Rail profile
It took many decades to improve the quality of the materials, including the change from iron to steel.
Minor flaws in the steel that may pose no problems in other applications can lead to broken rails and dangerous derailments when used on railway tracks.
Worn, heavy rail from a mainline is often reclaimed and downgraded for re-use on a branch line, siding or yard.
[2] Both wooden and strap-iron rails were relatively inexpensive, but could only carry a limited weight.
The metal strips of strap-iron rails sometimes separated from the wooden base and speared into the floor of the carriages above, creating what was referred to as a "snake head".
The long-term maintenance expense involved outweighed the initial savings in construction costs.
[4] The earliest of these in general use were the so-called cast iron fishbelly rails from their shape.
John Birkinshaw's 1820 patent,[5] as rolling techniques improved, introduced wrought iron in longer lengths, replaced cast iron and contributed significantly to the explosive growth of railroads in the period 1825–40.
The cross-section varied widely from one line to another, but were of three basic types as shown in the diagram.
The first steel rails were made in 1857 by Robert Forester Mushet, who laid them at Derby station in England.
Silicon is preferentially oxidised by oxygen and is added to reduce the formation of weakening metal oxides in the rail rolling and casting procedures.
To resist wear, a thin iron strap was laid on top of the timber rail.
The system had the flaw that every so often the passage of the wheels on the train would cause the strap to break away from the timber.
Buses are steered normally when off the busway, analogous to the 18th-century wagons which could be manoeuvered around pitheads before joining the track for the longer haul.
Its simple shape is easy to manufacture, and it was widely used before more sophisticated profiles became cheap enough to make in bulk.
It was notably used on the Great Western Railway's 7 ft 1⁄4 in (2,140 mm) gauge baulk road, designed by Isambard Kingdom Brunel.
It was designed to be laid straight onto the ballast, but the lack of sleepers (ties) meant that it was difficult to keep it in gauge.
Other lines which adopted it were the Hull and Selby, the Newcastle and North Shields, and the Manchester, Bolton and Bury Canal Navigation and Railway Company.
[11] When it became possible to preserve wooden sleepers with mercuric chloride (a process called Kyanising) and creosote, they gave a much quieter ride than stone blocks and it was possible to fasten the rails directly using clips or rail spikes.
It was an expensive method of laying track as heavy cast iron chairs were needed to support the rail, which was secured in the chairs by wooden (later steel) wedges or "keys", which required regular attention.
[13] One of the first British Standards, BS 9, was for bullhead rail, which was originally published in 1905, and revised in 1924.
It can also be found on heritage railways, due both to the desire to maintain an historic appearance, and the use of old track components salvaged from main lines.
[15] However, the process of replacing track in tunnels is a slow one, due to the difficulty of using heavy plant and machinery.
Grooved rail was invented in 1852 by Alphonse Loubat, a French inventor who developed improvements in tram and rail equipment, and helped develop tram lines in New York City and Paris.
Failure to clear the grooves can lead to a bumpy ride for the passengers, damage to either wheel or rail and possibly derailing.
The traditional form of grooved rail is the girder guard section illustrated to the left.
If the weight is carried by the roadway subsurface, steel ties are needed at regular intervals to maintain the gauge.
It can be set in trench grooves cut into an existing asphalt road bed for Light Rail (trams).
[citation needed] The American Society of Civil Engineers (or ASCE) specified rail profiles in 1893[20] for 5 lb/yd (2.5 kg/m) increments from 40 to 100 lb/yd (19.8 to 49.6 kg/m).
Attention was also focused on improved fillet radii to reduce stress concentration at the web junction with the head.
