the event’s weigh-in time and configuration.
- Classify locomotion. Ask whether your mechanism is a conventional wheel, rolling shuffler, walker or another category under that rulebook. Do not assume that a visual resemblance earns a bonus.
- List every weapon configuration. Include alternate modules, removable armor and tools that change mass or stored energy.
- Check weapon limits and approval triggers. Calculate any stated tip-speed limit, describe destructive effects and submit unusual systems for advance approval.
- Design the safety system. Provide visible weapon locks, accessible drive and weapon cutoffs, battery restraint and a safe transport method.
- Rehearse inspection and testing. Practice the exact lock demonstration, cutoff test and test-box procedure required by the event.
- Recheck shortly before travel. Rules can change, and a registration page can list different classes from a general specification.
How to handle changing rules and draft documents
Rule documents are versioned publications, not permanent laws. The official BattleBots rules page currently labels Design Rules Version 2027.01 and Tournament Rules Version 2027.01 as draft material, each marked last updated 10/01/2026. Battery rules are listed separately as Version 2020.0, last updated 09/30/20. The page also states that documents may be updated at any time.
That status matters: a draft can describe proposed requirements rather than operative instructions for a particular event. Verify which document governs your season, obtain the organizer’s latest announcement and ask whether a draft clause is enforceable before redesigning a robot around it. SPARC v1.4 is dated 8 October 2023, while NHRL’s cited rules and judging Q&A are from 2026; neither should be presented as a universal, timeless standard.
Common mistakes that cause avoidable problems
- Using a famous class name as a universal limit: A “3 lb” entry can have different bonus rules or weigh-in treatment in different leagues.
- Assuming a weapon is legal because it spins: Speed, destructive capability, format and approval requirements can all apply.
- Declaring only the primary weapon: NHRL requires weapon modules to be declared at safety inspection.
- Testing in the pits: NHRL prohibits driving around the pits and directs testing to a test box, subject to its stated exception.
- Relying on software disarm alone: A physical lock and accessible cutoff protect people when radio, firmware or batteries fail.
- Waiting until check-in to ask: Advance approval gives you time to change a weapon, mass distribution or safety system.
The reliable answer to any combat-robot rules question is therefore conditional: identify the organizer and current class rulebook, apply its definitions exactly, document every configuration and have the inspector confirm anything ambiguous before the robot is powered.
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