Characteristics

Figure 7-38.—Dumping the load. reading and understanding the operator’s manual for the model of dump truck you are assigned to operate. This section covers the basic characteristics and operations of dump trucks. CHARACTERISTICS A typical dump truck is equipped with a dump body that is hinged to the rear of a subframe which is mounted directly on the truck chassis. Dump bodies range in structural strength and size to support different operations. That is why it is important that the operator knows the design and capacity of the dump truck assigned to operate. You do not want to haul quarry rock in a dump body designed to haul and heat asphalt. The quarry rock can damage the dump body and render it useless for asphalt operations. The components of a dump truck body are shown in figure 7-36. A hydraulic hoist assembly is used to raise and lower the dump truck body. The hydraulic pump is driven by a propeller shaft connected to the power takeoff (PTO). A variety of ways are used to engage the PTO on dump trucks used in the NCF; therefore, consult the operator’s manual for specific instructions on how to engage the PTO and hoist assembly. DUMP TRUCK OPERATIONS During dumping operations, the truck should be on level ground or inclined uphill with the front of the truck facing downward. When the truck is in position, release the lower latches of the tailgate with the hand lever at the front left corner of the body (fig. 7-37.) Then engage the control for the dump truck body. Hydraulic pressure will begin to hoist the dump truck body, and as the body rises, the load will slide backward under the open tailgate (fig. 7-38, view A). If the load piles up and blocks the tailgate (fig. 7-38, view B), place the truck in low gear and move it forward until there is more space to dump the remainder of the load. If the load does not slide out easily, have someone dislodge it with a long-handled shovel, taking care not to stand in the immediate dumping area. When dumping a load of rocks or other large solids, see that the tailgate is latched at the bottom, but unfastened at the top, so that the tailgate can drop down and the load can drop, as shown in figure 7-39. Not all dump trucks have tailgate wings. On those that do not, you have to drop the tailgate down and support it with chains. To spread a load over a large area, Figure 7-39.—Tailgate rigged for dumping large material. 7-31