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B

uild Your Own
Combat Robot

Pete Miles
Tom Carroll

McGraw-Hill/Osborne
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Copyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America.
Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the
publisher.
0-07-222844-X
The material in this eBook also appears in the print version of this title: 0-07-219464-2.

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trademarked name, we use names in an editorial fashion only, and to the benefit of the trademark owner, with no intention
of infringement of the trademark. Where such designations appear in this book, they have been printed with initial caps.
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claim or cause arises in contract, tort or otherwise.
DOI: 10.1036/007222844X

For more information about this book, click here.

CONTENTS AT A GLANCE

1

Welcome to Competition Robots

1

2

Getting Started

21

3

Robot Locomotion

41

4

Motor Selection and Performance

61

5

It’s All About Power

79

6

Power Transmission: Getting Power to Your Wheels

103

7

Controlling Your Motors

127

8

Remotely Controlling Your Robot

157

9

Robot Material and Construction Techniques

183

10

Weapons Systems for Your Robot

203

11

Autonomous Robots

239

12

Robot Brains

259

13

Robot Sumo

275

14

Real-Life Robots: Lessons from Veteran Builders

305

15

Afterword

329

A

Prototyping Electronics

335

B

Resources and References

343

C

Helpful Formulas

355

Index

358

iii

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

This page intentionally left blank.

For more information about this book, click here.
Contents

ACKNOWLEDGMENTS,
INTRODUCTION,

1

XI

XIII

Welcome to Competition Robots

What Is a Robot?,

1

5

Combat Robot Competitions,
BattleBots,

5

7

Robot Wars,

9

BotBash,

11

Robotica,

13

FIRST (For Inspiration and Recognition of Science
and Technology), 14
Robot Soccer,

16

The Scope of This Book,

2

17

Getting Started

21

The Robot Design Approach,

23

The Game of Compromise,
Design for Maintenance,
Start Building Now,

29

31

33

Testing, Testing, Testing,

34

Top Ten Reasons Why a Robot Fails,
Sources of Robot Parts,

34

35

Cost Factors in Large Robot Construction,
Safety,

Safety in the Use of Shop Tools,
Safety with Your Robot,

3

35

36
37

37

Robot Locomotion

Robots with Legs,

41

42

Tank Treads: The Power of a Caterpillar Bulldozer in a Robot,
Building Tank Treads for a Robot,

Wheels: A Tried and True Method of Locomotion,
Types of Steering,

47

47

Wheel Configurations,

50

Selecting Wheels for Your Combat Robot,
Tires,

45

46

51

53

Mounting and Supporting the Wheels and Axles,
Wheel Drive Types,

54

57

Protecting Your Robot’s Wheels,

59

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

v

vi

Build Your Own Combat Robot

4

Motor Selection and Performance

Electric Motor Basics,

Determining the Motor Constants,
Power and Heat,
Motor Sources,

73

74

Internal Combustion Engines,

5

67

68

High-Performance Motors,

Conclusion,

61

62

76

77

It’s All About Power

Battery Power Requirements,

79

80

Measuring Current Draw from the Battery,
Battery Capacity Basics,

80

83

Preventing Early Battery Death,

84

Sizing for a 6-Minute Run Time,

85

Comparing SLA, NiCad, and NiMH Run-Time Capacities,
Electrical Wiring Requirements,
Battery Types,

91

92

Sealed Lead Acid,

93

Nickel Cadmium (NiCad),

95

Nickel Metal Hydride (NiMH),
Alkaline,

97

98

Lithium Ion,

99

Installing the Batteries: Accessible vs. Nonaccessible,

6

100

Power Transmission: Getting Power to Your Wheels

Power Transmission Basics,
Torque,
Force,

109
109

Mounting the Motors,

Methods of Power Transmission,
Chain Drive Systems,
Chain Sprockets,
Flat Belts,

115
117

118

118

Synchronous Belts,
V-Belts,

113

114

115

Buying the Chain,
Belt Drive Systems,

112

112

Thermal Considerations for the Motor,

Gearboxes,

103

106

Location of the Locomotion Components,

119

121

122

Mounting Gear Assemblies,
Securing Gears to Shafts,

7

86

122

122

Controlling Your Motors

Relay Control,

128

Poles and Throws,

128

127

Contents

Current Ratings,

129

How It All Works Together,
Variable Speed Control Basics,

132

139

Controlling Speed = Controlling Voltage,
Commercial Electronic Speed Controllers,

8

140
143

Remotely Controlling Your Robot

Traditional R/C Controls,

The R/C Controller’s Interface,
The R/C Servo,
Control Channels,

157

158
159

160

160

Radio Control Frequencies,

162

AM, FM, PCM, and Radio Interference,
Amplitude Modulation,

167

Frequency Modulation,

167

167

Radio Interference and Reliable Control,
Radio to Radio Interference,
Antennas and Shielding,

170

172

173

Antenna Placement,

174

Innovation First Isaac Robot Controller and Other Radio Modems,
Radio Modems,
Failsafe Compliance,

9

179

Robot Material and Construction Techniques

Metals and Materials,

184

185

General Machining Operations,

193

Tools You Might Need to Construct Robots,
Welding, Joining, and Fastening,
When in Doubt, Build It Stout,

195

201

Weapons Systems for Your Robot

Weapon Strategy and Effectiveness,
Ram Bots,

205

Wedge Bots,

208

Lifter Bots,

210

Launchers,

212

Clamp Bots,

215

Thwack Bots,

217

Overhead Thwack Bots,
Spinner Bots,
Saw Bots,

220

222

Vertical Spinner,
Drum Bots,

224

226

Hammer Bots,

228

193

195

Structural Design for Fastener Placement,

10

183

184

High-Strength Plastics,
Metals,

175

178

219

204

203

vii

viii

Build Your Own Combat Robot

Crusher Bots,
Spear Bots,

231
233

Closing Remarks on Weapons,

11

236

Autonomous Robots

239

Using Sensors to Allow Your Robot to See, Hear, and Feel,
Passive Sensors,
Active Sensors,

243

Thermal Sensors,
Tilt Sensors,

241

242
246

247

Bump Sensors,

248

Implementing Sensors in Combat Robots,

248

Sensing: It’s a Noisy World Out There,
Techniques for Improving Sensor Input,

249
249

Semiautonomous Target and Weapon Tracking,
Semiautonomous Weapons,

250

251

Implementing Semiautonomous Target Tracking,

251

Semiautonomous Target Tracking with
Constant Standoff Distances, 252
Autonomous Target Tracking,

253

Fully Autonomous Robot Class,
More Information,

12

253

257

Robot Brains

259

Microcontroller Basics,
Basic Stamp,
BrainStem,

266

Handy Board,
BotBoard,

260

264
267

267

Other Microcontrollers,

267

Microcontroller Applications,

268

The Robo-Goose,

268

The BrainStem Bug,

270

1BDI, an Autonomous Robot,

271

The Rover, Teleoperated with Feedback,
Summary,

13

272

273

Robot Sumo

275

How a Sumo Match Proceeds,
The Sumo Ring Specification,
Mini Sumo,

278
280

281

Modifying an R/C Servo for Continuous Rotation,
Building a Mini Sumo,

284

Mini Sumo Body Assembly,

284

Remote-Control Mini Sumo, 285
Autonomous Mini Sumo, 286
Edge Detector, 286

281

Contents

Object Detector, 290
Sensor Integration, 293
Performance Improvements, 297
Various Mini Sumo Robots, 297
International Robot Sumo Class,

299

Motors, 299
Motor Controllers, 299
Ultrasonic Range Detectors, 300
Infrared Range Detectors, 301
Laser Range Finding and Vision Systems, 301
Advanced Software Algorithms, 301
Traction Improvements, 302
Robot Part Suppliers, 302
Annual Robot Sumo Events,

14

303

Real-Life Robots: Lessons from Veteran Builders

Ronni Katz—Building Chew Toy,
Step 1: Research,

306

Step 2: Conception,

308

Step 3: Building the Bot,

310

Step 4: Creating Weapons and Armor,
Final Words,

311

315

Pete Miles—Building Live Wires,

316

Step 1: Making the Sketch,

316

Step 2: Securing the Motors,
Step 3: Adding Wheels,

316

317

Step 4: Adding Motor Housings and Controllers,
Step 5: Layout and Modeling,
Step 6: Scrambling,

