A day in the life of a jointed track

ΔG = αLΔT°. Free expansion For a free thermal expansion jointed track the rails expand and contract freely and the track components do not provide any resistance to oppose this rail length variation. The joint gap varies linearly relative to the rail temperature. The figure below presents the joint gap variation for a jointed track formed…

A (Hallade) moment to remember

For the track realignment methods (Hallade or similar) the existing alignment is surveyed by measuring the outer rail offsets (versines) to overlapping chords. One such setup is drawn below: A’, B’, C’ are points on the outer rail of the track and for point B’ the versine B’D’ =  vB ex is measured to the chord A’C’. We…

When a 20 m rail is 20 m long?

Perhaps I’m splitting hairs here, but it is a fair question to ask: When a 20 m rail is 20 m long? Please, have your say and feel free to comment below, after voting! And this is not a trap question like “Which weighs more: 1 kg of steel rail or 1 kg of feathers?”. Later edit: By…

Significance of jointed track parameter variation

Joint resistance The normal rail joints are designed to allow the rail length variation due to temperature. To do this the joints have a well-defined maximum gap and a set of installation parameters to provide an optimum behaviour at temperature variation and a good maintenance regime. Any modern rail joint has a standard bolt tightening torque…

Checking the versine survey precision

A field measurement of any kind is never exact and intrinsically contains errors (NJDoT Survey Manual – 2014). For track topographical measurements some of these errors are known and eliminated by applying appropriate corrections and compensations. Even after all known errors are eliminated however, a site measurement will still be in error by some unknown value. To minimise the…

Types of versines used for track realignment methods

There are three types of versines used for the track realignment and rectification methods (Radu, 2003): Measured (existing) versine – the versine measured with a real chord on the outer rail of the real existing track. This is the result of the versine (Hallade) survey and based on it are computed the track offsets (slues…

Track Realignment and Rectification

The running of the trains over the railway track is inducing vertical and lateral forces that, in time, are affecting the track alignment, changing incrementally the installed track and causing track irregularities.  On curved track this deterioration process is more significant due to the additional effect of the lateral (centrifugal) acceleration. When the irregularities become…