Page 353 - Robot Builder's Bonanza

322 BUILD ROBOTS WITH LEGS

• Polycarbonate plastic is a tough, scratch- resistant material commonly used as a substitute
for glass. You can cut it with hand or power tools. A thickness of 1/8″ is ideal for robot
making
• PVC plastic, in 6mm (about 1/4″) thickness. While not as strong as polycarbonate, PVC
is lots easier to work with, requiring nothing more than regular woodworking tools.
• ABS plastic, in 1/8″ or 1/4″ thickness. It’s a bit easier to cut and drill than polycarbonate,
and parts can be glued using a common and inexpensive solvent cement.
• Wood, but not just any wood, specifically aircraft- grade birch or other hardwood plywood.
The 1/4″ or 3/8″ sheets provide adequate strength, and parts may be glued using a quality
wood glue.
• Acrylic plastic is one of the least desirable of the materials commonly used to construct
walking robots. Though similar in appearance to polycarbonate, it’s not quite as strong and
is susceptible to cracking under stress. The repetitive bending of the plastic can permit
hairline fractures and “crazes” to form over time.

Scratch Build or Parts Kits

Perhaps the hardest aspect of building a walking robot is fabricating the leg pieces. So before
starting any legged robot project, take an honest look at your tools, skills, and budget, and
decide whether you want to build your own from scratch (that is, from raw materials) or
whether you want to assemble a walkerbot from premade parts. Because of the growing
popularity of amateur robotics, a number of online sources offer parts specifically designed for
constructing legged robots, anything from two legs on up.

BUILD YOUR OWN FROM SCRATCH
If you have reasonably good shop skills, you can consider making your own walking bot from
scratch, using your choice of wood, plastic, or metal. The most common construction in a
legged robot is the X- Y joint, so called because a pair of motors produces a linear movement
in both the X (right/left) and Y (up/down) planes. Shown in Figure 27- 3 is an X- Y joint cre-
ated using 6mm PVC plastic. A pair of R/C servo motors is attached to the joint using minia-
ture fasteners.

Figure 27- 3 Homemade X- Y joint
components for constructing a robotic
leg (among other things). The parts are
fashioned out of wood or plastic.

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