Step 8: Adding a Weapon,
Finally: The Show,

322
324

325

Afterword

329

The Future of Robot Combat,

A

317

319

321

Step 7: Building the Frame,

15

330

Prototyping Electronics

335

Breadboarding and Using Prototyping Boards for Electronic Circuits,
Wire-Wrapping Prototyping,
Soldering for Robots,

337

337

Soldering Printed Circuit Boards,
Soldering Wires,

339

Soldering Connectors,
Crimp-Style Connectors,
Static Sensitivity,

305

306

340

339

339

338

336

ix

x

Build Your Own Combat Robot

B

Resources and References

Robot Competition Web Sites,
Electric Motor Sources,
Battery Suppliers,

344

346

Electronic Speed Controller Vendors,
Remote Control System Vendors,
Mechanical Systems Suppliers,
Electronics Suppliers,

347

350

350

Robotics Organizations,

351

Other Robotics Resources,

C

346

347

348

Microcontroller Suppliers,
Reference Books,

352

Helpful Formulas

355

Chain Drive Centerline Distances,

356

Timing Belt Centerline Distances,

357

V-Belts,

343

344

357

Index

358

Acknowledgments

We would like to thank Mike Greene of Robot Science and Technology magazine
for putting the team together to write this book. Bob Gross, Andrew Lindsey,
Ronni Katz, Carlo Bertocchini, and Steve Richards provided a lot of top-quality
support and information, as well. Without their help, the quality of this book
would not be where it is now. We would also like to thank Carlo Bertocchini and
Grant Imahara for taking time out of their busy schedules to serve as technical editors. They provided valuable comments and insights that vastly improved our
work. Mark Setrakian, Peter Abrahamson, Christian Carlberg, Peter Menzel,
Larry Barello, Dave Owens, Jamie Hyneman, Vincent Blood, Clare Miles, and
Ken Gracey were of great help in providing excellent photos. A special thanks goes
to Dave Johnson for his help in interviewing Christian Carlberg, Grant Imahara,
Jim Smentowski, Stephen Felk, Donald Hudson, and Jamie Hyneman for the
“First Person” stories you’ll find throughout the book. Additional thanks go out
to the people at Vantec, Hawker, IFI Robotics, Parallax, Panasonic, National
Power Chair, Acroname, Futaba, and Grainger for their technical support and use
of some of their photos. Finally, we would like to thank Margie McAneny, Lisa
Wolters-Broder, Michael Mueller, and the whole team “behind the scenes” at
McGraw-Hill/Osborne for their patience and help in putting this book together.
Pete adds: I would like to thank my wife, Kristina Lobb Miles, for all of her tireless
help. With her brilliant skills in graphics manipulation, she was able to put together
most of the artwork and photos. Without her help, this project would not have
happened. She is a wonderful person and deserves a lot of credit. Tom Carroll,
too, deserves a lot of credit for putting this together. His infinite knowledge of robotics and ability to write lots of information in a very short time period is greatly
appreciated.
Tom adds: I would like to thank my wife, Sue, for her tireless support and
encouragement of my many robotics activities for the past 35 years. She has endured my many trips to all over that took me away from home and my family,
watched as various robots grew to completion in my shop, patiently waited as I
spent many hours in my office typing away at this book, and listened politely as
I talked for hours on end about robots. I would also like to thank Pete Miles for his
patience, organization, great knowledge, and tremendous effort at spearheading
this project. His wife Kris proved to be a most valuable asset at making the graphics
and manuscript flow to perfection. These two are a most incredible team, and without them, this book would have been only a pile of papers scattered on the floor.

xi

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

This page intentionally left blank.

Introduction

Some kids spend their free time playing sports. I spend mine building robots. You
may think that this is not a typical hobby for a teenaged girl, and you’re right. I am
part of a rapidly-growing community of combat robot builders from all across the
U.S., of all ages, and I’m not exactly new to the sport, either. I was at Fort Mason
San Francisco in 1994 watching the first robotic combat competition, Robot
Wars. I saw my dad win match after match with his flimsy, garage-built aluminum
contraption, and beyond all reason of my then seven-year-old brain, I was inspired. The next year, when I was eight, I had a flimsy, garage-built aluminum
contraption of my own, and I was ready to roll. Since then I’ve been hooked.
Through my few years of experience in the field of robotic combat, I’ve come to
realize that the actual battles—the end result of all my hard work—are not the
only things that I have to look forward to. Just as important to me are the people
and friends involved, the familiar sounds and smells of machine maintenance, the
ebb and flow of people excitedly preparing for competition, the long but rewarding hours of taking robots apart and putting them back together again, and the
feeling you get when you realize you’ve become a small but integral part of our
quirky little robo-community.
I hope this book will help you get started in the unique and exiting sport of robot
combat. Robot experts clearly explain everything you need to know to build a bot of
your own. For anyone thinking of building a robot, I strongly encourage you to give
it a try. You may not wind up with the super-heavyweight champ after your first
fight, but I guarantee it will be an experience you’ll never forget!
Cassidy Wright,
builder of Triple Redundancy, Fuzzy Yum Yum, and Chiabot
Orinda, California
January 2002

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

xiii

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About the Authors

A

bout the Authors...
Pete Miles has been experimenting with robots since the mid 1970s. He used to
scavenge every part he could from dumpsters at radio and TV repair shops, and he
still uses parts that he collected back then in his current robot projects. After serving in the U.S. Marine Corps as a tank killer, he obtained bachelor’s and master’s
degrees in mechanical engineering. He currently works as a senior research engineer,
developing advanced machining technologies using 55,000 psi abrasive waterjets
for Ormond LLC, in Kent, Washington. As he puts it, “There is not a material in
the world a waterjet can not cut, including diamonds.” Miles is currently an active
member of the Seattle Robotics Society, the world’s largest robotics club, and was
recently appointed to the SRS Board of Directors. He is an avid competitor in autonomous robot sumo, and enjoys building legged robots for various contests to
demonstrate that walking robots can be formidable competitors.
Tom Carroll has been involved with robotics for more than 40 years. He built his
first robot at age 14, and later worked as a robotics engineer on NASA projects with
Rockwell International for nearly 30 years. Carroll co-founded the Robotics Society of Southern California in 1978 and is now active in the Seattle Robotics Society.
He designed robots for the International Space Station, to explore the surface of
other planets and to assist astronauts in space. He founded Universal Robot Systems to design and build robots for such feature films as Revenge of the Nerds and
Buck Rodgers in the 25th Century. He is presently a novel and technical writer,
and spends much of his time developing a truly functional personal robot to assist
the “forgotten generation,” the elderly, and give them pride in independent living.
Carroll moved from Long Beach, California, several years ago and now lives in the
Pacific Northwest, on Orcas Island off Washington’s coast. Tom enjoys kayaking,
hiking, and traveling with his wife.

A

bout the Contributors...
Bob Gross became involved with robotics in 1978 by building a working facsimile
of R2D2. For fun, he has built winning autonomous robots for sumo, maze, navigation, wandering, and combat. Later, he produced three autonomous museum
robots that would fetch balls, go to various colored columns, or allow
teleoperated control. By day, Gross works as a rocket scientist and has a small
company that focuses on various aspects of robotics, including machine vision.
Dave Johnson is a technology writer and scuba divemaster. The author of
18 books, Johnson covers popular technology like mobile gadgets, photography,
digital music, and robotics. He’s also an award-winning wildlife photographer and the author of The Wild Cookie, an interactive kids’ story on CD-ROM.

xv

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Build Your Own Combat Robot

Ronni Katz is an adjunct professor of computer science at DeVry College of Technology in North Brunswick, New Jersey. She was an original member of “Team
Spike” at the first Robot Wars competition and has helped design and build combat
robots that have won and placed highly at numerous competitions. Katz is a
proud member of the Society Of Robotic Combat and produced the 1998 nonprofit instructional video Introduction to Robotic Combat, which helped many
beginners get their start in the world of sport robotics. Katz writes fiction under
the pen name of Ron Karren and has been published in numerous fanzines. Her
first military technothriller novel, Wing Commander, can be found at bookstores
nationwide. You can visit Katz online at QuestPress.com for news of her future
publications.
Andrew Lindsey has been competing in robotic combat since 1996. In addition
to competing in all three major televised robotics competitions, he was one of four
combat judges at the November 2000 BattleBots event. Lindsey lives in New Jersey and designs fiberoptic interface electronics for a living. He competes regularly
in the North East Robo-Conflict events in the New Jersey/Pennsylvania area.
Steve Richards has been fascinated by the prospect of fully-autonomous robotics
since his childhood. He founded and runs the robotics company Acroname, Inc. in
an effort to advance robotics through information, parts, and a robotics community.
When he isn’t milling, coding, wiring, or ranting about robotics, he also enjoys
running. He lives in Boulder, Colorado, with his wife, Karen. Richards admits
that the only truly successful autonomous creation he has been involved with is his
daughter, Annie.
Cassidy Wright has been involved with robotic combat since 1994. She built her
first bot when she was just eight years old. She is a teenager now, and the builder of
Triple Redundancy, Fuzzy Yum Yum, and Chiabot.

