Thinking of a Design - Novice
Text - Mike Jeffries
Images/Editing - Adam Wrigley
Last updated - June 2006

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Without some form of attack, combat robotics would be fairly boring. Weapons are what make combat robotics interesting, and there are many different approaches to weapon systems. Some rely on extremely powerful weapons, but use weaker drive systems. Others rely almost entirely on the drive and chassis of their robots. Most robots are somewhere between the two extremes. Some weapons require highly aggressive tactics to be effective, while others rely on the other robot being on the offensive. Each weapon system has weaknesses, so it is up to the builder to weigh the options and choose which one will work best for their robot.

-Rammer

Ramming robots are the most basic design in robot combat. A ramming robot relies purely on the strength of the chassis and power of the motors for success. Ramming robots often incorporate spikes or heavy chunks of metal on the front of the robot. Spikes on a ramming robot are used in the hopes that they will penetrate the armor of the opposing robot. Ramming robots with simple metal chunks on the front of the robot use their drive power to drive their opponents into arena obstacles at high velocities. They are also sometimes capable of breaking spinning weapons. Ramming robots are often thought of as boring, but with a fast enough drive system, they can be some of the most exciting robots to watch. Some of the more famous ramming robots are New Cruelty, Snowflake and earlier versions of Frostbite. They all have one thing in common; they are very hard to immobilize. They are invertible, durable, and have powerful drive systems. Ramming robots are commonly people's first attempts at a combat robot due to the simplicity of the build. Weight is less of a concern in most cases as ramming robots need fewer parts.

-Wedges

Wedge robots are similar to ramming robots. They share the need for a strong, powerful drive system, a strong chassis, and good armor. Wedge robots are one of the most common types in robot combat today. Even when not a primary weapon, the wedge is a vital part in many robots. For some, it's the backup plan if the weapon fails. For other robots, the wedge acts as part of the weapon, be it leading the opponent into spinning blades, or a hiding place for a powerful arm. These robots are all about mechanical advantage. They get under their opponent and use their drive power to send them careening over, batteries over baseplate, or shove them at high speeds into an obstacle like a rammer. Wedges and ramming robots are often mixed into one. A high speed drive system with a large, solid area to take beatings will often have a small wedge to help lead the opponent up and off the ground. Once the opponent loses traction, it becomes easy for the robot to take the opponent on a tour of the arena.

-Lifter

Lifting robots can be viewed as the next step up from a wedge robot. They perform essentially the same function. They both make the drive system of the other robot ineffective. There several different methods of constructing lifting arms.

The most basic is pushing or rotating a single hinged piece of metal. It is very effective in its simplicity. For this style of lifting arm, linear actuators are often used. Linear actuators act like pneumatic pistons, but slower and in a often lighter package.

Another popular lifting system uses a four bar linkage. Carlo Bertocchini popularized this with his robot Biohazard. This system allows the bar to lift and push at the same time. It also lets the arm tuck nicely back into a flat chassis. This system has proven extremely effective when built properly. Biohazards weapon system went virtually unchanged from the robot wars years through the fifth season of Battlebots.

Some lifters drive the arms with an electric motor. With that system, the arm is attached to a rotating shaft. The shaft has a sprocket or gear on it which is driven by an electric motor. These systems require heavy gear reduction to be effective.

Hydraulic lifting arms have sometimes been used, but are uncommon in combat robotics. They are too heavy and slow for most applications of this nature. This is partly due to what hydraulics use for actuation. As the name implies, fluid is used in hydraulic systems. Liquids have a much higher mass then O2 or CO2, which is used in pneumatic systems. Hydraulics are better for systems that require incredible amounts of torque and not much speed.

Lifting arms require a very strong drive and chassis system to be effective. If the chassis cannot take the abuse of a more aggressive weapon while the lifter is trying to get under its opponent, it will not be successful.

