The Steam
Turbine and Other Inventions of Sir
Charles Parsons,
O.M. by R H Parsons
(1942)
Reprinted by David Steinberg
with permission of copyright holders the British Council.
ILLUSTRATED
PUBLISHED FOR
THE BRITISH COUNCIL
BY LONGMANS, GREEN AND CO.
CONTENTS
OTHER USES OF THE STEAM TURBINE ON LAND
PARSONS' WORK ON SCREW
PROPELLERS .
MECHANICAL GEARING FOR MARINE AND LAND TURBINES
PARSONS' WORK ON
SEARCHLIGHT REFLECTORS
ILLUSTRATIONS
THE FIRST PARSONS STEAM TURBINE
PARSONS TURBO-ALTERNATOR AT CHICAGO
PARSONS TURBO-ALTERNATORS IN BARKING POWER STATION
LOW-PRESSURE ROTOR OF A 70,000 H.P. TURBINE
THE 'MAURETANIA' WITH THE 'TURBINIA'
SIR CHARLES PARSONS AND HIS WORK
Since
the amenities of civilised life depend almost entirely on the availability of
power for industrial purposes, those pioneers who have provided mankind with
the means of obtaining power more cheaply and abundantly will always rank high
among the benefactors of humanity. From this point of view no man has made a
greater contribution to human welfare than Sir Charles Parsons by the
revolutionary improvements he brought about in the use of steam. His name will
always be particularly associated in the minds of the public with the invention
of the steam turbine and its application to duties on land and sea, although,
as will be seen, his
contribution to the advance of science and engineering extended far beyond
the limits of a single invention. Even if Parsons had done nothing more than
produce the first practical steam turbine his fame as an engineer would have
been secure for all time. By its introduction he exercised an influence upon
industry that was comparable only with that of Watt about a century earlier,
though vastly more far-reaching in its effects by reason of the wider field
open to him.
When
Watt built his first condensing steam engines, the operation of pumping
machinery for mines was almost the only duty for which engines were required.
Towards the end of the eighteenth century steam engines began to take the place
of water wheels as prime movers for mills and factories, but as the dynamo had
not then been invented, the generation of electricity and all the industrial
development that depends on it lay still in the future. Nor was there at the
time, except perhaps in the minds of a few enthusiasts, any idea that steam
would ever be used for the propulsion of ships. There is no evidence that Watt
foresaw the immense field there would be for steam power in marine work, even
though his firm of Boulton and Watt constructed the engine that drove
THE
STEAM TURBINE
Parsons,
alone among his contemporaries, saw in the turbine principle the means of
escape from the limitations of the reciprocating engine, or perhaps it would be
more accurate to say that he alone possessed the genius and courage to
transform a possibility into a reality. That he foresaw from the outset the
wide diversity of the duties to which the turbine could be applied is clear
from his earliest patents, which also showed a remarkable understanding of the
conditions essential to success in meeting the requirements of each particular
case. Problem after problem was solved in the most admirable way, and. instead
of being merely an ingenious toy, as many people at first considered it, the
turbine steadily and surely won recognition as the standard type of prime mover
wherever the production of steam power was concerned. It can be constructed for
far larger outputs than any reciprocating engine, and it is moreover much more
economical of steam. Indeed, apart from the benefits that the work of Parsons
has conferred upon the present generation, the economy which he made possible
in the consumption of the exhaustible fuel resources of the world entitles him
to the gratitude of posterity.
For
those who are not acquainted with the principle of the steam turbine, it may be
well to explain briefly the nature of the great invention of Parsons. The
object that he set himself was that of producing power by utilising the
velocity of a jet of steam, instead of using the pressure of the steam to drive
a piston as in the ordinary reciprocating engine. It was evident that a jet of
steam could be made to turn a wheel by acting on blades set around its
circumference, or alternatively it could be used to develop power by its own
reaction when escaping tangentially from an orifice in a rotating wheel or arm.
Both devices had already been suggested by innumerable inventors, but the
hitherto insuperable difficulty in constructing a practical turbine by either
method lay in utilising the excessive velocity of the steam. Even steam at a
comparatively low pressure escaping into the atmosphere may easily be
travelling at more than 2500 feet per second, or over I700 miles an hour, while
twice this velocity may be attained by high-pressure steam flowing into a good
vacuum. To make use of such velocities effectively in a simple turbine, the
blades or other moving elements would have to travel at about half the speed of
the steam, for otherwise an undue proportion of the energy of the jet would be
uselessly carried away in the steam leaving the wheel. The blade speeds
required for efficiency would therefore be so high that they would be
prohibited by reason of centrifugal force alone, apart from other
considerations. That Watt, with his sound engineering instinct, had appreciated
this fact’ is shown by one of his letters to Boulton. His partner had expressed
fears as to the effect that the competition of a proposed steam turbine might
have on their engine-building business, but Watt had disposed of them with the
remark that ' Without God makes it possible for
things to move 1000 feet per second, it cannot do much harm'.
Although
there are to-day large turbines containing blades whose tips travel at speeds
even greater than Watt thought would be possible only by a special dispensation
of
The
principle of subdividing the whole expansion of the steam into a number of
stages, so that only comparatively moderate velocities have to be dealt with,
still forms the basis of all efficient turbine design. The secondary principle
of utilising the 'reaction' of the steam expanding in moving blades has remained
typical of the Parsons turbine. It is not, however, an indispensable
characteristic of an efficient turbine, and certain inventors subsequent to
Parsons, notably C. G. Curtis in the United States and Professor A. Rateau in
France, preferred for constructional reasons to confine the expansion of the
steam to fixed nozzles. Machines of the latter type, in which the steam drives
the blading of each stage by virtue of its velocity only, are known as
'impulse' turbines. Although they have attained an honourable position in the
industry, it is generally recognized that the 'reaction' principle, chosen by
Parsons for his original turbine, is conducive to the highest efficiency, so
that large machines which are nominally of the impulse type are now often
designed to work with a certain amount of reaction in their blading.
