Page 137 - Build Your Own Combat Robot

Build Your Own Combat Robot
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B elt Drive Systems
In addition to chain drive systems, a belt drive system can be used to transmit
power from the motor to other devices such as wheels and weapons. Many differ-
ent types of belt drive systems are available, but the three most common are flat
belt, synchronous belt, and V-belt systems.

Flat Belts
Flat belts are commonly used for applications that need high belt speeds, small pul-
ley diameters, and low amounts of noise. Flat belts are in common use when one
large motor drives several different pieces of machinery. They cannot be used for
applications in which absolute synchronization between two pulleys is required.
This is because these belts require friction to maintain motion, and slippage or
creepage can occur. Flat belts must be kept under tension to transmit power from
one pulley to another. Because of this, a belt tensioning device is required.
One advantage of this type of system is that a flat belt could be wrapped directly
between the motor shaft and larger diameter pulley attached directly to the robot
wheel. A similar application is commonly seen inside small electronic equipment
such as tape recorders and videocassette recorders, and you can find them turning
the rotary brushes in vacuum cleaners.
The drawback to these types of systems is that the two pulley surfaces must be
perfectly parallel. If they are not, the belts will run off the pulleys. To prevent this
from happening, flanges need to be placed on the sides of the pulleys to constrain
the belts in place.
For combat robotic applications, these types of belts can be used for spinning
weapon systems. If the weapon gets stalled, the motor will slip under the belt,
which helps to protect the motor from stalling and burning out. These types of
belts also offer little power transmission ability due to the small frictional area at
each pulley.

Synchronous Belts
Synchronous belts are more commonly known as timing belts. The name timing
belt is derived from their popular use in car engines, where they’re placed between
the cam and crankshaft and are used to synchronize the cams inside the engine.
Timing belts are similar to flat belts in their operation. The physical difference be-
tween these two belts is that the timing belts have teeth on one or both sides of the
belt. This allows timing belts to synchronize the speeds between all the pulleys that
are being driven by the belt. Figure 6-9 shows a timing belt.
Because the teeth on the belts are used to drive the pulleys, similar to the chain
drive systems, the belt tension requirements are much less for synchronous belts