How to Build an Antweight Combat Robot

Have you ever wanted to build a competitive combat robot? You probably thought it was too, much hardware or dangerous and expensive. However, a lot of combat robot competitions have a weight class for 150 grams, including Robot Wars. This class is called “Antweight”  at 1lb and sometimes called “Fairy Weight” at 150g.  These are crazy cheaper than the bigger combat robots and aren’t as dangerous. This makes them perfect for people new to combat robots.

NOTE: This article assumes that you have already built an simple RC robot. If you have not, go back and do that first. I do not recommend a specific part for use with your robot. This is to promote creativity and diversity amongst robots.

This video will tell you how to design and build an Antweight combat robot.

The Rules

The rules can be found here. The most important building rules that you need to be paying attention to are the size/weight requirements (4″ X 4″ X 4″ US 1lb) and the metal armor rule that says you cannot have metal armor more the 1mm thick.

Choose Your Weapon

A big part of the combat robot is the weapon of course. Brainstorm an idea for a weapon and make sure it fits within the rules. For your first antweight bot it’s highly recommended going with maybe a “flipper” or even a “pusher”. A pusher is the simplest weapon because there is no active weapon. The whole robot acts as a weapon by pushing the other robots around. This is effective because of the rule that states that half of the arena can’t be walled. You can push the other robot out of the arena. A flipper is just a weapon that wedges itself underneath another robot and pushes up to flip them over. A flipper weapon, when designed properly, can be the most effective weapon in the Antweight Class.

Grab Parts Before Designing

Choose your parts and design accordingly. If something doesn’t fit or doesn’t work while you are still designing, you save money because you can switch parts now. Again, do not buy the parts, yet!

  • Drive Servos Try to use servos instead of motors for a beginner’s weight because, with servos, you do not need a speed controller which saves money and precious weight on your robot. You should look for “micro” servos because they will save you a lot of weight. Be sure to make sure the servo is 360 modifiable. It’s recommended getting high torque servos for combat robots instead of high speed so it’s easy to push other robots around, even if you have a separate weapon.
  • Servos can be purchased here.
  • Still looking?, check out-out another section on that site that sells “Futaba” servos. Futaba is a different brand that makes servos. Sometimes they have different sizes than the HiTech brand.
  • For a Weapon motor (if you have an active weapon (i.e. aren’t creating a “pusher”), then you probably need a motor to move the weapon. If you have a weapon that needs to move really fast (i.e. a spinning weapon), then you should get a geared DC motor (Brushless generally works better, but brushed would work) with a speed controller. It’s not recommended using a spinning weapon for your first weight because they can be difficult to build and balance properly. However, if you are creating a flipper weapon, then you want to use a servo. It’s recommended to get a micro servo with extremely high torque so it can flip other robots with ease. Another thing to consider when looking for a weapon servo is the type of gears. If you use nylon gears and the motor gets a lot of stress, the gears can strip out over time. Try getting stronger gears made out of metal.
  • Choose Wheels When choosing wheels, be sure to remember the rule that says the robot has to be able to fit within a 4″ x 4″ x 4″ cube. This means you have to have wheels that have a diameter less than this. It’s recommended to use 2″ diameter wheel. Be sure that the wheels can easily attach to the servos securely. Another great technique to use in combat robots of any size is the ability to drive upside down. Yes, the controls will be a bit backward, but it can prevent you from losing the competition from being immobile. So consider making your robot shorter than your wheels so that it can drive upside down. You can purchase wheels here.
  • Choose a Transmitter/Receiver When purchasing a receiver make sure that it has what is called “Fail-Safe operation”. It is a rule to have this in most competitions and a safety feature. The AR500 Receiver does not have this. You will need to purchase a BR6000 Bot Receiver, or another receiver that has this feature. For a transmitter, it’s recommended using the Spektrum DX5e. If you built the Remote Controlled Robot found in the related wikiHows, you can reuse that transmitter, but you must buy a new receiver.
  • It’s highly recommended using a LiPo battery instead of a NiMH battery. LiPo batteries are lighter. However, they are more dangerous, expensive, and require a special charger. Invest the money in a LiPo battery and a charger to save on the precious weight.
  • The material the chassis and armor are made out of on a combat robot is extremely important because it is what prevents enemy weapons from piercing your electric components. There are three main choices that you should choose from: (Note: There are more, but these are the best for this particular weight class) Aluminum, Titanium, and Polycarbonate. Aluminum is lightweight and strong, but it can be expensive and hard to cut. Plus it can not be more than 1mm at all. Titanium is lightweight and extremely strong but is hard to cut and extremely expensive. This also is subject to the 1 mm thickness rule. Polycarbonate, or Lexan, is a lightweight, inexpensive, easy to cut, shatterproof, strong plastic that is sometimes used in bulletproofing. Polycarbonate is also a plastic so it can be as thick as you want, but it’s recommended to get it about 1 mm thick. It’s highly recommended using polycarbonate. It’s so durable that this plastic is the plastic that makes up the arena walls for antweight competitions. When you purchase it be sure to get extra, in case you mess up.

Create a Digital Design (if possible)

Design 3D on a computer, rather than 2D on a sheet of paper. However, the 3D design doesn’t need to look complex, a simple one made of rectangular prisms and cylinders will be sufficient.

  1. Add up the weight of the parts (in grams) and be sure they total less than 150 grams.
  2. If you don’t have CAD, download the student no-profit version of Sketchup or Fusion360
  3. Create the components you are using the size specs you wrote down.
  4. Design your chassis, axle support and armor. Be sure to make it less than 4X4X4 inches.
  5. Fit the components into the 3D chassis/armor model to see if they fit at the same time. This will also help you decide where the components will be.

Parts for typical Antweight

ZIPPY Compact 500mAh 3S 25C Lipo Pack –…

D822/17 Brushless Outrunner 1100kv –…

Afro Slim 20Amp Multi-rotor Motor Speed Controller –…

TinyESC –

Micro Gearmotor – 460 RPM –

OrangeRx R410X DSMX Compatible 4Ch/6CH Receiver –…

Turnigy 9X 9Ch Transmitter –…

OrangeRX DSMX / DSM2 Compatible Module –…

Garolite G-10 Plates – Fingertech Mini Power Switch

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