Jointed track breathing

Rail breathing Normally on the railway track the rail is fixed through a set of superstructure elements (fastenings, sleepers, ballast) that opposes the rail tendency to expand or contract due to temperature variations. This fixation is achieved through friction forces and once the rail axial forces are above these friction forces, the rail will start…

Joint Resistance Force

All the railway track fishplates for mechanical joints are designed to provide a gap to the rail web. This gap, together with the wedge shape of the fishplate section ensure, by tightening the joint bolts, the correct alignment of the rail head between the two jointed rails. The bolt tightening torque is developing in the bolt a…

Modern Railway Track

Motto: Tolle lege! Perhaps the best and most complete technical book about track is “Modern Railway Track” written by Dr Coenraad Esveld, Professor of Railway Engineering at Delft University of Technology.  A detailed Table of Contents of the second edition can be found here together with a brief selection of the book. The second edition, written…

White rails

When exposed to temperature variations, the rail tends to vary its length. If this tendency would be freely allowed, for a temperature variation Δt° the rail length L will vary by ΔL. This length variation is ΔL = αLΔt°. If, on the other hand, the expansion is not permitted in any way, and both ends of…

Track Longitudinal Resistance

There are two types of railway track superstructure from the point of view of the response to rail temperature variation: free thermal expansion (FTE) track superstructure which allows the rail to freely vary its length due to temperature variation. This superstructure does not provide reliable constant and easy to control and maintain track longitudinal resistance…

When can a rail be called long?

Thermal expansion When exposed to temperature variations, the rail tends to vary its length. If this tendency is freely allowed, for a temperature variance Δt°, the rail length L will vary by ΔL. This length variance can be computed as: ΔL = αLΔt° In this formula, α is the steel expansion coefficient = 11.5·10−6 mm/mm°C. If…

Maximum joint expansion gap

  A rail joint is a track component that connects two pieces of rail and it provides room for rail expansion and contraction due to the changes in temperature. The mechanical rail joint is designed to allow a gap variation and, as such, has two well defined limits of this gap. The minimum gap of a mechanical rail…

Buckling prevention

The track buckling happens in hot weather because of a multitude of factors but it is massively influenced by the track longitudinal and lateral resistances. Both these resistances have three levels of action: Figure 1. The three levels of track lateral and longitudinal resistance – between rail and fastening – at this level all the modern fastenings are behaving…