Build Your Own Combat Robot phần 6 potx

chapter 9

Robot Material and

Construction Techniques

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

HEN we human beings experience an injury or sickness, it’s fre￾quently our skin and bones that really keep us together. Carefully applied skin

grafts after a serious burn or injury can mean the difference between life and

death. Likewise, if you’ve watched a robot combat match, you know that a robot

is doomed if its skin is ripped off by an opponent. The same follows for the failure

of fasteners for a wheel assembly, a weapon, or a strategic internal system. If any

of these are torn off in the arena, that robot is most likely going to lose the match.

The information in this chapter will help you make your own decisions about

what materials and construction techniques you will use after thoughtful consid￾eration of the many types of elements and fasteners available. Each material has a

best application. Before you begin building, you should look up specifications in

suppliers’ catalogs and use logical design practices in the layout and construction

of your combat robot. Use common sense. Talk with friends who have done me￾chanical design. Look at successful designs and determine just what made the design

work so well, or what caused others to fail. Don’t be afraid to ask others for advice.

Get on the Internet and converse with those who have built a robot similar to what

you have in mind.

Metals and Materials

When you think of durability, you probably think of metals first. However, some

of the newer plastics offer many advantages over metals when it comes to building

robots for competition.

High-Strength Plastics

With virtually unmatched impact resistance, outstanding dimensional stability,

and crystal clarity, Lexan polycarbonate resin continues to be one of the popular

types of materials for use in combat robots. The product is a unique thermoplastic

that combines high levels of mechanical, optical, electrical, and thermal properties.

GE Structured Products is one of the leading suppliers of Lexan sheet material.

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At a recentBattleBot competition, GE handed out hundreds of hand-sized samples

of Lexan 9034 to robot designers, some of whom immediately put it to use on

their creations as protective armor or spacing material. Technical demonstration

videos were on display and product specification sheets were made available.

Even the BattleBox was designed with four “layers” of protection using Lexan

material to keep the deadly robots and flying parts from injuring spectators. Even this

material is not impervious to all types of damage, as a large chunk of one of the Lexan

panels had a large chunk torn out of it by a wayward robot in a recent match. Your

local plastics supplier may have the material on hand, can order it, or can direct you to

the GE Structured Products division (www.gestructuredproducts.com) nearest you.

Metals

Despite Lexan and other materials, metals are the material of choice for most ro￾bot structures and armor, and numerous types of metals are available for robot

construction. While newer experimenters are often confined to using only those

materials they can find at the local hardware store, surplus store, or junkyard, we

recommend using the highest grades of materials you can get your hands on to

construct your combat bots. (Appendix B at the end of this book will point out

vendors that can help you get the best materials.)

Metal supply companies are available in larger cities, but many potential robot

builders are not familiar with the best metal and materials to use for a particular type

of project. Although we don’t cover modern ceramics, plastics, and composites in this

chapter, a plethora of alternative options such as these are available out there.

The word strong as applied to the various durability characteristics of metals and

materials is often misused. For example, rather than look for a strong metal, you

might want a metal for a particular weapon design that can take a lot of bending

after being struck and not break, and you’ll find that a piece of spring steel works

well for that. Another part of your robot might call for a stiff rod, and you select

an alloy of stainless steel. Your wheel hubs must be light, tough, and easily ma￾chined on your small lathe, so you select aluminum alloy 7075. Two nice pieces of

brass seem to work fine as heat sinks for your drive motors. A thick piece of Kevlar

you find in a surplus yard is destined to be your robot’s sub-skin, to be covered by

a sheet of 304 stainless steel bonded to it. All of these materials have their

strengths and weaknesses.

Aluminum

Aluminum is probably the most popular structural material used in experimental

robot construction. It offers good strength, though it’s certainly not as tough as

steel. Its best characteristics are its ability to be machined, its availability, and its

light weight. You might be able to go to a junkyard and ask for aluminum, and the

sales person will lead you over to a pile of twisted metal. Enter a metal supply

house, and you’ll be asked “what alloy, what temper, and do you want sheet stock

Chapter 9: Robot Material and Construction Techniques 185