 

-Flipper

Flipping robots are essentially lifters run at much higher speeds. Flipping robots normally use pneumatics to power their arms due to the high flow rates available in pneumatic systems. Pneumatics can be used in any lifting system that can be operated by an extending rod. Flipping robots are able to throw their opponents into the air, possibly dislodging vital components or causing them to land in a manner that would prevent them from driving. Flippers are often preferred over lifters due to the increased spectacle they create. Flipping mechanisms normally require more weight then a lifter, as more power is needed to send a robot into the air than to tip it.

A prominent flipping system in European robots has the piston attached to a hinged plate that fires out of a wedge shaped chassis. The plate is hinged at the bottom, which causes the swing of the plate to not only lift the opponent but toss it away from the flipper robot. This mechanism gained much of its popularity with a robot called Firestorm. While Firestorm never won the Robot Wars championship, it was consistently a contender for the title.

Another common flipping arm is hinged at the back of the robot. It extends to the front, then bends down to meet the ground. There is then a spatula like plate that comes forward from it. The pneumatic piston is either mounted vertically or in a position that when the piston has reached maximum extension it will be vertical. This reduces the loss of force due to leverage some other systems have, allowing for a very powerful throw. These flipping arms tend to throw the opponent vertically and often spinning into the air.

Inertia Labs has many well known robots that use this type of flipping arm. Their robots; T-minus, Matador and Toro, have all seen great success using high powered pneumatic flippers. The success of the robot Toro even lead to a toy being made in its likeness. Both Toro and T-minus have had great success in their respective weight classes. Matador was the most amazing off all, with its incredible self righting maneuvers. After flipping itself in a match during the final season of BattleBots, Matador self righted by firing its flipping arm. This propelled Matador's 220lb body at least 6 feet into the air.

-Grabber

Grabbing robots were most popular during the BattleBots era. Most arenas used today do not have the powerful hazards of the battlebots arena. Grabbing robots would drag their opponents into these powerful hazards and use the arenas weapons to dismantle the opponent. A Grabbing mechanism could be achieved many ways. Linear actuators were used on occasion, as well as pneumatics.

Complete Control was a robot built by Derek Young. This robot is recognized as one of the better grabbers ever made. Complete Control had a lower forked arm and an upper arm shaped vaguely like a police baton. Complete Control would clamp down with the top arm, then rotate both back up, performing a robotic suplex on the opposing robot. Once Complete Control was able to get a hold of the opponent, the match was almost certainly over.

Grabbers are a good option against most opponents in the right arena. They do have one major weakness. If they face a robot with a spinning weapon mounted in an area the grabber tries to pass through, there is a very good chance that their grabbing mechanism will be forcefully removed from the rest of the robot, making its primary mode of combat inoperable.

Grabbing robots like Complete Control are often overlooked as a design capable of winning titles due to the lack of use of grabbing mechanisms in modern robotic combat. There are some weight classes where this method is no longer effective due to the type of robots in it, but there is still room for a dominating clamp bot in the current rules. If a robot goes outside of the arena barrier and into the polycarbonate wall or the buffer zone between the two, the match ends and that robot loses the match. A grabber designed to exploit this rule could dominate its division, assuming it was built strong enough to survive the powerful spinners in its weight class.

 

-Crusher

Crushing weapons can be very devastating when used properly. They are not nearly as common as spinning or flipping weapons, but are on par with them when you look at damage potential and combat effectiveness.

Crushing arms are normally powered by hydraulics or high torque linear actuators. They tend to be slow, but extremely powerful. The goal of a crusher is to penetrate the armor of its opponent and dig the spike into some vital component of the robot. Even if, after achieving penetration, nothing vital was hit, they still have a very firm grasp on their opponent. They can take them into any arena hazards or just drive them at high speeds into the wall.

An effective crushing robot needs to have an agile drive system, a solid chassis and a sharp arm. Due to the nature of the crushing robot, it needs to be able to get to the weak points on its opponents to be effective. If it has a sluggish drive system it would be much more difficult to gain hold of the opponent. The forces that are put into the chassis by the crushing arm are enough to warp a weak frame. A solid frame for the area that this force is transmitted into is vital. If the chassis is weak, there is the possibility of the robot bending it's chassis instead of puncturing its opponents armor.

The most well known crushing robot of all time is Razer. Razer is a robot that was made for Robot Wars and featured a powerful hydraulic crushing arm. Razer won multiple Robot Wars championships and was a top contender up until the last days of Robot Wars. The crushing arm of Razer would sometimes get so embedded into it's opponent that upon attempting to release the opposing robot from its grasp, it would simply pick them up.

-Hammer

Robots that use hammers as weapons are not as common as the other kinetic weaponed robots in robotic combat, spinners. Hammer robots have a few options when determining how to operate their hammer. They can pneumatically actuate it, either through a rack and pinion or by attaching the piston directly to the arm. There have even been some robots that have used springs to fire the arm. Electric motors have also been used to move an overhead hammer. Each method has been used effectively in the past.

The simplest method of actuating a hammer is to directly attach a pneumatic piston to the hammer arm. This system makes it difficult to get a large swing angle, but allows for a lighter weight weapon drive as well as a very simple construction. This method has been used on many top hammer robots. The simplicity of this system makes it an easy hammer design to start with.

Rack and pinion hammers have become increasingly popular in robotic combat. The Judge is a superheavyweight hammer bot with an incredibly powerful rack and pinion hammer. After it's debut season in Battlebots, the builder was 'asked' to change the design of the hammer head, as it was penetrating the steel battlebox floor. These hammer systems are somewhat heavier then the previous, but have a major advantage over them. These hammers can swing 180 degrees or more. The only rotational limit is the rack and pinion setup itself and the stroke of the piston pulling the rack. Adjusting the gear ratio allows for very precise control of the arms swing. For larger robots, this is one of the most popular systems.

Spring fired hammers were more popular in the late Robot Wars US years and early Battlebots seasons. These weapons use powerful coiled springs to shoot the hammer downward onto the opponent, then a heavily geared down electric motor to retract the hammer and ready it for the next swing. The spring can generate a great amount of power, but this weapon system is much slower than many of the other ways of actuating a hammer available to builders.

Running the hammer directly off a motor is a very simple method for making a hammer robot. Most of these systems are chain driven to achieve the proper speed and reduce the strain on the shaft of the motor driving it. These are faster, but often not as powerful as some of its pneumatic cousins. Beta, a robot made by a British team, uses a 15 horsepower electric motor to power its hammer. They use a 'snail drive' system. With a snail drive, the chain is wrapped on a piece of metal that changes diameter as the chain travels farther. This system gives the hammer more torque as it starts the swing while still maintaining a high speed at the end of the swing, as the ratio has changed between the motor and hammer arm. Snail drive is a very unique system in robotic combat. There are very few robots that have used this setup for their hammer. Most simply drive a sprocket or something similar off of the weapon motor. Beta was built for season 5 of battlebots, but due to a problem with their drive system they were unable to compete. The bottom of their robot had magnets to counteract the hammer trying to make their robot leap into the air when it fired. The magnets were too strong and caused the baseplate to become effectively stuck to the ground. The magnets on the baseplate were strong enough to hold Beta to a piece of steel while inverted.

-Thwack

There are two types of 'thwack' robots. One is a horizontal thwack robot. The other is an overhead thwack robot. Both types have been effective in combat, though horizontal is more popular, partly because it is much easier to make.

Overhead thwack robots have the entire main body of the robot rotate with the hammer. This means that the majority of the mass must be contained within the diameter of the wheels. The striking object tends to be lighter than on a horizontal thwack robot because a heavy weapon would be much harder to flip over the top of the robot. This type of robot is about balance and power. Properly balancing the rotating body of the robot is essential to getting a good swing. Swinging the weapon is achieved by quickly reversing the direction of travel and using that torque to rotate the body 180 degrees. If the weapon is too heavy, this won't work. If the weight is improperly positioned in the body of the robot, it will also not work. The most well known robot in this style is Overkill. Overkill has a free floating wedge on the front of the robot and a cylindrical body. The weapon is a massive steel blade cut to look like a knife.