A

bout the Technical Editors...
Carlo Bertocchini has been building competitive robots since 1993, and he worked
as a mechanical engineer until 2001. Now he divides his time between competing
in BattleBots matches and running his company, RobotBooks.com. He is the designer and builder of Biohazard, the world’s most successful combat robot. You can
learn more about his robots at www.robotbooks.com/biohazard.htm. Bertocchini
lives in Belmont, California, with his wife, Carol.
Grant Imahara is an animatronics engineer and modelmaker for George
Lucas’ Industrial Light & Magic in Marin County, California. He specializes in
electronics and radio control at the ILM Model Shop and has installed electronics
in R2D2 units for Star Wars: Episodes 1 and 2, and the famous Energizer Bunny.
For fun, Grant competes in BattleBots with his robot Deadblow, which set a record for the most number of hits in the first season of the show. Grant lives in a
loft in Oakland, California, where he also works on his robot in his spare time.

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chapter

1

Welcome to
Competition Robots

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

E L C O M E to the world of combat robotics. You’ve watched
them on TV. You’ve seen models of them on toy store shelves. You’ve seen them
featured on the covers of magazines. You might also be among the lucky ones who
have actually sat arena-side and watched in person as seemingly sane men and
women guided their creations of destruction toward another machine with the express goal of mangling, dismembering, and smashing the opponent.
Television has brought this controlled mayhem into the living rooms of America. You cheer wildly as your favorite robot with its spinning hammers rips the
steel skin off its foe. Your robot chases its limping target into a corner, only to
have a series of saw blades arise from the floor and send your hero sailing across
the arena. The TV cameras pan over to the operators of the losing robot; they are
smiling. Even in a moment of havoc, both sides are having fun. Parts and sparks
are flying, and smoke wafts upward from the hapless opponent as hazards and
weapons reach their targets. The crowd cheers and banners are waving. A winner
is announced, and then two new bots start at it.
You can not stop grinning. “This is cool!”
After the program is over, you turn to your friend excitedly and say, “I’m gonna
build one of those robots.”
“Yeah, right,” she says. “You can’t even program the VCR. Good luck building a robot.”
“Hey, I’ve got a book on how to build ’em. I’ll start small, maybe build one of
those little sumo robots. It’s a kick to watch those little guys try to shove each other
out of a ring. I have some friends who can help me get started. I’m going to do it!”
Robot combat has come a long way from its origins. The founding father of the
sport is Marc Thorpe. He came up with the idea for robotic combat while experimenting with attaching a remote-control tank to his vacuum cleaner to make
house cleaning more fun. After a few years spent developing the rules for a game
where two robots would duel in front of a live audience, a new sport was created:
Robot Wars. The first official combat robot event was held at Fort Mason Center
in San Francisco. It was a huge success. Since Robot Wars first came on the scene,
thousands of people have participated in building combat robots, and millions
have watched and cheered on their favorite bots. Many new combat robot contests—such as BattleBots, Robotica, and BotBash, to name a few—have been
spawned from the original Robot Wars competition.

2

Chapter 1:

Welcome to Competition Robots

This sport has become so popular, in fact, that many robots have become better
known than their human creators. For example, devout followers of robotic combat are familiar with such famous builders as Carlo Bertocchini, Gage Cauchois,
and Jamie Hyneman, but these mens’ robots—Biohazard (pictured in Figure 1-1),
Vlad the Impaler, and Blendo, respectively—are now bona fide household names
among the millions of people who watch BattleBots on TV.
The various robotic combat events have seen many different types of machines,
from two-wheel-drive lightweight robots to six-wheel-drive, gasoline-powered
superheavyweights. Even walking robots, more commonly known as StompBots,
have entered into the mayhem. Probably the most well-known StompBot is the
six-legged superheavyweight Mechadon built by Mark Setrakian. Setrakian has
even built a super heavyweight snake robot. Though his unusual robots have not
won any events, they’ve all been outstanding engineering achievements and great
crowd pleasers.
The weapons on these robots range from simple wedges and spikes to jabbing
spears, hammers, and axes, to spinning maces and claws, hydraulic crushing pincers, and grinding saw blades of every type, size, and color. The destructive power
of these weapons has been used for everything from scratching paint off a rival bot
to denting aluminum plates, punching holes through titanium and Kevlar, ripping
off another robot’s entire armor plating, and completely disintegrating an opponent in a single blow.
One of the most destructive robots the sport has seen to date is Blendo. This spinning robot, more commonly known as a SpinBot-class robot, totally destroyed
FIGURE

1-1

Biohazard, a
superstar of
robotic combat.
(courtesy of
Carlo Bertocchini)

3

4

Build Your Own Combat Robot

many of its opponents in a matter of seconds. It had such destructive force that it
was once banned from continuing to compete in a contest and was automatically
declared co-champion for that event.
Today, most combat robots are remote-controlled; but in the early years of Robot Wars, there were several fully autonomous combat robots. These robots ran
completely on their own, using internal microcontrollers and computers for
brains, and sensors to find and attack their opponents. Many people think autonomous combat robots would be too slow to compete because they would require
too much time to locate and attack an opponent. This isn’t always the case, however. The 1997 Robot Wars Autonomous Class champion, Thumper (built by
Bob Gross), won a match in 10 seconds flat. That’s Thumper in Figure 1-2.
Today, most autonomous combat robots are found in robot sumo events,
where two bots try to find and push each other out of a sumo ring. In this event,
bots are not allowed to destroy each other. Sumo builders face a unique challenge,
as they design their bots to “see” their opponent and push them out of the ring before getting pushed out themselves. This contest has become increasingly popular
in recent years, and new sumo events are popping up all over the world.
In the past, competition divisions consisted of man versus man, or team of men
versus team of men (let’s face it—it began as a male-dominated sport). Strength,
speed, agility, endurance, and strategy were the only factors that determined the
winner or loser. Thanks to robot combat, this isn’t the case anymore. At robot
competitions, ingenuity, creativity, and intelligence now rule the game. No longer are 6-foot 5-inch, 240-pound male “athletes” dominating the game. A
10-year-old girl with excellent engineering skills can now defeat a 250-pound former
FIGURE

1-2

Thumper, an
autonomous robot
built by
Bob Gross, won
big-time at
Robot Wars
in 1997.
(courtesy of
Bob Gross)

Chapter 1:

Welcome to Competition Robots

NFL linebacker, and a wheelchair-bound person can run circles around an Olympic
gold medalist. Robot combat has leveled the playing field so that anyone can
compete against anyone on equal ground.

