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
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!
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
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:
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
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 driverˇ¦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.
boom equipment on the roof of the Trolley Bus
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
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.
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.
Blay receiving a souvenir from Iain Seymour-Hart