Wednesday 12 February – Signal Engineering Report
When the Mid Hants Railway was born, there were only a couple of operational signals in use at Alresford. Over the years many more signals were installed, mainly at the London end of the station that required an increase in the number of signal wires from the signal box to operate each one. Within the station area, the majority of these galvanised stranded signal wires were run out from the signal box under the platform then in the "6 foot" (the space between the two platform tracks) supported in pulley wheels on posts hammered into the ground. To avoid trip hazards when loco crews were getting off the footplate, these wire runs were covered with a wooden boardwalk up as far as the board crossing at the end of the platform ramps. Over time the void under the boardwalk filled up with sludge and eventually the signal wires became partly buried in the mire causing many operational problems, especially in very cold weather when they could become frozen to the ground.
During the ‘closed season’ this winter, Bob Howes, our mechanical guru in the Signal Engineering Department was tasked with designing, fabricating and supervising a solution to this problem. It was decided to relocate the nine signal wire runs along the brick face of Platform 1 up as far as the platform Starting signal at which point, the wires would turn through 90 degrees and run under both tracks to meet up with the existing run on the far side of the track, then onto Sun Lane Bridge. This necessitated the fabrication of three new heavy metal plates on which all the pulley wheels are mounted. These steel plates are supported on concrete trestles dug into the ground. The route from the end of the platform up to the point where the wires cross the tracks created another trip hazard for loco crews so the wires are supported on pulley wheels through sections of concrete troughing that are dug into ballast at ground level and then covered by a new boardwalk, the planks required having been salvaged from the original walkway. From where the new wires emerge from under the signal box, smart new blue PVC covered wire has been used. The reason for this is twofold – they are protected from the elements thus minimising corrosion; and the PVC covering insulates them where they run under rails to avoid shorting out the track circuits.
The work was managed in stages and was finally completed, tested and commissioned at the end of January in readiness for the start of the 2014 season. Some of the old signal wires buried in the ‘6 foot’ were found to be badly rusted with some strands actually broken so the renewal was just in time. The vacated ‘6 foot’ area is now being dug out by the Permanent Way lads and will be in-filled with new stone ballast which will tidy up this very visible area and should aid drainage.
Next time you at Alresford, have a peek over the platform edge – but make sure no trains are around – and admire the spanking new blue PVC covered wires that will be operating our semaphore signals for many years to come.
Rod Wicks – Signal Engineering Dept.