INTRO: Radical concepts in engineering and interior design are being applied to the tilting trains due to take over Brisbane - Rockhampton services next year
BYLINE: Don Heumiller and Jerry Jirasek*
BYLINE: * Don Heumiller is an independent rolling stock design engineer advising Walkers Ltd. Jerry Jirasek is Senior Design Manager for Walkers Ltd.
NEXT MONTH will see the roll-out of the first of two six-car tilting trains for Queensland Rail’s trunk passenger route. They mark the culmination of 10 years of upgrading on the 1067mm gauge coastal line from Brisbane to Rockhampton. Passenger traffic doubled in five years following electrification in the late 1980s, notably tourists heading for destinations such as the Great Barrier Reef, and this prompted further investment.
With tilt technology firmly established elsewhere, it was a natural choice for the picturesque but curvaceous line, which will be the first in Australia to see regular tilting trains. Designed for 180 km/h, the trains will run at 160 km/h. Journey times fell from 14h to 9h 30min with electrification, and the tilt trains will cut another 2 1??2h, bringing the 622 km trip down to just 7h.
In October 1994, QR awarded a A$62·5m contract to a consortium of Evans Deakins Industries, Hitachi and Itochu. Design and construction is the responsibility of EDI’s Walkers subsidiary in Maryborough, with Hitachi supplying traction and tilt equipment.
Active tilt
Japanese suppliers have considerable experience of 1067mm gauge tilting trains using electric and diesel propulsion; since 1973 some 547 vehicles have been put into service (Table I). The QR tilt equipment is derived from JR-Shikoku’s Series 8000 EMUs.
A roller support built into the bogie frame allows the body to tilt towards the centre of curvature. This simple concept was first used for passive tilting, but vehicles built since the late 1980s have been enhanced with active tilt, using servo-controlled pneumatic cylinders between bogie frame and tilt beam.
A command unit in each cab is loaded with the track data for the whole route. By monitoring train speed and location data from the station protection AWS track magnets, the leading unit can instruct the tilt controllers on each vehicle. These directly control servo valves supplying air to the tilt cylinders on each bogie (Fig 1).
Effective tilting still relies on a low centre of gravity, providing a challenge to the vehicle designers. It was important to limit body mass, so that the existing Japanese bogie design could be used - most suspension and tilting components are configured for this bogie. The low mass had to be achieved within QR’s 1800 kN buffing load limit, against a Japanese standard of 500 kN.
Natural tilt also requires accurate lateral location of the centre of mass, so the vehicle sits level in normal running, and does not have a slight tilt either way. The final constraint is a 10% reduction in the width of the kinematic envelope, to avoid any interference with platforms or other fixed structures.
One problem with electric tilting trains is keeping the pantograph in contact with the overhead wire. The first Japanese natural tilt vehicles had a fixed rooftop pantograph, and were limited to specific routes where the contact wire stagger was minimised using additional masts. The most common technique uses a support frame between the bogie and pantograph, but this takes up a large space within the body, losing up to eight seats per pantograph.
To avoid the loss of space a patented pantograph control system has been developed. This converts the relative lateral motion between the bogie frame and bolster into a vertical shaft rotation, which is then converted back to a lateral movement between the roof and pantograph. On the QR units, the vertical shaft will be housed in the corner of a luggage rack on one car and next to a galley cupboard on the other, with no loss of seats.
Body structures
The trains will be formed of two half-sets, arranged MTM-MTM. Each vehicle will be different, with a range of equipment and facilities which combine to meet the overall requirement (RG 1.95 p41).
The bodyshells are made from GradeS301 high-strength stainless steel, with a low carbon content to improve corrosion resistance. Ultimate tensile strength lies in the range of 860 to 1000MPa, and yield strength between 520 and 600MPa. Special attention was paid to the forming and welding of this steel because of the hardness. Roll forming of the main structural members and sheeting increased the material strength through work hardening. As far as possible, fabrication was done by resistance spot welding to avoid heat distortion and maintain steel strength.
The underframe bolster and end unit are made from Grade350W/1 high-strength corrosion resistant carbon steel to reduce weight. Paints and sealants are used to avoid corrosion between the carbon and stainless steels.
The aerodynamically-styled leading and trailing cars have GRP composite mouldings. There is a one-piece upper moulding, two components covering the ’bull bar’, and a hinged portion over the multifunction coupler. Because only four ends were needed, the normal process of creating wooden moulds was dropped in favour of a fully sculptured foam and resin plug.
Considerable effort was required to meet the weight, centre of mass and balance limits. The low profile and low mass affected the bending stiffness, which was partly compensated by making some interior features load carrying. For example, the floor was made from corrugated stainless steel and aluminium, with flexible elements to provide a well damped vibration-isolated composite.
