Designing and Building Warrior Robots
By William Gurstelle
Chicago Review Press Incorporated Copyright © 2003 William Gurstelle
All rights reserved.
Stinger COURTESY A. J. KLEIN OSOWSKI
Given the amount of power and the number of dangerous items found on a typical fighting robot, it is almost inevitable that someday, something bad will happen. This chapter provides some basic, commonsense safety guidelines to get the new builder off on the right foot.
The largest fighting robots weigh over 300 pounds and are powered by large electric motors that have enough power to push a Ford truck uphill. These robots are outfitted with power saws spinning at ridiculous speeds, fast-moving hammers, and high-impact kinetic energy weapons. Many robots use high-pressure pneumatic systems that can burst through heavy pipe. Believe me, fighting robots can be as (or more) dangerous to the people in close proximity to them — the robot builders, the robot drivers, and spectators — than to other robots. The other robots are armored with quarter-inch steel plates. People are not.
I have seen high school kids with no training or education in high-pressure pneumatics attempt to compete with extremely suspect liquid CO2-powered lifting arms. I have yelled at inexperienced builders to not adjust unguarded chain drives wearing long, dangling sleeves. I have heard of close calls when bot drivers attempted to destroy junk, just for fun, in front of spectators, without regard to the inevitable shrapnel produced.
Robot fighting can be very dangerous. If you participate, realize the dangers and heed the instructions given here to mitigate them. Wearing safety glasses and gloves is not nearly enough. No list of safety rules is comprehensive enough to cover every situation.
The suggestions that follow are written to maximize safety. They are only guidelines. Every builder must make safety the number-one priority and accept responsibility to make the bot safe for everyone involved — the builder, the driver, and the spectators.
If you learn only one thing from this book, at least learn this: if you build a robot you do so at your own risk! If you build a robot, it is up to you to build it right and operate it safely. This book will help you. But in the end, all responsibility rests squarely on the shoulders of the builder.
If you are willing to take responsibility for your actions and are still interested in building a fighting robot, then heed these 10 rules. They do not guarantee your safety, but not following them practically guarantees a disaster.
Basic Robot Safety Guidelines
1. Figure out what you're doingbeforeyou do it. If you're going to build robots, don't be half-assed about it — go into it fully assed. Anything less is asking for trouble. If you don't know how to weld, learn how from someone who does. Never used a metal turning lathe? Read up on it. There's a right way and a wrong way to do everything. The wrong way may seem easier, but the right way is better and safer.
2. Always wear safety glasses. Almost every shop operation — cutting, welding, sanding, et cetera — involves the presence of flying metal, wood, or plastic chips. When necessary, wear personal protective equipment, such as welding gloves when welding, hearing protection when conducting noisy operations, and a face mask when using paints or solvents.
3. Get a copy of the rules for any competition you are considering entering. There is always a section on safety rules. Read it for two reasons: (1) it provides guidance for building a robot safely, and (2) you won't waste time designing an illegal bot.
Every tournament has its own unique rules regarding safety. The rules pertain to both the construction requirements of the warrior robot and the procedures that must be followed during the tournament. Some tournaments are very particular about the type of radio controls allowed, and some are more concerned about restraints and tie-downs. Because competitions differ, every builder should obtain a copy of the event rules from the tournament organizer well before the actual event in order to make certain the robot is in strict compliance.
4. Robots are remote-controlled vehicles and they are subject to radio "glitches." This means they may turn on or off unexpectedly. Glitches occur frequently and come from a variety of sources. Besides a simple signal glitch, your robot may also be subject to radio interference from another contestant's radio transmitter, a commercial radio dispatch system, or even a garage door opener. Never place yourself in a situation where an unexpected radio transmission can activate your robot and hurt you or others.
5. There must be an easy-to-reach, easy-to-activate main cutoff switch on the outside of your robot. No matter where you compete, even if you just bang around your garage and scare neighborhood children, your robot must be fitted with a kill switch or removable link. This vitally important safety device is designed such that when it is deactivated or removed, no current flows from the battery to anything else. The drive motors, the weapon motors, the electronics — everything shuts down immediately. This safety device should be completely mechanical; that is, there cannot be any electrical components such as relays or sensors involved.
There are at least a couple of ways of doing this. The first way is to make or purchase a heavy-duty removable link that is easily inserted and extracted from its base. The link is positioned into the circuit in series with the batteries. Removal of the link stops all current flow. The trick is to make it foolproof and easy to pull out when needed, but not so easy as to allow it to be knocked loose by impact during a match.
