THE SIGNAL BOX

PHOTO GALLERY

Caledonian Railway

LARBERT NORTH

Opened: 1892

Closed: ——

Location code: Sc16/16


Larbert North signal boxThe style of box built by the Caledonian Railway's Northern division in huge numbers up to 1889 was very plain and basic (see Forteviot), but from 1889 onwards some enhancements were made to the design. At Larbert North, opened in 1892, it is immediately noticeable that the plainness of the brick base was relieved by arched locking-room windows - although they have subsequently been removed and bricked up! The finish of the roof has been tidied up by the provision of "fascia boards", too.

Another box of this type, even larger, is illustrated at Stirling Middle. This design was built through to 1902 and again after 1908 following a flirtation with a rather more ornate design as illustrated at Grangemouth No3.


Inside Larbert North boxInside the box, we find the ubiquitous Stevens & Sons style frame, although this example is believed to have been installed during LMS days and bears the unknown manufacturer's markings of R H & Co. In fact, the Scottish Region of British Railways continued to have this type of frame built right through to the end of the 1970's, the last batch being installed along the line through Huntly.

The levers wear BR "coffin-lid" badges - a type used by the Scottish Region for a while. Relatively few of the levers were out of use (spares are painted white) at the date of this view, although the South box had already closed.


Tyers F block instrumentThe large wooden block instruments were manufactured by Tyer & Co. Large numbers of these were installed in Scotland by the LMS to replace more primitive two-position instruments at important locations, although few remain in use today. Another example can be seen on the instrument shelf at Dingwall South on Highland Railway territory.

These instruments probably date from the 1940's. The commutator handle with a rotary action is very similar to those on the Tyer's "Black Box" instruments (see High Ferry) and on the North Eastern's instruments. The reason that the instrument is built on such a large scale is that the bell is also contained inside the case - audible through the gauze-covered opening on the side. The bell is rung to the adjacent box by means of the small brass plunger provided bottom right. Higher up the instrument is an emergency release for occasions when the distant signal had failed in the wrong position which electrically prevented the signalman from working the instrument in the normal manner. The plunger would normally be sealed behind glass, but this feature was not catered for after the introduction of the 1960 signalling regulations and is probably actually disconnected.

Beneath the instrument is a "Welwyn Control" release. Unless a train is registered as having left the block section by track circuit occupation, the signalman is electrically prevented from setting his instrument to "Line Clear" for a second time. For the few occasions when he might need to do this, this device allows him to "stop and think" by forcing him to turn the handle approximately 75 turns before the release takes effect. This system was introduced after a famous accident at Welwyn Garden City in 1935. The one illustrated here is an early one; later ones had a crank-handle fitted to make the turning operation rather easier.


Wire adjusting equipment at Larbert NorthA particularly neat feature found at Larbert North is a cabinet containing the wire adjustment apparatus. Most signal boxes have some apparatus allowing the signalman to adjust the length of the signal wires for far-away signals to compensate for temperature changes. For distant signals perhaps a mile away, the difference can be quite dramatic.

Whereas in most boxes the gear is usually placed untidily behind the levers, at Larbert they are neatly lined up against the end wall and surrounded by a cabinet that, when closed, also makes a useful bench seat. The T-handle is removable and exchangeable between the different sets of gear. The hand-painted labels are an unusual luxury, and the instruction on which way to turn the crank I have never seen elsewhere!

The apparatus itself, although not fully visible here, is of the worm and gear type used throughout the LMS system, and doubtless dates from the renewal of the lever frame during that company's ownership. Earlier Stevens frames used a ratchet system on the front of the levers - see Taynuilt for an example.

Larbert North box is currently still operational, although there are rather more levers out of use these days.

View a diagram of the layout in 1961.



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All photographs copyright © John Hinson unless otherwise stated