Rail 101 - Rail Shapes 1

There are many different types of rails, and I’ll briefly try to explain some of them and their typical uses. This article is part of a series I'm starting to explore some of the basics of rail. You can find my first article exploring the length of rails here. If you'd like to follow this series of articles then follow the #rail101 tag for more like this

Vignole rails / Flat bottomed rails.

This type of rail is the most standard type of railway rails you’ll find. There are many different shapes and sizes of them but they share a few common features. They are symmetrical (vertically) and they have a flat base to enable them to sit on pads/sleepers.

This type of rail is the most common and makes up the vast majority of rails in service.

If you need to look up some dimensions of the myriad of profiles available then take a look at the British Steel railselector which I commissioned when I worked there.

Brief video of the railselector in action

Crane rails

Visually similar to flat bottomed rails – these aren’t usually grouped with railway rails as they are used in different applications. Symmetrical and having a flat bottom, their biggest difference to normal railway rails is their weight and much thicker web. This is needed to support very large axle loads from crane vehicles. Crane rails are also typically continuously supported i.e. they don’t sit on discrete pads/sleepers/ties.

Check rails

These are a special rail which the train actually does not run on top of. Rather they run against them in areas where extra steering forces for the axles may be needed, such as very sharp curves or to provide additional safety when a switch and crossings. They essentially restrain the flat back of the wheel to direct it around sharp curves or to the correct route set at switches and crossings. Various rails can be used as check rails – even normal flat bottomed rails in come circumstances, however generally the most common check rail section used today is 33C1 with virtually identical equivalents U69 and UIC33 depending on which specification is being used.

Grooved rails

Grooved rails as their name implies, have a groove in them. This deep and wide groove is used to provide flangeway clearance for railway vehicles such as trams. Typically laid into road or grass type areas the grooved part of the rail stops the road surface fouling the space needed for tramway wheels to pass. Grooved rails may also be called tramway rails, but this isn’t a name I like as many tramways also contain a significant proportion of normal railway rails too leading to potential confusion.

A grooved rail is like a flat bottomed rail made up from a head, a web and a foot. However grooved rails because of the groove also have an extra part, often known as the keeper, (as it keeps the road away from the wheels), or sometimes the horn (as it perhaps looks a little like a Rhinoceros horn???)

As these rails are typically set into the road surface in use you see very little of them, just the head, the groove and the top of the keeper are visible. The keeper sometimes serves a double function, not only restraining the road from obstructing the rail wheels, but also it is sometimes used to provide a built-in check rail. The back of the wheel contacts the keeper to provide extra steering forces as a tram negotiates a curve.

On a personal note I’m not exactly enthusiastic about using the keeper as a check rail. The keeper thickness is generally quite small and so the wear allowance is also small. Also if there is a failure of the keeper, the wheelset then travels the wrong side of the keeper and pulls the axle into a derailment which is not ideal. I’m aware it is normal practice in many networks, so perhaps my concern isn’t justified. But this is my article so I’ll voice it anyway!

Guard rails

Guard rails are used to control the path of a rail vehicles when the normal guidance from the rails has failed. That means they are only there to guide the train when things have already gone very wrong. Typically they are seen around bridges, tunnels and other vulnerable areas where a derailment could be catastrophic if the vehicle left the route. Many different standard rails are used as guard rails, so you’ll not usually see a separate rail section named as a guard rail. Some people in the industry also call check rails - guard rails which can add a little confusion.

Image from Wikipedia of a bridge in the USA showing guard rails inside the normal "running" rails

To keep this article length to within my aim of a tea-break read, the second part of this article can he found here

I hope you have enjoyed this bite-sized insight into the world of rail. Please check out my other articles for more rail related content. Contact me if you you think I can help add value and remove cost from your railway.

If I've missed any names or important categories of rails then please comment below. Likewise if you know someone who may like a tea-break rail read then feel free to share this with them