Page 352 - Robot Builder's Bonanza

SELECTING THE BEST CONSTRUCTION MATERIAL 321

Figure 27- 2 Commercially
manufactured hexapod kit featuring
3- DOF legs. The extra degree of
freedom in the legs provides a more
defined stepping action. (Photo courtesy
Lynxmotion.)

OPERATING TERRAIN
Bots with 2 DOF per leg work best on smooth, unobstructed surfaces— a kitchen floor or a
hallway with wood laminate are good choices. The surfaces shouldn’t be too slick, unless you
add rubber pads on the robot’s feet. Otherwise, the contraption will tend to skitter on the floor
as it frantically moves its limbs. It’s comical but not too productive.
The more sophisticated 3- DOF robots with four- or six- legs can be used on more challeng-
ing terrain. This is because they’re endowed with an additional articulation that permits the
legs to literally step up and down rather than just swing in and out, which is typical of the
simpler 2- DOF designs. The full leg- lift helps the robot clear low objects and even thick car-
pet nap.
Many of the more elaborate ready- made walking robot kits are designed with this feature.
Figure 27- 2 shows an example: its third DOF permits the legs to lift up vertically, clearing
obstacles at least 1/2″ to 1″ in height. Of course, these designs are more expensive because
they require three servos per leg and additional leg hardware.

Selecting the Best Construction Material

Walking robots need to be strong yet lightweight. The heavier the robot, the less likely it can
stand on its own two feet, so to speak. Pine lumber and soft plywood are pretty much out,
because they’re too bulky and heavy for the strength they offer.

There’s lots more about wood, plastic, and metal in the chapters in Part 2 of this book. Be sure
FYI to see Chapter 7, “Working with Wood,” Chapter 9, “Working with Plastic,” and Chapter 11,
“Working with Metal.
Materials choice, in order of preference, is:

• Aluminum, cut and drilled to shape. For walking robots under 1 foot high, thickness
ranges from about 20 gauge (0.0320″) to 8 gauge (0.128″). Premade parts are often cut
by a powerful waterjet machine controlled by a computer, then bent using special jigs.
When building your own, the likely tools are hacksaw, drill press, and bench vise.

27-chapter-27.indd 321 4/21/11 11:52 AM