INTRO: Train procurement in Britain has seen radical change following privatisation. Roger Ford describes how manufacturers are creating standard designs to be bought off-the-shelf rather than made-to-measure
IN MANY European countries state railways continue to have a major say in the design and technology of new traction and rolling stock. Procurement against a performance specification has been gaining ground, but this official policy often masks a continuing close relationship between the railway’s engineering department and its suppliers. In Britain little trace is now left of such relationships.
Privatisation of British Rail in 1994-95 saw the traction and rolling stock engineering functions formed into consultancies and sold to the private sector. Meanwhile, responsibility for procurement passed to the train operating companies who had won franchises lasting from seven to 15 years. Many of the franchisees were bus operators who had no experience of train procurement. A significant factor was that new trains were often the subject of binding commitments on service dates, with the likelihood of penalties in the event of late delivery. This meant that the franchise owners needed to minimise risk in their rolling stock acquisitions.
As a result, invitations to tender were issued on the basis of simple performance specifications, with the manufacturer sometimes having the option to determine the fleet size to meet a specified service frequency. Under this regime, the technical requirements were contained in Railtrack’s Group Standards, plus the new rolling stock acceptance process based on safety cases. Responsibility for design, and thus the risk, was firmly with the manufacturer.
For train builders Adtranz and Alstom, an immediate legacy of privatisation was a 1064 day hiatus in orders for rolling stock. Both manufacturers used this period to develop fresh concepts in train provision for the emerging private market.
Central to this work was the belief that, to be affordable in the new market, prices would have to be significantly lower than the £1m per vehicle of the last build of British Rail suburban electric multiple-units. Talk of £600000 per vehicle was common, and one franchisee confidently expected to buy diesel multiple-units for just £400000 per car.
Contrasts in manufacture
Adtranz focused on the need to reduce manufacturing costs and shorten delivery times from its Derby plant. Key to this was a change in the bodyshell construction method. Instead of seam welding long aluminium extrusions in jigs to form a rigid monocoque shell, the aluminium structure starts as individual underframes, with sides and roofs fabricated separately.
These are then fitted out to an advanced stage with interior trim, glazing and underfloor services before being bolted together to form a ’tube’. Cabs and ends are manufactured separately, and then bolted to the main structure. Quick release connectors for electrical and other control systems provide links into the cab.
This approach greatly simplifies the fitting out schedule. For example, fitting windows and trim, such as panelling and luggage racks, to the bodysides does not interfere with activity on the vehicle floor or ceiling, as would be the case when fitting out a conventional complete shell.
Another advantage is that staff work under ideal conditions with windows, for example, swung into place using handling equipment on the shop floor with the apertures at chest height. The roof can be inverted for wiring, lighting, air-conditioning ducts and ceiling panels to be installed.
With the vehicle ’tubed’, but before the bolt-on ends are fitted, toilet modules, air-conditioning units and other components are installed. All can be supplied on a just-in-time basis directly to the production line. Each line using this system has an output of up to four vehicles a week.
Rival builder Alstom chose a different approach. The emphasis was on the product and the opportunities for train service provision, including whole life maintenance and even finance packages. This was known as the Juniper project.
Manufacturing techniques remained traditional, including the reversion to steel construction, partly because of the resulting ability to source bodyshells internationally from within the group. On its EMUs, Alstom also retained the integral cab.
However, the contract with Fiat to supply the Pendolino Britannico for Virgin West Coast (RG 10.98 p707) has increased the pressure on Alstom’s Birmingham plant. In this case the bodies will be of extruded aluminium profiles, with shell fabrication at Savigliano in northern Italy. But final assembly and fitting out is in Birmingham, and the contract required the trains to be put together and delivered in record time. This put further pressure on the Birmingham factory, and as a result, production processes are being refined.
Alstom is aiming to reduce the time between a painted shell arriving on the assembly line to a complete vehicle in test from the current 10 or 12 weeks to just seven. This will be achieved through the development of a generic assembly station.
A pilot workstation has been set up and is being used to assemble the first of a fleet of 40 three-car EMUs for ScotRail. One change is to move from two lines of workstations down each side of an assembly bay to a single central line of stations. This means fewer workstations in a given floor area, but the resulting all-round access is better suited to today’s modular assembly techniques with components arriving just-in-time. The net result should be higher output.
Alstom intends to use the generic workstation ’footprint’ on all eight production lines. This should give the Birmingham factory a single shift output of 400 vehicles a year combined with a 10% reduction in unit costs. Once developed and proven, the generic workstation concept will be applied to all the factories in the Alstom passenger trains group.
This highlights a further benefit. Any line in the factory will be able to build any train with the minimum set-up time. Combined with the development of standard designs, this should cut delivery times and allow work sharing during periods of local peak demand.
Market mix
Initial franchise commitments suggested that the bulk of the market would be for 20m long suburban EMUs, with DMUs a niche market. Adtranz won all the initial DMU orders from franchisees with its 23m long Turbostar design. However, growing interest in DMUs saw Alstom take two major orders with its Coradia concept, including a 200 km/h variant.
