# Special designs

## Expansion joint

Movements (due to longitudinal forces) of the rail on bridges (e.g. due to braking and acceleration) and major temperature effects are compensated by dilatation joints (expansion joints).

An expansion joint consists of two jaw and tongue rails, which can move against each other.  Expansion joints are generally fitted over moveable bridge bearings, in areas where there is mining subsidence, at the tunnel mouth or in steep sections of the line. Expansion joints are installed in order to absorb stresses (displacements) in the ballast bed caused by movements of the bridge frame.

The drag shoe ejector is used to eject drag shoes, if they are used when shunting to brake the wagon before it reaches the shunting department. The device consists of a wing rail and a tongue rail, with a gap of 10 mm between them. The wagon pushes the drag shoe forward allowing it to slide on the wing rail into a collecting basin. On the opposite rail a check rail is fitted which prevents the derailment of the train.

In order to obtain the most effective braking effect before ejecting the drag shoe, these are fitted at a certain distance (depending on weight and speed of the wagon) in front of the ejecting device. This task, however, is now generally done by electronically controlled track brakes.

## Compensation rails

In the old jointed track and today in continuously welded rails the rail joints (fish-plated joints or welded joints) of the opposite rails should lie parallel to each other. As a result, the rails which lie in the curve are shorter on the inner side than on the outer side. This rail which is shorter than the parallel one is called the compensation rail. It is possible to work out by mathematical calculations the lengths of both rails and thus manufacture them to the exact length before installation.

## Guide rail

Guide rails can be installed in curves with a radius of r = < 300 metres in order to relieve the outer rail of the curve. While running through this curve the wheel should be made to run on the inside of the guide rail and thus prevent wear and tear on the outer rail of the curve.

This rail must be fitted on the inner side of the track, if no rails with a minimum tensile strength of 880 N/mm² are present there. The distance to the normal inner curve rail should be 60 mm. Also an infeed or outfeed should be present at the beginning and end, so that the wheel is not derailed or does not climb up. The guide rails are not welded but connected together by fish plates in lengths of 15 metres, so that they can take the temperature and the track can creep.

Guide rail

## Guard rail

Guard rail on ballastless track

If the vehicle is derailed it should get the necessary support so that the wheel can be held on the rail or in the gauge. The distance between the guard rail and running rail is 80 mm. These guard rails are used on uneven bridge tracks, on layouts which are unusual and with longer transition lines with a steep slope to a gradient free track.

The guard rails serve as a derailment protection so that climbing up of the wheelset on the running rail is prevented, since the opposite wheel runs against the inner guard rail.

In the case of a tread width of approximately 135 mm and a groove width of 80 mm for the guard rail the wheel cannot derail.  Guard rails are not welded together, but connected by fish-plates in lengths of about 15 m.

## Guide Rail

Guide rail with catching device