Gyrobus

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See also: Electric bus

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.

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[edit] 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 speeds of up to 3,000 rpm by an electric motor. 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 / felt desirable (eg: bus stops en route, at termini, etc). To obtain tractive power, condensers would excite the flywheel's charging motor so that it become 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.

Charging a flywheel took between 30 seconds and 3 minutes, and, in an effort to reduce the time this took, the supply voltage was increased from 380 volts to 500 volts. It can only be speculated whether such frequent delays would have been acceptable had the gyrobuses survived—in commercial service—into the modern era, especially on longer routes where several charging stops could have been required or on busy, heavily trafficked roads.

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, 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 (or otherwise!) towards the upper end of that distance.

The demonstrator was first displayed (and used) publicly in summer 1950, and, to promote the system, this vehicle continued to be used for short periods of public service in a myriad of locations at least until 1954.

In 1979, General Electric was awarded a $5 million four year contract by the United States government, the Department of Energy and the Department of Transportation, to develop a prototype flywheel bus*. [1]

*Editors note: Further information on this project would be appreciated!

In the 1980s, Volvo briefly experimented with using flywheels charged by a small Diesel engine and recharged via braking energy. This was eventually dumped in favor of using hydraulic accumulators.

In 2005, the Center for Transportation and the Environment, working with the University of Texas at Austin, Center for Electromechanics, Test Devices, Inc., and DRS Technologies sought funding for the development of a prototype gyrobus. [2]

[edit] 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 Léopoldsville in Zaïre (former Belgian Congo and currently known as Kinshasa in the Democratic Republic of the Congo). Here there were 12 vehicles (although apparently some reports erroneously 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 t, carrying up to 90 passengers, and having a maximum speed of 60 km/h (about 37 mph).

However, all did not go well, with there being major problems related to excessive "wear and tear". But it seems that a significant reason for this was because the bus drivers often took shortcuts across unpaved roads, which after the frequent heavy rains became nothing more than quagmires and marshes. Other problems included breaking 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 dumped next to a bus garage and left to rust.

The third location to use gyrobuses commercially was Gent, Belgium. Three gyrobuses started operation in late summer 1956, but instead of being the first of a proposed multi-route network they did not last very long, being withdrawn late autumn 1959. It seems that the operator was blaming them for being unreliable, "spending more time off the road than on", and that their weight damaged road surfaces. They were also seen as being energy hungry, consuming 2.9 kWh/km—compared to between 2.0 kWh/km and 2.4 kWh/km for much larger trams that carried several times the numbers of passengers. One of the three gyrobuses has been preserved, and is sometimes displayed as a curio (or even used to carry passengers!) at Belgian exhibitions, transport enthusiasts' bazaars, etc.

The three gyrobuses connected Gent with near small town Merelbeke (the route Gent Zuid - Zwijnaarde - Merelbeke). The one of them survived and was reconstructed. Now you can see it in old tram depot in Merelbeke. The flywheel is situated in the middle of the bus (almost over the whole width), the axis of rotation is vertical.

[edit] Advantages

  • Quiet
  • "Pollution free" (Pollution confined to generators on electric power grid)
  • Gets along without tracks (Once thought of as an advantage because the route could be varied at will)
  • Can operate flexibly at varying distances

[edit] Disadvantages

  • Weight, a bus which can carry 20 persons and has radius of 20 km, must carry a flywheel which weighs 3 t.
  • The flywheel, which turns at 3000 revolutions per minute, requires special attachment and security—because of the external speed of the disk is 900 km/h.
  • Driving a gyrobus has the added complexity that the flywheel acts as a gyroscope and so always has the same attitude, even when the bus goes around curves or corners.

[edit] External links

Buses
Articulated bus – Double-decker bus – Guided bus – Gyrobus – Low-floor bus – Midibus – Minibus
Motorcoach – Party bus – School bus - Transit bus – Trolleybus
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