Introduction

Seminar Report on Gyrobus 2012-2013

INTRODUCTION

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.

A gyrobus is a special bus which does not use a normal engine. It has a big

flywheel of steel or other materials (weighing about one ton) rotating at very high

speed (RPM). By rotating at such high speed, the flywheel stores large amounts of

kinetic energy. This big wheel moves the wheels of the bus. At special stations,

electric engines accelerate the flywheel so the bus can still run. There are not many

buses of this kind because they are very expensive

Dept. Of Electrical & Electronics Engg. G.P.T.C, Muttom


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.

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. It is not clear whether vehicles that require such frequent delays would have

been practical and/or suitable for modern-day service applications.

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.

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 favour of using hydraulic accumulators. During the 1990s, CCM had

developed a flywheel for both mobile and stationary applications.



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.



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.

One of Ghent's gyrobuses has been preserved and restored, and is displayed

at the VLATAM-museum in Antwerp. It is sometimes shown (and used to carry

passengers) at Belgian exhibitions, transport enthusiasts' bazaars, etc. The tram

depot in Merelbeke has been closed since 1998, but it still stands, as it is protected

by the law.



Interior of the Gyrobus G3 (front)

Interior of the Gyrobus G3 (back)



Engine of the Gyrobus G3

Loading up the flywheel



TECHANICAL SPECIFICATION

The Gyrobus prototype was built on the massive chassis of an FB W lorry dating'

from 1932. The flywheel (MFO called it the gyro) was positioned in the centre of this

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.

The principle of operation would be that the bus would "dock" into an overhead

gantry located at selected stops. Contact blades would automatically rise and deliver three

phase electricity to the flywheel at 380V.

This choice of voltage permitted the normal mains power supply to be used,

so minimising the technical installations required. The flywheel could equally be

charged by plugging it into a socket. This was the usual charging procedure at

depots.



The flywheel was spun up with a three-phase asynchronous motor. The same

motor acted as a generator when disconnected from the ground supply. The choice

of an asynchronous brushless machine helped reduce friction within the flywheel

assembly to an absolute minimum. Once in generator mode, power from the

flywheel would be fed to the 52kW asynchronous traction motor, which was

arranged longitudinally behind the rear axle. Capacitors controlled the motor

torque. The arrangement could be reversed, with energy recovered by the motor during

braking or on downhill runs being fed back to the flywheel.

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 fywheel could continue spinning

for more than ten hours. The bus would, however, be plugged in at the depot overnight to

keep the flywheel at 2850 rpm. This was done to permit a quick start in the morning and

also because a full recharge would have posed a heavy load on the grid, A recharge from

standstill could take 40 minutes. The bus could run at up to 55



TYPES OF GYROBUS
YVERDON

The first order was placed by a private company in Yverdon. The Societé

aonyme Gyrobus Yverdon — Grandson (GYG) inauguarted a bus service between

those two places in 1953 using a fleet of two Gyrobuses, numbered 1 and 2. Like

the prototype, these used a chassis by FBW, a body by CWA, and electrics by

MFO. In contrast to the prototype, however, the chassis was purpose-designed for



Gyrobus use, and weight savings were achieved. In keeping with the times, an

angular body style was adopted. The route was 4.5km long and had four recharging

points. In order to speed-up the charging process, the charging voltage was raised

from 380V to 500V in 1954. The small fleet was joined by the prototype that year,

with the new arrival being numbered 3.

The extremely light loadings of the route caused financial difficulties and led

to service cuts. Rather than turing the company's fortunes around, these led to even

greater difficulties. The high electricity consumption and other costs led GYG to

replace its Gyrobuses by diesel minibuses in 1960.

LÉOPOLDVILLE



The next order came from Léopoldville in the Belgian Congo (today

Kinshasa in D.R. Congo). The 12 buses ordered were largely similar to those of

Yverdon and were numbered 101-112. The operator, Société: des transports en

commun de Léopoldville (TCL) used them on a four-route system of about 20km,

making it the largest Gyrobus system ever operated. However poor operating

conditions and the tendency for drivers to deviate from the official routes and drive

on rough unmade roads lead to heavy wear and tear. Consequently, TCL made

generous use of its warranty rights with MFO to obtain spare parts. The outbreak

of war in 1959 finally put an end to Gyrobus operations in Léopoldville.