The second way is to use a high amperage capacity (sometimes called a high ampacity) cutoff switch. These are available at auto part or marine stores that cater to the racing crowd. These switches often utilize a key or Allen wrench that must be inserted into the switch in order to turn it on or off. Automotive and marine supply stores often sell a variety of battery cutoff devices.
6. Watch your fingers! A robot drivetrain may consist of gears, belts, pulleys, shafts, roller chains, sprockets, and what not. These things will remove your finger if they catch it while moving. Be extra careful when working around your drivetrain, and put in guards whenever possible.
7. Many robots are extremely heavy — use proper lifting techniques. Be certain your dollies and other carrying devices are rated to accept the weight placed upon them.
8. Always be attuned to the possibility of shrapnel. Whenever your robot charges into something, robot parts, steel wreckage, concrete chunks, plastic shards, nuts and bolts, pointy things, sharp things, and heavy things come flying out at random trajectories and at high speed. If it happens in the arena behind Plexiglas, that's probably OK. If it happens in your driveway with the neighbor's kids watching nearby, that's real trouble.
9. Working with high-pressure fluids requires caution, an understanding of fluid power, and great attention to detail. Many robot builders use fluid-powered lifting arms or poking devices to make great weapons. Become familiar with fluid power by reading Chapter 15 in this book, and talk to experienced builders or engineers to make sure you are proceeding in a safe and proper manner. There are plenty of other good weapons systems that are less complicated to construct.
10. Guards should be placed securely over all hazardous surfaces until the robot is in the battle area. Many builders affix sharp, pointed weapons to their mechanical warriors. The guards should be fabricated from study plastic or other suitable substance and held tightly using a bungee cord or other securing device.
HOW TO DESIGN A ROBOT
A1 COURTESY TEAM BOBBING FOR FRENCH FRIES
"And I say, we must move forward, not backward! Upward, not forward! And always twirling, twirling, twirling towards freedom!"
— KODOS (IN THE FORM OF BOB DOLE) FROM THE SIMPSONS
The first thing to understand about robot building is that it is all about trade-offs. This is what makes robot building so interesting. While a big budget is definitely a major advantage, there is no way to build the single, ultimate fighting robot, because there's no getting around certain trade-offs.
Trade-offs are the decisions you have to make that force you to "go weak" in one area when you "go strong" in another. No single robot can be strong in all areas. Robot building is essentially an exercise in optimization and choosing between mutually exclusive alternatives. Here is a listing of some of the tradeoffs:
* Speed trade-offs
Speed versus torque
Speed versus driving control
* Time trade-offs
Time to design versus complexity of weapon and drive systems
Time to build versus complexity of weapons and drive systems
* Weight trade-offs
Motor power versus weight
Armor thickness versus weight
Weapon power versus weight
* Cost trade-offs
Cost versus weight
Cost versus component quality
* Energy storage trade-offs
Capacity versus weight
Capacity versus recharge time
A robot that is faster, more maneuverable, lower in cost, more heavily armored, and can push harder than any other robot at the tournament is perfect — but impossible to design. A crap-bot that is slow, weak, and cheap is easily designed and built, but what's the point?
The unalterable truth is that no one robot can have it all. So the first step is to decide what you want your robot to do. Many builders are inspired by robot designs they see on television. They sketch out what they like about a robot and perhaps decide how they can improve upon it. When someone comes up with a great new idea, such as gyroscopic based steering control, or aluminum alloy armor, other robot builders jump in and copy the idea. This is OK, as it moves the entire sport upward.
Robot Fighting Styles
Besides the physical trade-offs of size, weight, power, and speed, there are style trade-offs as well. Early on, the smart builder will make a reasoned, conscious decision about what sort of fighting style the robot will assume, and then optimize the physical attributes that maximize that style's effectiveness. An example or two will clarify this point.
Two robots face each other at the start of the match. When the starting flag goes up, the robots accelerate as fast as they possibly can, plunging head on into each other. Parts fly off, belts rip and shred, wheels spin unattached across the arena. The stronger bot emerges victorious and the weaker bot is left immobile in the ring. These matches don't last long, but the crowd usually loves them. I call this style of fighting "robo-jousting." This is a good strategy for fast robots with at least some forward-facing armor, small battery packs, and/or large kinetic energy weapons.
