Page 305 - Robot Builder's Bonanza

274 MOUNTING MOTORS AND WHEELS

Figure 24- 8 The concept behind using
a metal or plastic gear as a flange for
mounting a wheel to a motor shaft. Attach
the face of the gear against the wheel hub;
the gear provides a hub that can then be
secured to the motor shaft.

• Use a reducing bushing, which is basically a short length of hollow tube. The inside of the
bushing is sized to match the motor shaft; the outside, the wheel hub. You then carefully
drill a hole through the bushing. Use a longer setscrew, if needed, to make it extend
through the bushing and make contact against the shaft.

Using Flanges
But what if the wheel lacks a setscrew? One solution is to use a flange that does have a set-
screw, and a hub with a properly sized bore that matches the motor shaft. You attach the
flange to the wheel using fasteners, then mount the flange to the shaft.
A flange is anything smaller than the diameter of the wheel and that has a setscrew and
hub compatible with the motor shaft you want to connect it to. Specially made flanges are
available through Lynxmotion, Jameco, Servo City, and other online retailers. The flanges
come in different bore sizes. Cost is modest.
A convenient ready- made flange is a surplus gear. Drill two or three holes through the face
of the gear and matching holes into the wheel, being sure to keep the gear and wheel concen-
tric. Mount the flat part of the gear against the wheel (see Figure 24- 8), then attach the assem-
bly to the motor shaft.

Mounting Wheels to R/C Servos

Servos reengineered for full rotation are most often used for robot locomotion and are outfit-
ted with wheels. Since servos are best suited for small- to medium- size robots (under about
3 pounds), the wheels for the robot should ideally be between 2″ and 5″ in diameter, and
lightweight.

WHEELS ENGINEERED FOR R/C SERVOS
By far the easiest way to attach wheels to servos is to use a wheel that’s specially engineered
for the job. Many specialty robotics retailers sell wheels meant for use with the standard- size
Hitec and Futaba servo.
Now for the bad news: Your choice of wheel diameters is pretty limited. You’ll find just a
few sizes, with 2- 1/2″ (give or take a few fractions of an inch) the most common. If you need
a smaller or larger size, you can always make your own wheels, as detailed next.

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