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Tilting trains hold the key to Virgin's ambitious franchise

01 Oct 1998

INTRO: Virgin Rail's order for 54 tilting trains for its West Coast franchise is the largest contract for Pendolino technology. It is also the most difficult application. Roger Ford reports on how Alstom and Fiat are facing up to the challenge

WHEN Virgin Rail received two bids for its new fleet of tilting trains for the Virgin West Coast franchise in 1997, it soon became apparent that the offer of a Pendolino to the British loading gauge from the joint venture of Alstom and Fiat Ferroviaria was the only credible one. But this did not lift the pressure on the Anglo-Italian grouping.

Both the timescale for delivery and the critical role of the new trains in Virgin's ambitious franchise bid meant that the real challenge was not to beat Adtranz, but to deliver an offer Virgin could fund and which would also meet the most demanding performance specification for any tilting train yet delivered.

On March 3 1998 Alstom-Fiat was named as preferred bidder for the contract to supply 54 trains and the subsequent maintenance of the fleet. Capital value of the deal is around £480m.

Commercial background

Under British Rail a number of proposals to modernise the West Coast main line fell through. The most recent had been InterCity 250 (RG 7.90 p521), which would have seen the line upgraded progressively so that it was eventually cleared for 250 km/h.

With privatisation, modernisation of the route linking London with the major conurbations in the West Midlands, northwest England and Glasgow became a political issue. Thus the InterCity West Coast franchise included what was known as Passenger Up Grade 1. This included the upgrading of track and power supplies to allow 200 km/h operation by either conventional or tilting trains.

Virgin won the franchise on this basis, but then negotiated a more ambitious Passenger Up Grade 2. The key features of this are 225 km/h operation with tilting trains and an increase in frequency in and out of London to 11 trains an hour.

This is the first substantial high speed train fleet to be procured and operated entirely within the private sector. Funding arrangements were due to be concluded by the end of September; as part of the deal, the manufacturers will share residual value risk.

Substantial liquidated damages will be incurred in the event of late deliveries or service problems with the new trains. This risk is partially offset by Alstom-Fiat supplying the fleet on the basis of total train service provision.

Train formation

Under the contract the size of the fleet is determined by the manufacturer based on meeting 48 daily diagrams. Alstom-Fiat will build 54 eight-car trains to meet this requirement.

Each train will be formed of two symmetrical half sets with three motor cars and a trailer carrying the pantograph and transformer. There is provision for future lengthening to 10 cars with the addition of further trailers. Currently, Virgin is proposing two styles of accommodation with different levels of service depending upon demand and time of day.

A complicating factor in the seating layout is the current ban on passengers travelling in the leading vehicle of trains at over 160 km/h. This stems from a commitment given to HM Railway Inspectorate after the Polmont derailment in 1984. Alstom-Fiat is preparing a Quantified Risk Analysis to demonstrate that passengers in the leading vehicle of the new trains will not be exposed to significantly greater risk than those in current multiple-units at 160 km/h.

From the HMRI viewpoint the key issue is the ability of the leading coach to cope with striking an obstacle, typically a concrete sleeper, at 200 km/h. In meeting this requirement, the focus is on obstacle deflection and the load on the leading axle. The aim is to develop an engineering solution supported by the QRA. Rearward facing seats in the lead vehicles will contribute to the analysis by increasing survivability.

Crashworthiness is a separate issue. Here, nose ends will be able to absorb 3 MJ of energy, three times the Railtrack group standard. Intermediate vehicle ends will absorb 2 MJ. In addition, the front portion of each driving vehicle will be allocated to van space.

Mechanical parts

Aluminium alloy bodyshells will be fabricated by Fiat at its Savigliano plant using double-skinned hollow section extrusions supplied by Alusuisse. The bodies will be 23m long compared with the 26m of Pendolini to date. The shorter body has resulted in more equipment being roof mounted, notably the air-conditioning modules.

Fiat will install swing-plug doors and gangway connections and supply a painted watertight shell to Alstom's Birmingham plant for fitting out. This will include mounting all the underframe equipment, fitting out the interiors and cabs and installing the roof-mounted equipment.

Cars will be pressure-sealed, but maximum levels for aerodynamic pressure pulses, both in tunnel and the open have been specified. The most demanding case is open-air operation at 225 km/h where the pragmatic requirement is for the maximum pressure pulse to be no greater than that generated by a passing IC125 at 200 km/h.

Aerodynamic studies on nose shape and body profile are being carried out by Fiat at the group's research centre in Torino. Tilting trains require a reduced cross section to remain within the loading gauge. This involves narrowing the cross section above the waist line which is particularly noticeable inside vehicles built to the British loading gauge.

Further complication is introduced by the need to allow for tilt system failure modes, in particular a hard failure which would tilt the train fully over. Analysis showed that at a handful of locations a hard failure could result in the train fouling a lineside structure.

Reducing the cross-section to restore clearance at these locations made the vehicle unacceptably narrow. As a result, track-mounted transponders will be used to switch out the tilt, with the train on plain track, before each location with restricted clearance. This system is being developed; Fiat has never had a hard failure on a Pendolino in over 75 million km of running.

Tilting bogies

Fiat SIG of Switzerland is supplying a version of its generic bogie developed for Swiss Federal Railways' ICN tilting train. A feature of this design is the use of a single air bag secondary suspension above the tilt system. One benefit of this is to provide more space at bogie level, allowing suspension linkages to be optimised.

Alstom-Fiat is also using the SIG-developed tilt system in which the body rotates on rollers running on a curved track (Fig 2) in place of suspension links used on the Pendolino. Also new for Pendolino is electric tilt actuation, with a motor driving a screw jack. Maximum tilt angle will be 8í with 80% compensation of lateral acceleration.

A similar electric tilt system will be used to maintain the pantograph head level as the body tilts. This is also being fitted to the Swiss ICN. In effect, compensatory tilt is applied to the pantograph in curves. Previously, mechanical linkages from the bogie were used.

Performance

Virgin will be the first European operator of tilting trains at 225 km/h on existing infrastructure. Railtrack is upgrading the track for high speed and high cant deficiency. When the fleet enters service, it will be fitted with the standard Pendolino system which holds the body off the lateral bump stops at high cant deficiency curving.

In addition, learning from experience with the IC225 ride, high levels of lateral inter-car damping will be provided. An active lateral suspension system is to be installed when the operating speed is increased to 225 km/h in 2005.

Dual-rate braking is specified, with 6% g above 200 km/h and 9% below. Subject to the receptivity of the overhead line, the 12 powered axles will provide regenerative braking, defaulting to rheostatic. Friction braking will be provided by two ventilated discs on each motored axle and three on the unpowered axles.

Although each train will have two pantographs, the overhead line will accept only one in use at a time. As a result, the new trains will have a 25 kV bus line linking the two transformer cars. This is another first in Britain.

Distributed traction will use Alstom's standard Onix 800 three-phase drive which is also being used in the company's Juniper electric multiple-units for the British market. Each transformer supplies three power cars, each car having two powered axles. Traction motors are body mounted, driving the inner axle of the adjacent bogie through a right angle gearbox.

Power from the transformer is converted to 1000V DC in a PMCF rectifier-chopper on each power car. The PMCF feeds a pair of interlaced IGBT Onix inverters which supply the two 425 kW traction motors. Total power consumption from the overhead line is limited to 6·7 MW per train.

Auxiliary power is taken from a tertiary winding on the transformer. An auxiliary converter feeds 400V AC auxiliary power down the train plus a 110V DC supply for the electric tilt and battery charging. Adjacent cars can cross feed auxiliary supplies.

Project management

All the Birmingham project team will be housed in a 70m x 20m open plan office, known as 'The Studio', built in a former assembly shop. Within The Studio, each project team, responsible for the cab or the interiors for example, will have its own zone, including space for full-size mock-ups.

Each zone will be self-contained in terms of access to data processing and computer-aided design facilities. There will also be zones for manufacturing and factory planning functions. Representatives of major subcontractors will also have space in The Studio.

At the peak of the project around 100 people are expected to be working in The Studio, which will also have video conferencing and meeting rooms. The aim of this innovative approach is to improve communications between the many specialist groups which contribute to a modern train, using a true concurrent engineering approach.

Delivery

Alstom is scheduled to receive the first bodyshells in July 1999, with assembly of a pre-series train starting in August. This train will roll-out in February 2000.

Factory testing is expected to take until the end of May. For acceptance and validation test running, Alstom will electrify the former BR Research test track at Old Dalby.

Acceptance testing, including around seven months at Old Dalby followed by running on the main line, should be completed by March 2001, but the pre-series train will be retained for continuing development work.

Fitting out of the first production train starts in May 2000 with delivery early in 2001. Production will then ramp up, reaching one train a week from set No 7 onward. At this rate, all 54 trains will be commissioned in time for the May 2002 national timetable change.

To achieve this output, there will be four assembly flow lines at Birmingham, each with eight stages. A vehicle will spend between two and three days on each stage.

Old Dalby will also be used for commissioning the production trains. Speeds of up to 190 km/h will be possible, and Alstom is expecting to find the majority of snags at this point. o

CAPTION: Artist's impression of the nose treatment reflecting the well-known Virgin brand image

CAPTION: Fig 1. Current proposals for the train layout may change later. Note the rear-facing seats in the leading car

CAPTION: Fig 2. The Fiat-SIG tilting mechanism, swing bolster with single airbag and bogie-mounted TBTC antennae

TABLE: Table I. Journey time aspirations

London to Distance km Current 2002 2005

Birmingham 185·5 1h40 1h15 under 1h15

Manchester 304 2h30 2h00 1h45

Liverpool 280 2h45 2h00 1h55

Glasgow 646 5h20 4h20 3h50

TABLE: Table II. Provisional train formation

Vehicle Class Seats Facilities

Driving Motor/Van First 18 Van + kitchen

Motor First 37 Disabled facilities*

Trailer/Pantograph First 44

Motor First 46

Motor Standard 60

Trailer/Pantograph Standard 50 Disabled* /servery