Kent Rail

Eurotunnel Tri-Bo

Shuttle Locomotives


During 1988, Eurotunnel began submitting design proposals to the Intergovernmental Commission (IGC) and Safety Authority relating to the nature of rolling stock which would traverse the Chunnel between Cheriton (Folkestone) and Coquelles (Calais). Whilst Eurostar was to be a passenger-only operation, Eurotunnel’s proposed services would provide a direct substitute – and rival – to the ferries. Essentially, the company was to run an end-to-end shuttle service, this having the single aim of conveying travellers with vehicles, both business and leisure. With reference to the IGC and Safety Authority, these were joint British/French official bodies to which Eurotunnel was answerable to: approving stock design, commissioning infrastructure, and setting safety standards, were all roles of these organisations. The Safety Authority had made it clear to Eurotunnel that during transit, passengers need not be separated from their vehicles, therefore rolling stock design could proceed on the basis that no separate passenger accommodation was required. However, Eurotunnel had to prove a safety case for this; by July 1989, results of fire tests and evacuation procedures for proposed stock had been submitted by the organisation to the Safety Authority for consideration. In December of the same year, the green light was given to proceed.

The 1980s was turning out to be a good decade for Brush Traction Limited: in 1988, the company had been awarded a contract by British Rail for the construction of one-hundred Class 60 diesel-electric locomotives, valued at £120 million. This had been preceded in 1986 by an order received from New Zealand Railways for the construction of twenty-two electric locomotives built to a gauge of 3 foot 6 inches. Unusually, the latter demonstrated a Bo-Bo-Bo wheel arrangement; this meant that there were three independent bogie sets consisting a pair of axles each (hence ‘’Tri-Bo’’). Advantages with this wheel arrangement included a greater distribution of weight across each axle, in addition to allowing tight curves to be negotiated with ease. Subsequently, in 1989, Brush received its third customer, when in July of that year, Eurotunnel placed an order for thirty-eight electric locomotives. This contract was worth an estimated £80 million, and required Brush to draw on its previous experience of constructing locomotives with a Bo-Bo-Bo wheel arrangement. Eurotunnel had specified an electric with considerable power: it had to be capable of hauling a load of 2400 tonnes whilst ascending a gradient of one metre in every ninety. Two of these locomotives would be allocated to each shuttle, in top-and-tail formation, with 800 yards worth of shuttle rolling stock sandwiched in-between them. A pair would be required to move a fully-laden shuttle service through the tunnel at maintained speeds of 87 MPH. Unsurprisingly, to undertake this task, their power output would be unprecedented, with each locomotive producing no less than 7,724 HP (5.76 Megawatts).

Construction of the Shuttle locomotives was generally based on a enlarged platform of the aforementioned New Zealand fleet, bringing the Eurotunnel electrics up to Standard Gauge. Further to the earlier mentioned advantages of a Bo-Bo-Bo wheel arrangement, such a design was also favoured since each bogie could be independently-powered by a separate set of traction equipment. Chunnel safety requirements had particular emphasis on back-up procedures to get a train out of the tunnel, should any failures occur. For locomotives destined to operate under the Channel, on-board electrical systems were duplicated to ensure that failure of one component could be offset by the presence of another in reserve, thus reducing the risk of a train becoming stranded in the tunnel. Therefore, if one bogie set on a Shuttle locomotive became inoperable, it had no bearing on the functioning of the remaining wheel sets. Six traction motors, built by ABB (Asea Brown Boveri Ltd, a Swiss engineering firm operating on a global scale) were to be spread evenly across the three bogies, each producing approximately 1287 HP. Locomotive braking was to be constituted of two alternate systems: rheostatic and regenerative. The former sees the reversal of the traction motors to slow the wheels down; the latter involves returning current to the National Grid. In doing this, the moving wheels are actually powering the traction motors, instead of vice-versa, which produces, rather than uses, electricity.

