How to Build a Heavy Weight Robot.

If you are under 16, get your parents / guardians permission first, besides you will want them to be your number one sponsor.

So, you want to build a heavy weight robot. There are two approaches :-

Design & Build is the way to go if money is not an issue. You let your imagination run riot on paper and then try to make it work. This can be expensive and frustrating when you run out of cash.

Scrounge & Build is far more realistic. You collect anything that may be of use from the cheapest sources, scrap yards, surplus stores (Display Electronics), car boot sales, the tip, etc. You then arrange it in such a way that it becomes the ultimate killing machine.

Barry was built buy starting with the Design & Build approach and when the money ran out we moved across to the Scrounge & Build. We would advise anybody starting to build, to spend as little money as possible. Whatever you buy will be wrong, and there is great satisfaction when your Junk yard bot knocks out a company sponsored robot costing £3000. Also you wont be as disappointed as we were when you only move 2.93 metres over the start line!

The following is a step by step guide to building a robot. We are keeping it as general as possible because we don't want millions of Barry's in the next series. This information is based on our own experiences and those of other teams both in the UK and the USA.

Design Process

Weapons - The most important feature on your robot.
All the exciting weapons are banned - Hilti guns, Expanding foam, Tesla coils, Water, Explosives, etc. All you are left with is hammers and cutters. If you can imagine trying to cut or hit a moving object, remotely from 30 yards you can begin to understand why they don't work. All the robots lose because they breakdown, get stuck or occasionally get flipped or are pushed out of the arena. Lets face it, if you were being cut or hit, you would just move away.
The only exception to this is the recent introduction of some useful axes and hypnodisc's cutter.
If you aren't up to building a killer weapon, a robot with no weapons is boring, so you may as well go for effect rather than practicality. We had the idea of an arm coming over holding a frying pan, not very effective but fun all the same. Another idea was a stick holding a live rabbit, we can't imagine anyone messing with that.

Wheels / Tracks / Castors - The most crucial part of your robot.
The starting point of any robot. These are the key to your robots look and its performance. The wrong wheels and your Robot is doomed.
Tracks are not advised, if they were the way to go, all cars would be fitted with them. The playing surface is plywood, not sand or mud, tracks are difficult to make and vulnerable to breakage.
Wheels, pneumatic are best because of the extra traction. The balloon tyres on Barry are road going trailer tyres with steel rims. Far too heavy but they look the part.
Castors, needed to keep the bodywork from dragging along the floor, make them as large as possible. The house robots used small ones from a settee and they had to be welded back on between games!

Petrol Engine versus Electric Motor - Go electric.
98% of robots use electric power, this is because it is easier to control. With an engine you need a clutch or method of stopping the robot without stalling the engine and also a mechanical method of reversing. These problems don't exist with electric motors, try to get the best that you can find or afford. The bigger robots use wheel chair / golf cart technology - not cheap. You could use car or motor bike starter motors, they are cheap but not very effecient, they are only used for 5 seconds at a time and then their battery is recharged. They are not used for 18 holes of golf or to take granny to the shops and back.

Gearbox - you will need one
The main problem with electric motors is that they give their maximum torque (turning power) at maximum speed. A robot would never reach full speed of a directly coupled motor and therefore the motor would only be using part of its full output so a method of reducing the speed is essential. You can gear down the drive with the choice of sprockets and chain connecting the motor to the axle but this alone is not enough. Most motors, maximum speed is about 3000 rpm and the fastest controllable speed required on the set is about 10 mph, assume you are using 10 inch diameter wheels, you would need a gearbox with a reduction of about 10:1. Some motors, those used in wheel chairs and kiddy cars, have a gearbox attached. Some robots have used rechargeable screwdrivers, they have everything you need incorporated - motor, gearbox, battery, charger.

Speed Controllers - will let you down
This is the bit that goes between the radio and the motor. Nearly all breakdowns at robot wars were due to speed controllers failing. The simplest, cheapest and probably the most reliable are simple switches or relays. Assuming you want to make your robot go backwards as well as forwards, useful in a maze, you will have to arrange a simple voltage reverser operated by a servo. The only disadvantage is that your control will be a little jerky, it's all or nothing. Killatron uses this system to good effect. Speed controllers offer greater control with proportional control in both directions. With the larger robots, the currents and voltages used make the model car speed controllers redundant. You either need to build your own, not difficult using an astable to switch a bank of transistors, or buy someone else's. When a robot stalls i.e. hits another robot or the set, the current through the motors goes off the scale and the controllers burn out. There is nothing more annoying than the speed controllers failing, if you are going to spend any money, this is where to spend it. The most popular at this years event where VANTEC from the states and 4QD from Cambridge. 4QD have a fixed flat rate for repairing their boards (£12) which is useful if they have been sawn in half by a chainsaw! The house robots and Barry used 4QD controllers.

Steering - Use tank steering.
Over 95% of the larger robots use 2 wheels, 2 motors and 2 speed controllers and steer like a tank. There are several advantages, once the wheel-motor-controller is sorted out you just double it and the steering is done, you can turn around in your own length and you can spin on the spot.

Radio Control - Buy every crystal in the shop
You can only use 27 Mhz or 40 Mhz. At this years event there were up to 8 teams on the same frequency! We suggest you borrow or buy the cheapest radio and get yourself a bucket full of crystals. Don't go for dual controls, because the chance of getting both pegs at the same time is nil. One guy this year was on 35 Mhz, the band reserved for aircraft, at least he had his own channel!

Batteries - Must be gel
The rules insist on gel cells and they are expensive. We can't understand it, you can use chainsaws and petrol powered brick cutters but they are worried about battery acid. We suggest you go for small ones and have a few in reserve. The ones on Barry are too big and have never run out, the games in the show only last for 3 minutes at the most.

Chassis - Space frame
If you can weld or can get it welded, tubular steel is the best. It is light, strong, cheap and easily fabricated. Some were made of MDF but we wouldn't recommend it. The design of the chassis affects the shape of the whole robot and the location of all the parts. We prefer the frame chassis approach rather than the make a box and put everything in it approach. It gives the robot a more purposeful look and there is little wasted space.

Body Work - Wedges are boring!
It is fairly obvious that the best shape is a wedge but, yawn, if we all made wedges, all the robots would merge into one design. Which is your wedge? The one over there, between the orange wedge and the green wedge. Try to give your robot a style or personality. With Barry we tried to go for the Jeep / Harley Davidson look. Chrome & black, knobbly tyres, camouflage and a spoiler. We could have put it all in an aluminium wedge but then it wouldn't be Barry. Another reason for not needing to enclose everything in aluminium is that :-

Practice / Testing - You will need lots.
Human nature is to keep working on a project up to the deadline. Especially something as nebulous as an entrant for robot wars, they can always be improved. We were still building Barry on the day before we left for the studio, which may explain why Amy stuffed it into a pit. You need to set a deadline at least a week before filming to allow time for testing and practice. It is better for something to fail in the workshop rather than at the studio.

We hope that helps a little and good luck. If you have any burning technical questions contact us through the comments page.

Take care, especially if you are under 16, Barry has no sharp weapons but we nearly broke someone's leg and knocked a lathe over in the workshop with him.