In another type of match, the robots circle back and forth, across the arena. They jab and parry but don't engage right away. At some point they lock horns and begin to push. They push with everything they've got, going right up to motor stall torque. Eventually, one robot's motors overcome the other's and it pushes the opponent into a kill saw or a fire-belching pit. I term this "sumo-style" fighting. The greatest sumo wrestler in the world is Hawaiian-born Konishiki, who is a giant — big, hulking, and exceedingly strong. A sumo-style approach is a good choice for Konishiki-like bots: heavy and powerful with real torquey motors and big batteries.
Of course, there are many different styles of fighting, and each style requires a different robot design and different components. Decide what you want your robot to be and design it based on that decision.
The Robot Design Process Explained
Imagine that you're sitting with friends at the local coffee shop, in your school cafeteria, or at the neighborhood pub and you're discussing what would make a kick-ass, hell-of-a-cool fighting bot. One person volunteers to take notes. The next day, a sketch is circulated:
As you can see from this sketch, you estimate that this robot design will:
* Weigh about 225 pounds based on six driving motors, drive control, armor, weapons, wheels, and frame.
* Have a high-pressure, air-powered lifting arm that can toss a 150-pound opponent nine feet up into the air.
* Have a maximum speed of 16 Mph.
* Be able to deliver 650 inch-pounds of torque at the wheels.
* Have dazzling strobe lights to disorient other drivers.
* Protect itself with 74-inch titanium skirting on all sides.
* Have a movable, cranelike arm capable of picking up an opposing bot and dropping it on arena hazards.
* Use a 10-inch carbide-tipped saw blade for ripping through the opposing bot's armor.
This robot is too expensive for you to afford, but you will get sponsors to pay for most of it.
This would be a great robot all right, but there are a few big problems:
* The weight estimate puts us near the bottom of the heavyweight weight class. This means you will go up against robots that weigh as much as 100 pounds more!
* Further investigation into the lifting arm shows that no one in the group has any experience with high-pressure pneumatics.
* Strobe lights are prohibited by tournament rules.
* The titanium costs a lot of money and is hard to machine.
* The movable cranelike arm requires multiple precision-made four bar linkages and exceedingly complex controls. This will blow the budget and take more time to build than you can afford.
* The carbide-tipped saw blade engine is too big to be contained in the robot body.
* Nobody will sponsor and give money to a bunch of untested robot builders. So you go into round two of the design discussion and keep what you like, throw out what won't work, and modify the rest.
* You cut it down to four motors and wheels and go down in weight to qualify for the middleweight bracket.
* You only use titanium on the sides of the bot, and minimize the machining required.
* You trash the strobe light, movable crane, and carbide saw ideas.
* You decide that a lifting arm is good, but settle on a more practical design for it.
* You decide on a budget for this robot of about $1,600, which you can afford by yourself.
Setting Up a Team
Early on, you need to assemble your team. How big a team do you need? It all depends. Excellent robots have been made by individuals, two partners, trios, and groups approaching the size of Mike Tyson's entourage. The right number depends on what the individuals know and what each can contribute. Usually, each person wears a multitude of hats. In general, teams, whether they consist of one member or eight, need to fill the following roles:
A WORD ON PERSONALITY
Your robot needs a personality. In order to impress judges, spectators, your friends, and the other bot builders, your robot must be more than just a metal, rubber, and Lexan box. Make your fighting robot say something subtly or boldly about you and your team. Make it all-American with a red, white, and blue paint job and have it fly the flag when you enter the arena. Make it black and yellow and vaguely resembling a bumblebee. Make it something extraordinary and cool. But don't make it just another gray, steel, wedge-shaped bot with big motors, big torque, and nothing else. Building a fighting robot is your chance for radical self-expression. Win the hearts of the audience. Make people remember it-win, lose, or draw.
The head designer has overall responsibility for the electrical and mechanical engineering of the entire robot. This person should be familiar, or willing to become familiar, with DC motors, radio control systems, electronic speed controllers, mechanical driveline systems, and basic mechanical engineering principles.
The head builder is responsible for taking the design from the design team and turning it into reality. This person should know about, or be willing to learn about, metalworking, welding, the material properties of metals and plastics, and basic shop practices. (Continues...)
Excerpted from Building Bots by William Gurstelle. Copyright © 2003 William Gurstelle. Excerpted by permission of Chicago Review Press Incorporated.
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