W

hat Is a Robot?
Now that you’ve made up your mind to build a robot, you’re probably sitting
back wondering just what you’ve gotten yourself into.
“What is a robot?” you ask yourself.
Surprisingly, there are many definitions, depending on whom you ask. The Robot Institute of America, an industrial robotics group, gives the following definition: “A robot is a reprogrammable, multifunctional manipulator designed to
move material, parts, tools, or specialized devices through variable programmed
motions for the performance of a variety of tasks.” These people, of course, are
thinking only of robots that perform manufacturing tasks.
Now that you’re thoroughly confused, Webster’s New World Dictionary defines robot as “any anthropomorphic mechanical being built to do routine manual work for human beings, or any mechanical device operated automatically,
especially by remote control, to perform in a seemingly human way.”
Hmmm. Now we seem to be talking about human-formed robots, like in the
movies, or it could be the description of a washing machine, or maybe the Space
Shuttle’s “robot arm.”
Where did the term “robot” come from? Back in the 1920s, a Czech playwright
by the name of Karel Capek wrote a short play entitled R.U.R., which stands for
Rossum’s Universal Robots. The word robot came from the Czech word robota,
which means indentured servant or slave. In Capek’s play, the robots turned on
their masters, which became a theme in many movies and stories in later
years—robots doing bad things to people. Only in more recent movies have robots
become friends of humans and started doing bad things to other robots.
To this day, those in the field of robotics still argue about what exactly constitutes a robot. Many people think that if a machine doesn’t have some sort of intelligence (that is, a microcontroller inside), it isn’t a robot. Some might look down
their noses and claim that only a multiarmed machine driven by a Pentium 4 processor with 512 megs of RAM and fed by 100 sensors is really a robot. Those at
NASA might feel the same way about the Space Station’s Canada Arm. All this arguing really doesn’t matter, because everyone has their own definition of what a
robot is—and everybody is right.
Whatever you choose to call a robot is a robot.

C

ombat Robot Competitions
Before we start talking about types of robot competitions, let’s cover a brief history
of the events that gave rise to this sport. Organized robot competitions have been

5

6

Build Your Own Combat Robot

around since the late 1980s, and have been rapidly growing ever since. The following is a short history of some of the most popular robot contests around today.
There are many other competitions aside from those listed here, and new ones are
turning up each year.


Late 1980s The remote control and autonomous robot sumo contest
is invented by Hiroshi Nozawa of Fujisoft ABC, Inc., in Japan.



1989 Inventor and entrepreneur Dean Kamen founds FIRST. This
nonprofit organization, “For Inspiration and Recognition of Science
and Technology,” pairs up school-age children with local engineers
to build robotic projects.



1992 Marc Thorpe discovers that his experiments with building a
radio-controlled vacuum cleaner to help with the housework can be
turned into a new sport called Robot Wars.



1992 FIRST Robotics hosts its first competition with 28 high-school teams.



1994 Marc Thorpe creates Robot Wars. This is the first major competition
where robots face off against each other in an arena in front of a live
audience. The first event is held at Fort Mason Center in San Francisco.



1997 Mentorn Broadcasting produces a six-episode series of Robot Wars
for BBC television in the U.K.



1997 BotBash, a similar event to the original Robot Wars, holds its first
event in Phoenix, Arizona.



March 10, 1999 BattleBots is founded by Trey Roski and Greg Munson
in San Francisco.



August 14, 1999 BattleBots hosts its first event in Long Beach, California,
with 70 robots competing.



January 29, 2000 BattleBots appears on pay-per-view television, and
airs the second BattleBots event from November 1999.



August 23, 2000 BattleBots begins airing as a television series on
Comedy Central. The show quickly shoots up in ratings and finishes
its first season as one of the most popular shows on cable TV.



April 2, 2001
competition.



April 4, 2001 Robotica begins airing as a television series on
the Learning Channel. Early indications show the program is
a hit among viewers.



August 20, 2001 The new Robot Wars Extreme Warriors, a spin-off
from Robot Wars, premieres as a new television series on TNN.

BattleBots registers over 650 robots at its Spring 2001

Chapter 1:

Welcome to Competition Robots

As you can see, the history of robot combat is relatively short in comparison
with baseball or football, but all sports have to start somewhere. With its current
growth rate, it won’t be long before this becomes one of the most popular sports in
the world.
As with any game, there are different rules and goals for each event. Following
are brief descriptions of some of these contests. The exact details of the events
should be obtained directly from the event organizers.
BattleBots

BattleBots is probably the most popular robotics event in the United States. A
large fan base has been accumulating ever since these competitions started airing
on cable TV. BattleBots is a single elimination fight-to-the-death contest where
one robot tries to destroy another in a 3-minute time frame. If one of the robots becomes incapacitated for 30 continuous seconds, or is destroyed, that robot loses
the match. If both robots are still fighting at the end of the 3-minute time frame, the
winning robot is declared by how many points they scored. There are three official
judges who award up to 5 points each for aggressiveness, damage, and strategy,
for a total of 45 points. The robot with the most points wins the match.
If your robot is fortunate enough to survive the match, it has only 20 minutes to
undergo any repairs before the next match. If the robot faces another fight soon
afterward and cannot be repaired in the 20-minute time frame, it must forfeit the
next match.
The main BattleBots arena is called the BattleBox. Weighing in at 35 tons, this
“box” consists of a steel floor measuring 48-feet-by-48-feet, and walls that tower 24ft
high. The walls of the BattleBox are made out of Lexan (a highly resilient
polycarbonate) ranging in thickness from one inch at the base of the walls to
3/16 inches at the top. There are two 8-foot-by-8-foot entry doors where the robots enter. Within the BattleBox there are a set of hazards and weapons, which are
as follows:


Kill Saws These are 20-inch-diameter carbide-tipped SystiMatic saw
blades that can cut through virtually any material. They can spring up
with many pounds of force, easily tossing 340-pound superheavyweight
robots into the air.



Pulverizers These monster aluminum hammers are used to smash any
unfortunate robot that gets under them.



Hell Raisers BattleBots competitions occasionally employ these 3-footby-4foot plates that move up 6 inches, wreaking havoc in a robot’s motion.



Ram Rods The ram rods are a set of six carbide-tipped spears that
shoot up 6 inches from the BattleBox floor with over 60 pounds of force.

7

8

Build Your Own Combat Robot

FIGURE

1-3

Two-wheel-drive,
spike-wielding
Toe Crusher,
built by
Christian Carlberg.
(courtesy of
Christian Carlberg)



Spike Strip Around the perimeter of the BattleBox is a strip of 180 metal
spikes—each one 1-inch in diameter and 3 inches long—that point toward
the center of the BattleBox.



The Vortex This is a 3-foot-diameter disk that will spin the robot around
if it rolls on top of the vortex.



The Augers These huge rotating screws mangle any robot unlucky enough
to get caught in their grip.

There are four different weight classes for wheeled BattleBots, as shown in
Table 1-1.

More Than

Maximum

Lightweight

25 pounds

60 pounds

Middleweight

60 pounds

120 pounds

Heavyweight

120 pounds

220 pounds

Super heavyweight

220 pounds

340 pounds

TABLE

1-1

BattleBot Weight Classes n

Chapter 1:

Welcome to Competition Robots

Walking robots get an extra 20-percent weight increase bonus, so the weight
classes for walking bots are 72 pounds for lightweights, 144 pounds for middleweights, 264 pounds for heavyweights, and 408 pounds for superheavyweights.
All of the details about BattleBots, including rules and regulations, can be
found online at www.battlebots.com.
Robot Wars

Robot Wars is where it all began—two robots fighting to the death. In the early
days of Robot Wars, there was an arena filled with hazards, including spikes, buzz
saws, and a swinging bowling ball. Robots fighting in this competition had to
avoid the hazards while attacking opponents. Not only were there remote-control
robots fighting, there were also autonomous machines competing.
Since Robot Wars moved to the United Kingdom in 1997, the event has
changed quite a bit. Before the bots get a chance to go to the big fight, they now
have to pass a series of obstacle course tests. These obstacles include crashing
through brick walls, climbing over teeter-totters, passing between two closing
walls with spikes, avoiding large pendulums, knocking over large metal drums,
and steering clear of fiery pits.
FIGURE

1-4

The vicious-looking
Razer has been a
crowd favorite for
several years
running at the
U.K. Robot Wars.
(courtesy of
Vincent Blood)

9

10

Build Your Own Combat Robot

To make the events a little more challenging, the contestant bots have to contend
with “house” bots whose main purpose is to destroy anything fool enough to come
near them. The smallest house robot is Shunt. At 231 pounds., this powerhouse can
pull a Land Rover and wield a deadly axe. Dead Metal, weighing in at 247 pounds.,
is very effective at using its buzz saw and deadly pincers. The 256 pound titaniumarmored Matilda wields a chain saw on her rear, and the 264 pound Sergeant
Bash with his deadly flamethrower can cook his victim when it gets caught in his
front pincers. Finally, there is Sir Killalot, at a massive 617 pounds. His pincer
claws can cut through the toughest armor and then lift a 220- pound hapless victim—to be dropped into the fiery pit.
The lucky winners of the obstacle courses get to move on to bigger and better
fights. Below is a list of three of the most popular events that bots must pass in
more advanced Robot Wars competitions, prior to moving on to the final round:

Pinball
In the pinball tournament, bots must navigate around a course and hit certain objects, each of which is worth a different number of points. The bot with the most
points wins the tournament. Bots score 5 points for hitting barrels, 10 points for
the multiball, and 5 points for each multiball in the pit. Crossing over the ramp is
worth 20 points, going through the car door gate is worth 25 points, and moving
the sphere out of the pit is worth 25 points. Hitting Matilda’s and Sergeant Bash’s
guarded targets are worth 50 points each, and getting past Dead Metal to its target
is worth 75 points. All of this must be accomplished in 5 minutes.

