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Bots /The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 2

Chapter 2 Getting the Parts 35

perpendicular to their normal direction of travel. There’s a close-up of this
unique wheel system in Figure 2-8.

Figure 2-8
One of the
omni-direc-
tional roller
wheels used
for the robot.
When rotating
around the
axle, the
wheel rolls
like a normal
wheel. But the
embedded
rollers also
allow the
wheel to pull
off a clever
trick: it can
roll in line
with the axle.

These wheels are produced by North American Roller Products
(www.narp-trapo.com). Unfortunately, these folks don’t sell their products
directly to consumers. To purchase these wheels, you will need to go to a re-
tailer that carries them.

In addition to Acroname, the other location we have found for these wheels
is Mr. Robot (www.mrrobot.com).

Be sure you buy the right ones. The wheels you will need for the PPRK are 4
cm omni-directional wheels. Are you a monster truck fan? Cool. You’ll be
happy to know that both Acroname and Mr. Robot sell larger omni-direc-
tional wheels. Be sure to email us some pictures of your Monster PPRK with
oversized wheels.

How Do the Wheels Work?
The ability of the PPRK to travel in a straight line relies on the physics of
motion. Any force applied to an object can be resolved into component
forces in any arbitrary coordinate system. Alternately, any two or more
forces can be summed into a single resulting force. For example, in the
normal X-Y (Cartesian) coordinate system, every force has an X compo-
nent and a Y component.

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Monday, May 12, 2003 10:17:29 AM