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Quainton News Archive - Quainton News No. 59 - Spring 1986

Quainton Road's Junction

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S W A Newton - The first signal box at Quainton

When the Great Central Railway main line from Leicester was built, the London extension made its junction with the Metropolitan Railway about 600 yards north of Quainton Road station, where the Verney Junction line of the Met. diverged. An independent signal box was constructed in 1897 by the Metropolitan Railway in the 'V' between the two railways, about 200 yards south of the road overbridges. Later It was positioned on the down side of the line near the junction signals. Perhaps it is a surprise to find that this junction became one of the first in the country to be operated by another signal box, some distance away at Quainton Road. This work was carried out and was described in the Railway Magazine in April 1923. The text is reproduced, also the diagram, by kind permission of the Editor, John Slater, to whom we are much indebted.

"The signal box at Quainton Road is at the south end of the down platform and it is thence , 721 yards distant, that the facing points of the junction in question are now worked, also signals 12, 13, 14, 15, 43 and 44 on the accompanying signal diagram. The trailing points are left free and lie normally spring-worked for the branch line. The facing points, also the six signals named, are worked electrically.

Track circuit control has entered very prominently into the scheme and the various circuits are shown on the diagram.

These are self-explanatory, but it may be desirable to emphasize these points: (1) that the up junction signals are so controlled that, if a train on the opposite track has over-run its home signal, neither signal can be lowered; (2) that, after a down train has passed the starting signal 45, the facing points cannot be changed; (3) that, after a train has passed signal 15, the facing points cannot be changed from normal to reversed until the whole of the train has passed the signal box. From telephone boxes fixed near signals 13, 15, 43 and 44, communication can be made with the signal box. A loud-sounding annunciator on the telephone will call men to it, e.g. the fireman when his engine is standing foul and holding the other line.

Power for operating the facing points is obtained from a 24-volt accumulator battery of 40 ampere-hours capacity and, for operating the signals, from an 8-volt accumulator battery of 40 ampere-hours capacity. These batteries are in duplicate, so that one set may be sent away for re-charging, which is done every two months. For lever locks, indicators, track circuit control relays, etc. 12-volt accumulator batteries of 60 ampere-hours capacity are used. The accumulators, relays, etc. are situate in a special hut on the up side of the line.

The mechanism of the facing points is the General Railway Signal Company's low voltage switch and lock movement, which, along with other of that company's specialities, was supplied by the British Power Railway Signal Company Limited, 3a Dean's Yard, SW1. The initial movement actuates the rocker shaft and withdraws the plunger. The switches are then moved to their new position and the final movement shoots the plunger again. The points are detected in each position and the plunger, when 'home', by signals 43,44 and 45.

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The facing points lie normally for the main line and the lever in the locking frame is held by a track circuit extending from K to P and from M to N, so that, once a train has passed signal 45, the road cannot be changed until the train has passed over the junction. When normal it is, moreover, controlled by a track circuit extending from E at the up main home signal to R opposite the signal box. This prevents the points, after an up main line train has passed 15 signal, being set for the branch, until the whole of the train has passed the signal box. The indicator, lettered '42 points', shows when the points are locked by track circuit. There is, therefore, no necessity for a facing point locking bar - and none is provided.

A circuit closer on No. 42 lever, provided the track circuits concerned are clear, causes the control relay in the battery house to be energised and current to be switched on to the points. About 20 volts is required for operation and the time taken is 18 sees. A three-way indicator is provided above No. 42 lever in the signal box to show the movement of the points. When fully normal, the indicator points to 'main'; when fully reversed, to 'branch'; and, when being moved or if out of order, to 'wrong'.

Provision has, of course, to be made for emergency working, such as the points becoming track-locked, either through a track failure or a possible change in the order of trains, necessitating 42 points having to be altered after they have become track-locked by the presence of a train on the track. This is done by a special switch. This is of the barrel type and can only be moved in a clockwise direction. There are three positions on the switch, the wiring for the normal working being taken through position l. Should the switch be moved off this position, it cannot be restored until the lineman arrives and releases the same - the lineman making a note to that effect in the train register book. In using the emergency release, the signalman operates the switch to position 2. This releases the lock and permits the lever being pulled to operate the points. To obtain a signal for the route set up, the switch is now moved to the third position and the signal lever can then be operated. The wiring is so arranged that the signal lever cannot be returned to normal until such time as the train has cleared tracks J - K and L- M ahead of the junction. After clearing, the signal lever can be put to normal and the signalman, by alternate use of Nos. 2 and 3 positions of his switch, can carry on with his work until the lineman arrives and removes the fault , whereupon normal working is resumed.

It frequently happens in junction working that a relatively unimportant train is held at the junction home signal whilst a more important train is accepted and allowed to pass on the converging route. Where the signal box is close to the junction, the signalman can assure himself by actual observation that the first train is at a stand, but, in a case like this, other means have to be employed. As already pointed out, there is a track circuit extending for 200 yards outside each of-the junction home signals and, although the indicator may be showing 'occupied', it does not necessarily follow that the up train is at a stand, as required by the regulation. This is ensured at Quainton Road by a 'fireman's call' plunger being provided immediately to the rear of these signals in the telephone-box. Drivers are instructed that, on being stopped at these signals, the fireman must immediately notify arrival to the signal box on the bell provided for the purpose - and until this notification is received by the signalman that man is not allowed to accept a train from the converging direction. This effectually prevents any risk of two trains fouling the junction at the same time.

The signals are actuated by the General Railway Signal Company's low voltage mechanism fixed at the bottom of the post. Circuit closers on the respective levers cause current to pass through the track circuit relays concerned to the control relays, which in turn allow the operating current at 8 volts to go to the mechanism. A signal is lowered in 5 sees. and the holding-off current is 0.008 amperes.

Should circumstances arise which necessitate the actuation of the facing points by hand, a crank handle is taken out of a case in the battery room, the withdrawal of which from the case breaks down the circuits to 15, 43, 44 and 45 signals, so that they cannot be operated and train movements must be controlled by hand signalling. The crank is then placed on the pin seen projecting upwards from the point mechanism and the points actuated thereby.

All track circuits are double insulated and bonded. The operating wires at the junction are VIR lead covered Nos. 12 and 14 gauge and run in casing fixed on stakes. The cable between the signal box and the junction is buried. It terminates at each end in test boxes and contains the necessary control wires. Separate return wires are provided which terminate in sealed test boxes. The track relays are the General Railway Signal Company's 4 ohm direct current, with SP graphite contacts, and the line relays are the same company's 960 ohm, with SP graphite contacts. The inter-locked detector and point control relays are the British Power Signal Company's pattern wound to 20 and 1,000 ohm resistance. The lever locks are the railway company's own pattern, with 100 ohm resistance, and the track indicators are the Automatic Telephone Manufacturing Company's, with 3,000 ohm resistance.

For information and facilities for inspecting this work, we are indebted to Mr. W. Clow, now Superintendent, Southern Area, London and North Eastern Railway, Mr. Harry Blundell, then Chief Engineer, Great Central Railway, and Mr. A.F. Bound, Signal Superintendent."

The text in this Quainton Railway Society publication was written in 1986 and so does not reflect events in the 25+ years since publication. The text and photographs are repeated verbatim from the original publication, with only a few minor grammar changes but some clarifying notes are added if deemed necessary. The photos from the original publication are provided as scans in this internet version of this long out of print publication.

Editorial - Quainton News No. 59 - Spring 1986

Text © Quainton Railway Society / Photographs © Quainton Railway Society or referenced photographer
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Page Updated: 12 October 2015