In
addition to laying down the broad lines necessary to success in the development
of the new kind of prime mover, Parsons had many practical problems to solve
before his ideas could be embodied in an actual machine. Not only had a
suitable form of blading to be invented and appropriate manufacturing methods
devised, but the design generally had to conform to conditions quite outside
the range of ordinary engineering practice. For example, to obtain the desired
blade velocity in the small turbine he first constructed a rotational speed of
no ,000 revolutions per minute had to be adopted. This was over
fifty times as fast as the fastest reciprocating engine of the day, and It
involved the invention of a new kind of bearing which would permit of a long
rotor, inevitably out of mathematically perfect balance, running at such a
speed without vibration. Means had also to be provided for the continuous
lubrication of these bearings, and a totally new method of controlling the
speed of the machine had to be devised. Again, it was realised that the flow of
the steam would result in an end-thrust on the blading, and to prevent this
being transmitted to the bearings, where it might have caused trouble, Parsons
neutralised it by the ingenious expedient of admitting the steam midway along
the rotor and causing it to flow equally towards each end. His subsequent
invention of 'dummy pistons' rendered the double flow principle unnecessary for
machines of moderate output, but without it the large and efficient high-speed
machines of to-day could hardly be built. A study of Parsons' first turbine
patent, taken out in 1884, will show how clearly he appreciated the
difficulties in his path and how thoroughly he had considered the means of
overcoming them. Again, obvious as the principle of expanding the steam by
stages now appears to us, the invention must be regarded in the light of the
state of the art at the time. The only previous attempts to develop any useful
amount of power from steam, otherwise than by causing it to drive a piston, had
taken the form of machines driven by the reaction of jets issuing from the ends
of rotating arms, on the lines of the classical Aeropile of Hero of Alexandria.
The famous Cornish engineer, Richard Trevithick, had constructed what he called
a ''whirling engine' on this principle in 1815, and other more or less workable
machines of the same kind had been made from time to time, but the lessons to
be drawn from them were rather of warning than encouragement. It is true that
various inventors had propounded plans for the more rational utilisation of
steam in machines of the turbine type, but no such machines had assumed a
practical form and steam engineers in general believed that any attempt to
supersede the reciprocating engine as a prime mover was foredoomed to failure.
The success of Parsons' first little turbine marked the beginning of the most
revolutionary change in the history of steam engineering. By developing power from the velocity of steam rather
than from its static pressure,
the turbine was exempt from the
mechanical limitations of the reciprocating engine. Its invention has enabled
the power that could be produced by a given weight and size of machinery to be
multiplied a hundredfold and it has provided that purely rotational motion at
high speed so desirable for the
driving of electrical generators and many other classes of machinery. In
addition to these advantages, it has brought about a remarkable economy in the use
of steam.
THE
TURBO-GENERATOR
The
most obvious field for such a
high-speed prime mover as the turbine was in the driving of electric
generators, and it was for this
purpose that it was originally designed. The dynamos of those days were small machines
driven usually at 1000 to 1500 revolutions per minute by a belt from the flywheel of a reciprocating
engine. Parsons required a dynamo that could be driven directly by his turbine
at a speed of 18,000 revolutions per minute, in order that the combination
should constitute a small, simple and self-contained generating unit. None of
the established dynamo makers would have considered for a moment the construction of a machine so completely outside
the range of previous experience. It must be remembered that at the time
electrical engineering was in a very elementary condition and dependent mainly
upon empirical knowledge, for two
years had still to elapse before Hopkinson propounded the theory of the
magnetic circuit and laid down the fundamental principles of the design of
electrical machinery. Parsons faced the question with the same boldness that he
showed in the design of his turbine and he achieved an equally striking
success. Both electrical and mechanical problems had to be solved, for the alternations of magnetism in
the core were vastly more rapid than in any machine yet built, while the
mechanical stresses to be provided against will be realised from the fact that a centrifugal force of 5.5 tons was developed by
every pound of metal at the surface of the armature. The dynamo was of the
bi-polar type with an output of 75 amperes at 100 volts. Both turbine and
dynamo fulfilled the anticipations of their designer, and after many years of
useful work this historic unit was presented to the
It
required much persistence on the part of Parsons before his turbo-generators
were able to enter their proper field of central station work. By 1888, although
about two hundred of them were in service, they were employed almost
exclusively for ship-lighting duties, and no electric light company had yet
taken any notice of them. Parsons therefore decided that he would, himself,
have to effect the introduction of the turbine into the industry that it was
destined to dominate; so, aided by friends, he founded the
Progress
thenceforward was rapid. The success of the turbine in saving the chief London
station of the Metropolitan Electric Supply Co. from being shut down altogether
in 1894 on account of the nuisance caused by its reciprocating engines
attracted general attention and definitely established its footing in the
industry. Larger and larger units were continually called for, and with every
increase in size the advantages of the turbine became more apparent. Parsons'
earlier machines had been constructed at the works of Messrs Clarke, Chapman
and Co., in which firm he was a partner, but in 1889 he founded the present
firm of Messrs C. A. Parsons and Co., Ltd., at Heaton, near
The
growth of electricity supply consequent upon the invention of the turbine
created a demand, not only for larger generating units, but also for higher
transmission voltages in order that more extensive areas might be economically
served. In the early days the practice had been to generate at about 2000
volts, and to step up this pressure when required by means of transformers.
Ferranti had given a lead in the direction of higher generating voltages in
1889 by designing large slow-speed alternators to generate single-phase current
at 10,000 volts for his famous Deptford Station. These machines were, however,
recognised as exceptional and they had little or no influence on the industry
generally. The first real advance towards modern conditions was made by Parsons
in 1905 when he supplied a pair of 1500 kw. turbo-alternators generating at
11,000 volts to the Frindsbury Power Station in
Enough
has been said to indicate, in some small measure, how much the electrical
industry owes to Parsons. He not only provided it with the turbo-generator, but
led the way for more than a generation in every important development of
power-station machinery. Excepting the introduction of the cylindrical form of
rotor for turbo-alternators by the late C. E. L. Brown, who was building
turbine machinery on the Continent under Parsons' patents, it may fairly be
said that there was no notable improvement in the design of high-speed
electrical machines that did not originate in the Heaton Works. Moreover,
whenever a larger type of machine was called for, Parsons was ready to
construct it, even if far beyond the capacity of anything previously built,
provided only he was satisfied that the requirements could be successfully
fulfilled. His enterprise was never restrained by considerations of what had
been done, but only by what could be safely accomplished with the materials of
the day. Typical of his engineering courage was the jump from 350 to 1000 kw.
in 1900, and the still more spectacular leap from 6000 to 25,000 kw. in 1912.
He was an equally great pioneer in all matters pertaining to efficiency. As
long ago as 1900 he made the first practical experiments with regard to the
reheating of steam in the course of its expansion, and later proved the
benefits of this procedure in the important power stations of
Parsons,
again, was the first engineer to take practical advantage of the possibility of
effecting an improvement of the thermodynamic cycle of a steam turbine plant by
the regenerative heating of the feed water, a development for which he
acknowledged his indebtedness to the original proposal of Mr James Weir in 1876.
He applied this principle in the Blaydon Burn Power Station in 1916 by heating
the feed water progressively by means of partially expanded steam extracted
from the turbine at different pressures, a procedure which has since been
adopted as an indispensable feature of every efficient steam power plant in the
world. The result of these advances, coupled with innumerable other
improvements due to his prolific brain, enabled him to construct generating
units capable of operating with a heat consumption of no more than 9280
B.T.U.per kw. hour, a figure that even to-day could hardly be surpassed by the
largest and most efficient machines in existence.
