Introduction:
In the 1960s, British Railways modernised the signalling in the West Midlands as part of the 25kV Electrification Project. Westinghouse was the signalling contractor for new Power Signal Boxes at Wolverhampton, Birmingham, Walsall and the Down Tower at Bescot. Control of the North Stour was transferred to Wolverhampton Power Box and a number of the mechanical boxes I'd been familiar with were either abolished or downgraded to Shunt Frames. However, Princes End box was retained as a Fringe Box to Wolverhampton. This involved significant changes. After these changes at Princes End, I had the opportunity to work the box (unofficially) a number of times, as described in an earlier article. Although the main line signalling installations are still in use, after the Princes End Branch was closed the track was lifted and very little remains today of this once-important freight route.
This fairly recent view Wolverhampton Power Box shows that it is little altered externally and (unlike some Power Boxes like Trent, Saltley and Derby) retains its flat roof. Larger overhanging fascias have been fitted, presumably because of difficulties viewing the signalling console in strong sunlight
Principal Changes at Princes End
This simplified and approximate diagram shows Princes End as a Fringe Box, showing the single line to Wednesbury on the left and the double track to Tipton Curve Junction (controlled by Wolverhampton PSB) on the right. Clicking on the image displays a higher-resolution version which can be downloaded or printed
Continuous track circuiting was introduced on the Up and Down lines on the Wolverhampton side of Princes End Box so that the former Absolute Block working could be replaced by Track Circuit Block (TCB) working. Although a single-stroke bell and 'tapper' was provided to communicate with Wolverhampton Power Signal Box, in general trains were sent and received using a Train Describer. The Up Home 1 signal was replaced by a 3-aspect colour-light and the Down starting signal was replaced by a 4-aspect colour-light. To accommodate the necessary equipment, a relay room was built on the Up side, a few yards on the Wolverhampton side of Princes End box. The relay room was a substantial flat-roofed affair in blue brick, similar in design to all the relay rooms provided in connection with the Wolverhampton re-signalling. In addition, steel Location Cases ("Locs") were provided periodically along the route to house relays and other equipment associated with track circuits and signals. The Location Cases, Relay Room and Princes End Signal Box were interconnected, as necessary, by rugged signalling control cables laid in sectional concrete troughing at the side of the running lines. Each troughing section comprised a 'U' shaped duct closed by a flat lid. The Signalling Power Cable and Telecommunications cables also used the concrete troughing.
The Drawings:
I was interested in the methods of electrical control employed and took every opportunity to study the changes which had been made. Eventually, I managed to obtain prints of some of the drawings which had been used during the installation and commissioning phase. I've made 'quick and dirty' photographed copies of these drawings - the index to these photographed copies is here. Alternately, the links in the section 'The Contractor's Drawings' below take you directly to an image of each individual sheet. The image can be downloaded or printed. The assistance of British Railways back in the late '60s in furnishing these drawings is acknowledged.
'Red Lined' Drawings:
Some of these drawings had required change during installation and commissioning and had been 'Red Lined'. The required changes were made by hand (in red) on dyeline copies of the affected drawings. On completion of the work, the changes would have been permanently incorporated on the drawing 'Master' held in the design offices. In the mid '60s these Masters were usually drawn in ink on translucent linen or plastic drawing film, so as to be durable and suitable for using to take dyeline copies. Once the Masters were updated and reviewed, fresh, corrected dyeline copies could be issued for record and maintenance purposes. There are some inconsistencies between the sheets presented here but hopefully these will not prevent some understanding of the principles involved.
Drawing Symbols and Labelling Conventions:
The symbols for the various circuit elements are drawn in the simplified style now used. They're probably a little harder to follow than the earlier symbols (mentioned in the post Spring Vale Electrical Controls). The student also has to get used to the letter codes used to label components. A group of letters and figures is used to identify each component. For instance, the designation '19GCR' means [19][Signal][Proving][Relay]. Once you've mastered the principal codes, understanding diagrams becomes much easier.
Lever and Signal Controls:
There is one drawing prepared by British Railways (LMR). This drawing (NW630385/8) shows requirements for new Lever and Signal Controls as a table. The remaining drawings detail how those requirements are implemented.
The Contractor's Drawings:
The remaining drawings detail the electrical controls at Princes End and these were prepared by Westinghouse for British Railways. The Westinghouse drawings were numbered L2689/x where 'x' was the sheet letter or number. The list of sheets was as follows:-
/A :Index
/B :Layout of Relay Room
/C :Layout of Relay Rack (currently unavailable, sorry)
/D :Power Supply Layout (currently unavailable, sorry)
/E :Layout and Allocation of Fuses
/F1 :Cable Terminations (Relay Room)
/F2 :I'm afraid sheet /F2 has not survived.
/G :Contact Analysis
/1 :5(N) Lock & 6 Signal Selection, Control, Lighting & Indication Circuits
/2 :19 Signal Selection, Control, Lighting & Indication Circuits & 462 TJR circuit
/3 :Incoming & Outgoing TPR Circuits
/4 :Filament Failure & (PO) Indication Circuits
/5 :Track & Signal Indication Circuits
/6 :18(N) Lock & Single Line Working Circuits
/7 :Typical Unit Wiring.
I've also included a drawing fragment showing the Key Token Instrument wiring here.
In the next instalment (here) we'll look at some of these sheets in a little more detail.
[For a long time, many of the above links stopped working, as explained here. I've finally restored most of them. Hope it helps: 28-Dec-2015]
