|Great Western Railway
Signalling of the Camerton Branch
These brief notes were compiled originally with assistance from members of the Signalling Record Society in connection with a display at a local exhibition. The notes provide a general outline of the subject and are not intended to be a comprehensive coverage. The precise history of all these installations is still unclear and sadly there appear to be very few surviving diagrams, photographs or official records. More details are needed to enable a complete record to be compiled.
The Camerton Branch was opened in 1882 as a single-track railway from a junction at Hallatrow (on the Bristol & North Somerset Railway) to a terminus at Camerton. A new passing-loop was provided at Hallatrow, and signal-boxes (SB) were constructed at both stations by contractors McKenzie & Holland. Subsequently the B&NSR became part of the Great Western Railway. By 1889 the line was being controlled on the one engine in steam (OES) principle and in due course Camerton SB was reduced in status to a ground-frame (GF).
In 1910 the branch was extended eastwards to a junction at Limpley Stoke on the Bathampton - Trowbridge - Westbury line and Camerton became a through station with a passing-loop. A new SB was opened at Camerton and additional SBs and passing-loops were constructed also at Dunkerton Colliery and Dunkerton station, although both Camerton and Dunkerton stations each had only a single platform. Only at Dunkerton Colliery did the signalling permit two passenger trains to cross, the non-platform loops at Camerton and Dunkerton being restricted to goods trains. The original SB at Limpley Stoke was closed and replaced by two new boxes, North and South, the North box controlling the actual junction with the branch, whilst a new box had been opened at Hallatrow the previous year. The only public level-crossing was at Monkton Combe and this was protected by distant signals, with two GFs being provided to control the signals and the siding points. Other GFs were installed at various intermediate sidings on the line.
All the new SBs were constructed in brick by the Great Western Railway to their contemporary Type 7D design, although Limpley Stoke North had a wooden top that tapered towards the north end. Although several of the signal-box lever-frames were installed around the same time, a mixture of different patterns was used including GWR 3-bar Horizontal Tappet (HT) and 3-bar Vertical Tappet (VT) frames with levers at 4 centres. In the HT and VT designs a cam plate was attached to each lever above its fulcrum; operation of a lever forced down a roller working in a slot in the cam plate, which drove a down-rod connected to the tappet irons. Interlocking was affected by notches in the tappets acting on brass nibs fixed to moveable cross bars. In addition to actual levers fitted to work all the various signals and points, a number of spaces were provided in each frame to cater for any future expansion of the layout.
The Camerton Branch was divided into four "block sections":- Limpley Stoke North - Dunkerton - Dunkerton Colliery - Camerton - Hallatrow. Each section was equipped with a pair of Electric Train Tablet instruments, one in the signal-box at each end, which were interlocked electrically. Each instrument contained a number of tablets, which were metal discs (usually brass and approximately 4 diameter) engraved with the names of the section signal-boxes. A train was permitted to enter the single-line only when the driver was in possession of a tablet for the section; only one tablet could be removed from a pair of instruments at any time and both instruments would be locked then until the tablet was replaced in one or the other. The instruments are believed to have been the Tyers No 7 pattern, and although this type was quite common in the British Isles, the GWR only installed a few sets during a short period about 1908-16; the Camerton Branch was one of very few GWR lines to be equipped throughout and it is believed to have been the most extensive installation.
Passenger traffic was stopped in 1915, and although it resumed again briefly in 1923, it ceased altogether in 1925, after which the line was used for goods traffic only. The SBs at Dunkerton and Dunkerton Colliery were closed during the Great War and their loops taken out of use, although the boxes may have re-opened for a short time in the mid-1920s. The original line from Hallatrow to Camerton closed in 1932, after which Camerton became the terminus of a line approaching from the east, having been originally the terminus of a line from the west and then a through station - possibly a unique history. The SB at Camerton was closed in 1938 and it is believed to have been replaced then by two GFs, one at each end of the station.
By that time the ETT instruments had been taken out of use and thereafter the entire line from Limpley Stoke to Camerton was worked as a single OES section, using a wooden train staff fitted with an Annett's key for unlocking the various GFs in the section. Limpley Stoke North had been reduced to a GF in 1927, although it did not close finally until 1962, and the South box controlled the station until it closed also in 1969.
© CJL Osment 2002