Gyrobus
[
attachment=36747]
A Gyrobus is an electric bus that uses
flywheel energy storage, not overhead wires
like a trolleybus. The name comes from the
Greek language term for flywheel, gyros.
While there are no gyrobuses currently in
use commercially, development in this area
continues.
Development
The concept of a flywheel-powered bus was
developed and brought to fruition during the
1940s by Oerlikon (of Switzerland), with
the intention of creating an alternative to
battery-electric buses for quieter,
lower-frequency routes, where full
overhead-wire electrification could not be
justified.
Rather than carrying an internal combustion engine or batteries, or connecting to overhead powerlines, a gyrobus
carries a large flywheel that is spun at up to 3,000 RPM by a "squirrel cage" motor.[1] Power for charging the
flywheel was sourced by means of three booms mounted on the vehicle's roof, which contacted charging points
located as required or where appropriate (at passenger stops en route, or at terminals, for instance). To obtain tractive
power, capacitors would excite the flywheel's charging motor so that it became a generator, in this way transforming
the energy stored in the flywheel back into electricity. Vehicle braking was electric, and some of the energy was
recycled back into the flywheel, thereby extending its range.
Fully charged, a gyrobus could typically travel as far as 6km on a level route at speeds of up to 50 to 60 km/h,
depending on vehicle batch (load), as top speeds varied from batch to batch. The installation in Yverdon-les-Bains
(Switzerland) sometimes saw vehicles needing to travel as far as 10 km on one charge, although it is not known how
well they performed towards the upper end of that distance.
Early commercial service
The first full commercial service began in October 1953, linking the Swiss communities of Yverdon-les-Bains and
Grandson. However, this was a route with limited traffic potential, and although technically successful it was not
commercially viable. Services ended in late October 1960, and neither of the two vehicles (nor the demonstrator)
survived.
The next system to open was in Léopoldville in Belgian Congo (currently Kinshasa in the Democratic Republic of
the Congo). Here there were 12 vehicles (although apparently some reports suggest 17), which operated over four
routes, with recharging facilities being provided about every 2 km. These were the largest of the gyrobuses, being
10.4 m in length, weighing 10.9 tonnes, carrying up to 90 passengers, and having a maximum speed of 60 km/h
(about 37 mph).
There were major problems related to excessive "wear and tear". One significant reason for this was that drivers
often took shortcuts across unpaved roads, which after rains became nothing more than quagmires. Other problems
included breakage of gyro ball bearings, and high humidity resulting in traction motor overload. The system's
demise, however, came because of high energy consumption. The bus operator deemed that 3.4 kWh/km per gyrobus
was unaffordable, so closure came in the summer of 1959 with the gyrobuses being abandoned.
The third location to use gyrobuses commercially was Ghent, Belgium. Three gyrobuses started operation in late
summer 1956 on a route linking Ghent and Merelbeke (the route Gent Zuid - Merelbeke). The flywheel was in the
center of the bus, spanning almost the whole width of the vehicle, and having a vertical axis of rotation.
The Ghent - Merelbeke route was intended to be the first of a proposed multi-route network. Instead its Gyrobuses
stayed in service for only three years, being withdrawn late autumn 1959. The operator considered them unreliable,
"spending more time off the road than on", and that their weight damaged road surfaces. They were also considered
to be energy hungry, consuming 2.9 kWh/km—compared with between 2.0 kWh/km and 2.4 kWh/km for trams with
much greater capacity.
Further developments
After the Gyrobus was discontinued in all locations, there have been a number of attempts to make the concept work.
Recently, there have been two successful projects, though the original idea of storing energy has been changed
considerably: In Dresden, Germany there is the "Autotram", a vehicle that looks like a modern tram, but moves on a
flat surface, not on tracks. It has run since 2005 and is powered by a flywheel, though the wheel is small and only
used to store energy from braking. The main source of energy is a fuel cell. The second successful vehicle was the
Capabus, which ran at the Expo 2010 in Shanghai. It was charged with electricity at the stops - just like the Gyrobus
was. However, instead of using a flywheel for energy storage the Capabus utilized capacitors.