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Looking to the Past to find Solutions for the Future: A Trolley Bus for
the 21st Century.
Academic and support
staff of the Department of Automotive Engineering of the Hong Kong
Institute of Vocational Education (Lee Wai Lee) went to see the Trolley
Bus Project recently developed by Citybus Ltd. The visit took place
during the morning of the 19th January 2002 at 10:00am and
turned out to be a most friendly and informative event.
Ir John Blay, Consultant
Engineer for Citybus Ltd, warmly greeted the 20-odd visiting team, led
by Head of Department, Ir Iain Seymour-Hart. The trolley bus project
site was located along Ocean Park Road next to the Hong Kong School of
Motoring and near to Ocean Park, Aberdeen, Hong Kong Island.
Many beautiful mature
trees surrounded the site, exemplifying the 'environmentally friendly'
nature of the trolley bus. The development of this super-modern version
of a trolley bus was in response to concerns regarding the degree of
noise created and amount of tail pipe emissions emitted by conventional
diesel buses, especially in the urban areas. A further consideration
being that in a few years time diesel fuel is likely to increase in
price as demand grows and supplies dwindle.
Furthermore, Citybus
operate about 1,100 diesel buses which all need regular oil changes,
replacement of filters and brake facings thus creating a large amount of
waste product which must be disposed of locally. In comparison, a
trolley bus requires much less maintenance and produces very little
waste product compared to its diesel counterpart. On the other hand, a
trolley bus system would need the installation of an infrastructure of
poles and cables to supply electrical energy along the routes it would
ply.
At the project site,
twin overhead cables, supported by a series of vertical poles, had been
erected to form a large semi-circle covering about half of the perimeter
of the enclosure. However, the cables and poles were not so noticeable
in the presence of the tree indicating how such a system could easily
blend into a natural environment. It was easy to appreciate how
pedestrians would be able to enjoy fresh air and a much quieter
environment, right in the heart of the city, if trolley buses were to
replace diesel buses. If used in and around housing estates, trolley
buses would create much less disturbance especially late at night.
When the visitors first
spotted the trolley bus, they were impressed with its ultra-modern,
colourful appearance and the clever design of the driver's cab controls
which were just the same as the ones found in existing diesel buses. The
trolley bus had been installed with air conditioning, a compressed air
braking system and had two passenger decks. It could easily be mistaken
for a conventional double decker bus, except for the two booms on its
roof and was probably the only double deck, air conditioned olley bus
itrn the world. A real 'first' for Hong Kong!
Citybus Trolley Bus
Trolley Bus Technology
John Blay described the operating principle of the trolley bus to the
visitors. Basically, the power supply system is 380volts, 3-Phase, which
is transformed to 485volts, 3-Phase and then rectified, by solid state
silicon rectifier modules, to 600volts DC, the whole system having a
capacity of 500KW. This power is connected to the two overhead power
lines to supply the needs of the trolley buses anywhere along the
system. Trolley buses slowing down, being retarded or going down hill
would generate electricity and supply this back to the power lines for
either (i) use by other trolley buses or (ii) to be stored in a flywheel
for later use.
The twin power lines can be seen above the Trolley
bus
The trolleybus collects its electrical energy through its poles
(supplied by Kummler & Matter, Zurich) and delivers it to its main
control panel. From this control panel the power is then fed to the four
separate power modules, described as follows:
1. The traction inverter and AC motor for driving the
vehicle.
These are manufactured by Ansaldo of Genoa, Italy and are water cooled.
The motor has a normal maximum power of 180KW and a peak output of
230KW. External feeds are arranged to the inverter from (i) the
accelerator pedal, (ii) the forward / reverse selector, and (iii) the
brake pedal, in order to determine power demand, direction of travel
(forwards or backwards) and brake regeneration.
The engine compartment
2. The air conditioning Inverter and
AC motor. These are
also manufactured by Ansaldo and are again water cooled. The motor has a
maximum output of 100KW although only about 50KW, maximum is required.
This motor drives three air conditioning compressors and one alternator
(24volts DC) using normal vee-belts.
Drive arrangement with three pulleys connected by
vee-belts
3. The air compressor,
manufactured by Atlas Copco. These are of
the 'Scroll' type driven by a 4 KW motor, manufactured by Brook Hansen.
Both are both air cooled.
4. The power steering pump.
This is driven by a 7.5KW motor, manufactured by Brook Hansen.
In addition, there is a Fischer Panda (Germany) diesel generator
providing a nominal 100KW of power, at 600volts DC, for offline
operation and depot mobility. The boom bases are fitted with an
electro-pneumatic system to enable the driver to lower or raise the
booms from the driver’s seat. An electrically (24volt DC) driven fan is
used to cool the radiators for the Ansaldo equipment, and also for the
diesel generator.
The Fischer Panda diesel generator set
The traction motor drives through a constant ratio reduction gearbox to
the standard rear axle which is the sole means of driving the rear
wheels of the trolley bus.
The Traction Motor
The bus is a converted 10.6 Dennis Dragon, manufactured in 1993, with a
Duple Metsec body assembled by Caetano of Portugal. The roof structure
had to be strengthened to take the extra load from the boom equipment
and the brake resistors. As much as possible of the original bus had
been retained.
The boom equipment on the roof of the Trolley Bus
The overhead booms can be lowered or
raised by the driver, without him leaving the comfort of his seat. This
would be done when the bus was being moved in and around the bus depot
where there would be no need for overhead wires. In addition, in case of
a power failure the trolley bus driver could simply lower the booms and
drive the bus using the electrical power generated by his on-board,
diesel powered generator set.
Close-up of the boom activators
The trolleybus has been
found to out perform the diesel powered equivalent, whilst being
quieter, and non-polluting. This was evident when members of the
visiting team were given the opportunity to drive the trolley bus.
The
maneuverability of the Trolley Bus can be appreciated here
Team member, Dr. Sydney
Ho, an avid trolley bus fan, test drove the trolley bus and found the
maneuverability and acceleration quite startling. He found that the
trolley bus could even overtake parked vehicles or other buses stopped
at bus stops and move from the any one of the lanes of a 3-lane
carriageway. Whilst operating, he found that it was smooth and quiet and
considered it a must for future 'clean and quiet' travel in and about
Hong Kong.
One team
member made the point that when fuels become more difficult to locate
and likely much more expensive the trolley bus will become more cost
effective. In addition, it's quite and smooth operation would make it
very soothing for its passengers on their way to and from work.
All good
things must come to an end!
After everyone had been
offered the chance to drive the trolley bus is was decided to bring to
an end this truly exciting visit. John Blay was presented with a
souvenir and a banner, by Iain Seymour-Hart, and warmly thanked for
giving up his valuable time to demonstrate this quite unique trolley
bus. In reply to a request to bring along AE students, John welcomed
such visits so that this wonderful idea can be exposed to the next
generation of Automotive Engineers.
John
Blay receiving a souvenir from Iain Seymour-Hart
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