Types of Combat Bots
This tutorial is an overview of the types of combat bots and introduces what it takes to make an effective beetleweight bot. Modified from the work of previous BattleBots leads and aspects of the BattleBots Bible (RioBotz Combot Tutorial 2.0). Includes links/photos from the BattleBots website highlighting example bots.
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Step 1: Getting Started
There are many types of combat robots out there. Some are complicated, and others, very very simple, like wedges. For this project, we will not be designing a wedge for a couple of reasons. One, these designs are generally uninteresting and are not complex to design or build. Two, wedges aren't fun. And last, but not least, you don't want to be that guy.
Because there are several types of combat robots, it can be difficult to decide which kind to build. No type of bot is the best, and a well-designed bot can win against a bot of any type. That being said, some types of bots are better suited to face others. For instance, wedges tend to flip over spinners, which tend to cut off hammers, which tend to puncture/damage wedges. Thus, it's important to keep in mind what kinds of bots yours will fare well against.
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Step 2: Weaknesses
When designing your team's robot, it is important to consider the types of weaknesses that your robot can have. Let's consider the weaknesses that a drum spinner has:
- the length of time it takes for the weapon to spin up
- the chance someone gets underneath your robot, thus dodging out on hitting your weapon
- your juicy back
- wheels
- electronics dying
It's important to note that you can't really prevent all of these weaknesses and compromises must be made in terms of your weight limit and other aspects of your design.
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Step 3: Structural Design
The shape of your robot as a whole is a huge determining factor of how well your robot will do. For instance, a number of bot designs rely on spinning weapons. With the amount of mass that’s spinning at high speeds and the amount of angular momentum that it generates, problems may arise if your center of mass is incorrectly placed. Correctly placing your center of mass may also allow you to push harder, or just not flip yourself over when you suddenly accelerate.
Another huge part of structural design is understanding the types of impacts you want to protect against, these can include top, bottom, side, front, and back impacts. A simple way to deal with protecting against these impacts is to use deflection by having angled or rounded shapes to stop direct impacts. Here are some example sketches:
Keeping all of this in mind, let's take a look at some of the types of bots you can design...
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Step 4: Vertical Spinners
Vertical spinners generally use disks with very few teeth, or bars, spinning on a vertical plane. They damage their opponents when the opponent is hit, and when the opponent hits the ground.
Vertical spinners should have a wide base so that they don't tumble when turning due to the gyroscopic effect of the weapon.
Because the impact force is transmitted to the ground, and not sideways, they won't be flung to the sides due to their own impact. Unfortunately, these bots have a harder time making quick turns, and are especially vulnerable to very low wedges and tough rammers.
Take a look at Witch Doctor (above), and Nightmare (below), two different types of vertical spinners.
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Step 5: Horizontal Spinners
Horizontal spinners have a disk/bar that spins at high speeds, and can be called an undercutter when the weapon spins very low near the ground. The weapon should spin as fast as possible, and accelerate to a speed that can cause significant damage in less than 4 seconds.
Most horizontal spinners are not invertible, which is one of their greatest weaknesses. Some bots, offset spinners, compensate for this by moving their blade forward, making them invertible, although somewhat less robust.
Tombstone (above) and Son of Whyachi (below), are two notably different, yet insanely effective horizontal spinners.
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Step 6: Full-Body/Shell Spinners
Shell spinners spin their entire ring or shell-shaped armor, making it almost impossible for the opponents to reach them without being hit by their weapon. Like horizontal spinners, these bots should accelerate to a speed that can cause significant damage in less than 4 seconds.
One main disadvantage is that shell spinners are generally not invertible.
Full-body spinners are generally 2-wheeled robots, invertible, and rotate all their structure in the same place at high speeds. Usually, they have one or more rods with an axe, hammer, or some sort of piercing weapon; the energy of the drive motors (which need to have a high RPM) are used to power the weapon, leaving more weight for the armor. The wheels should be narrow, but not too far apart; the closer the wheels are to each other, the faster the final angular speed of the bot will be, but the slower the acceleration will be.
A great example of a spinner is Gigabyte (pictured below).
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Step 7: Drumbots/Egg Beaters
Drumbots and egg beaters have either a spinning drum or egg beater, and are generally powered by belts or chains that are horizontally mounted in front of the robot.
Drumbots/egg beaters are more compact versions of vertical spinners, with less moment of inertia in the weapon, allowing the drum to accelerate quicker. Because they have a low center of gravity, they are relatively stable and can be invertible.
Two impressive heavyweight drumbots include Minotaur (above) and Yeti. See RailGun Max (below) or Black Dragon for examples of heavyweight eggbeaters.
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Step 8: Other Types of Bots
There are many other types of combat bots, although not all are practical for the beetleweight class. We wouldn't recommend pursuing any of these designs because they (a) employ passive weapons (e.g. wedges, rammers) or (b) aren't practical on the beetleweight scale (e.g. crushers, spearbots). That being said, here are some different types of bots:
Wedges are armed with a sloped plate shaped like a wedge.
- generally have a very resistant drive system
- rarely cause direct damage, but are incredibly effective against spinners, making them flip over when hitting the wedge
- win when they enter under bots and drag them under the arena, or flip them at high speeds
- ideally, make the front of the wedge out of thick metal plates chamfered at the edge to withstand the opponents' impacts
Rammers are ramming robots that damage the opponent by pushing them against the borders of the arena or throwing themselves against them.
- have wheels with high traction and a sturdy drive system
- need robust armor and to be highly resistant to impacts
- don't have a weapon other than their passive shields
- need to be capable of pushing at least two times their own weight
- generally effective against spinners and drumbots
Lifter bots are capable of lifting their opponents, aiming to immobilize them/turn them over.
- efficient against bots that depend on traction, like rammers and wedges
- generally uses a slow linear actuator or pneumatic system
- batteries should be placed as far behind as possible in the bot so it can act as a counterweight when lifting an opponent
Launchers/Flippers fling their opponents high into the air, damaging them when they hit the ground.
- good against opponents with weak chassis and internal components (e.g. batteries) that are unprotected against impacts
- generally, these bots need pneumatic components
- one successful launcher/flipper bot is Bronco (pictured below)
Hammerbots are bots with hammers/axes that hit the top of their opponents.
- weapon can be fired quickly and repeatedly, and is independent of the drive system
- hammer/axe system works as a mechanism to right itself if it gets flipped
- best against robots with weak top armors, but vulnerable to spinners
- check out the heavyweight bot BETA (pictured below)
Sawbots have toothed or abrasive disks that are powered at high speeds.
- can easily cut through sheet metal, but less effective at cutting through metal plates
- good at causing cosmetic damage, which can be a determining factor if a match comes down to a judge's decision
- saws should rotate downwards to eliminate chances of a bot getting stuck on an opponent, bending, or breaking
Spearbots have long, thin weapons that are generally pneumatically actuated to penetrate the walls of an opponent's armor to damage vital internal components.
- needs to have a resilient and sharp weapon
- high traction so that the robot doesn't move too far backwards during an attack
Crushers are bots that use hydraulic claws to slowly puncture and crush their opponents.
- once an opponent is caught, it is nearly impossible for them to escape, ending the match
- because they need to be hydraulically powered, they are incredibly heavy, and need to have lightweight drive systems
- Kraken (pictured below) is one example of a crusher-type bot
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Step 9: Next Steps
If you still need inspiration, you might find it helpful to take a look at some of the other heavyweight bots that have competed on the BattleBots TV show. Keep in mind that a successful heavyweight design may not translate well to the beetleweight weight class, and that it's impossible to do everything they can on the heavyweight scale (e.g. pneumatics).
Once you know what type of bot you want to build, start to think about how you will design your weapon and structure, and start sketching! Check out other tutorials/stay tuned for future meetings where we'll go over the aspects of this project, like weapon design, in greater detail.
