Wednesday 31 December 2008

MIC - Lamps

The Mutual Improvement Classes of the old steam railways continue for today's preservation volunteers. This is one of a series of posts from notes of talks given by Jan. To find them all, select label 'MIC'.

When is a train not a train?
When it hasn't got a tail lamp.

On the running line, the red tail lamp is important to signify that a train is complete. Even in day time, it indicates clearly the last vehicle.

Some overseas railways hang a distinctive marker board on the last vehicle - often red marked 'LV'. In India I've seen red flags pressed into use but the nicest Last Vehicle marker I spotted was a spray of purple/red flowers! In Myanmar, they paint the 'LV' marker on the guard's van, making it important that the train is correctly marshalled!

At night or in conditions of poor visibility, the tail lamp must be lit. The traditional tail lamp uses a burner comprising a woven wick fed with paraffin from a vessel. The burner and vessel can be removed from the lamp housing for filling and maintenance. The complete lamp is designed to stay alight even in severe, windy conditions, provided it's correctly cleaned and 'trimmed'. Although the burner produces only a small, yellow flame, the red 'bulls-eye' lens produces a remarkably visible indication when viewed from the rear. At night, when the train itself cannot be seen, the tail lamp is the last line of defence against being run into from the rear. Loose-coupled, slow-moving freights improved their chances of being seen by carrying two additional red lights - one on each side the brake van - as well. When turned into a loop or additional running line, the side light nearest the main line was changed to white, so that a following train on the main line would not be panicked into thinking an accident was imminent. Side lights always project a white light forwards, so that the footplate crew could confirm that the whole train was following.

The person most interested in observing the tail lamp was the signalman, who had to satisfy himself that the whole train had passed clear of his section before allowing a second train to approach. Special bell signals were provided for 'train passed without tail lamp' and 'tail lamp out when should be lit'. As important as making sure that a train has a tail lamp is making sure that it has only one. If vehicles are attached at the rear, the original tail lamp must be removed and moved to its new position. If the locomotive was carrying a tail lamp when on its way to work the train, then this must be removed when the loco is attached to the train.

Loco lamps are a slightly different pattern from tail lamps. They normally have a clear 'bulls-eye' lens and a removeable red shade so that one lamp can do duty as a head lamp (white) or tail lamp (red). Engines normally have 4 lamp irons at each end, one near the chimney, one over each buffer and one in the centre of the buffer beam. Different combinations of lamps are used to indicate the class of the train. Remember that headcodes like 'top and left' are described looking from the footplate - from in front of the engine it looks like 'top and right'. The Great Western used a different pattern of lamp iron, so only GW-pattern lamps can be used on GW engines. When lamps are not in use, they must be carefully stowed to prevent damage. Ex-GW engines have special lamp irons on the left running plate near the smokebox for this purpose.

When a train is double-headed, the train engine should not display headlamps but the pilot engine should carry the correct headcode for the class of train being assisted.