Traction Equipment Replacement

What do you do with a multiple unit that is at least “middle aged” and whose propulsion unit has become outmoded?     Many operators withdraw such units especially if the body structure is made of steel that is starting to show significant corrosion or other evidence of its age and might soon require costly body-work repairs.    Here are current approaches to such a problem where the rolling stock is being given new life at a cost far less than that of new rolling stock.

London Underground (LUL) D78 stock is being withdrawn from service and if scrapped would generate only a little money for LUL in the process.    However Vivarail Ltd, chaired by the ever resourceful Adrian Shooter (recently retired from Chiltern Railways) has worked out a way to reuse this stock and at the same time enable a company like Northern Rail to get rid of its hated “Pacer” dmus.    Vivarail is purchasing most of the D78 stock which will be delivered to Long Marston Sidings where they will be converted into 76 two or three car DEMUs.    There will be 156 driving cars and 70 trailers.    It is hoped that the first 3 car prototype will be completed this spring or early summer and be tested on Long Marston’s 3km long test track.      If all goes well the first unit will be cleared to operate on Network Rail tracks by this autumn.     The modernised units will be described as “D Stock” but could end up being designated Class 278.    The existing DC motors are still capable of further service and would have an easier time if they receive power through a new diesel engine-driven alternator via a rectifier rather than taking the power directly from the fourth rail system.      The coach bodies are basically aluminium so the steel corrosion that so often spells doom for other older stock does not apply.    The entire interior of the coaches will be completely replaced so the future passengers will feel that they are in new rolling stock.    The bogies were replaced ten years ago so are good for a good many years to come.   The top speed of the revamped trains will be about 60 mph – but they will be used on stopping services where stations are only 2-3 miles apart and where therefore there will be little scope for reaching higher speeds.

The plan is to supply new looking units that will be attractive to the customers, will cost much less than brand new stock, and will be ready for use much sooner than new-builds from train builders that already have substantial order books.    The D Stock can be seen as an ideal way to replace Northern Rail’s Pacers.     This is an innovative plan that makes new use of old stock that can be found new life and operate on non-electrified routes.     To many future passengers the retirement of the bouncing Pacers will be the best news of all!

The renewal of traction motors is happening on other lines around London.   Southeastern’s fleet of class 465/0 and 465/1 Networker emus have always had inverter-fed AC motors but this equipment has undergone an upgrade starting in 2009.       Hitachi won the contract to fit new inverter units to these emus together with new AC traction motors.     An inverter unit converts DC current taken via the third rail to variable voltage, variable frequency AC current which is then supplied to the AC traction motors.    This has proved to be a most reliable system and is less costly to maintain than chopper control with DC motors.     South West Trains class 455 fleet of 91 four-car sets was supplied with DC motors and camshaft/resistor control.    This is considered to be nearly life-expired.    The units are being given new life by the fitting of AC motors with inverters.

The newest development concerns London Underground’s eighty five 8-car tube trains operating on the Central Line.      These were built by BREL at Derby Works with DC traction equipment supplied by Brush and ABB.    In 1992 the use of DC choppers with DC motors was a traditional approach, favoured by LUL which was reluctant to move with the times, and in truth this technology was already out of date.    Move on 20+ years and the increasing unreliability of the DC equipment meant that sometimes the required seventy six trains was not available to meet peak service requirements.    Now LUL wishes to replace the DC equipment with up to date AC equipment.     The eight-car trains are in fact four self-contained pairs with all axles motored.      A  total of 2,800 traction motors ( including spares) will be required.    LUL is seeking to place a turnkey contract with a supplier that will design, build and test new equipment that will do the job.   There are not many suppliers that are capable of taking on such a job but the contract will be lucrative.    Watch out for developments.


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