Gent

The third operator to acquire Gyrobuses was the Belgian SNCV/NMVB.

Three buses numbered G1 to G3 (later 1451-3) were supplied by the usual

consortium, but presented a more rounded front-end, maybe more in line with

Belgian tatses. The Gent — Merelbeke service replaced a tram line in 1956. This


line was and remained an island operation. It was especially the high costs of

electricity that led to abandonment in 1959. One vehicle has survived and is

preserved in the tram museum in Antwerpen. This vehicle, the only know Gyrobus

survivor, visited Yverdon in 2003 to mark the 50th anniversary of that system.

Other gyro applications

Besides these Gyrobuses, it should be noted that similar flywheels by MFO

found use on various mining locomotives in Switzerland, Belgium and in Africa.

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.



A further recurring issue was the high cost of electricity (or shall we say low cost

of fuel). Furthermore, the manufacturers would appear to have been unfortunate in

their choice of pilot projects, with many of the problems being external rather than

strictly technical. Not necessarily a disadvantage but certainly a point worth noting

was the dynamic behaviour of the vehicle. The spinning flywheel acts like a giant

gyroscope and so resists changes in orientation. This had to be taken into account

be the driver and so induced an adapted driving technique. At the same time, this

gyroscope effect led to a very smooth ride. As reduced comfort through eratic

driving is precisely an argument that is often used against buses, this is certainly

something worth looking into

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.



ADVANTAGES

 "Pollution-free" (Pollution confined to generators on electric power grid.)

 Runs without rails (An advantage because the route can be varied at will.)

 Can operate flexibly at varying distances



DISADVANTAGES

 Weight: a bus which can carry 20 persons and has a range of 20 km requires

a flywheel weighing three tonnes.

 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.

 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.



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.



CONCLUSION

Since 1955 there have been some practical applications of electrogyrobuses.

Such buses are equipped with a flywheel unit consisting of an asynchronous motor

and generator coupled to a flywheel and of electric traction motors. The unwinding

of the flywheel of an electrogyrobus is accomplished with the aid of an electric

motor. The stored kinetic energy is sufficient for traveling a distance of 4-5 km.

The efficiency of an electrogyrobus is not better than 50 percent. The weight-to-

work ratio of the flywheel unit is 322 kg/kWh (32 times greater than that of the

currently used electrochemical current sources). The unit operational expenses of

an electrogyrobus are 5 percent greater than those of a trolleybus and 20 percent

greater than those of an autobus. Experimental electrogyrobuses have been

operated on some interurban runs, for instance, between Ghent and Merelbeke

(Belgium). The electrogyrobus is an auxiliary means of passenger transport on

short runs; it is also usable in transporting dangerously explosive objects.



REFERENCES

 "the GYROBUS: Something New Under the Sun?". Motor Trend: p. p37.

January 1952.

 Access to Energy Newsletter, Archive Volume: Volume 7, Issue/No.: Vol. 7,

No. 8, Date: April 01, 1980 03:23 PM, Title: Anniversary of the Grand

Disaster, Article: The Flywheel Bus is Back

 Center View (CTE) Spring 2005



CONTENTS
 Introduction : 01

 Development : 02

 Early commercial service : 05

 Techanical specification : 09

 Types of gyrobus : 13

 Advantages : 18

 Disadvantages : 19

 Further developments : 20

 Conclusion : 21

 References : 22



ABSTRACT

Since 1955 there have been some practical applications of

electrogyrobuses. Such buses are equipped with a flywheel unit

consisting of an asynchronous motor and generator coupled to a

flywheel and of electric traction motors. The unwinding of the flywheel

of an electrogyrobus is accomplished with the aid of an electric motor.

The stored kinetic energy is sufficient for traveling a distance of 4–5 km.

The efficiency of an electrogyrobus is not better than 50 percent. The

weight-to-work ratio of the flywheel unit is 322 kg/kWh (32 times

greater than that of the currently used electrochemical current sources).

The unit operational expenses of an electrogyrobus are 5 percent greater

than those of a trolleybus and 20 percent greater than those of an

autobus. Experimental electrogyrobuses have been operated on some

interurban runs, for instance, between Ghent and Merelbeke (Belgium).

The electrogyrobus is an auxiliary means of passenger transport on short

runs; it is also usable in transporting dangerously explosive objects.


Introduction

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