Glens's Guide to Building a Beetleweight

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This is not meant to be comprehensive guide on how to do everything this is just meant to be an overview of what you need to get started and where to go to find more information.

Safety

Combat robots are dangerous that is one of the reasons why putting them in an arena and watching them destroy each other is fun. This means that they are also capable of destroying you. Despite this building robot can be done in a safe manner if you think about what you are doing and take a few precautions. All the weapons you can build basically rely on the transfer of large amounts of energy into the other robot whether by spinning, flipping, launching, ect. So simply don't test these sorts of weapons in situations where you are not adequately protected. Do it in an arena or equivalent area with safety measures in place to ensure you don't get hurt!

Secondly a driving robot (even without a weapon) running into your ankles could easily break one, or cause sever damage, so make sure your robot can be properly controlled and have some form of barrier it can't drive over between it and yourself before letting it loose for testing. When testing your robot on the bench you should always have your wheels elevated.

There is many other things which I haven't covered here but if you have any doubts before doing something don't do it.
I take no responsibility for any injury sustained by building anything shown in this guide. If you don't have the skills, tools or patience to do it properly and safely STOP NOW

We now return you to your regular program.

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Rules

Most events now use the standard RFL rules set. Jump to the Rules Section and have a read before you go much further.

Just quickly before you ask. "Why can't I build an EMP or use radio jammer or use a gun on the robot?" Have a think about what would happen...
With an EMP you would put the two robots in the arena one would set off EMP... other robot would sit still. Not going to be the most interesting thing to watch. There is a reason why there is restrictions on the weapons. Whether it is for safety, to keep things interesting or just prevent undue damage to the arena. The rules have been refined over 10 years so they are pretty well thought out. So just ask yourself why before complaining about the restrictions.

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What will you need?

To start your path to competing in the beetleweight division your going to need some crucial parts no matter what style of robot you decide to make, this guide will serve as a brief run through of what you will require, mainly;

Radio controller
Drive train
Batteries
Speed Controller
Armour
Weapon

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Radio Controller

You will need some form of radio controller in order to control the robot! You can also make an autonomous robot as these are within the rules, but that is beyond the scope of this article. Most controllers are standard RC hobby type units. There have been many custom solutions in the past involving RF computer gear (zigbee etc) and even Infra red doorbell controllers in one case, but with the current price and reliability of Radio control gear, as low as $35-40, you will find that this is the most popular solution and the one we will focus on.

If you don't have one already

Jump on HobbyKing∞ and grab a 2.4ghz any model you like should pretty much work these days. A Hobbyking T6A V2 6channel radio is <$50 including shipping and is a good place to start. Just don't forget to grab the PC programming cable.

For more info on radio choices then jump to the Radio Control section

If you already own a radio

The important question now is "Is it a digital radio?"
Any 2.4ghz radio will be digital and some of the older radios have digital signal encoding which make them much more robust to interference. These should all work fine in a robot.

If you have an older style radio, such as a 36-40mhz aircraft radio or a 27mhz ground radio, either FM or AM, then it *MAY* be possible to use. In featherweight competitions their use has largely been discontinued, even banned in some events, as the interference that is a problem with these types of radios can be a serious problem with the larger robots. However on the much smaller scale of a beetleweight size robot, they are still permissible.

Personally i would recommend you stay away from them and just go for the cheap 2.4ghz radios mentioned above. It is a small investment you will use for years upon years for all your robots and the frustration saved from battling with interference issues, which often occur sporadically at events (trust me i know all too well!), is well worth it, not to mention having a giant 30cm long wire antenna trailing from your small robot is just asking for someone to attack it! The 2.4ghz radios have extremely short antennas that can be buried inside even a metal robot so that is one worry you wont have.

Just a few years ago a digital radio would have set you back $300+ however now you can get one for <$50 which you just put in your robot and it works. No making antennas, no sitting there scratching your head as to why the robot isn't working. So my advice is save yourself the pain and just spend the few dollars on a proper radio. It is well worth it.

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Drive Train

There are many options out there for the drive train. The small size of these robots opens up a world of possibility when it comes to selecting drive motors and gearboxes.

At the simplest level, you can simply buy a cheap toy radio control car and liberate the drive units from them, Giving you a pair of gearboxes, motors and wheels all ready to use. If you get lucky you may even have a controller and radio all ready to go! You must make sure that the car has "tank steering" however, If it has standard car steering then you will likely only get one drive unit.

These toy drives are often quite powerful and fast and are a good way to build a robot quickly. However the main downfall is they are often hard to mount with wierd mounting points if they even have any at all given some are cast into the plastic frame of the toy and are rarely very durable, requiring replacement every event or so. So you have to use your own discretion there to find a suitable car to hack.

Stitchface is a prime example of a robot using this drive train. It even won the event!

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Batteries

In general the two favorite types of batteries are LiFe or LiPo batteries.

LiFe batteries

LiFe batteries are probably the most commonly used battery in combat robots. They are robust, can be charged fast, don't fail violently and can be abused and generally survive. The most common form of cell used is the A123 cell which is used in dewalt cordless drills. Unfortunately no convenient source for these batteries is known at this time. eBay has them but sellers often rip you off with fake or used cells so be very very wary.

LiPo batteries

Lipoly batteries are the other main type of batteries now used. They are similar slightly light in power to weight than LiFe but have lower rated charge and discharge rates and are more unstable. Fortunately lots of progress has been made in the last few years which make these batteries suitable for use in robots. Our friend HobbyKing∞ has us covered here with a huge selection of batteries. For just a drive system I would grab a 4 cell (4S) battery with 2 amp hour (Ah) capacity or bigger with a rated discharge rate of at least 40C.

For more information see the Batteries & Power section.

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Speed Controller

Speed controllers are another item which you will require and are usually the most expensive part of your robot.

My recommendation would be to go to Robot Power∞ and buy an XXL controller. This is probably the most proven controller out there. (Check forums for more up to date info)

There is other options, personally I use my own custom Hacked ESCs, based on Hobby King controllers but be prepared to do lots of research if you want to save some money.

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Armour