Jackson 6700 switch tamping machine
A tamping machine
or ballast tamper
is a machine used to pack (or tamp
) 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 (usually over 250 kg (551 lb)) 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. When the sleeper is laid down again, the sagged rails now sit at the proper level. In cases where frost action has caused adjacent rails to rise higher, ballast tampers can raise rails above their original level to make the line level again. "Lining" rails doesn't involve ballast tamping, it merely ensures the rails are perfectly parallel and straight as possible. Combining tamping and lining into a single machine saves time and money, as only one machine needs to be run over the track to perform both functions. Read more...