Part of the new signalling diagram in Kidderminster Station box showing the dual control of the Network Rail signals reading onto the Severn Valley.
SIGNALLING NOTES - Chris. Hall
I have a little more time for this article - the Editor has given me a month (until the end of October) to get it written. Since I wrote the last set of 'Notes' in mid April, we have been rather busy at Kiddeminster. As with all our work there is very little to see 'on the ground' but we now have the most comprehensively signalled link to Network Rail of any heritage railway, as a result of the last four years' hard work. This now provides the capability to run all types of train on and off the Severn Valley railway as ordinarily signalled moves. Previously passenger trains required special arrangements and extra staff to set up and supervise the movements in each case and were limited in number.
The visible results of our work from the operating floor of the box comprise the following seventeen new indications (refer to the previous article in issue 178 for the functions of the six new levers that we installed):
These new indications on the block shelf are to show the signalman that the new equipment is functioning correctly (and not, as some might say, provided just to confuse them) - those commencing 'DR' (Droitwich-Ryecroft) are indications of Network Rail equipment (and not 'worked from Droitwich Spa' as one of our Guards was overheard to say!).
One example of how the new facilities will work is for a train proceeding towards Network Rail - our signalman will observe that 47a signal is at Danger and that the derailer (48) is showing normal detection (to protect the running lines) before reversing 49 lever to give the West Midlands Signalling Centre (WMSC) a release to be able to operate DR724 points (the crossover connecting SVR to the Main Line). They can then reverse these points once they are in a position to do so. I have referred, in many cases, to lever numbers: the signal box diagram is rather large to print in the magazine and so there is a link to a full size diagram here.
Signal no. 10 (Up Main to Exchange Line Inner Home) is conditionally approach released until the new colour light signal (DR7835) has been cleared to a main proceed aspect. Otherwise it can only be cleared once the train has been checked and the lamp AFTJKE (AF track circuit timer indication lamp) lights to show when the approach releasing on this signal (and 4, 15 and 16 signals) is free. Signal 10 can only be cleared if DR7835 is correctly lit and so both the Red and Proceed (Yellow or Green) aspects are indicated by means of a red and green lamp.
Track circuits DD, DE, DRFH and DRFJ will then light up as the train proceeds onto the Down Kidderminster. DR7835 will auto-replace to Danger and DR724 points will self-normalise when the route is released. Most points in a modern colour-light controlled area will remain in the 'last called' position but some will normalise after the passge of a train where they provide trapping or flank protection. Our signalman will observe points DR724 showing normal and can then normalise lever 49. Rule 65 requires the signalman to satisfy himself by means of the indications provided that the signals are working properly - this movement has used ten of the seventeen new indications.
The new signals operated by lever no. 47 for shunting in and out of the Carriage Works are an interesting mixture of old and new technology. Ground Signal 47a is worked mechanically by conventional signal wire directly from the lever. Position light signal and route display 47b is actually physically part of the new Network Rail LED Colour Light Signal DR7835. In this case a switch box on lever 47 operates a circuit to the WMSC Solid State Signal Interlocking (SSI) (i.e. computer controlled) which in turn drives the route and signal aspect. Some might argue that this makes it the SVR's only colour light signal!
I hope this illustrates the complexity of the work we have done (the last article was a bit brief as it tried to cover over three years' work in just 4 pages). Just one element of the work we carried out was to fit trapping protection on the three-way point at the exit from the Carriage Works. We ordered three derailers (two left hand and one right hand) in early April. Fortunately we had a drawing from which we could identify exactly what length of rail would be needed to fit each derailer and the drive travel (about 4") required. By 27th May the new dereailers had not arrived (but delivery was imminent). However we had been able to bury two large concrete bases to which we had attached a point machine, another three concrete bases to take some ½" x 3" steel strip and you can see from the photo below that we are drilling some of the eighteen holes required using our magnetic drill (the orange thing).