Brush Traction subcontracted body shell construction to Qualter Hall & Co Ltd, a Barnsley-based engineering firm specialising in projects ranging from the fabrication of moving dock cranes, to the formation of mine shafts, and the building of railway vehicles. The body shell was to be all-steel, and alone contribute 30 tonnes to the locomotive’s overall weight. Construction of the first examples ensued through 1991, and each shell was assembled by making more than 10,000 welds to amalgamate 5000 individual components. The shell framework was to be clad with steel sheeting, the longest single sections of which were 52 feet long – these particular lengths would form the main body sides. To iron out any imperfections to produce a truly smooth, flat surface, each 52 foot body side panel was subjected to a stretching exercise, which involved applying a force of 40 tonnes across the length of the sheet, extending it by over a quarter of an inch. The first completed body shell was sent to British Rail’s Research Division at the Railway Technical Centre, Derby (reputedly the world’s largest railway research facility), to undergo physical tests to ascertain how much applied stress and strain it could cope with. In March 1991, the shell was subsequently delivered to Brush Traction at Loughborough for fitting out of equipment. In July of the previous year, Brush had been awarded another Chunnel-related contract; this was for the construction of an initial twenty £3 million Class 92 locomotives. Assembly of these was undertaken concurrent with the fitting out of the Shuttle locomotives; each type had one half of the Loughborough workshop.

17th August 2007


A member of the original locomotive batch, No. 9037 ''Gabriel Bauquier'', is seen departing Cheriton with a morning Passenger Shuttle service. The wagon behind the locomotive is a telescopic hood, which folds forward at the arrival point to allow vehicles to disembark. Beyond the hood wagon is a rake of single-deck passenger carrying vehicles. These are always positioned at the front of a shuttle formation, and are designed to accommodate high vehicles such as coaches. Twelve of these single-deck wagons are present in each formation, in addition to twelve double-deck wagons, each rake being joined in the middle by another telescopic hood. © David Glasspool

17th August 2007


Another member of the original locomotive fleet, No. 9029 ''Thomas Allen'', is seen leaving Cheriton with a Freight Shuttle. Worthy of note behind the locomotive is the passenger carriage: known as the ''Club Car'', this air-conditioned vehicle provides accommodation for HGV drivers during transit through the tunnel. It was deemed at the design stage that it would be safer for HGV drivers to be separated from their vehicles during the course of the journey. Food and drink are served onboard the carriage, which contains 52 seats and toilet facilities. © David Glasspool

17th August 2007


A trio of Tri-Bo locomotives are observed at Cheriton, all fronting Freight Shuttles, complete with Club Cars. The furthest is No. 9704, one of the 9,387 HP machines ordered in the year 2000, whilst next to it is No. 9802 ''Stuart Burrows''. In the background are two rakes of single-deck carrier wagons, whilst beyond these, marked by the black fence, is the terminal entry lane from the South tunnel. Unlike standard terminus practice, where a top-and-tailed formation would have each locomotive facing forwards at least once on a two-legged trip, on the Eurotunnel system, the same locomotive always faces the front. The entire Channel Tunnel system - Cheriton and Coquelles (Calais) terminals - is arranged in a giant figure of eight formation. For instance, when a train arrives at Cheriton from Coquelles, it is first sent around a curve at the western extremity of the terminal to double-back on itself; therefore, when it enters the platforms, the locomotive which hauled the shuttle from France will be hauling it back again, in turn leaving the same Tri-Bo trailing at the rear. Notice that the arrangement is described as a figure of eight rather than a plain oval: at Cheriton, Shuttles will round the curve in a clockwise direction, whilst at Calais, trains round the curve in an anti-clockwise direction. The thinking behind this design was to equalise the wear of the wheels on each side of the locomotives and rolling stock. © David Glasspool


Next: the History Continues >>


Return to the Kent Rail Homepage or alternatively, check for Updates.

Website & Copyright information - Links - Contact the Webmaster


All content is copyright © David Glasspool