رافعة جمالونية
الرافعة الجمالونية gantry crane هي crane built atop a gantry, which is a structure used to straddle an object or workspace. They can range from enormous "full" gantry cranes, capable of lifting some of the heaviest loads in the world, to small shop cranes, used for tasks such as lifting automobile engines out of vehicles. They are also called portal cranes, the "portal" being the empty space straddled by the gantry.
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The terms gantry crane and overhead crane (or bridge crane) are often used interchangeably, as both types of crane straddle their workload. The distinction most often drawn between the two is that with gantry cranes, the entire structure (including gantry) is usually wheeled (often on rails). By contrast, the supporting structure of an overhead crane is fixed in location, often in the form of the walls or ceiling of a building, to which is attached a movable hoist running overhead along a rail or beam (which may itself move). Further confusing the issue is that gantry cranes may also incorporate a movable beam-mounted hoist in addition to the entire structure being wheeled, and some overhead cranes are suspended from a freestanding gantry.
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معرض
A ZPMC gantry crane used for construction of the British aircraft carrier HMS Queen Elizabeth
A primitive gantry crane to put a stagecoach on a flat car. The drawing is exhibited in Deutsches Museum Verkehrszentrum, Munich, Germany.
1 short ton (0.89 long tons; 0.91 t) capacity portable gantry crane
