The gyrobus is an electric bus that utilizes a flywheel for energy storage instead of overhead wires, designed in the 1940s by Oerlikon as a quieter alternative to battery-electric buses. It features a flywheel capable of spinning at 3000 rpm and can cover 5 to 6 km between charges, which take 2 to 5 minutes; however, its weight and complexity pose challenges. Despite historical hurdles in market presence, rising fuel prices and pollution concerns may renew interest in this technology with modern advancements.

1. Gyrobus
Name: Umesh Kumar Meher
Regd. No. : 1001110211
Branch : MECHANICAL ENGG.

2. 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.

3. • 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

4. 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

5. • 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.

7. 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).

8. • 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.

9. 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.

10. • 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.

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

12. 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.

13. 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.