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Signalling on a Model Railway with David Stirling from the Signalling Record Society.

 

This was a very well attended meeting with the room bursting at the seams. We began with a photo of a very complex array of semaphore signals from Rugby station where the building of an overbridge had necessitated the addition of a second tier of signals, to ensure the sky was behind them, making them clear to see. Drivers had to have intimate knowledge of the route to interpret the signals.

 

David explained the purpose of railway signals, which is to indicate to drivers when it is safe to proceed. As well as signals around stations and at the end of sections, they are also needed to protect level crossings, rotating platforms and swing bridges. Block working was introduced in the late 19th century; before that, a time delay between trains was thought to be sufficient to keep them safe; it was not! Railway companies varied in their application of signalling. The Board of Trade was responsible for introducing and enforcing rules on the railways, however, the railway companies rarely ‘retro-fitted’ newly introduced equipment until track layouts were changed. Accidents and near-misses were often the impetus for change. The 1873 Wigan accident was followed by new rules about facing point locks to ensure a train could not ‘split’ the points.

 

We looked at a variety of signalling diagrams showing the likely location of signals. On the approach to a station, there would be a Distant signal. In the past, this was square ended and the driver would stop at it. Later it gained its characteristic fish tail and indicates the state of the following signal which might be a Home signal or sometimes an Outer Home. These are stop signals. At the end of the station is the Starting signal (sometimes an Advanced Starting). The Distant signal could only be ‘Off’ when all the signals ahead were also clear.

 

David told us about various different layouts and the safety features associated with them like catch points and locking bars. Signals also have to protect converging tracks and crossovers. There were a variety of Shunt or Ground signals often used to protect the main running line from trains coming out of goods sidings; catch points were sited here for the same purpose. Loose coupled goods trains were a particular problem despite having a brake van at the opposite end from the loco. A violent snatch on the couplings could break the train and leave wagons free to roll out of control. On single track lines, tokens were used to ensure only one train could be in a section at a time. We saw some examples of token exchangers; devices which delivered the token for the road ahead, while collecting the previous section’s token.

 

It was a very informative evening about a complex aspect of railway operation.

 

Nick Coppin