Tuesday, 17 June 2008

Deepfields in Detail

In an earlier post I introduced Deepfields signal box. Here's the simplified box diagram:-

The official signal box diagram was mounted in a glazed wooden frame and suspended above the equipment on the block shelf from the roof. My simplified diagram (dating from 1961) omits some of the information which appeared on the official box diagram, such as the gradient profile, the distances from the box to running signals, details of Spares (levers fitted but without function, painted white) and Spaces (locations without a lever but where one could be fitted at a later date).

A few years later, in 1964, I made two pages of notes about the lever frame and block shelf. By this time, the down sidings had been taken out of use and levers 9, 10, 11 and 12 were painted white, as spares. Mechanical locking bars 25 and 31 (a perennial source of trouble) had been replaced by new track circuits T2, T3 and T4. A brief explanation of the type of information included in the notes is given below.

Pull Plates: These are the cast labels or 'badges' fixed to the front of each lever with two machine screws into tapped holes in the lever. They listed the numbers of the other levers which had to be reversed before that lever could be pulled - sometimes called the 'lever leads'.

Back Plates: These were mounted on long wooden boards arranged behind the levers, mounted from the floor on cast brackets angled for better visibility of the Back Plates. Behind each lever were one or two cast Back Plates, fixed to the wooden boards with two woodscrews. Text on the backplates described the function of the lever.

Levers:The levers were numbered, starting at '1' on the left (facing the frame). Each type of lever was painted in different colour or style to identify its function. The pull plates and back plates were painted in the colour of the associated lever, with the raised letters and figures picked out in white. The standard colours in use at Deepfields were:-
Yellow (Y): Distant Signals
(or weight bars operating Distant Signals).
Red (R): Stop Signals (including shunting signals)
Red with White Band: Stop Signals released by the Block.
White (W): Spares.
Black (B): Points.
Blue (BL): Facing Point Locks.
Black with White Arrows: Detonator Placer
(arrows point down for Down Line, up for Up Line).

Block Shelf: This ran the length of the frame, suspended above the levers from the roof on round rods. Whilst some railways (like the Great Western) literally had a 'shelf', in the form of a horizontal plank, the L&NWR used a wooden box section, a sort of hollow beam. The horizontal upper surface mounted block instruments, block switches, lamp repeaters and sometimes additional bells or signal post telephones. The vertical front mounted signal and weight bar repeaters, sealed releases and the like. The rear of the box section was a series of hinged doors usually secured by turnbuckles. When open, the doors gave access to the electrical wiring feeding the equipment mounted on the block shelf.

Notes on the left half of the frame:

The block shelf appears near the top of the view, showing the equipment which it supports. Below the lever numbers are the 'pulls' and below that the text on the back plates. In the case of signals, a single back plate suffices, such as 'DISTANT DN MAIN' on lever 1. Points usually have two back plates. The upper one describes the route with the lever normal, the lower one the route with the level reverse. In the Notes, the two sets of text are separated by a slash, for instance 'UP & DOWN MAIN'/'CROSSING' on lever 13. Near the bottom of the Notes is a code letter for the lever colour and any special remarks. Well, the Notes probably raise as many queries as they answer, so more explanation will be added as possible.

The repeater for lever 1 is a 'Slot Indicator', as Deepfields controlled the yellow to green transition of Bloomfield's Down colour-light Starter. The Blocked/Clear indicator near lever 2 is an early type of mechanical Signalman's Reminder appliance. The repeater above lever 3 is the Track Circuit Indicator for TC1450, the track circuit extending towards the Down Starter. Because the Down Starter is some distance away, there is a Slack Adjuster to control the wire tension. This was the L&NWR typically heavy-duty pattern with an adjustment knob altering the signal wire via a worm gear. The block instrument communicating with Bloomfield Junction was near lever 18, next came the Block Switch and the Spring Vale main-line block instrument. Signal 23 was a short arm signal reading to the Up & Down Goods and provided with a repeater on the block shelf. There are track circuit indicators for T3 and T2. There is an Emergency Sealed Release for the Facing Point Lock, lever 25, allowing the points to be moved if there's a track circuit failure. Mounted on a bracket above the block shelf is the Track Circuit Indicator for TC1449 (the Up Home Berth Track) Circuit).

Notes on the right half of the frame:

Lever 31 originally controlled the the Locking (Clearance) Bar in addition to the Facing Point Locks, but the introduction of Track Circuit T4 had eliminated the need for a Locking Bar. There is now an Emergency Sealed Release for the Facing Point Lock, lever 27, allowing the points to be moved if track circuit T4 fails. The block instrument for the Up and Down Goods Line is special. It is a 6-segment permissive but 'Line Clear' is given by either Deepfields for Up trains or Spring Vale for Down trains - not both! Near lever 34 is an electric bell used to announce movements to or from the Up Sidings via crossover 32/33. The block shelf gets heavily-populated as we approach the Up signals at the right hand end of the frame. There's a signal repeater for the Up Goods Home (lever 37) and a weight bar repeater for lever 38 (the 'slot' on Spring Vale's Up Goods signal). Lever 39 is the Up colour light Starter, so there's a signal repeater, plus a track circuit repeater for T1 on the approach side. After an Up train had cleared T1 on its way to Bloomfield, the colour light was automatically replaced to danger, even with the lever still reverse in the frame. As this happened, a buzzer gave a short 'burp' to advise the signalman. There was a repeater for the Up Home, lever 40 and then two weight bar repeaters for the inner distant (lever 41) and the outer distant (lever 42). The Blocked/Clear indicator near lever 41 is the mechanical Signalman's Reminder appliance for the Up line. There were Slack Adjusters provided on the Up Goods slot, lever 38 and the Up Inner and Outer Distants, levers 41 and 42. The Up Distants were always a pain to get 'Off' and there was an inclined footboard to the right of lever 42 against which the signalman could brace his foot during the 'throw'. Finally, the was a fairly modern modular Signal Lamp Repeater, covering the Up Main and Up Goods home signals and the Up Inner and Outer Distants.