Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

176 Chapter 5 Tracked Vehicle Suspensions and Drivetrains
Figure 5-8
rockers
Road wheels on
motion is especially beneficial at higher speeds, and the rocker layout
used on wheeled vehicles is almost as effective on tracks. The rollers are
mounted in pairs on rockers between the drive sprocket and the idler
wheel. The rockers (Figure 5-8) allow the track to give a little when traversing
bumpy terrain, which reduces vertical motion of the robot chassis.
Careful tensioning of the track is essential with movable road wheels.
The most complex, efficient, and smooth ride is produced by mounting
the road wheels on sprung axles. There are three main types of suspension
systems in common use.
• Trailing arm on torsion spring
• Trailing arm with coil spring
• Leaf spring rocker
The trailing arm on a torsion spring is pictured in Figure 5-9. It is a
simple device that relies on twisting a bunch of steel rods, to which the
trailing arm is attached at one end. It gets its name because the arms that
support the wheel trail behind the point where they attach, through the
torsion springs, to the chassis. The road wheels mount to the end of the
trailing arms and forces on the road wheel push up on the arm, twisting
the steel rods. This system was quite popular in the 1940s and 1950s and
was used on the venerable Volkswagen beetle to support the front
wheels. It was also used on the Alvis Stalwart, described in more detail
in Chapter Four.
You can also support the end of the trailing arm with a coil spring, or
even a coil over-shock suspension system that can probably produce the
smoothest ride of any track system (Figure 5-10). The shock can also be
added to the torsion arm suspension system. The advantage of the coil