Sumo
The Sumo event is held on an elevated ring, and the contestant bot goes up against
a house bot. This is a timed event to see how long a bot can stay in the ring before
being pushed off by the house bot. Most of the time, the house robot wins this
event, but once in a while a challenger will be successful in pushing a house bot to
its doom. The bot with the longest time on the sumo ring wins that event.

Soccer
Robot Soccer is an event where two bots try to push a white ball into the other
bot’s goal. A house bot is positioned in the arena to assist in the game. “Assist” is a
relative term because the house bots have a tendency to capture the ball, thus leaving the other two bots to fight. Once the time limit expires, a judge determines
which robot is the winner.
Robot Wars has several other events that are less common, one of which is the
Grudge Match. In this competition, if your bot has a grudge against another
bot—including a house bot—it gets the opportunity to fight that bot one on one.

Chapter 1:

Welcome to Competition Robots

Another event is the Tag Team match, where two bots team up against two other
bots. A popular event is the Tug-Of-War, where a contestant bot is attached to a
house bot via a rope. Between the two bots is a pit. As you guessed, the contestant
bot must pull the other bot into the pit. Yet another popular event is the Melee.
Here, three or more robots fight against each other and the last one standing wins
the melee. (BattleBots has a similar event to the Melee, which is called the Robot
Rumble.)
Table 1-2 lists the weight classes for Robot Wars.
The official Robot Wars Web site is at www.robotwars.co.uk.
BotBash

BotBash is a smaller-scale version of BattleBots. The rules of the contest are very
similar to BattleBots, with the big difference being that BotBash is a double elimination tournament. This means your bot can lose one round and still be able to
fight on. This is a nice change for bot builders because if a battery connector falls
off, or some other unforeseen problem arises in a match that causes you to lose,
you can still prove that your bot is the best by winning the remaining rounds. Another big difference is that the BotBash bots have lower weight limits. Tables 1-3
and 1-4 list the BotBash weight classes for the wheeled and walking robot classes.
As with BattleBots, there is a 3-minute time limit; and if both bots are still fighting,
a winner is declared by points. Here, the three judges award one point each for aggression, strategy, and damage, for a total of nine points.
Each year, the BotBash tournament offers different events aside from
one-on-one battle. In the past, they’ve featured a Capture the Flag event where two
cones (flags) are placed at opposite sides of the arena and the bots race to capture the
opposing bot’s flag. The bots can plan either an offensive or defensive role to attack
or protect the flag. The bot that touches the other bot’s flag first wins the match.
Other events at BotBash include obstacle courses and sumo events. Occasionally,
BotBash tournaments feature autonomous events. Because the rules and events for
each tournament change each year, builders must keep up-to-date on the rules and
regulations. The official BotBash Web site is at www.botbash.com.

More Than

Maximum

Featherweight

0 pounds

25 pounds

Lightweight

25 pounds

50 pounds

Middleweight

50 pounds

100 pounds

Heavyweight

100 pounds

175 pounds

TABLE

1-2

Robot Wars Weight Classes n

11

12

Build Your Own Combat Robot

FIGURE

1-5

Spike III, a
third-generation
robot built by
Andrew Lindsey, a
long-time combat
robot competitor.
(courtesy of
Andrew Lindsey)

More Than

Maximum

Class A

0 pounds

12.9 pounds

Class B

13 pounds

30.9 pounds

Class C

31 pounds

58.9 pounds

Class D

59 pounds

115.9 pounds

TABLE

1-3

BotBash Wheeled Robot Weight Classes n

More Than

Maximum

Class A

0 pounds

24.9 pounds

Class B

25 pounds

55.9 pounds

Class C

56 pounds

87.9 pounds

Class D

88 pounds

172.9 pounds

TABLE

1-4

BotBash Walking Robot Weight Classes n

Chapter 1:

Welcome to Competition Robots

Robotica

Robotica is a new type of robot combat where bots must complete several courses
before they can fight each other. This type of contest has different design requirements; brute strength doesn’t guarantee that the bot will win the contest. Bots
need to be more agile and creative to solve each challenge. In this contest, you
must keep up-to-date on the rules because the challenges change dramatically
each year.
There is only one weight class for the Robotica robots. The maximum weight is
210 pounds., and the robot must fit inside a 4-foot-by-4-foot-by-4-foot cube at the
start of the match.
To give you an idea of the different types of events Robotica contestants face,
the following are details on qualifying obstacle courses from the first two television seasons.

Season One
In the first season of Robotica, bots had to survive three different preliminary
rounds. The first event was the Speed Demons race, where two bots raced around
a figure-8–shaped track in opposite directions. The first bot that finished eight
laps won the race. If the 2-minute time limit expired with both bots on the track,
the race was ended. Points were given to each bot for each lap finished. The bots
were allowed to crash into each other when their paths crossed.
The second event was the Maze event. Here, the bots had to navigate to the center of a maze and overcome several obstacles, which included a teeter-totter ramp,
a weighted box, spiked paddles, speed bumps, a guillotine, and a waterfall. The
first robot to the center won the event. Points were given to each bot for each obstacle successfully navigated.
The final event was the Gauntlet event. Each bot had to crash through five increasingly difficult obstructions. The obstacles included a pane of glass, a wall
made of pint-sized metal cans, small bricks, stacked cement blocks, and a large
weighted box. Two bots ran identical parallel courses, and the first bot that
moved the weighted box won the event. Points were also awarded for each obstacle the bot went through.
The bot with the most points after the three events won the preliminary round
and got to fight the winner of another set of events. The final match, called Fight to
the Finish, took place on a 16-foot diameter ring 8 feet off the ground. To win this
event, your bot had to push the opponent off the ring to its death on spikes below
the ring.

13

14

Build Your Own Combat Robot

Season Two
During the second season, the preliminary events changed from three events to
two events. The first event was the Gauntlet. In this new version of the Gauntlet,
the bots had to run through a diamond-shaped track. Both bots started at the same
point but went in opposite directions. They had to crash through a number of obstacles on the first two legs of the diamond track, including a wall of wood,
weighted cans, a wall of bricks, and then a cement wall. After all this destruction,
the bot then had to crash through the debris field created by the other bot. Once
the bot completed the diamond track, it then climbed a ramp to destroy a series of
glass columns. When all the glass columns were destroyed, the bots had to climb a
final ramp to the victory zone. Bots got points for each obstacle successfully navigated. The bot with the most points won the event.
The second event was the Labyrinth. The bots had to navigate through a series of
challenges, after each of which was a glass wall to be broken through by the bot.
The challenges included a 20-pound box, a suspension bridge, spikes shooting up
from the floor, a flip ramp, a sand pit, and a set of steel cargo rollers. When all challenges were successfully navigated and all six glass walls were broken, a seventh
glass wall was revealed. The first bot to break the final glass wall received bonus
points. To make things more difficult, a set of Robotica “rats” with buzz saws are
constantly attacking the bots to impede their progress. Points are awarded for each
obstacle successfully navigated, and the bot with the most points wins that event.
The bot with the most points after the two preliminary events moves onto the
Fight to the Finish event. As with the first season, the bots try to push each other
off the ring. The first one falling out of the ring loses the overall match.
As you can see by the different events, Robotica is more challenging than a purely
destroy-your-opponent type of robot combat. But in order to win Robotica, it still
comes down to having the strongest and most powerful bot.
The official Robotica Web site is at www.robotica.com.
FIRST (For Inspiration and Recognition of Science and Technology)