Although
the technical merits of Parsons' work in the development of turbines and
electrical generators can only be fully appreciated by experts, the benefits
that have accrued from it are obvious to all. It is sufficient to contemplate
the part played by electricity in our domestic and industrial well-being to
realise how greatly we are dependent upon a cheap and abundant supply. This has
come to be regarded as one of the necessities of civilised life, and it is very
certain that the service we now enjoy would have been utterly impossible
without the turbo-generator. The cheapness of electricity produced by a steam
power station depends mainly upon three factors, namely the quantity of fuel
required to generate it, the capital charges on the station and equipment, and
the expenses of running and maintaining the plant. On all of these the
influence of turbine machinery has been profound. A modern station can be
operated with a fraction of the fuel that would have been necessary for the
same output in the days of the reciprocating engine, chiefly because the
turbine can take advantage of a far greater range of expansion of the steam.
The capital and labour charges are less because of the larger sizes of
individual turbine units, while the maintenance costs are much reduced on
account of the much greater simplicity and reliability of turbine machinery.
The economy of fuel that has been due to the work of Parsons is incalculable.
In the power stations of
OTHER USES OF THE STEAM TURBINE ON LAND
Although
the steam turbine finds its greatest field of usefulness on land in power
stations and in driving the electrical generators in private plants, it has
many other industrial applications. Turbines were employed at a very early date
for driving centrifugal pumps, fans and blowers, all of which were naturally
suitable for direct operation by a high-speed prime mover. Parsons also
realised that if a turbine were driven by power, instead of being used to
produce it, the machine could be used as a compressor. Many compressors for air
and gas were constructed by him on the principle of the reversed axial-flow
turbine. Better results, however, appeared at the time to be obtainable by
machines working on the centrifugal principle, so that the axial-flow
compressor fell into disuse. The researches in aerodynamics carried out in
recent years have now led to a better understanding of the action of the blades
in an axial compressor, with the result that the earlier difficulties have been
overcome, and the present tendency is to revert to the type of machine originated
by Parsons, especially when the highest efficiency is imperative.
The
perfection of toothed gearing, to which Parsons contributed so greatly by his
invention of the 'creep' system of cutting the teeth of gearwheels, opened up the
whole industrial field to the turbine, as it was then no longer confined to the
driving of such high-speed machinery as could be directly coupled to it. It was
successfully applied even to the driving of steel rolling mills and other
duties of a similarly exacting nature, and was often used to replace ordinary
steam engines for driving the main shafts of factories. Even when reciprocating
engines were retained, the ability of the turbine to work with steam at very
low pressures was frequently taken advantage of by installing turbines to
develop extra power from the exhaust steam of the engines which had hitherto
been blown to waste. Under other circumstances turbines could be used to
generate the whole of the power required, and supply at the same time any
desired amount of partially expanded steam at a given temperature and pressure
for heating and process work. In all
these developments Parsons took a leading part, providing turbine machinery to
meet the most diverse requirements and thereby enabling factories and
industrial undertakings to produce their own power much more cheaply and
efficiently than before.
THE
STEAM TURBINE AT SEA
The
use of the steam turbine for the propulsion of ships was among the claims made
by Sir Charles Parsons in his original patent of 1884, but he confined his
energies at first to the task of establishing the position of the turbine on
land, and it was not until 1894 that he took steps to apply it to marine
duties. His works at Heaton were then so fully occupied with turbo-generators
that he decided to establish a separate organisation, with works at
Wallsend-on-Tyne, to deal with the special problems involved in marine
propulsion. This company, which became known later as The Parsons Marine Steam
Turbine Co., Ltd., proceeded immediately with the construction of a little
vessel whose fame is now historic. This was the Turbinia[1] with a length of 100 feet and a
displacement of 44 tons. After much experimental work with her propellers, the Turbinia attained a speed of 34 knots, which
was a very remarkable achievement, since the fastest destroyers of the time
could hardly exceed 27 knots. The fact that the steam turbine was inaugurating
a new era in marine practice was brought home to the public in an unmistakable
manner at the great Naval Review held in 1897 to celebrate the Diamond Jubilee
of Queen Victoria. A vast fleet, representing not only the might of the British
Navy, but the sea-power of other leading nations as well, was assembled off
Spithead when the little Turbinia,
with Parsons himself in control of the machinery, created a sensation by
racing down the lines of warships at a speed obviously greater than that of any
other vessel afloat. The Admiralty could not ignore such a demonstration, and
entrusted Parsons with the construction of a 30-knot turbine-driven destroyer,
H.M.S. Viper[2], but so grudgingly was the order
given that Parsons and his associates were required to deposit a sum of no less
than £100,000
as a security, in case the vessel should not come up to expectations. These,
however, were more than fulfilled, the Viper attaining a speed of
over 37 knots when officially tested over the measured mile with turbines
developing 12,000 H.P. A second turbine-driven destroyer, built about the same
time, was taken over by the Admiralty and added to the Navy under the name of
H.M.S. Cobra; but
shortly afterwards both of these boats were lost at sea by accidents quite
unconnected with the nature of their machinery, so that the little Turbinia became once again the only
representative of the turbine principle afloat.
The
lives of the Viper and Cobra had been brief, but their
performance had attracted the attention of certain enterprising engineers
connected with the Merchant
The
first turbine vessel to cross the
The
greatness of the contribution that Parsons had made to Naval progress will be
understood from the words used by the First Lord of the Admiralty in
justification of the decision to adopt turbine machinery. The turbine system,
he said, had been decided on 'because of the saving in weight and reduction in
the number of working parts and reduced liability to breakdown; its smooth
working, ease of manipulation, saving in coal consumption at high powers, and
hence in boiler-room space, and saving in engine-room complement; also because
of the increased protection provided with this system, due to the engines being
lower in the ship'.