The other type of thwack robot spins its entire body horizontally to cause damage by spinning the drive motors in reverse directions. The impact points on the robot can be connected directly to the body of the robot, like with the robot Tesla's Tornado, or a mass can be attached to the end of a pole, as with the robot Mjollnir. Both methods have been effective in the past. The main difficulty with this design is that translational movement while the weapon is active is difficult. There are solutions to this, though. The 'Melty-Brain' system allows slow translational movement by rapidly altering the speed the wheels are rotating at. Variants of this same concept are used on most robots of this style that have translational movement while spinning.

These robots tend to be very well armored and have drivetrains on par with rammers and wedges. The horizontal thwack robots are good for beginners as they are simple to make and have a weapon.

-Spinner

-Vertical

Vertical spinners come in two varieties, bar and disk. Both do basically the same thing. The idea with a vertical spinner is to use the ground to your advantage. When a spinning object hits a robot, half the energy goes to each robot. Vertical disks use the ground to absorb that energy while trying to send the remaining parts of its opponent skyward. Vertical spinners require a lot of strength in the frame that supports the weapon to avoid warping during impacts. Many vertical spinners have a support going straight down from the shaft of the spinning disk to help absorb the impact.

Vertical spinners are prone to gyroscopic issues when turning. When you spin an object at a high velocity there is significant gyroscopic force attempting to keep it from turning in any other directions. If you try to turn too quickly with a vertical spinner, it may tip to one side. Depending on the tip, you will either flip yourself over or lose enough stability that you must stop, let the robot get back onto the ground, and continue turning. The hazard here is that when you are doing this, the other robot is able to better position itself for a counter attack. Vertical spinners tend to have very wide drive systems to counteract this force.

Nightmare is one of the most well known vertical spinners in the sport. Nightmare has what seems like a minimalist frame in a Y shape to hold all of its components. Extending from the middle of the Y is the weapon support. Nightmare has a giant disk that spins at a high enough speed to send a 220lb robot armor over wheels when it hits its opponent at full speed. Nightmare has a very wide base which allows it to turn without many gyroscopic issues. The wheels are far enough forward that no other supports are needed to keep the disk from hitting the ground when it strikes an opponent.

Vertical spinners are very effective in most combat situations. Their main weakness is against horizontal spinners. If the two weapons meet, the vertical spinning weapon will likely be damaged to the point it will no longer properly operate. They often damage the horizontal one as well, but it has been more common for the horizontal spinner to come out on top because of the weapons arrangements.

-Drum

Drum weapons are the cousin of the vertical disk. Unlike vertical disks, drums tend to have a fairly small diameter. They are also normally very wide, often covering the majority of one side of a robot. Gyroscopic forces become less of an issue with the drum design, though are still a factor. Drums also have a much wider impact area. They are spun at very high rpms compared to other spinners. Depending on the design, drums may be made to provide a big hit, or many smaller hits in rapid succession. However the reduced inertia of the slender drum causes big hits to be harder than with a disc robot.

Drum weapons gained popularity during the Battlebots era when El Diablo and Little Drummer Boy took the MW division by storm. These two early drum robots played a major role in drum weapons becoming common among combat robots.

The only material that appears on almost all drums is steel. It is used for the weapon teeth of the drum. The drum itself can be made of aluminum, steel or titanium in varying thicknesses dependent on the weight class and width of the drum.

Some builders have experimented with weapons that are a cross between a drum and a vertical spinning disk. They have had some success, but suffer from the gyroscopic instability issues that face vertical spinners.

 

-Horizontal

Horizontal spinners are the most popular type of spinner in robotic combat right now. The horizontal spinner is a wide category. It includes shell spinners, overhead spinners, front mounted spinners, and undercutters.

Shell spinners have a rotating mass that surrounds the chassis of the robot. These spinners develop a high amount of kinetic energy when spinning due to the large mass of the spinning object. The shells also double as a kinetic armor when the weapon is operational. When the metal shell is spinning at a high rpm it becomes very difficult to penetrate. This type of weapon is used on heavyweight Megabyte. It is one of the most feared robots in its class. Shell spinners are most effective when the shell is short in height and has angled sides. A low center of gravity keeps them stable after powerful impacts. Angled sides help deflect any impacts from opposing robots. These robots tend to use unibody frames. Unibody frames are either made out of a single piece of material, or made out of welded together pieces of a material, making the structure, including any armor, a single piece.

