FAQ >> PORTABLE TRUCK-MOUNTED CRANE BOOMS

PORTABLE TRUCK-MOUNTED CRANE BOOMS

Another type of lifting equipment is the portable boom attached to a flat-bed truck to load and unload material. This type of boom has comparatively little horizontal reach flexibility but does swing on a turntable support mechanism at its base on the truck. These booms are not designed for erection purposes but for material handling where the loads are not more than 10-20 tons, at the most.

The truck-mounted crane booms are removable from the truck beds on which they are mounted. There are two forms of this portable type of equip- ment. One is the articulated, short height knuckleboom, which is frequently used to load material on and off the truck. They operate somewhat like the human arm with hydraulic controls to make the movements from the "shoulder" at the truck bed through the "elbow" to the "wrist" and "hand" at the load pick up end. This type of boom may have an attachment such as grapples, forks, or other boom attachments. The other form of truck-mounted boom is the telescoping variety similar to an hydraulic crane.

The truck-mounted knuckleboom with its multidirectional action makes this boom good for handling small packaged or palleted materials. The footing of the loader boom may be attached to the truck bed, or it may have the ability to travel along a flat bed or platform to reach materials and deposit them with greater horizontal range. The knuckleboom weighs more than a ton. Its load capacities range from a maximum of about 8000 lb with a 5- to 10-ft boom to one-third as much with a boom about three times as long. The largest units made have somewhat greater range and capacity, approaching a 10-ton limit.

The high-lift telescoping boom is generally attached to a truck bed next to the cab to distribute the load to all axles of the truck for the best stability. With the boom fully extended it can reach more than 80 ft and a jib can be added to reach as much as 140 ft. To improve the stability of such a high setup the boom supports have outrigger feet on the ground outside both sides of the truck bed.

The approximately 20-ft basic length of the retracted boom section allows it to be carried on a truck bed for traveling between uses. The boom can assume various angles in the vertical plane from a high of 800 above the horizontal for maximum height and lift down to essentially horizontal for an extended reach horizontally.

The load capacity of a telescoping boom ranges up to nearly 70.000 lb, but reduces geometrically with increasing height and radius of the boom just like any crane-type equipment. The truck-mounted telescoping boom, with its load capacity and working radius up to 24 ft, or so, is useful to handle stacks of bundled materials or small trusses transported by the truck and to be delivered to upper levels of a building. These materials could be loaded on the truck bed with the boom. Then the boom is retracted and stowed on the truck for travel to the place where the material would be unloaded for the construction.

A truck crane is designed for a more permanently attached boom and does not have much flat platform area to carry materials. That type of lifting and hoisting equipment is considered and discussed as a mobile crane in the next section.

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