Most
of the reasons which caused the Admiralty to renounce reciprocating engines in
favour of turbines in Naval vessels applied with equal force to a large part of
the Mercantile Marine. Indeed, the conditions of service of fast liners,
required to make uninterrupted passages at full speed across the ocean, enabled
the turbine to make an even more advantageous showing than in war vessels,
which were rarely required to navigate at full speed. In 1904 the British Government came to an arrangement with the
Cunard Company, under which the latter should construct two new liners with an
average speed of at least 24.5 knots, in order to be serviceable, not only as
fast mail carriers but also as Naval auxiliaries in the event of war. The
question of their propelling machinery was referred to a strong Commission
representative both of the Admiralty and the leading shipbuilding firms, who
reported definitely in favour of the turbine. This decision, coupled with that
of the Admiralty to adopt turbine propulsion exclusively in the Navy, shows how
enormous had been the change in practice since the first appearance of the Turbinia only ten years before. The two new
liners, the
Enough
has been said to show that the success of the turbine at sea was no less
striking than its achievements on land, and its supremacy over the
reciprocating engine for all the most important classes of service was even
more rapidly established. It permitted vessels to be driven at speeds that had
previously been impossible, and enabled those speeds to be maintained in the
roughest of seas. In warships the turbine machinery could be protected more
effectively than engines, the fuel economy was greater and the maintenance
costs less. Commercial vessels benefited similarly in speed and economy by
turbine propulsion, while the space available for cargo and passengers was
increased and vibration was lessened. The cumulative effect of these advantages was sufficient to
establish the turbine, within a few years only, as the recognised prime mover for all the Navies of the world, as well as for all the
fastest ocean liners. The subsequent introduction by Parsons of gearing between the turbines and
the propellers was another great step in advance, for it not only diminished
the size of the machinery and increased its efficiency, but it enabled the
ordinary cargo vessel to profit equally by the employment of turbines.
The
turbine, however, has never altogether succeeded in ousting the well-tried
marine engine from slow-speed
cargo vessels. On the contrary it did much to give the engine a new lease of
life, for by the addition of a turbine to develop power from the exhaust steam
of the engines, the efficiency of the
machinery was considerably increased. A combination of this kind was patented
by Parsons in 1906, and was first used on a commercial scale in the 10,000-ton
S.S. Otaki in 1908. This
vessel showed a reduction in service of 12 per cent in fuel consumption as
compared with her sister ships equipped with engines only, the saving amounting
to 750 tons of coal on the
round voyage to
The
insistent desire of shipowners for an even greater economy of fuel led to the
development of the marine oil engine, which, after the end of the war of
1914-18, began to challenge the supremacy of turbine machinery, particularly
for mercantile vessels of slow and moderate speed. The turbine, however, had
the advantage of much greater mechanical simplicity, and Parsons sought to
bring its fuel consumption more nearly into line with that of the oil engine by
urging the adoption of higher steam pressures and temperatures at sea. Although
marine engineers had been converted to a belief in turbines and gearing, they had
always been conservative in the matter of boiler practice. In 1926 conditions
in the mercantile marine did not much exceed a pressure of 200 lb. per sq. inch
and a temperature of 500°
F. In Naval work matters were somewhat better, but not much, as the steam
pressure in warships was only about 275 lb. Practice on land was very much more
advanced. At that time many central stations were already using steam at 500 or
600 lb. pressure, superheated to 750° F. or over, while in some cases
pressures of the order of 1400 lb. per sq. inch had been adopted. Parsons felt
very strongly that marine engineers ought to take advantage of the economies
resulting from higher pressures and temperatures. Knowing that a practical
demonstration was the surest and quickest way of convincing the sceptics, he
arranged for the equipment of a small passenger vessel, the King George V, with geared turbines of 3500 H.P.
to work with steam at 550 lb. per sq. inch, superheated to 750° F. The steam was
supplied by water-tube boilers of the Yarrow type. The King George V was the pioneer of high-pressure
steam at sea. Although the installation was a comparatively small one, and the
conditions of a river steamer making short trips with frequent stops were not
the most favourable for the experiment, the machinery fulfilled the
expectations of its designers, the full-load trials made after a short period
of commercial service showing a steam consumption of only 8.01 lb. per shaft
horse-power hour of the turbines. This enterprise of Parsons once more opened
up a new field for marine engineers, and higher pressures at sea soon became
general. Within the next few years there were a number of
PARSONS'
WORK ON SCREW PROPELLERS
The
application of the steam turbine to marine propulsion gave rise to many
incidental problems, by the solution of which Parsons made notable
contributions to the progress of marine engineering. One of the earliest
difficulties he encountered was due to the high speed of the propellers. The
first machinery of the Turbinia
consisted of one turbine driving a single propeller at 2000 R.P.M. The
results of the trials were disappointing. Different designs of propeller were
tried but the best speed that could be obtained was only about 20 knots. It was
clear, either that the turbine was not developing its rated power, or that the
efficiency of the propeller was extremely low. To settle this question Parsons
devised a special apparatus to measure the torque exerted by the turbine on the
propeller shaft. This instrument was the prototype of the modern torsion meter,
and by its use he assured himself that the fault was in the propeller and not
in the turbine. About the same time similar difficulties in obtaining the anticipated
speed were experienced in a new class of very fast torpedo-boats which were
fitted with reciprocating engines. Both Parsons and the Naval authorities
arrived at the same conclusion, namely, that the trouble was caused by the
inability of the water to follow the rapidly moving propeller blades, so that a
vacuous space was left behind the blade tips, with a consequent loss of
propulsive power. This phenomenon, now known as 'cavitation', is also liable to
occur in centrifugal pumps and water turbines when conditions are favourable to
it. Parsons met his immediate difficulties by providing the Turbinia with three shafts each carrying
three propellers so that the whole propulsive power was divided among nine
propellers. With this alteration the vessel attained a speed of over 34 knots.
Many
men would have rested content to have successfully circumvented their
difficulty, but Parsons realised the importance of a thorough investigation of
the whole question of cavitation, as this was clearly going to be a matter of
concern to designers of high-speed vessels. He therefore constructed a tank
with glass sides in which a model propeller could be run at high speeds. The
propeller was strongly illuminated by intermittent light, the speed of the
flashes being regulated in accordance with the revolutions of the propeller so
that the blades could be made to appear stationary or only revolving very
slowly. It was recognised that cavitation would be favoured by working with
water near its boiling-point, so the first experiments were made with hot
water. It was found, however, more convenient to attain the same result by
maintaining a vacuum above the water in the tank, and the nature of cavitation
was exhaustively studied in this manner. The knowledge gained by these investigations
led to great improvements in the design of high-speed propellers, and the
methods of study initiated by Parsons have since become generally adopted.
Closely
allied with the phenomenon of cavitation is that of the erosion of propeller
blades, although the connection between the two was not at first realised.
