Spring Vale Electrical Controls (Part 1)

In the 1950s, mechanical signalboxes were still very common, where semaphore signals were operated by wire and points by rodding from a mechanically-interlocked lever frame in the box. Block Signalling Instruments were used to authorise the passage of trains between signal boxes. Over the years, various other electrical controls were applied, on a piecemeal basis, according to perceived risk.

Introduction:

As an example, we can look at the situation which applied at Spring Vale Sidings box in 1961 (after remodelling). There's a brief description of this signal box here. It's helpful to keep in mind the layout, shown below. Clicking on the layout gives an enlarged image which can be downloaded or printed.

The Drawings:

A group of six drawings detailed the electrical controls and a set of dyeline prints was kept in the equipment cupboard at the box for use by the Signal & Telegraph Lineman during his visits. The drawings were controlled by the London Midland Region Divisional Signal Engineer's Office at Crewe. I managed to obtain a partial set of drawings which have been scanned. The index to these drawings is here. The image can be viewed in various sizes, downloaded or printed. The assistance of British Railways back in the '60s in furnishing these obsolete drawings is acknowledged.

Drawing Symbols and Labelling Conventions:

The symbols for the various circuit elements are drawn in the style used back then and, in general, the symbols are peculiar to railway signalling so they may be unfamiliar. Nowadays, much simplified symbols are used (although these are probably harder for the novice to follow). The student also has to get used to the letter codes used to label components. A group of letters and figures is used to identify each component. For instance, the designation '20RGCR' means [20][Red][Signal][Proving][Relay]. Once you've mastered the principal codes, understanding diagrams becomes much easier.

The Drawing Set:

This set of drawings was numbered CW.137/59/x, where 'x' was the sheet number. These drawings were prefaced by a Contents and Ordering page. The 'Contents' gave details of the drawing pages and 'Ordering' was a brief stores description of the various electrical items. The list of sheets was as follows:-

1 : Controls (I'm afraid this sheet has not survived)
2 : Block Control
3 : Lever Locks
4 : TPR's, TPS & TXR
5 : Repeating
6 : Bonding (later version)

There is also an earlier bonding diagram, before remodelling here and a later diagram outlining alterations to be made here.

Each of these sheets can be viewed in various sizes, downloaded or printed.

In the next instalment (here), we'll look at these sheets in a little more detail.

[For a long time, many of the above links stopped working, as explained here. I've finally restored most of them. Hope it helps: 28-Dec-2015]