Truck-Mounted Cranes

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 operation. 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. Truck-Mounted Cranes 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. 12-3