Coradia illustrates one advantage of steel bodyshell construction. With Alstom’s Spanish shell production line fully occupied with Juniper, manufacture of the Coradia shells was switched to Ganz Hunslet in Hungary. These units also have bolt-on cabs.
More recently (RG 4.99 p223) Bombardier has won a contract to build a fleet of 78 tilting and non-tilting diesel multiple-units for Virgin CrossCountry. These will use traditional assembly techniques, although they will be sourced from different European factories within the group and assembled in Britain.
The main market for EMUs is for London commuter services. Both the Electrostar and Juniper vehicles are designed to match the kinematic envelope of British Rail’s MkI slam-door stock that is gradually being phased out. In the case of DMUs, the dimensions have been determined by the need for maximum route availability. This has generally meant a reduction in interior width compared with the more route-specific units built for British Rail.
Traction
Another distinctive feature of the trains now coming off the Derby and Birmingham production lines is the modularity of traction equipment. Whereas previous EMU designs would have had all axles motored on one or more cars, both builders have exploited their compact IGBT-based high power three-phase drives to give distributed power along the train. Conductor shoes are fitted on each powered bogie, so reducing the risk of a train ’stalling’ because the shoes are located over a gap in the conductor rail.
In both Electrostar and Juniper, each traction module powers both axles on a single bogie. The four-car units have three vehicles powered, while the eight-car Juniper Gatwick Express sets have five distributed traction packages.
This modular approach has several advantages. It simplifies the provision of redundancy, an important factor when trains are being supplied against reliability guarantees.
Alstom has rated the three ONIX packages on the Juniper four cars so that the train can keep to time on 75% power. Should a traction package fail, the remaining two packages switch to their full rating automatically to maintain the required performance level.
Railtrack’s acceptance process for new rolling stock has focused attention on the signalling interference characteristics of the three-phase drives. Two factors complicate this issue.
First, the safety case based acceptance is concerned with potential interference under credible fault conditions, rather than normal operation when modulation strategies can minimise return currents at signalling relay frequencies.
Second, to protect residual value, the Electrostar and Juniper EMUs are dual voltage (25 kV 50Hz and 750V DC) so that they can operate throughout Britain’s electrified network. This has required the suppliers to demonstrate that the trains are compatible with a very wide range of track circuit frequencies. Alstom expected to receive an acceptance certificate for operation of the Juniper in revenue earning service this month.
Standardisation
While the pilot contracts for the EMUs are making slow progress, largely determined by the protracted approvals process for the electric traction packages, later contracts should progress much faster.
Central to this expectation is the fact that Adtranz and Alstom have developed designs and production techniques for what are effectively standard trains. Operators still seek to differentiate their new trains, but even interior layout and design is circumscribed.
New trains must meet the Rail Vehicle Accessibility Regulations of Britain’s disability legislation. These regulations are highly prescriptive, ranging from the layout of toilets for the disabled to the size of priority seats. One operator has had to seek temporary exemption under the RVAR for a train designed before the regulations were promulgated because the priority seats were 6mm too narrow.
Manufacturers already are seeing the benefits of standardisation. Alstom reports that the latest order for ScotRail’s three-car Juniper EMUs was able to use 85% of the drawings prepared for the 30 four-car sets for South West Trains.
Where aspirations have not been met is on price. It is clear that the two manufacturers were talking up a price war in the early bidding which did not reflect real costs. Typical prices are currently around £3·5m for a four-car EMU, while DMUs cost £1m per vehicle.
With the first of this new generation of standard trains now entering service, operators will be anxious to see whether they deliver the promised costs and reliability. However, without the unique constraints of the British market, it is doubtful whether such standard designs will be adopted by other railways.
CAPTION: Steel-bodied Juniper EMUs take shape in the Alstom plant in Birmingham for South West Trains (left) and Gatwick Express (right)
CAPTION: The Juniper integral cab structure is designed to meet the latest energy-absorption requirements
CAPTION: Above: An inverted Turbostar DMU underframe is fitted with equipment, piping and cabling prior to assembly in Derby
Right: A Turbostar roof section waits to be fitted to the sides and underframe already assembled in the left of the picture
CAPTION: The first of 44 four-car Class 357 Electrostar EMUs being built by Adtranz for LTS Rail is now undergoing commissioning at East Ham depot. Adtranz is also supplying 40 four-car and 15 three-car Class 375 Electrostars to Connex South Eastern, and on July 2 Connex Rail announced it was to order a further 29 three-car and 9 four-car sets for its South Central franchise
Builders rise to standard trains challenge
Train procurement in Britain has seen radical change following privatisation. Roger Ford describes how manufacturers are creating standard designs to be bought off-the-shelf rather than made-to-measure. Adtranz has switched from monocoque bodyshells to individual underframes, sides and roofs which are fitted out before being bolted together. Alstom has opted to source bodyshells from other plants for rapid fitting out in Birmingham, where generic ’assembly stations’ are being developed
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