Preston Station - Past & Present

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2. Project Approval & Planning
3. The Work at Preston
4. Signalling & Power Box Commissioning
5. Electrification, Catenary & Electricity Supply
6. Delays
7. Locomotives
8. Media
9. It's Official!
5. Electrification, Catenary & Electricity Supply
The principle contractors for the electrification on London Midland region were Pirelli Construction Co. Ltd and British Insulated Callenders Construction Co. Ltd. (BICC)

This work involved the raising of many existing structures:

219 bridges between Weaver Junction and Gretna had to be modified to some degree.

90 bridges had to be completely reconstructed.

40 were raised bodily between 12 and 18 inches.

22 were widened or realigned for Highway Authority road improvement schemes.

There were also 77 other lineside buildings and outdoor switch gear plinths constructed.

By February 1971 Pirelli-General was ready to commence mast foundations between Weaver Junction and Preston, whilst BICC was the contractor north of Bolton-le-Sands and mast foundation work was due to start there in Spring 1971. By August 1972 electrification masts had started to appear in the station. Between Weaver Junction and Gretna 9,337 masts were required and in the first year 1,991 had been erected.

Special trains used to were used to erect the masts and overhead wires. The first one makes holes for the structures using rail mounted equipment, these can be grabs or augers depending on the ground conditions.

This next train would pour concrete foundations, normally there are eight units on a train each capable of mixing six cubic yards. A total of 11026 concrete foundations were needed on the London Midland section, there also seemed to be a short train which was used around the Preston area.

This would be followed by a mast erection train, the typical type of mast used on the Weaver Junction to Gretna section were a simple girder type. These masts are located approx 60 metres apart and the works trains carried between 60 and 100 masts and an eight man gang could erect a train load in eight hours.

Finally this would be followed by a wiring up train of specially modified coaches with a flat top to enable the gangs to complete the wiring.

pic1This picture taken by Bill Ashcroft shows a northbound Class 104 DMU leaving the former platform 4.  The modifications to Fishergate Bridge clearly visible, this work was to provide the necessary clearance for the overhead traction wires. A new foot was added to the existing girder beams and the original foot them removed. In the background can be seen the brand new parcel platform and goods lines.
The overhead wires in areas of multiple tracks were supported by a method called of construction is called ‘head span’ wiring, this entailed using cross support wires stretched between the masts. The catenery wires being supported on the cross wires. The use of ‘head span’ type of construction surrendered the use of an independent mechanical support for each contact wire and this further reduced its impact on the environment and also reduced cost.

The head span method was one of the key items which enabled the cost of the electrification to be reduced by some 25% over the cost of the electrification south of Weaver Junction, which used steel portal construction. The head spans were usually prefabricated off site.

Added to this the two wire catenery used north of Weaver Junction was designed to further reduce the cost of the electrification, and without which it is unlikely the electrification would have got the go ahead.

The 1966 line to Euston used mark 1 compound catenary with a maximum permitted speed of 100mph. Experiments showed it ‘hogged’ making it higher mid span giving poor current collection. Whereas a contact wire with some sag led to a design of simple catenary that gave good current collection well in excess of 100mph.

The Mk1 catenery had cadmium-copper main and auxiliary wire and a level cadmium-copper contact wire with copper wire droppers.

The sagged type was designated Mark 11 and consisted of hard drawn copper catenary wire and a hard drawn copper contact wire with bronze strand droppers.

By the time the west coast scheme was under consideration aluminium conductor steel reinforced (a.c.s.r.) conductors were in use on transmission lines and on other railways and tests were made on some 8 miles north of Crewe. Subject to modification this became known as Mk111A and was adopted for the Weaver Junction - Glasgow scheme, it showed a saving of £200 a mile over hard drawn copper and the use of stainless steel droppers gave a further reduction of £110 per mile. The Mk111A reduced the separation between the catenery wire and the contact wire, simplifying the support design and with a reduction in the height of support masts.

A number of the steel portal structures were used just north of Fishergate Bridge; these span all the tracks, but were not the norm on this project due to cost. This area contained some of the longest spans of the whole project and the structures were needed due to the track density and complexity. This type of structure was used extensively on the Crewe, Manchester, Liverpool and London electrification.

Electricity Supply
The overhead traction wires north of Preston are supplied from feeder stations at Catteral near Garstang, and Natland between Milnthorpe and Oxenholme. With intermediate track sectioning cabins at Bay Horse, Hest Bank, Burton and Holme, Grayrigg, Tebay and Harrison’s sidings. While power for the Weaver Junction to Preston section is taken from the National Gird at Parkside at 132 Kv. Track sectioning cabins on the southern section were located at Action Grange, Wigan, Euxton and Preston.

Feeder stations and track sectioning installations are monitored by the Electric control room at Crewe. When the electrification was completed the Crewe control room supervised supply from Rugeley (Staffs) to Tebay.

A new lab coach was used to test the operating conditions of the overhead equipment. It was called MENTOR (Mobile Electrical Network Testing Observation and Recording).

Finally in May 1973 the section from the south to Preston was energised.