Tracklayer

Tracklayer 

a machine that transports and lays railroad ties and rails. It is used in the building of new railroads and the repair of existing ones.

Tracklayers were first used in the USSR during the 1930’s. The most widely accepted method of laying track is the sectional method, in which complete sections of track are laid. These sections, which are preassembled in track machine stations, are identical in length to the standard rail length, which in the USSR is either 12.5 m or 25 m.

Tracklayers that move on rails consist of a tracklaying crane, flatcars with rollers that transfer sections of rails and ties, and one or more motor-driven flatcars that transport stacks of sections along the length of the train and are also used for maneuvering operations.

The tracklaying crane is self-propelled and has a horizontal boom, beneath which the flatcar bearing the stack of sections is located. Trolleys equipped with hooks move along the boom and lift the top section of the stack. The section is moved forward along the boom and laid on the ballast base or the roadbed. After the section is connected to the previously laid section, the crane and flatcars proceed along the newly laid section and begin laying the next one. Such tracklayers are also used as dismantling machines: the tracklayer grips the section in front of it and loads the section on itself. It then moves backwards, disengaging and gripping the next section. Tracklayers on rails cover up to 1,200 m/hr. The crane’s lifting capacity is 4.5–21 tons and the time for laying one section is 1–2 min.

Tractor-driven tracklayers with caterpillar treads are used in the construction of new railroads. They have a boom that is supported in front by the tractor and in the rear by a gantry that spans the track. The gantry is mounted on two trolleys that are supported by caterpillar treads and placed on the roadbed, aligned with the ends of the ties. Flatcars or trolleys loaded with stacks of sections are located under the gantry. Winches mounted on the boom hoist the top section of the stack. The tracklayer moves forward with the section and deposits the section on the ballast base. After connecting this section with the previously laid one, the flatcar and its stack of sections are moved onto the new section by means of a traction winch. The next section is then gripped, and the laying process is repeated.

Tractor-driven tracklayers have greater maneuverability than tracklayers that move on rails and can lay track ahead of bridges, pipelines, or overpasses under construction, thus reducing the railroad’s construction time. They cover 1–2 km per shift.

Gantry tracklayers are used abroad. They consist of several light gantry cranes that move on rails or on angle brackets temporarily installed along the ballast base. The stacks of sections are located under the gantries. Cranes grip the top section, move it forward, and lay it in place.

Future improvement of tracklayers will include automated controls and the development of a continuous method of laying track.

S. A. SOLOMONOV