Fishplate extinction

For those that thought a fishplate was something used to serve your dinner upon I should probably explain that this is a railway related article, not one discussing the best way to serve your rainbow trout supper.

 Most people in the rail industry today will know what a fishplate is, but will future generations ever contemplate the origins of the name for this disappearing part of rail infrastructure?

 For those that are unfamiliar with fishplates, these are strips of steel (usually) that join two ends of a rail together via bolts through holes in the rail to allow the ends of the rails to remain aligned with each other as a rail vehicle passes over them. Some readers may be old enough to remember the ‘click-ety-clack of trains’ passing over this jointed track and it is still present in some routes. Used for centuries the origins of the fishplate name seem to be unclear. Other names for the same item used are Joint bar, splice bar, and tie plate but there are probably other names used particularly when the bolts are seized!

Some believe the name is derived from the French “ficher” which means to fix or peg (I hope), others that the name came from the ‘fish’ used to strengthen ships masts in a similar manner. I have also heard reference to the plates used to join fishbellied cast iron rails, and others referring to the cast fins that were present in early items. Some even believe the name came from the early items looking like the kitchen fish serving plate. The first formal mentions of the name came in 1847's where patents were filed for this item used to join rails. Whatever the origins of the name, the humble fishplate seems to be an item undergoing rapid decline.

The patent application drawing for a rail fishplate (1847)

The rail industry generally regards joints in the rail as weak points, as they require more maintenance and fail more frequently than the parent rail and I would not disagree. There has been a drive to decrease the number of joints required in track and therefore a drive to increase rail lengths. The longest single piece rails are now 150m I believe, with 100+m available from several suppliers including our two British Steel rail plants in Europe.

There have of course been developments in welding rails to form long lengths of continuously welded rail (CWR) to reduce the number of physical joints required. The end result is a massive reduction in the ‘clickety-clack’ of rail travel and a huge decrease in the number of fishplates in use. With the increasing use of welding (such as mobile flash butt) to join rails together on site (see video below), combined with the high profile accident in France in July 2013 where 6 people lost their lives, being likely caused by a faulty fishplate joint, I have to ask "Are the days of the humble fishplate are numbered?", such are the industry drivers to eliminate this sort of rail joint.

A Network Rail mobile Flashbutt welder in action

However fishplates do have some key advantages in some cases. In most forms the fishplate joint allows for thermal expansion. The joint is not completely rigid and so allows thermal expansion and contraction of the rail to take place. With the short rail lengths that usually accompany fishplate use, this means track is not significantly stressed, unlike CWR. This poses some advantages on particularly tight curves where CWR usage may be impractical as the curve tries to ‘pull straight’ when the CWR is in tension. Equally other areas where rail stresses can prove problematic, (such as around switches), mean that fishplates are still the default solution to some problems. There are some excellent articles written by Constantin Ciobanu that show how fishplates accommodate the thermal expansion of rails. An article here discusses jointed track "breathing" and I love this animation showing how the fishplate allows movement of the rails due to thermal expansion - taken from his article here explaining where the originals of "short" and "long" rail names.

 Animation showing how thermal length change of rail is absorbed by the fishplated joint

Whilst use of the humble fishplate clings on in some area of new track such as switches and crossings and very tight curves, do you think our future rail engineers will ever need to tension the bolts and check the gaps?

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