Expansion Joint

Our ground is a reclaimed swamp, former coal waste tip subject to periodic inundation with brackish water when the sea entrance to the adjacent creek is blocked by sand build up. As a result corrosion is a major problem and in-ground structures rarely last more than 10 years before needing replacement. There is a constant on going programme of refurbishment. Aluminium would have an even shorter life due the enhanced corrosion in such a salty environment.

Our normal rail sections are made from 10 x 25 mm flat bar welded to ties of 12 x 25 mm flat bar which are in turn screwed to hardwood sleepers. Transitions and other curves are formed in a jig before welding. All Steel is mill finished mild steel.

This Expansion Joint is a slight modification of our usual design which was in turn derived from something originally created by the Sydney Live Steam Locomotive Society.
It has been fabricated from pieces of 12 x 25 mm bar MIG welded to the end of our usual 10 x 25 mm bar stock that we use for rail, hence the slightly offset appearance of the outside rails. The catch rails are formed from offcuts of 10 x 25 mm bar with the last 30 mm bent as shown and welded to the steel ties.

Construction

Overhead view
The 150 mm (6") ruler is for scale showing the general arrangement. The wooden sleepers (that have not been screwed down in this picture) rest freely on the support which is embedded into the ground underneath the joint.

Side view
This shows the milled slots on which the joint slides.

Side view
This shows the milled slots on which the joint slides. A section of standard rail awaiting refurbishment can be seen in the background.

Support structure
This is constructed from standard sections of heavily galvanised steel profile. This is bedded into the ground (see next picture) and ballasted so that the top of the longitudinal section (where the spanner placed for scale rests) is level with the normal ballast level. The wooden sleepers rest on this section but are not fixed to it in any way.

Disassembled joint
This shows how each section is constructed so that the inner half rail is the fixed part with a tapped hole to suit the bolts being used.

Two Views
The end of the portion carrying the catch rails showing how they have been anchored to a short section of steel tie so that they do not move out of position in service.

Detail view
The assembled joint.

Detail view
The assembled joint

Installation

Sub Frame
View showing the subframe being try fitted into the ground between the adjacent track sections

Sub Frame
View showing the substructure placed in ground. The subsurface has been dug out so that the tops of the longitudinal rails is 30-40 mm below the general ground level.

Sub Frame
The sub frame is shown ballasted into place. The expansion joint assembly has been attached to the adjacent rail sections and the bolts on the fishplates tightened finger tight. The length of the subframe has been constructed so that it supports at least two sleepers of the adjacent tracks sections.

Installation
The expansion joint is almost finished in this picture. Ballast has been placed and rammed in around the sub frame to hold it firmly with any ballast holding the wooden sleepers of the joint itself brushed away. In this picture this final clearing has not been completed at the left hand end.