FIRST does not condone competitions where two bots try to destroy each other.
However, we are including FIRST in this list because their competitions are very intense and aggressive, and are becoming extremely popular among robot enthusiasts.
The FIRST Robotics Competition is an annual design competition that brings
professionals and high-school students together in teams to solve an engineering
design problem. One of the goals of competition is show students that science, engineering, and inventions are fun and exciting, so they will be inspired to pursue
careers in engineering, technology and science. A big part of the event is having
students work directly with corporations, businesses, colleges, and professionals
to help support them in building bots for the competition. This is a fast-paced
competition that starts shortly after the beginning of a new year. Each team has

Chapter 1:

Welcome to Competition Robots

only six weeks to design and build their bot. After that time, they compete in regional contests and later move on to the final championship.
In 1992, the inaugural year of the FIRST competition, there was only one contest with 23 teams entered. Since then, the contest has grown significantly. In
2001, there were 14 competitions with a total of 535 teams entered. FIRST has
grown to include Canadian and Brazilian teams, as well.
Each year the goal of the contest changes, and nobody knows this goal until the
first day of the six-week countdown. During this six-week time period, teams must
figure out the rules and goals of the contest and design and build their bot. During
the actual contest, a team is paired up with another team, and those two groups of
people must work together to solve the prescribed challenge against two other
teams. The particular contests are designed so that teamwork is required in order to
score enough points. During most of the preliminary rounds, the contest officials
decide team pairings. In the finals, a team is allowed to choose its partners. The
FIRST organizers believe this helps promote teamwork and cooperation.
FIRST robotics is an extremely challenging and exciting contest. Many of today’s famous combat robot warriors cut their teeth in competition robotics by
competing in FIRST, either by participating as a member of a high-school team or
serving as a mentor to a FIRST team. A lot of the technologies and skills needed for
building combat robots are used in designing FIRST robots.
The official FIRST Web site is www.usfirst.org.

FIGURE

1-6

Team Titan
Robotics from the
International School
in Bellevue,
Washington, built
Prometheus for a
FIRST competition.
(courtesy of
Larry Barello)

15

16

Build Your Own Combat Robot

Robot Soccer

Probably the most difficult robot sport is Robot Soccer. This is an autonomous
game where a team of bots works together to score goals against another team of
bots. The rules of the game are similar to those in actual soccer games. Bots use advanced vision systems to track the soccer ball, monitor the location of the opposing team’s bots, and know where their own teammates are. All of the bots play
their positions just as human players do. There is a lot of cross-communication between all of the bots playing. This contest is usually performed by university students developing algorithms for artificial intelligence. We reference this contest
because a lot of the technologies being developed for Robot Soccer players may
soon migrate down to combat robots. At some point in the future, there may even
be autonomous soccer teams in popular competitions like BattleBot.
More information on Robot Soccer can be found at www.robocup.org.
Before you start building a bot for a particular contest, you should get a copy of
that contest’s current rules and regulations. You can usually find this information
on the organization’s official Web site. Keep in mind that some of these competitions have long and complex regulations for builders to follow, and the rules do
change from time to time because the contests are evolving into a mature sport. You
need to be very familiar with the robot specifications and safety requirements for
the contest you have in mind, as they’ll have a significant effect on your bot’s design.

T

First

death from a chain on
he sport of
Person
the ceiling. Lexan walls
robotic combat
separated the audience
has been called
from the inevitable flying shrapnel
“American Gladiators for people
and sparks. The floor of the arena
with brains” and the “sport of the
future.” However, back when I first was so dented, dinged, and pitted
by the last day that you were sorry
signed on board with my armored
harbinger of destruction, it was just your robot wasn’t equipped with
off-road capabilities.
a small bunch of guys getting
Someone was nice enough to
together in San Francisco’s Fort
set up a primitive closed-circuit TV
Mason Center for what could only
be described as Rockem’ Sockem’
so that we in the backstage “pit”
Robots for grownups.
area could see what was happening
The crowd was small but
in the arena and know when we
enthusiastic. The hazards in the
should get on-deck for our matches.
arena were walls that pushed in
While we toiled away on our bots,
our spot in the pit was so close to
and out, some spinning blades
that popped up whenever the guy
the action that we could almost
watch the battles if we stood on
running them was alert enough to
press the lever, and a large metal
our chairs. The sound of saws
grinding metal and the smell of
ball looming from on high that
swung like a giant pendulum of

overcooked batteries, fried wires,
and oil filled the air.
It was heaven.
It was also my robot Spike’s
first time competing as a
lightweight. We came in third, but
where we wound up didn’t matter.
Just being a part of the action was
thrilling enough. If you needed a
screwdriver or blew a gasket,
someone was there with a spare to
help you get your bot back into the
fray. When our Tekin speed control
turned into a smoking slagpile, we
got a loaner from the guy we were
going to be up against in the next
match. In the pit, we were all on
the same team, working toward a
common goal. However, once our
bot was in the arena, all bets were
off, and it was mano a mano: let
the best-made machine win.

Chapter 1:

Welcome to Competition Robots

First
The hardest part
the blink of an eye! We
Person
for us was just
met some of the most
continued
getting there. We
incredible (and nicest)
had no sponsors and
people. The designs we saw
had to pay our own way for
and the creativity of the engineers
everything. It was tough, and it
and imagineers behind their bots
took months to pay off that credit
inspired us. The generosity in the
card, but I would do it all again in
sharing of ideas, tools, and even

T

parts amazed us. We became
part of this amazing community of
robot builders and battlers and the
camaraderie warmed us. It was
one of the best weeks of my life.
—Ronni Katz

he Scope of This Book
Building a bot is not that difficult—if you’ve done your homework on the basic elements involved. It may take you a while to figure out how to do new things, and it
might take a long time before you build your dream machine, but consider your
first project a learning process—patience and persistence are key when you’re
building a bot.
Robotics is one of those fields where you need to be able to wear a lot of different hats. That means you must know a little bit about a lot of things, including motors, electronics, wiring, computers, radio transmitters and receivers, batteries,
gears, belts, bearings, chains, sprockets, metals, plastics, drilling, cutting, threading, bending, and welding—just to name a few.
You don’t have to be an expert in all of these categories—you just need to understand the basics behind each one. Most combat robots are built by a team of
people. Each team member is knowledgeable about certain areas of robot building. When you get a group of people together who all know different pieces of the
process, it reduces the burden on each individual for having to be an expert on everything. After you have built a couple of bots and competed in a few contests,
you’ll become something of an expert in all of the different categories because you
will have been involved to some degree with every part of building the bot.
Probably the number-one question that gets asked of a bot warrior is, “How do
I build a robot?” Well, nobody can give you a quick answer. It usually takes
months to years to learn how to build a bot. There is just too much stuff you need
to know. Most of the time, people learn just by doing it. We all make mistakes,
and we learn from them.
The scope of this book is to help you, the new robot builder, get started in the
exciting field of constructing combat robots. After reading this book, you will
have an understanding of all the elements that go into building a bot. Usually, the
new robot builder is surprised to find out that there are so many different things
that go into this process. This is because most people only see the finished product—the beautiful, gleaming El Diablo or Nightmare or Deadblow—they don’t
see the blood, sweat, and tears that went into building it.