Erosion had become such a serious problem that in 1915 the Admiralty appointed
a Committee to report on the subject. In view of Parsons' experience of
propeller design, he was requested to serve on the Committee, and it was he who
suggested that the erosion was probably a secondary effect of cavitation. His
view, which is now generally accepted, was that the vacuous spaces typical of
cavitation were continually collapsing, causing a hammering by the water on the
metal of the propeller. This. hammering might easily attain a destructive
intensity owing to the absence of any appreciable quantity of air or gas in the
cavity to soften the blows. It was typical of Parsons that he would accept no
theory, not even own, that could not be supported by experiment, so he set
himself to test his idea. The method he adopted was as simple and direct as it
was ingenious. He made a hollow brass cone with a small hole in its apex which
could be closed by a plate of the metal to be operated on. This cone was held
face downwards in a tank, and when filled with water it was forced suddenly
downwards until arrested by a rubber cushion on the bottom of the tank. The
resilience of the rubber permitted the water in the cone to continue its
downward motion for a moment after the cone had stopped, thus causing a vacuous
space to occur at the top of the cone. This space immediately collapsed, and
the returning water was found to strike the plate with a force often sufficient
to puncture it. Pressures as great as 140 tons per sq. inch were obtained in
this way, and the results of the experiments left no doubt that the damage met
with in propeller blades could be fully accounted for by the hammering action
consequent upon cavitation, as suggested by Parsons.
MECHANICAL GEARING FOR MARINE AND LAND TURBINES
The
steam turbine is essentially a high-speed prime mover, and it therefore shows
to its best advantage when directly coupled to machinery that can be run at the
economical speed of the turbine. This speed is, fortunately, suitable for a
large range of electrical machines, but the smaller sizes of alternators and
most continuous current generators require to run at less than the optimum
turbine speed, which indeed may be altogether too high to make direct driving
advisable or even practicable in many instances.
The
obvious way of arranging for the speed of the turbine to be independent of that
of the driven machinery is by interposing speed-reducing gear between' the two.
The use of gearing in connection with steam turbines was originated by Dr de Laval in
The
reason for the discrepancy between the most efficient speeds of a turbine and a
propeller lies in the enormous difference in the density of the media-steam and
water-in which they are respectively working. A turbine can only be made to run
slowly with efficiency, either by constructing it with a very large diameter in
order to maintain the peripheral speed of the blades, or by using a very large
number of blade rows so as to reduce the steam velocity per stage. In either case the dimensions become
excessive. Parsons realised that the only real solution to the problem was to
be found in providing some connection between the turbine and the propeller
shaft which would enable each to run at the speed most conducive to efficiency,
and he therefore turned his attention again to the possibilities of mechanical
gearing. He commenced by carrying out exhaustive experiments to determine what
tooth-speeds could be employed and what power could be transmitted consistently
with safety and durability. The results were so encouraging that new
possibilities were opened up for turbine machinery both on land and sea. To
make a practical test of the use of gearing in marine work, The Parsons Marine
Steam Turbine
By
1919, or only ten years after the first experiments with gearing in the Vespasian, it
was estimated that no ,000,000 H.P. were being transmitted through
gearing in warships and merchant vessels, and as much as 25,000 H.P. had been
transmitted by a single gear-wheel. The introduction of gearing in connection
with marine turbines gave rise to a new problem. So long as it was the practice
to couple turbines directly to the propeller shafts, it was possible to arrange
that the thrust of the propeller should be largely counterbalanced by the axial
pressure of the steam on the rotor blading, so that only a small differential
pressure had to be carried by the thrust-block. With geared turbines no such
counterbalancing was possible, and the thrust-block had the duty of
transmitting the whole of the propeller thrust to the structure of the vessel.
The old multi-collar thrust-block had served well enough with reciprocating
engines, and had indeed been retained in the Vespasian, but the type
was no longer adequate for the higher shaft speeds of turbine-driven vessels
generally. Fortunately, about this time, the pivoted-pad type of thrust-block,
in which the whole of the end-thrust could be carried on a single collar, was
invented by Mr A. G. Michell in
During
the war of 1914-18 single-collar pivoted-pad thrust-blocks were fitted to Naval
vessels totalling 10,000,000 H.P., and the construction of such a ship as
H.M.S. Hood, in which
36,000 H.P. had to be transmitted through each of the four propeller shafts,
would have been impossible without this type of thrust-block.
Simultaneously
with the application of gearing to marine purposes, an equally bold departure
was made by Parsons in land practice. He supplied a 750 B.H.P. turbine running
at 2000 R.P.M. for the onerous duty of driving a rolling-mill for the
production of ships' plates. The rolls had to run at 70 R.P.M., and this speed
was obtained by the interposition of double reduction gearing between the
turbine and the mill. The plant proved a most gratifying success, and there
could no longer be any doubt that the use of mechanical gearing would enable
the turbine to drive the reciprocating engine from almost its last strongholds.
In
order that gear-wheels should work quietly and without deterioration under the conditions
of speed and power imposed by their new duties, it was of course essential that
their teeth should be extremely accurate both as to form and pitch. In the
ordinary method of gear cutting, every error of pitch that may exist in the
master wheel of the gear-cutting machine will necessarily be reproduced in the
wheel being cut. No master wheel can be mathematically perfect, and the
accuracy desired by Parsons was greater than any ordinary gear-cutting machine
could provide. He therefore turned his attention to the production of better
gears, and to this end he devised what is known as the 'Parsons Creep
Mechanism'. By this mechanism the work-table of the machine was caused to
rotate slightly faster than the master wheel, with the result that any errors
existing in the latter were distributed spirally round the wheel being cut,
instead of being concentrated at one part of the circumference. The consequence
was that the unavoidable defects of the master wheel were, for all practical
purposes, completely eliminated in the work.
This
method of 'creep-cutting', invented by Parsons in 1912, created an entirely new
standard of accuracy for mechanical gearing, and made it possible to produce
gear-wheels that could be relied on to transmit any desired power with
quietness and durability. Thenceforward the turbine was free from all
limitations imposed by the speed of the driven machinery, for each could be run
at its most efficient rate, the connection between the two being made by
appropriate gearing. Geared turbines were soon employed as the propelling
machinery for steam ships ranging from slow cargo vessels to the fastest
warships and liners, for even in the case of fast ships it was recognised that
high-speed turbines and gearing were more economical in service than
direct-coupled machines running at a speed dictated by the requirements of the
propeller. The improvement brought about by gearing may be illustrated by the
following comparison. With the early direct-coupled marine turbines the steam
consumption was about 15 or 16 lb. per shaft horse-power hour, while by 1923
geared installations could operate with a consumption of less than 10 lb. of
steam for the same power, which could be reduced to 8 lb. or less if the steam
was superheated. If we take into account the simultaneous increase of the
efficiency of the propeller due to its lower speed, it is fair to say that by
the introduction of gearing Parsons effected a further economy in fuel
comparable with that originally brought about by the application of the turbine
to marine work.
On
land there was not the same scope for geared turbines as in marine practice,
but the introduction of gearing has nevertheless widened the field and improved
the performance of turbine machinery in many directions. Continuous current
dynamos, centrifugal pumps and small alternators have in general to be run at
speeds considerably below the economical speeds of small turbines. By the
incorporation of gearing into the unit, these and other machines can be driven
by efficient high-speed turbines, thus leaving a very small field for the
reciprocating engine in industry.