By 27th May we had fitted the point machine and one crank with the holes being drilled for the second crank. Tony's tool box (of legendary weight) is in the foreground. [Photo: Dave Stowell]
There are another two smaller concrete bases in the picture (to support the point rodding from the machine to the cranks). By the following weekend, the derailers had arived and we carried out a small modification to fit detection. We were then ready to fit them to the rails. Each derailer required three holes 1" diameter (to fit 24mm bolts) to be drilled through the rail. We started well (the first derailer was fitted just next to where the check rail had been cut short to accommodate it, by the 240/110V transformer (the yellow thing in the photo). Clamping the derailer mounting to the rail with a point clip we were able to drill through using our magnetic drill. The drill was being blunted fairly quickly as the rail was rather hard and we had to buy a couple of reduced shank 1" drill bits but we managed fairly well. The remaining two derailers were more difficult as there was no room for power tools (except for the pilot hole, about ¼" diameter, which we could just fit in an electric drill between the two sets of rails). We therefore had to drill these holes using a hand rachet - we had to apply so much pressure to get the drill to cut the hard rail that we were breaking chunks of metal from the cutting edge. Fortunately we had a rather large box of square taper drill bits of various sizes. Several weekends later, the next photo shows the derailers fitted, sitting in the 'normal' position, and the detection rods and contact boxes were being arranged like a jigsaw puzzle.
By 29th July the derailers have been fitted and we were deciding where the detection contact boxes should go. [Photo: Dave Stowell]
We had realised that detection would be required - there was (just) room to fit a contact box to each derailer. The final photo shows the completed installation - two more concrete bases had been planted to support the new disc signal and a troughing run provided for the cable to the point machine. Meanwhile a new location cupboard had been installed and fitted out to control the point machine, a new power supply transformer had been fitted and the circuit controller (driven by the lever) adjusted.
By Tuesday 21st August (five days before D-Day) we were working every day to meet the deadline. We still have to dismantle the cranks and rodding to paint them black but they drive satisfactorily from the point machine and lever 48 in the box. [Photo: Dave Stowell]
During testing on Sunday 26th August 47b signal is cleared, showing route 'W' (to Carriage Works). [Photo: Chris Hall]
The week leading up to the Bank Holiday weekend had been reserved as our annual working week "just in case". The final few runs of wiring in the box had been put in and terminated and, only a few weeks before D-Day a 37-core signalling cable duly arrived from Network Rail to be terminated in our signal box on the cable frame. (Another story would be required to explain how we had moved wiring and relays to create the space for 37 new cable terminations.) As soon as we had prepared the end for terminating, they asked for it back (to relay the main line) but we got it back on the Tuesday before the Bank Holiday and we were able to complete work that day so that we could hand it over to the testing team. The new 37-core interface cable to Network Rail carries 6 signalling control and indication circuits from the SVR to the WMSC and 8 circuits from the WMSC to the SVR. Kidderminster Station box is now a fringe box to WMSC and all classes of train can be signalled to and from the Severn Valley under Track Circuit Block Regulations between our box and WMSC with full interlocking between both boxes. WMSC, situated in Saltley in Birmingham is one of the new generation of "super" signalling centres which will eventually control the signalling in the entire West Midlands and surrounding area.
The commissioning and testing (by an independent tester not involved in the design or installation) over the Bank Holiday weekend went very successfully which is quite an achievement when you consider the complexity of the project. As well as the changes and additions to the signals and lever frame we had run about a thousand yards of wiring and installed 26 new safety relays inside the signal box (plus 5 relays in location cupboards) to provide the new functions and interface. The testing was signed off by Monday 27th August. Each different function and route had been tested (with no trains running on the Network Rail side and a possession of the Main Line between the Advanced Starter and the Carriage Works on our side). Some extended route locking was provided post-commissioning to prevent our signalmen pulling poits prematurely.
A final reminder that this article and the photographs associated with it, as well as other S&T information, can be viewed in full colour on the unofficial S&T (signals) web site at http://www.svrsig.org/ (or look for 'svrsig' on google).