To lower the centre of mass, the large extended-range air-conditioning units are squeezed into the underframe, rather than the more conventional rooftop location or a split system. The trailer cars also carry a heavy 25 kV transformer, which resulted in the first bend mode frequency at tare condition being lower than the 10Hz required. This was overcome by incorporating structural window glazing.
The design load requirements included an 1800 kN end compressive force and anti-collision force of 1100 kN, combined with a seated passenger load, plus four standees per m2 and a 1·3 dynamic factor. Finite element analysis of a full length half model body structure was performed using Patran pre and post processor and Nastran Analysis Software. Verification on a test rig at Walkers showed good correlation with the FEA results.
Bogies
The bogies are being built under licence from Hitachi. The bolsterless design uses self-steering primary suspensions of coil spring and conical rubber elements (Fig 2). Secondary suspension is a combined air spring in series with a rubber element, controlled by levelling valves with a built-in time delay to conserve air.
A separate tilt beam sits on top of the bogie frame roller assembly. Besides the main vertical load rollers there are smaller rollers to constrain the beam longitudinally against traction and braking forces. The only other components associated with the tilting system are the air actuator cylinder, an extra lateral damper and a linear displacement transducer.
Traction motors are bogie mounted, and drive the axle-mounted gearbox through a compact flexible blade coupling. To minimise noise, measures have been taken to reduce vibration at source. Damping material has been added to the flat areas of the gearbox outer plates, ring damped wheels are used, and the motor cooling fans are designed to avoid resonance.
Space constraints on the motor bogies dictated use of wheel-mounted disc brakes with combined hydraulic brake actuator and callipers. These are powered by separate air-hydraulic boosters for each axle. The trailer bogies have conventional axle-mounted disc brakes, but with ’air-off’ spring-applied parking brakes. Where possible, compartments within the bogie frames are used for air reservoirs.
Traction and auxiliaries
Each motor car will have all four axles powered by 190 kW three-phase AC traction motors. One IGBT converter/inverter feeds each pair of motors, ensuring a high level of redundancy. The equipment is light and compact with low noise emission. As the IGBT requires no external insulation to the cooling units, large capacity de-ionised water heat pipes provide environmentally friendly cooling. No blowers or fans are needed, eliminating any maintenance of rotating parts.
Microprocessor controls oversee the traction and braking functions, and record fault data for analysis by maintenance crews. To minimise effects of electromagnetic interference, most cables are enclosed in metallic conduits.
To ensure on board services are not interrupted when passing through neutral sections, two auxiliary converters feed a common DC link through the train. For all cases of train speed and neutral section length, only one pantograph will be de-energised at a time. The DC link feeds compact inverters on each car. All large auxiliary motors have their own dedicated inverter with built in soft-start.
The air-conditioning unit incorporates humidity control, and has been designed for quick changeover with few mounting points, automatic seals and plug-in electrical connections. Longitudinal ducts above the overhead baggage lockers distribute air to each window area, to ceiling registers and to the end vestibules and toilets.
VHF and UHF radio communication will be provided for the train crews, as well as individually
controlled public address, intercom and pager systems. Public payphones will be
provided in cars 1 and 5.
Interior design
The interiors are based on airline concepts, including enclosed overhead lockers to supplement the baggage storage spaces at the end of the cars. GRP mouldings are used extensively, presenting an easily maintained and attractive finish. Aluminium trihydrate is added to achieve an acceptable fire rating. The moulds were treated to provide a surface texture effect.
Interior partitions and doors are clad with melamine-faced aluminium. Seating and partitions are solidly fixed to the sub-structure, rather than to the flexibly-isolated lightweight low-noise floor.
High quality aircraft seats are used, with the rotating and reclining first class seats incorporating armrest tables. An armrest on all seats has control for reading lights, music selection and plug for headsets, while first class seats also have attendant call buttons. Passengers in both classes will have access to hearing aid loops, phone and fax services, videos, music and radio programmes.
Pneumatic sliding-plug external doors are coupled with pneumatically operated folding entrance steps to suit the various platform heights along the route. Inter-car gangways are 1m wide, and without doors. Sound transmission to the saloons is minimised by a double bellows and internal saloon doors.
Interior sliding doors are fitted with infra-red sensors and manual push buttons. The sensors will assist with the meal trolley service provided from on-board snack bars in cars 2 and 5. These have aircraft style heating and cooling facilities for pre-prepared food, which is served at-seat in both first and economy class. Passengers will also have the option of purchasing food from a servery in car 5.
On-board video monitors in each vehicle will show films, the forward view from a cab-mounted camera, or journey progress using a global positioning system. First class passengers will have 240V outlets for personal computers.
Semlet vacuum toilets with a high-capacity waste retention tank are provided in both economy and first class cars. All are provided with electric hand dryers and baby changing tables, whilst the toilet in the leading first-class vehicle is designed for people with disabilities and wheelchair users.
Fault management and reliability
As there are only two trains and no spare vehicles, reliability is of great importance. Part of the contract covers performance targets in three areas:
