PHOTO GALLERY: NORTH BRITISH RAILWAY
OPENED: 1902 CLOSED: 1969
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Whilst most boxes of the North British Railway’s 1873 to 1908 design were sturdily built in brick, a few were built in timber where local conditions were unsuitable for heavier signal boxes. As can be seen here, Thornton North was built on an embankment separating two levels of lines.
Thornton Junction comprised a complex area of routes on the section of the East Coast main line between the Forth and Tay bridges, in an area where much coal mining took place – generating considerable amounts of freight traffic. Thornton North signal box was actually one of the smaller signal boxes here.
The main line passes to the left of the box in this view. A heavy freight waits patiently in the Down Goods Loop but by the looks of it the more important train it is being held for will pass soon.
On the right, at a lower level, is the double-line branch to Leven and East Fife. There was no connection between the two lines at this box.
This interior view shows three of the four pairs of old-style NBR three-wire, three-position block instruments. On these the commutator was held in position by a pin. The instruments show their ancestry as telegraph instruments by having commutators (unused) on the non-pegging instruments as well as the operational ones on the accepting ones.
Four switches of the type used for closing switches on the North British Railway can also be seen – of each pair one is the actual closing switch and the second applies additional battery power to the circuit to cater for electrical line resistance over long sections.
The lever frame, which totals 26 levers, is a typical Stevens & Sons product of their Glasgow works, as found in many NBR boxes. This example has the levers spaced at 5¼” although many later examples were spaced at 4¼”. The lever plates are cast metal with raised numbers , with the descriptions on a painted board behind the levers. The “hooks” with ratchets on the front of the levers are wire adjusters to cater for expansion of signal wires in warm weather.
Thornton North signal box was abolished on 30th March 1969.