PARSONS' WORK ON SEARCHLIGHT REFLECTORS
The
importance of the part played by Parsons in the development of efficient
searchlights is better appreciated by Naval and Military technicians than by
the general public. Searchlights were, of course, already in use at the
commencement of Parsons' engineering career. They were employed by the British
Navy in 1876, and their value was demonstrated in the Egyptian campaign of 1882.
The advantage of using an accurately parabolic reflector to project the beam of
light from the arc was recognized from the first, but owing to the difficulty
of making a true parabolic shape, the earliest reflectors for searchlights were
formed with spherical surfaces. The light was reflected from a coating of
silver deposited on the back of the glass from which the mirror was made, and
the glass was given an increasing thickness from the centre to the rim so that the consequent difference in
refraction experienced by the rays should cause them to be projected in a
fairly parallel beam. Large mirrors of this design were very heavy and
expensive, and they were liable to become fractured in service owing to the
differential expansion when subjected to the heat of the arc.
Parsons
set himself the problem of producing at reasonable cost, a silvered reflector
that should be of uniformly thin glass and of the ideal parabolic curvature. He
worked out a process of manufacturing such reflectors while he was a partner in
the firm of Clarke, Chapman and Co., of
Parsons,
however, did not confine his efforts to the perfection of parabolic reflectors for throwing straight parallel shafts
of light. For certain purposes,
as for example when a large
area such as a harbour or the landing ground of an aerodrome has to be
illuminated, what is required is a flat divergent beam. To produce such beams,
Parsons invented and devised methods for
the manufacture of a most ingenious form of reflector, curved to a parabolic form in the vertical plane and to an elliptical form in the horizontal plane, both
curves having a common focus. The parabolic curvature resulted in the light
issuing in a beam of uniform depth, while the effect of the transverse
elliptical curvature was to cause the rays first to converge into a vertical
line at the secondary focus of the ellipse, and then to diverge at a
predetermined angle. Searchlights equipped with such reflectors therefore not
only projected a fan-shaped beam of the required type, but the whole of the
light was able to pass through a narrow vertical slot situated at the secondary
focus. Consequently the searchlight could be operated behind a loop-hole where
its chances of being damaged by rifle fire would be very slight. Another of
Parsons' inventions in connection with searchlights that has proved of the
greatest value in navigation, particularly to ships passing through the
The
interest that Parsons took in matters connected with optics was no doubt
largely hereditary, his father, Lord Rosse, having been a well known astronomer
and famous as the constructor of the great 6-foot reflecting telescope at his
country seat at Birr, in Ireland. An early outcome of this interest was the
development of parabolic and parabolic-elliptic reflectors for searchlights, by
which Parsons contributed so greatly to military and naval defence. He built up
what became probably the most important business in the world devoted to the
manufacture of such reflectors, but it was not until after the first great war
that he turned his attention to optical work generally.
His
first step was to acquire in 1921 a controlling interest in the firm of Ross,
Ltd., of Clapham,
With
the great reduction in the demand for optical glass that was brought about by
the termination of the war, the Derby factory fell upon evil days, and in spite
of the warning that had been received as to the danger of depending upon
foreign countries for an essential war requirement, it appeared probable that
the works would have to be closed. At this juncture Parsons appeared upon the
scene, and inspired far more by public-spirited motives and by scientific
interest than by any idea of making money, he purchased the entire factory in
192I. Under the name of the Parsons Optical Glass Company, the undertaking
acquired a new lease of life, thanks to his energetic direction. The making of
optical glass had always been very much of a secret process, understood by few
and conducted along more or less traditional lines. Such conditions inevitably
lead to a stagnation of practice, and to the conservation of somewhat primitive
methods of manufacture. Parsons was not bound by the precedents of the
industry, and he at once applied his wonderful mechanical and scientific
knowledge to the improvement of the processes employed. He devised better ways
of melting the glass and of stirring it in when molten, while he also
introduced the practice of running the melted glass directly into a mould for
immediate transference to the annealing furnace. By these and other
improvements he was able to make exceptionally good discs of optical glass of
any size required and possessing such special properties as might be demanded,
Under his management the works produced about one hundred different kinds of
glass for optical purposes, each best suited for some particular duty.
Parsons
certainly did a great deal to establish the excellent reputation that English
optical glass now enjoys all over the world, but according to his friend and
colleague, Dr Gerald Stoney, F.R.S., he spent a fortune in the task, for his
enterprise is said to have cost him something like £60,000. After his death the
factory was acquired by the old-established firm of Chance Brothers of
Birmingham, whose name is well known in connection with optical glass
manufacture.
His
success in producing large discs of optical glass for the objectives of
astronomical telescopes led Parsons to take an increasing interest in the'
telescopes themselves, the construction of which appealed both to his
scientific and mechanical instincts. He had, from his childhood, been well
acquainted with the Grubb family of DubIin, who had built notable astronomical
instruments, and he had made glass for the lenses of some of their telescopes.
During the first world war, Sir Howard Grubb and Sons, Ltd., transferred their
optical works to
There
is always an interest in the life and personality of men whose achievements
have been an outstanding contribution to the record of human progress. Parsons
was undoubtedly one of these men, and his name is likely to rank in history as
that of the greatest engineer that the nineteenth century produced. Although he
owed his success to his own genius and enterprise, he was nevertheless
fortunate in his parentage, upbringing and circumstances of life. Charles
Algernon Parsons was born in
He
commenced his engineering training by a four years' apprenticeship at the
Elswick Works of Sir William Armstrong and Co. This was followed by two years
with Messrs Kitson and Co. of
Another
of his inventions was the 'Auxetophone'[4],
a device for the amplification
of musical and vocal sounds without any of
the tone-distortion inseparable from reproduction by means of a mechanical diaphragm. The
principle of the instrument was
the production of the sound by
suitably controlling the flow of compressed
air through a valve, in imitation of the
action of the vocal cords in
the human throat. The valve could be operated by a needle travelling over a
gramophone record or by any other convenient way. Auxetophones were
used with success to reinforce
the sounds of the
'cellos and double-bass fiddles of Sir Henry Wood's Orchestra in the Symphony
Concerts at the Queen's Hall in 1906, and met with the enthusiastic approval of
the great conductor. The musicians, however, objected to the consequent
reduction of the number of performers, and the experiment had to be abandoned.
The Auxetophone was as remarkable for its mechanical perfection as for the
volume and purity of the sound it produced, but its usefulness came to an end
with the invention of the amplification of sound by electrical means[5].