Shell spinners, if unbalanced to a great enough extent can perform a move known as 'pulling a Mauler.' The maneuver is named after the late, great, and original shell spinner, The South Bay Mauler, which later became Mauler 5150. Pulling a Mauler is when the robot is thrown into a gyroscopic dance of death. The chassis of the robot is often rotated at a high rpm as the robot shakes and shoots around the arena, only to eventually land on its top and lose. Some shell spinners have the shell ride on a fixed shaft with a bend at the top. The bend will cause the robot to right itself when flipped. The bend stays in alignment with the chassis, so when the shell is on the ground, the chassis starts spinning. The bent pole hits the ground and sends the robot back on its wheels.

A variant on the shell spinner is the ring spinner. They operate on many of the same principles, but only spin an outer ring instead of a shell. This allows them to be invertible, as there is nothing blocking the wheels from coming out the top of the robot.

Overhead spinners normally use bars. They can look like an inverted lawnmower. This weapon is not as powerful as a shell spinner, but it is easier to build and weighs less. The weight savings allow for a stronger drive system or frame. The simplicity makes it an easier project for a new robot builder. These weapons, when used right, can be extremely effective.

Hazard uses an overhead bar. It went through many battlebots seasons undefeated and almost unchanged. The weapon would slice through the armor of its opponent, ripping apart vital components and scattering them about the arena. Hazard used a hinged wedge to guide low robots into the bar. Hazard has lost a total of three times in its competition history. Twice at an event called steel conflict, to heavily armored wedges. It's other loss was in season 5 of Battlebots. Hazard lost in the semi-finals to the robot T-minus built by Inertia Labs. Hazard's weapon was its undoing in that fight. T-minus was able to get under the front wedge of Hazard. When they tried to flip Hazard the wedge went up and caught Hazard's own blade. The weapon became jammed. Hazard, unable to use its weapon, lost the fight soon after.

Front mounted spinning weapons are almost identical to overhead spinners. Instead of having the blade on the top of the robot, it is mounted into a frame that comes out one side of the robot. This allows the blade to be lower to the ground and the robot that wields it to be taller without losing effectiveness.

Undercutters do just what the name implies. They cut underneath the robot. The idea with this weapon is to remove the wheels and anything else sticking out the bottom of your robot as quick as possible. Undercutter blades ride very close to the ground, which makes them very difficult to avoid in a match. The blades often have a material beneath them to prevent them from hitting seams in the arena floor. Some common materials are UHMW plastic, bearings and the shaft of the weapon.

All horizontal spinners have problems with over and under-steering. When you spin a large mass at a high velocity it causes the chassis to want to rotate. The rotation of the weapon will cause the robot to turn much faster in one direction and have trouble turning the other. It will also have some difficulties driving in a straight line.

 

-Flamethrower

Fire based weapon systems have been legalized in some events in recent years. They are very ineffective in combat applications. They do however put on a nice show. People associate fire with danger and pain. This association creates an illusion of damage and that is often all that is needed to grab attention. Flamethrowers are primarily weapons for show. They are effective against robots made of flammable materials, but there are not many flammable robots fighting regularly. Sometimes, if aimed towards the correct spot, they can also overheat the electronics systems of some robots.

-Swiss Army Bots

Swiss army bot is a category for robots that have multiple weapons. The Master is a prime example of a 'Swiss army bot.' The Master has a base chassis that all attachments are mounted to. The Master has used a chainsaw, a gas powered saw, a long razor sharp blade, a lifting arm and many more strange attachments. This modularity allows it to pick the weapon best suited to its opponent. A Swiss army bot, in the rock, paper, scissors analogy, is like knowing what the other person is going to throw, and adjusting your throw to beat it. The weapons are not as effective as weapons that aren't designed to be interchanged. They all have to fit it the same spot, so some features have to be compromised to make the weapons interchangeable. Another prime example of a swiss army bot, is the generic 4-wheeled chassis being used in the images accompanying this article.