17

18

Build Your Own Combat Robot

In this book, you’re going to learn how to lay out your ideas and come up with a
good plan before starting to build your bot. You’ll learn the basics behind a lot of
technical subjects, some of which are listed here:


How electric motors work, how to pick the right motor, and how to use it



The various locomotion methods and the various methods to get your
motors to drive your bot’s wheels



Different types of batteries and how to size them for the right job



What’s required to actually drive a motor, and how to choose the right
radio control system



How to minimize radio interference so your bot will do what you want,
when you want



Wiring issues to keep in mind when building a bot



Materials and how to assemble them into your bot’s body



Armor for your bot



Weapons for your bot



Sensors you can build into your bot for use of automatic weapons, or to
create a fully autonomous bot



How microcontrollers can help you control your bot and allow it to run
on its own

In this book, you’ll learn about two different bots that were actually built for
Robot Wars and Robotica, and you’ll even learn how to build a working mini
sumo bot. As you read the stories behind the building of each of these bots, you
will learn what the builders did to construct them and why they chose their own
particular approaches, what worked, and what didn’t.
What this book doesn’t cover is the explicit step-by-step details of building
combat robots. The main reason we chose not to do this is that we don’t want to
prescribe an exact kind of bot for you to build. There are so many different types
of bots to choose from, and an infinite variety of designs you could adopt, and the
last thing we want is to see hundreds of the same identical bot competing in different contests. We want you to use your imagination! Do something different. Have
fun. Be creative. Make a six-legged mama robot that deploys a half-dozen baby
robots. That would sure be fun to watch!
For those of you who would like more explicit details anyway, we have included a set of appendixes with references to other outstanding books and sources
for information and robot parts. These lists should give you all the information
you ever wanted about robot books and resources.
Okay, now let’s get started!

chapter

2

Getting Started

Copyright 2002 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

S we said in Chapter 1, it’s good to let your imagination run wild
when you begin making plans to build a bot. However, while you can dream up all
kinds of crazy ideas for a robotic creation, keep in mind that you may not have the
time—or even the technology—to build most of them. We can’t begin to tell you
how to design the “perfect bot,” any more than we can convince you of what the
perfect car or television set is. Everybody has their own idea of what’s best. Yes,
we authors have our biases and feel comfortable with certain techniques and designs that have been tested over a number of years, but a prospective bot builder
can easily arrive at a better idea than anything we’ve come up with in the past.
Read this book and others, talk with respected people and experienced combat
warriors, sketch out your ideas, and then just go for it.
Start your design process by deciding on exactly what you want your bot to do.
If you’re planning to build a machine for BattleBots, you’re going to have to take
an approach quite different from the one used for making small autonomous machines designed to run a maze or blow out a candle in the popular Trinity College
Robot Firefighting Contest. A bot designed to act as a servant in your home may
be every bit as heavy and complex as a warrior bot, but it doesn’t need to be able to
survive the blows of a weapon of another machine or travel nearly as fast.
Experience has shown that electronics and computing power are not the limiting factors in bot construction; it’s the mechanics, sensors, and related software
development that choke a project to a stop. “How do I physically build the thing?
What type of sensors can I use? How do I write the code and what language should
I use?” are the questions that flood experienced builders’ minds.
Of course, if you’re building a BattleBots-style (radio control) machine, you
probably won’t need any software, and the “sensors” are your own eyes as you guide
it across the floor of the battle arena. Physical and mechanical design are most critical in these large bots. They require more sophisticated machining techniques
than most bots because they must endure an environment that is far more hostile than
the average home.

22

Chapter 2:

Getting Started

First

L

can compete, such as
ike I said in
Person
BattleBots, Robotica,
Chapter 1, I got
or Robot Wars.
started in robot
The sport has changed a lot in
combat for the fun. When I came
five years. Because robot combat
on board, there was no TV coverage
has gotten more commercial, the
or anything fancy. Tickets were
sold locally, and it was promoted
standards by which entries are
judged have gotten far more
through grass-roots efforts. A
stringent. When I first competed,
friend and I happened to learn
the rule book was maybe five to
about it via the Internet and were
seven pages of safety tips. Now,
two of only a handful of people
who came to the competition from the rule book for competing in any
of the major contests is 60 pages
outside California.
of dos and don’ts, plus another
Back in those early days,
50 pages of technical specifications
getting people involved was a
that competing bots must adhere
challenge because everything was
so new and no one was really sure to. It isn’t just a game anymore. It
has become serious business for the
how to promote the idea. Now, of
people involved, and the promoters
course, there are lots of popular
organizations where robot builders expect those who enter to bring a

T

robot that is both safe and exciting
to see in action.
If you’re going to build a bot, let
it be your love of the sport—not a
desire for glory or fame—that
brings you into the arena. People
thinking of getting into this with
visions of becoming “The Rock” of
BattleBots had better check their
servos at the door. Chances are
your first entry will die a quick,
smoldering death, so keep your
ego in line. As long as you’re there
for the joy of the game, you will
have as much fun bashing,
smashing, and chopping your
opponents into miniscule metallic
bits as I did!
—Ronni Katz

he Robot Design Approach
The first step in designing a new bot is deciding which contest the bot will be built
for and getting a copy of that contest’s current rules and regulations. The rules
outline the weight and size limits for each weight class, as mentioned in Chapter 1,
and list weapon types that are allowed and not allowed. They also list safety requirements, electrical requirements and restrictions, and radio control restrictions.
Read and understand the rules thoroughly. This will set the initial physical constraints in your bot’s design.
If you’re designing a robot for multiple contests, you should obtain sets of rules for
all of them and make a list of all the common rules and non-common rules. When
you have this information put together, you’ll be able to create a list of the most restrictive rules for each of the contests, which will help you guide your overall bot
design. Building a bot to the most restrictive rules will allow your machine to be
entered into each contest without significant modifications.

23

24

Build Your Own Combat Robot

Even if you’re just building a bot for fun, we recommend getting a copy of one
of the main contest’s rules. A good example of rules and regulations can be found on
the BattleBots Web site (www.battlebots.com). Their safety guidelines and restrictions should be followed in all bot building. Most of the rules are there for the
safety of builders and spectators alike.
Once you have the physical constraints written down, you can start laying out
the conceptual design of your bot. Sketch out what you would like your bot to
look like and do. Include the unique features and weapons you would like your
bot to have. A lot of this is paper-and-pencil or CAD (computer aided design)
work. Next, make a list of performance goals you’d like to achieve, such as how
fast you want your bot to go or how much weight you want it to be able to push.
How much must the armor withstand in punishment, and how will your bot’s
weapon attack the enemy? This is all top-level generic design information; you
don’t need to get into nitty-gritty details like miles per hour or pounds of pushing
force yet. That comes later.
The second list includes what you are aiming for—the ultimate goal. Some people call this the brainstorming part of the design process. The ideas come out here.
As is the case with any brainstorming session, there is no such thing as a bad idea.
Let the ideas flow, and come up with some cool bot concepts. It is usually good to
come up with a handful of them.
After this, the conceptual ideas must be trimmed down to meet the physical
constraints of the contest. Yes, this means you’re going to have to toss out your
idea for a laser-guided rocket launcher. (It’s a great idea, but it’s not allowed in
any combat robot event.)
In all competition robots, the following subsystems are part of each bot. Each
of these subsystems relates to the others and affects the overall design of the bot:


Robot frame



Drive motors



Power transmission



Batteries



Wheels



Electronics



Radio control system



Weapons



Armor

Probably the first consideration in your robot’s design is how you’re going to
make it move. Your choices are many, and could include slithering, swimming,
floating in the air, or even climbing up a wall or rope. More than likely, though,
you’re going to want a mobile bot that travels across a floor, and this will mean
legs, “tank” treads and tracks, or wheels.

Chapter 2:

Getting Started

Wheels are the most effective way of providing propulsion to a bot. They are
cheap, and easy to mount, control, and steer, and there are several methods you
can use. We’ll discuss all this in Chapter 3. There are many sources of bot wheels,
from toys for the smaller bots to small trailer tires for larger machines. Some
builders have used wheels from industrial casters, lawnmowers, go-karts, and
even small bicycles. Your choice depends on the size and steering configuration of
your bot’s design.
The majority of bots use differential or tank-type steering (also known as “skid
steering”). This means that the bot uses different speeds for left and right wheels (or
sets of wheels), causing the bot to go straight, or to one side or the other. Having one
wheel stopped and the other moving makes the bot pivot on the stopped wheel, and
vice versa. Having one wheel move forward and the other in reverse makes the bot
spin about its center axis. (We’ll discuss this in more detail in Chapter 3.)
Once you choose your locomotion method, the first set of major components
you need to identify are the motors. Most motors operate at speeds that are way too
fast to control the robot. So, you’ll need a gear reduction. Some motors have built-in
gearboxes, while others require a speed reduction system. This can be in the form of
gears, sprockets, belts, or even gearboxes. Chapter 6 will talk about these various
power transmission methods. The advantage of a gear reduction is an increase in
the torque to the wheels, which gives your bot more pushing power. Another reason
you should select your motors first is that they will dictate your electrical power
requirements, which affects the battery and motor speed controller selections.

