The most common gantry cranes feature two supports. One of the pillars can be rigidly connected to the axle (rigid or spatial support), and the other one is hinged (flexible or flat feet). In gantry crane with a span (distance between the crane rails) of less than 25 m both bearings are hard. Track each of the pillars of heavy crane (lifting capacity of 1,000 tons or more) may consist of two or more rails (undercarriage in this case have the spatial equalizer suspension). In some cases the rails are placed at different levels of support at different heights. The semi-crane design implies the bridge resting on one side of runway, and the other one – on the support legs. Trucks are moving the bridge crane. The mechanism of the trolley as lifting mechanism can be mounted on a trolley (autonomous trolley) or on a metal bridge structure. Lifting mechanism is oftentimes mounted on the metal, and a truck equipped with a movement mechanism. Gantry crane has a metal structure: mechanisms of lifting cargo, the trolley and crane movement. Grab cranes are equipped with a special gripper and winch mechanism in the presence of lifting mechanism circuit grapple. If there is a need for orientation of cargo, the carriage is provided with a rotatable part as steel truck cranes.
The weight of cable trolleys considering the weight of cargo and towing winch accounts for 5-10% of weight of the nominal load. The cable trolleys are used only by cranes of group mode of 1K – 3K, since rolling cargo rope pulley block on blocks significantly increases the resistance of the trolley, which leads to accelerated wear of the rope. To prevent excessive sagging hoist rope it is necessary to increase the mass of the cargo suspension. Suspension trolley for these cranes is typically produced in two type: monorail and double rail.
At monorail cable trolley to reduce bending moment, bending monorail suspension frame blocks are made with spherical support elements. In addition to the limited life of the monorail, an unsustainable position of the truck cab and in the transverse direction. Lateral swinging carts and mobile booths, which can not be rectified using the thrust rollers adversely affect the working conditions of the crane. In the event of lateral loads on the trolley or in case of eccentricity in mechanisms to traverse when lifting cargo pressure rollers have an impact on the bottom chord of the bridge. In some cases, the design implies additional monorails, which increases metal consumption structure. This solution is widely applied in case of heavy loads and work on sophisticated sites, the design is practised by such industry innovators as Granada Material Handling, gantry hoist and overhead crane manufacturing experts supplying the demand across UK and EU markets.
The most common type of cranes implies trolleys moving on rails laid on the lower belt. The frames of these trucks ensure uniform load distribution on rail guides. When using trucks with cargo winches at one end of the frame the hinge connection for crossbeam carrier racks with running wheels is hinged. The cable trolleys cross member is attached to the end of a beam on with the pulleys. In this case, the reduced height of the trolley, which allows the frame of beams running wheels mounted on the ends of the axis of the crossbar. To improve the layout of joints resistant to the bridge, in the small-sized motorized vehicles gears are used or gear movement is performed with central drive.