and provide power for either swinging the crane or
traveling the crane.
The swing-travel jaw clutch
requires the operator to engage a button or push a lever
to select for swing or travel operations. Other models
have a separate steering and swing lever, allowing both
functions to be operated at the same time.
Use caution when traveling with a crawler crane on
and around slopes. Some older types of crawler cranes
do not have travel brakes and power could be
disengaged, causing the crawler to freewheel.
On-the-job maneuvering is easy because of the
small turning radius of the crawler crane. Additionally,
the crawler crane does not require the use of outriggers
for stability, so it requires less room for setting up. On
some models of crawler cranes, the tracks can extend
outward, providing the crane with more stability.
Crawler crane models, on which the crawler tracks can
extend, are rated at 85 percent of the minimum weight
that can cause the crane to tip at a specified radius with
extendable tracks are rated at 75 percent. Crane radius
measurement is measured from the center of rotation to
the center of the hook after the boom deflects forward
when under load, as shown in figure 12-4.
Depending on the make and model, most crawler
cranes have a 360-degree working area. This working
area is divided into operating areas called quadrants of
The crane capacity is based on the
quadrants, such as for over the side, over the drive end,
and over the idler end, for a crawler-mounted crane (fig.
12-5). The capacity of the crane may change when
rotating a load from one quadrant to another. This
information is provided on the crane load chart.
The truck-mounted crane (fig. 12-6) consists of a
truck carrier and house (upper revolving unit) and is
categorized under the 82-00000 USN number
registration series. The truck carrier can travel from
the basic boom, Crawler models that do not have
different jobsites at 20 to 35 mph.
Figure 12-6.Truck-mounted crane.