FIGURE

2-1

The welded frame
structure of Minion.
(courtesy of
Christian
Carlberg)

25

26

Build Your Own Combat Robot

Chapter 4 will discuss motor performance requirements, and Chapter 7 will describe various motor speed controllers.
The next step is designing the bot’s frame. This is the core structure of the bot that
holds the motors, drive shafts, bearings, gearboxes, wheels, batteries, and motor
controllers. The core structure should be solid and rigid, as the rest of the bot will be
attached to it. Remember when you’re designing the frame to leave space for the
batteries, motor controllers, and weapon actuators. Another point to keep in mind
is your robot’s center of gravity. Keep it as low as possible to improve stability.
Okay, so you’ve determined your power requirements. Next, you need to know
the current draw specifications from the robot motors. It is best to estimate this based
on worse-case situations. The last thing you want to see happen is your bot stop in
the middle of a match because it ran out of energy. Assuming that your bot is running
at stall-current conditions all the time is the absolute worse-case scenario, but this
estimate is unrealistic since stalling the motor for 5 minutes will destroy the motor. However, assuming your robot is running at 100-percent stall current draw
for 20 percent of the match time, and at 50 percent the stall current for the remaining amount of time in the match, should give you a good estimate on the maximum
amount of current that you will need. Select your batteries based on the information
contained in Chapter 5. Once the batteries are selected and the dimensions of the
batteries are determined, a battery housing should be designed for the bot. The battery housing holds the batteries in place and protects them inside the bot.
Knowing what the current requirements are for your bot determines the motor
speed controller. You’ll find information about motor speed controllers in Chapter 7.
When you’re installing the motor speed controllers, you should have features in
the design to allow for cooling. Motor controllers get very hot when near-maximum
currents are running through them. You may even need multiple-speed controllers,
depending on how many motors you’re using.
FIGURE

2-2

A robot using two
Victor 883 motor
controllers and the
Innovation First
Robot Controller for
motion control.
(courtesy of
Larry Barello)

Chapter 2:

Getting Started

Now, it is time to add the weapons to the design process. You need to design a
support structure to support the weapons and their actuators. The support structure should be mounted to the main frame, and the support structure needs to be
very strong. As Newton’s Second Law says, “For every action, there is an equal
and opposite reaction.” In other words, any force your weapon imparts onto an
opponent will elicit equal reaction from the opponent onto your bot. Thus, the
weapon support structure needs to be able to withstand those forces. Chapters 9
and 10 discuss construction and weapons techniques.
The last part of the mechanical design process is the armor. You should design
your armor to be replaced, because it will inevitably get damaged during combat.
You don’t want to damage your own bot just trying to replace the armor, so it
needs to come off fairly easily—when you want it to. Sometimes the armor and the
frame are the same thing. In other words, there is no armor other than the frame itself.
Chapter 9 discusses the various materials that make good armor.
At any time during the mechanical design process, you can select which radio
control system and “robot brains” you want to use. For driving a bot, you need at
least two control channels—one for forward and reverse, and the other for turning left and right. This is true for bots that have channel mixing. With no mixing,
you would use one channel for the left wheels and one for the right wheels. Additional channels are for controlling the special features.
You might want to automate some bot functions, like shooting a spike when
the opponent gets within 1 foot of your bot. Here is where you specify the types of
sensors for detecting the opponent and figure out how to mount them inside your
bot. You’ll probably need to have a microcontroller inside the bot to process and
interpret the sensor results in order to control the weapon. Before you implement

FIGURE

2-3

A robot showing
how badly its
armor was
damaged at
a BotBash
tournament.
(courtesy of
Andrew Lindsey)

27

28

Build Your Own Combat Robot

any computer-assisted functions, your bot should be built and tested with all manual control. Once the bot works to your satisfaction, then you can add the automatic features.
All of the preceding design steps should be done, as much as possible, on paper
or CAD before you start cutting parts to assemble the bot. This will save you from
having to remake parts due to design changes. You don’t absolutely need to have
CAD software to do this, but CAD does give you more professional-looking results. You can use regular old-fashioned graph paper, too. Some people have even
used chalk on their garage floors to design bots in full scale. Do whatever you’re
most comfortable with.
t i p Expert machine designers use CAD (computer-aided design) software; so if you want
professional-looking results, you should consider getting a CAD program. CAD is so widely used
among roboteers, in fact, that PTC (makers of Pro/E CAD software) has sponsored the last
three seasons of BattleBots. Each team who showed up at the competition and asked for it
got a free one-year license of the software, which normally retails for $21,000. Other CAD
packages are available for a lot less money.

FIGURE

2-4

This robot, Slap
Happy, was built
using plywood as
templates before
metal parts
were fabricated.
(courtesy of
Dave Owens)

Chapter 2:

FIGURE

Getting Started

2-5

AutoCad was
used to design
Live Wires
prior to
fabricating parts.

The Game of Compromise

There has probably never been a bot made that didn’t involve some level of compromise on the part of the builder. This is where your time-, money-, performance-, and availability-related trade-offs occur. We builders rarely get the
chance to use the best parts available, and therefore must settle for what we can
get. This is where you need to let go of your idea for a dream bot and start looking
at your project more realistically.
For example, say you want your bot to move at 20 mph and you want to use
8-inch diameter go-kart wheels. To move at this speed, the wheels need to turn at
840 rpm. Now you have to find a motor that can deliver that speed. You search all
of the magazines and catalogs you can find, scour the Internet, and you still can’t
find a motor that will give you the speed you want. This means you’ll need to build
a gearbox that can change the motor speed to the desired 840 rpm wheel speed.
Here you will be faced with lots of options, such as spur gears, sprockets, belts,
worm drives, and so on. In your search for motors, say you also found some gear
motors—you pick a few motors, and then calculate what gear reductions you need
to get the right wheel speed. At this point, you have several motor and gear options
to choose from to get your robot to move at 20 mph. So, now you have to choose
which combination you want to use.

29

30

Build Your Own Combat Robot

Before blindly picking one, you should look at how this selection will affect
each of the other systems at work in your robot design. For example, for a given
horsepower rating on the motors, a 24-volt motor will draw about half the current
as a 12-volt motor. That’s a good thing, right? Not necessarily, because running at
24-volts will require two 12-volt batteries—which increases the battery storage
area and robot weight. That’s a bad thing, right? Well, again, not necessarily. A
12-volt battery might not be able to deliver the current to drive a 12-volt motor,
but will have plenty of current for driving a 24-volt motor.
This is why you make the system interface drawings first. When you pick a
component to use, you update the interface requirements, such as weight, voltage,
current, spacing, the need to add new subcomponents or delete old components,
and so on.
A bigger part of the compromising process occurs when you build your bot
around existing parts. Obviously, life gets a little easier when you can build with
stuff you already have, but often this means getting a bot that’s less flashy than
you envisioned. For example, say you were planning to include heavy-duty motors
on your bot, but the ones you had in mind are hard to obtain, and you happen to
have a couple of wheelchair motors lying around the garage (bot builders tend to have
this kind of stuff lying around). You may choose to use the motors you already
have, rather than going on a wild goose chase for the other motors. So, these motors now become a fixed specification, and you’ll need to compromise on your
bot’s performance goals. That 20-mph robot you were planning might only go
10 mph now, and can only push half the weight you originally wanted.
Probably the biggest area of compromise comes with cost considerations. Say you
found the ideal motors you want, but they cost $800 each and you need four of them
for your four-wheel-drive bot. Like most beginners, you can’t really justify spending $3,200 for motors. So you either find different motors, such as $100 cordless
drill motors, or change the design from a four-wheel-drive bot to a two-wheeldrive bot.
Again, ideally, you should design the entire bot on paper or CAD before you
start constructing it, although this usually isn’t as much fun. Most people find designing and building at the same time more enjoyable because it allows you to see
the progression of the bot from day one. Other people enjoy the design process
more than the actual building. If you enjoy building, team up with a good designer. If designing is your thing, then find yourself a good builder to partner with.
When your bot is completed, you should create a new set of drawings showing
how the bot was actually built—especially all of the electrical wiring. These drawings will come in handy when you need to repair or improve the bot at later dates.
It’s easy to remember everything that went into building the bot when we first finish building it. But we soon forget certain details, which can create problems when
maintenance is needed. These as-built drawings will save you a lot of headaches
down the road.


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