How Does a Dump Truck Work?

by Jack Gerard

Construction of a Dump Truck

Though there are several different dump truck designs, the basic components of dump trucks remain more or less the same for all of them. The main body of the dump truck is generally based on that of a flatbed truck, with one axle beneath the cab and anywhere from one to three axles beneath the dump box. The dump box itself generally has a tailgate that is hinged at the top so that it will open automatically when it is being dumped. The dumping mechanism is powered hydraulically in order to prevent compression problems that can sometimes be encountered when using pneumatic systems. The engine of the dump truck can be either gasoline-powered or diesel-powered, but is generally a large internal combustion engine regardless of the fuel type used.

Dumping Mechanisms

The hydraulic dumping mechanisms used in dump trucks are generally one of two types. The most common type involves the use of one or more hydraulic pistons to lift the end of the dump box that is nearest to the cab. This causes the entire dump box to tilt, dumping whatever is contained within it. The other type of dumping mechanism that is found in dump trucks consists of a reinforced panel mounted vertically within the dump box itself, which has hydraulic cylinders holding it in place. The cylinders push it toward the back of the dump box, pushing anything within the box toward the back where it will be forced out through the hinged tailgate. The lifting type of dump mechanism is more popular with manufacturers because it is a simpler mechanism to produce and maintain, but some construction companies and other dump truck users prefer the other mechanism because it doesn't require extra vertical clearance to use.

Powering the Dump Truck

Power for both the dump truck itself and the dumping mechanism is provided by the truck's internal combustion engine. The truck itself is powered in the same means as any other gas- or diesel-powered truck, while the pumps that power the hydraulic cylinders are powered by the power take-off (PTO) connected to the truck's transmission. This means that the truck has to be running before the dumping mechanism can be used. In order to prevent potential accidents, the PTO generally cannot be engaged unless the transmission has been placed in the neutral position beforehand.

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