a track machine that lays rails and ties during the construction of new railroads and the repair and maintenance of existing ones. Track jacks were first used in the USSR in the 1930’s.
Track jacks are operated cyclically or continuously. Those designed for cyclic operation move on tracks and are used on sections where track must be lifted for repairs. Hoisting tongs engage the rails. The machine has bedplates, which are moved by hydraulic jacks or jackscrews and supported by the ballast between the ties or on the sides of the roadbed. As the bedplates move out, the rails and ties are lifted together with the machine. Additional ballast is applied to the roadbed and the rails and ties are set back in place on a higher level. When the bedplates are raised, the machine’s wheels rest back on the rails and the machine can move to a new section, where the lifting process is repeated. Track jacks develop a force of up to 340 kilonewtons (34 tons-force) for a height of up to 40 cm. Some track jacks have a mechanism that shifts the rails and ties horizontally; such machines are used to straighten tracks.
Track jacks designed for continuous operation are called crawler track jacks and are used in the construction of new railroads. Two freely revolving caterpillar treads are mounted on a wedge-shaped plate located on the track jack. The plate is set under the track being raised in such a way that the ties are supported by the caterpillar treads. The plate is usually attached by cables to a tractor-mounted ballast regulator, located some 15 m ahead of the machine. When the track jack moves at a speed of 2.2–3.8 km/hr, the rails and ties are lifted to a height equal to the thickness of the plate (about 20 cm).
S. A. SOLOMONOV