Plug (track construction)
Plug is in the construction and in maintenance of tracks with ballasted method applied to vertical unevenness (height) and horizontal displacements (direction) in the track position by lifting and / or moving of the track, switches and crossings by relining the sleepers with gravel to remove. In the past, this was done manually with a winch, ballast fork and tamping hoe, today, however, mostly mechanically using leveling, straightening and tamping machines that are partly self-propelled .
With mechanical tamping, four steel tamping picks are dipped vibrating from above into the ballast bed for each rail-sleeper support point when the track is slightly raised. The pimples vibrate horizontally at a frequency of 35 Hz. Small paddles on the ends of the pimples agitate the gravel as it slides under the sill and compacts as the vibrating pimples are slowly pulled up. Tamping machines have been tamping two sleepers at the same time since 1965, today mostly three, since 2005 also four sleepers. Fundamental patents for the so-called asynchronous pressure-vibration tamping were granted in 1953.
Modern tamping machines level the track and stabilize it dynamically while they work continuously at 500–1000 meters per hour and also work on areas of switches and crossings. They can be part of a track construction train .
In technical jargon , the tamping of the ballast bed is called gramping and the machine is called a track tamping machine , gramper or gramping device.