No account of Parsons' scientific
work would be complete without some reference to the important researches he
carried out with the object of making diamonds by the crystallisation of carbon[6].
This was a subject in which he was interested all his life, and he attacked the
problem with his usual energy and ingenuity. To obtain pressures and
temperatures at which the liquefaction of carbon might be possible, he employed
a 2,500-ton hydraulic press and a battery capable of giving a current of 50,000
amperes. Another method which he devised to obtain extreme pressures and
temperatures consisted in firing a bullet from a service rifle into a hole in a
block of steel fixed a few inches in front of the muzzle. The carbonaceous
substance to be experimented upon was placed at the bottom of the hole. By
these and other means he obtained pressures up to 5000 tons per sq. inch and
temperatures exceeding 15,000° C. He also repeated the experiments by which
Moissan had claimed to have produced microscopic diamonds. Moissan had obtained
his pressure by taking advantage of the contraction of molten iron when
solidifying, but Parsons came to the conclusion that Moissan had been mistaken,
the minute crystals thus obtained being merely some form of carbide. Parsons
continued his researches intermittently for about twenty-five years, and,
admitted that he had spent some £20,000 on them. His experiments were numbered
by thousands, but he never succeeded in producing even the smallest crystal
that would pass the crucial test of a diamond, namely that it should disappear
without leaving the slightest trace when ignited in oxygen. He was therefore
forced to the conclusion that the secret of Nature remained still to be
discovered. Whatever aspect of Parsons' work is considered, one is struck by
the extraordinary ability, energy and courage which he brought
to bear on every problem in hand. The results he achieved have revolutionised
whole branches of engineering and exercised a profound influence upon the
structure of civilised life. Yet the means by which his mind was guided are,
for the most part, as inexplicable as manifestations of genius always must be.
His success in developing the steam turbine was certainly not the outcome of
any theory of thermodynamical processes, for such theories were at the time in
a rudimentary state. Nor was he ever known to make the slightest use of the
formal procedure of mathematical reasoning, though his mathematical attainments
were high enough to have gained special distinction for him at
On
Parsons' engineering courage there is no need to enlarge. A man who would take
the responsibility for the 70,000 H.P. turbines of the
One
of the most delightful features of Parsons' character was his extraordinary
modesty. Even when at the zenith of his fame he seemed unable to realise that
his achievements had been exceptional or that his ability was anything out of
the ordinary. This natural humility of his disposition led him to expect other
people to possess an insight equal to his own, and he was always ready to
listen to any reasonable argument and to discuss it on terms of equality. His
manner was kindly, courteous and considerate to all, though he was capable of
an occasional abrupt explosion of impatience with stupidity of thought or
action. His public and private benefactions were many. He contributed freely of
his knowledge to the proceedings of scientific and technical societies, and
many of them in return conferred upon him the highest distinctions in their
power. The leading European and American technical institutions also showed
their appreciation of his merits by electing him to honorary membership, while
nine Universities awarded him honorary degrees. The bestowal upon him of the
Companionship of the Order of the
Sir
Charles Parsons died on
CHARLES
PARSONS; His Life and Work by
Rollo Appleyard, LONDON, CONSTABLE & CO
LTD 1933
Annex 1
Parsons
on Internal Combustion Turbine[7]
Quotes from CHARLES PARSONS; His Life and Work by Rollo Appleyard, LONDON,
CONSTABLE & CO LTD 1933
“DEAR
SIR CHARLES,
I
so well remember being told it was a "vital objection" to the
Turbine-the large number of blades! "An insuperable objection!" I
always think your triumph so great because of the multiplicity of your enemies!
However, I am only writing this to suggest to you whether it is feasible to try
your fascinating plan in one of the seven new Admiralty vessels under order
with internal combustion engines. The last three of 10,000 tons displacement
are yet unallocated.
We
are looking forward to seeing you on November 2I, and I hope Sir John Jellicoe
will be with us, it's all important he should be; he is the coming man, or
rather he has come! I wish you
could see your way to the continuance of the Turbine in connection with the
Internal Combustion principle. Remember, we can't have funnels
for future fighting! And we want the armament amidships or
more amidships than boilers will allow of. It means victory to see the enemy
before they see you and to be absolutely devoid of a puff of inadvertent black
smoke through some accident with the oil-spraying apparatus!
Yours
truly,
FISHER.
4.11.12.
“:
I do not think the internal combustion turbine will ever
come in. The internal combustion turbine is an absolute impossibility.”
(Response of Charles Parsons p. 178)
Had
Parsons responded to Fisher’s request he might have been the inventor of the
gas turbine.
[1] For details see chapt V of CHARLES
PARSONS; His Life and Work by Rollo Appleyard,
LONDON, CONSTABLE & CO LTD 1933
[2] For details of Cobra and Viper see chapt VI of Appleyard
[3] “In the summer of 1893 Parsons made
some experiments on the effect of steam-jacketing small steam-engine cylinders,
by placing the whole of the cylinder and valvechest inside the boiler.
The increase of economy was so marked that he was led to try whether a small
toy engine could be made to sustain its own weight in the air by the
lifting-power of the plane when propelled by an airscrew on the crank-shaft.
The boiler was seamless steel 2.5 inches diameter, 14 inches long, and 0.01 to
0.015 inch in thickness. The steam cylinder, single-acting, of cast steel, was
1.25 inches diameter, with a 2-inch stroke. The piston was of thin cup form, of
tool steel. The admission valve was cylindrical 5l16 inch diameter, cutting off at ¾ stroke.
Some parts of the engine were hard-soldered, and some were soft-soldered. The
working pressure was therefore limited to about 50 lb. per square inch. The
total weight of the apparatus, with its 3-oz. charge of water but without lamp
or burner, was 1.25 lb. He says in his own note:
Steam was raised by
placing the boiler on a spirit lamp, and when 50 lb. was registered on the
gauge, and the engine started, it raised itself in the air vertically to a
height of several yards-the revolutions of the engine were about 1,200 and the
I.H.P. 0.25 horse-power. The same engine was then mounted on a framework of
cane covered with silk forming two wings of I I feet span, and a tail, the
total area being about 22 square feet. The total weight was now 3.5 lb. When
launched gently from the hand in an inclined. . . direction, it took a circular
course, rising to a maximum height of about 20 feet. When the steam was
exhausted, it came down, having traversed 80 yards.
It was clearly seen by the
experiment that for practical commercial success of this class of steam
apparatus an air condenser is essential, as the weight of water used in a few
minutes' run equals the total weight of engine and boiler. Without a condenser,
the length of flight must be limited to a very few miles, and it would seem
that the chief problem that workers in the field have to solve is to obtain an
efficient and light dry-air condenser.
