Build Your Own Combat Robot

Metals
Aluminum
Chapter 9: Robot Material and Construction Techniques 185
At a recent BattleBot 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.
Despite Lexan and other materials, metals are the material of choice for most robot
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 machined
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 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