Last November, Japan's Railway Technical Research Institute unveiled the world's first multi-voltage gauge-changing trainset. Following tests on JR West, the unit will be run at up to 250 km/h in Pueblo from April

Kazuhiro Oda, Senior Chief Engineer, Vehicle Technology Development Division, Railway Technical Research Institute

DURING JANUARY, a prototype three-car electric multiple-unit with gauge-changing bogies was put through its paces at up to 100 km/h on the narrow-gauge tracks of West Japan Railway. Next month it will be shipped to the standard gauge test track at Pueblo, Colorado, for a programme of performance and endurance tests due to last until September 2000. These will include runs at up to 250 km/h.

The gauge-changing trainset is one of the key elements of the Ministry of Transport's Success 21 policy launched in 1994. Amongst other initiatives for improving Japan's transport in the 21st century is a specific strategy to make the railways more convenient to use. The country has a long legacy of different gauges, with the main national network built to 1067mm gauge, and various private lines and the shinkansen routes laid to 1435mm. Some Tokyo metro routes even use 1372mm gauge.

Traditionally, passengers have had to transfer between trains at break-of-gauge points, but as part of Success 21, MoT sought ways to reduce this inconvenience. After considering the scope for regauging lines or converting them to mixed gauge, the Ministry's Technical Committee put forward proposals for gauge-changing trains as a more cost-effective and less disruptive solution. Under MoT leadership, Japan Railway Construction Public Corp is conducting a study into future shinkansen network construction, and the Railway Technical Research Institute has been contracted to develop the trains (Fig 1).

During the three years 1994-97, considerable research was undertaken into the technologies needed for gauge changing. Components such as bogies and traction motors were constructed and tested on a narrow-gauge track at Kunitachi, in the western suburbs of Tokyo. A prototype gauge-changing ground installation was also built for evaluation, and the prototype bogies were run through it over 1000 times. The bogies also underwent dynamotor testing at a simulated maximum speed of 500 km/h.

To provide safety assurance, ensure reliability and assess track loading implications prior to the start of revenue services, a four-year test programme was agreed in 1997. This began with the construction of the three-car prototype for performance and endurance testing. The unit was delivered to Kunitachi in November 1998. There it underwent dynamotor testing and low-speed trials through the gauge-change installations for the rest of the year. During the trials on JR West and at Pueblo, the train is expected to accumulate 450000 km by the end of next year.

Setting the parameters

The first step in developing the new trains was to determine the basic parameters. The trains would be self-propelled electric multiple-units, as is the vast majority of existing Japanese rolling stock. With all wheels motored, the train would be able to pass freely through the gauge-change installation under its own power. In addition, the prototype is a multi-system EMU, making it the world's first multi-voltage gauge-changing trainset.

The gauge-changing installation (Fig 2) is 22m long. A linear bearing support rail similar to a roller conveyor runs parallel to the track at the same level as the bogie frame. This support rail runs the whole length of the transition section and overlaps the standard gauge and narrow gauge approach sections at each end.

While the support rails remain level, the standard and narrow gauge approaches slope down so that the transition section is 55mm lower than the normal rail level. Over the 5000mm long transition section, the running rails are replaced by inner and outer guide rails which reposition the wheelsets for the other gauge.

As the train passes through the approach section, the lowering of the running rails gradually transfers the weight of the cars onto the roller support rails. With the axleboxes fully supported at the bottom of the slope, a locking pin at the end of the axles drops out to release the wheels. These are then guided to the new gauge as the train continues. As the wheelsets start to rise again, weight is transferred back onto the axles, lifting the locking pin back into the axlebox and securing the wheelset for the onward journey.

A key to successful operation is the maintenance of traction throughout the transition process. With adhesive weight transferred to the support rails and the gap in the running rails, the wheels cannot transmit power during regauging. The prototype three-car EMU has six bogies, of which no more than three can be in the gauge changer at the same time in the worst case situation. This leaves three bogies operating normally, and with all axles motored this is sufficient to keep the train moving.

We currently envisage that gauge changing will take place at a speed not exceeding 15 km/h. In commercial operation gauge changers would be located at junction stations where trains would normally be stopping, so the low-speed running will not cause any operating inconvenience.

Prototype trainset

The three-car EMU prototype (Fig 3) has lightweight bodyshells assembled from aluminium alloy. The passenger saloons are pressure sealed to eliminate air pressure variations during high-speed operation through tunnels. On the prototype the passenger space is all occupied by test instrumentation, monitoring over 400 signals for both static and dynamic data. This includes temperatures, accelerations, displacements, stresses, voltages and currents.

At the heart of the train, the bogies and wheelsets incorporate various innovations. The outer end of each axle is surrounded by a cylinder which carries the wheel, free to slide back and forth along the axle. The wheels are motored directly, and the axle itself does not turn (Fig 4). A Z-shaped linkage steers the axles to improve curving performance.

Each wheel is powered by a 95 kW permanent magnet three-phase synchronous motor, with four IGBT inverters per bogie to provide individual control of each wheel. RTRI is also building another design of gauge-changing bogie with the wheels driven by conventional geared transmissions.

The high-speed performance and endurance tests at Pueblo are due to start from April, and we hope to complete the first phase of the technical feasibility study by March 2001.

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