page_title: Tamping machine
section_title: Tamping units
hierarchical_section_title: Tamping machine / Standard tamping machine arrangement / Tamping units
caption_attribution_description: English: System7 fully hydraulic tamping head
context_page_description: A tamping machine or ballast tamper is a machine used to pack the track ballast under railway tracks to make the tracks more durable. Prior to the introduction of mechanical tampers, this task was done by manual labour with the help of beaters. As well as being faster, more accurate, more efficient and less labour-intensive, tamping machines are essential for the use of concrete sleepers since they are too heavy to be lifted by hand. Whilst also available as a plain tamper with no lifting or lining function this article will focus on the multi function machines.
  Early machines only lifted the track and packed the ballast. More modern machines, sometimes known as a tamper-liner or tamping and lining machine, also correct the alignment of the rails to make them parallel and level, in order to achieve a more comfortable ride for passengers and freight and to reduce the mechanical strain applied to the rails by passing trains. This is done by finding places where the sleepers have sunk from the weight of the passing trains or frost action, causing the track to sag. The tamper lifts each sleeper and the rails up, and packs ballast underneath.
context_section_description: The Tamping units of most Tamping machines will consist of:
  A set of tines either 8 or 16 per sleeper divided evenly between front and rear of sleeper
  Mounting or "guide" rods that allow the unit as a whole to move up and down in a linear motion
  Support frame
  Squeezing arms
  Tine mounts, can be either part of the squeezing arm or attached to it via a pin to allow swiveling depending on type of tamping machine
  To generate the vibration needed for penetration and consolidation there are two leading methods commonly used:
  Using a hydraulically driven eccentric shaft attached either to the end of the squeezing cylinders or acting as the pivot point for the squeezing arms
  Using a special squeezing cylinder and valve assembly to oscillate the tines
  A less common method more often seen on tamping head attachments for excavators is to use a motor driven vibrator assembly that is directly bolted to the support frame.
caption: System 7 fully hydraulic tamping head
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