Gyro bus

Gyrobus

Name: Umesh Kumar Meher

Regd. No. : 1001110211

Branch : MECHANICAL ENGG.

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.

• The concept of a flywheel-powered bus was developed and brought to originality during the 1940s by Oerlikon

(of Switzerland), with the intention of creating an alternative to battery-electric buses for quieter, where full overhead-wire electrification could not be justified.

History

Rather than carrying an internal combustion engine or batteries, or connecting to overhead power lines, a gyrobus carries a large flywheel

that is spun at up to 3,000 RPM by a "squirrel cage" motor/generator.

Working Principle

• The flywheel was positioned in the centre of the chassis between the axles. This disc weighing 1.5t and with a diameter of 1.6m was enclosed in an airtight chamber filled with hydrogen gas at a reduced pressure of 0.7 bar to lower "air" resistance. The flywheel would spin at a maximum of 3000rpm.

Flywheel

Flywheel

Power for charging the flywheel was sourced by means of three contact blades 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).

Contact Blades

• Charging a flywheel took between 30 seconds and 3 minutes; in an effort to reduce the charge time, the supply voltage was increased from 380 volts to 500 volts.

• Given the relatively restricted range between charges, it is likely that several charging stops would have been required on longer routes, or in dense urban traffic.

To obtain tractive power, capacitors would excite the flywheel's charging motor (Electric motor generator) so that it became a generator, in this way transforming the energy stored in the flywheel back into electricity.

• In normal operation the flywheel could slow down from its initial 3000 rpm to 2100 rpm. In emergencies the speed could further be reduced to 1500 rpm, but this would negatively affect the performance of the vehicle. Below this speed a proper functioning of the transmission could no longer be guaranteed.

• Under normal conditions, the Gyrobus could cover 5 to 6km between charges (taking stops and traffic into account). A charge would then take two to five minutes.

• In idle mode, the flywheel could continue spinning for more than ten hours.

• A recharge from standstill could take 22 minutes.

Advantages

• Quiet• Pollution-free• Runs without rails• Can operate flexibly at varying distances

Disadvantages

• Weight: a bus which can carry 20 persons and has a range of 5 km (3.1 mi) requires a flywheel weighing 3 tone .

• The flywheel, which turns at 3000 revolutions per minute, requires special attachment and security—because the external speed of the disk is 900 km/h (560 mph).

• Driving a gyrobus has the added complexity that the flywheel acts as a gyroscope that will resist changes in orientation, for example when a bus tilts while making a turn, assuming that the flywheel has a horizontal rotation axis.

Conclusion• One of the main obstacles facing the Gyrobus was its inability to

gain a firm market presence and so cut down manufacturing costs through economy of scale.

• In today's environment, many of the factors that disadvantaged the Gyrobus have changed.

• Fuel prices are rising and concerns over pollution and smog have led to experiments with such inefficient and dangerous storage technologies as hydrogen cells (which appear to be more in political favour than technologically sound).

• Would a simpler, safer and more comfortable alternative not do the same in a friendlier manner?

• Modern power electronics would help reduce power consumption whilst also enabling faster charging. Modern materials could help reduce the overall weight of the bus while retaining the required robustness. Maybe the Gyrobus is far from dead.

THANK YOU