Page 133 - Build Your Own Combat Robot

Build Your Own Combat Robot
114
FIGURE 6-5
Direct-drive power
transmission
showing a wheel
directly mounted to
the gearbox.
(courtesy of
National
Power Chair)

Methods of Power Transmission
In previous chapters, several methods of interconnecting the motors with the
wheels have been discussed. In direct-drive methods, the motor or gearmotor’s
output shaft is connected directly to the wheels (see Figure 6-5).
Indirect-drive methods include a chain, belt, and even a series of flexible cou-
plings. The following sections will discuss various chain and belt drive systems.
Numerous types of flexible shaft couplings are available, such as universal joints,
shear couplings, spider couplings, grid couplings, offset couplings, chain cou-
plings, gear and sleeve couplings, bellows couplings, and helical beam couplings.
The main advantage of these shaft couplings is that they can connect two shafts
that are slightly misaligned. Figure 6-6 shows a Lovejoy flexible coupling. A
Lovejoy coupling is a spider coupling. They come with three different parts: two
bodies and a spider. The shaft bodies come with different bore diameters so that
different shaft diameters can be coupled together. The spider’s material is made
out of urethane, Hytrel, or rubber. The selection of the spider material is based on
the applications the coupling is going to be used for.
For high-powered robots, careful design of the components and mounting lo-
cations will be needed to minimize shaft misalignment.

FIGURE 6-6
A Lovejoy
flexible coupling.