Photographs of this primitive aeroplane were taken at
the time by Mr. Gerald Stoney, showing the engine and boiler, with the
propeller revolving in a horizontal plane. A vertical sail attached to the
boiler prevented its too rapid rotation from the torque of the propeller. The
note by Parsons continues:
The difficulty in
maintaining the steam by a lamp was not satisfactorily overcome, but very
satisfactory results were obtained by using methylated spirit in the boiler
instead of water, and burning the exhaust under the boiler. Great difficulty was
experienced in maintaining the flame when the apparatus was flown, owing to the
currents of air from the propeller.
When working with
methylated spirit flame, the evaporation per square foot of heating surface
reached the extraordinary figure of the equivalent of 120 lb. of water
evaporated per square foot of heating surface. It seems to me that the problem
of aerial flight can be attacked much more favourably by means of cigar-shaped
balloons propelled by gas or oil engines.
[4] ON
The two huge trumpets,
resembling ventilating shafts on an ocean steamer, which have been in use
during the past week on the Queen's Hall Orchestra, have been looked upon by
many Promenade Concert Patrons as part of an improved system of Ventilation.
The supposed Ventilators are, however, parts of a new invention by the Honble.
Charles A. Parsons called the Auxetophone, respecting which he supplies the
following explanation:
The Auxetophone is a
pneumatic device for increasing the volume and richness of tone of stringed
instruments, and is worked by air supplied by a blower in the basement of the
building. The Auxetophone consists of a small comb-like valve made of aluminium
which is connected to the front wood of the instrument near the"
bridge," and vibrates in response to the tones produced by the player.
This valve controls the exit of the air from a small box fed from the blower
into a large spiral-shaped trumpet which emits sound-waves identical in quality
and intonation but richer in tone and larger in volume than those produced by
the instrument itself unaided by the Auxetophone.
At the Queen's Hall, the
Auxetophone has so far been applied to one Double Bass only, but it is claimed
that it is also applicable to the Violoncello, Viola, and Violin, and some
other stringed instruments.
The
history of the invention was sketched. by Parsons himself in 1921 in a letter
to Sir Ambrose Fleming. From this account it appears that
I worked at this subject
as a hobby in my workshop at home and tried many types of valve-double beat,
slide-valves with multiple openings, then a form of valve made of sheet metal
on edge like a fireworks cracker, and lastly the" comb-valve "- much
the best because it delivered a flat-faced sound wave into the trumpet and it
is not liable to be impeded or struck by small particles of dirt. It is similar
to Short's. I made valves of comb pitches from one-fiftieth of an inch for
reproducing from faint phonograph records, up to some .of 0.25 inch pitch for
attachment to double-bass stringed instruments. The very fine ones were made of
hard gold, the rest of magnalium. The air-valve reproducer was shown at the
Royal Society about 1904, on a gramophone. Professor Johnston Stoney, F.R.S.,
was much interested, suggested the name" Auxetophone," and treated
the matter mathematically.
If the motion of the
valve is expressed in a series of sine terms (Fourier), then the sound-wave
produced is the first differential, and consequently the harmonics are much
increased in amplitude above the fundamental, and the tone much increased in
richness. This was found to be the case when used on the gramophone or when
actuated from the bridge of a stringed instrument.
It was shown soon
afterwards in the Library of the Royal Institution and notices appeared in the
papers, and then Short's letter reached me. Previously I had not made any
patent search and was not aware of his patent.
It appeared that Short had
played an instrument on the top of the
The valve you have
(taken to pieces) was made by Short in our shops (at Heaton) and was played on
a double-bass at the Promenade Concerts at the Queen's Hall all one winter
about 1906.
We spent much time and
money in endeavours to introduce it on violins, 'cellos, and double-bass
instruments, but were eventually blocked or boycotted by the Musical
Fraternity, because they found it would reduce the number of executants from
one-fifth to one-tenth for the same volume of sound. I dropped the whole
matter….
The limiting factor to
greater magnification of sound by means of an air-valve seemed to be viscous
resistance in passing through minute apertures. Experiments showed that this
was very marked below 1/1000 inch aperture. Hence there results a limit to the
fineness of the comb. I was never able to obtain an actual magnification of the
voice by means of an air-valve. Your (Fleming's) ionic valve has solved this
problem.
The
three patents of Parsons were …
No.
10,468/1903. Improvements in Sound Reproducers or Intensifiers applicable to
Phonographs, Gramophones, Telephones and the like.
No.
10,469/1903. Improvements in and relating to Musical Instruments.
No.
20,892/1904. Improvements in and relating to Reproducers or Resonators for
Gramophones, Phonographs and the like.
In
these he states that after careful consideration of the conditions, the
dynamical forces, the velocities of sound-waves and the displacements, the
velocities of transmission of vibrations in metals, and the velocities of flow
of air and gases through small orifices, it became clear " that none of
the previous experimenters have understood the problem sufficiently to make a
successful apparatus." He was referring to earlier devices in the form of
" relays" chiefly for intensifying the sounds of the human voIce.
The
first of the patents describes his relay that operates by means of an elastic
fluid, a valve comprising a stationary grating or valve-seat and a movable
grating or valve-cover on the side of less pressure, opening substantially
normal to the gratings, and so constructed that the area of opening is
approximately proportional to the displacement of the valve; it also describes
his compressed-air box containing a filter for the air. The valve-cover is
" mounted on a weigh-bar in rigid connection with the reproducing
style-holder of a gramophone." This weighbar is capable of oscillating,
rotation ally only, about its own axis.
The
second of the patents describes, amongst other details, a violin in which the
sounding-board is replaced by a reproducing device controlled by a valve,
" operated from the vibrations of the strings."
The
third of the patents includes a description of a sound-reproducer in which a
rod slides in a hole or holes, in one or both of the parts of the valve to be
connected; this rod is lubricated with a viscous material, to avoid"
scratching " sounds. He adds, " the viscous connection may be made
with a mixture of bicycle cement and castor oil or dub bin, or any thick oil,
glue, vaseline, or similar substance."
The
air-pressure employed by him in his early experiments was from two to three
pounds to the square inch. The supply-tube communicating between the valve and
the trumpet was usually provided with a longitudinal dividing strip to prevent
resonance.
The
weigh-bar requires explanation. In some of the later auxetophones it consisted
of a short piece of metal of rectangular section, having on one of its sides a
projection forming a socket for gripping the gramophone needle. This bar was
suspended between a pair of end-springs. The end-springs-narrow, straight,
flat, and flexible-were inserted into the bar in the direction of their
lengths. They were then held firmly in a pair of saw-cuts in the stiff frame of
the apparatus. When thus mounted, the gramophone needle was capable of slight
rotary motion, with twist of the springs.
The
valve-cover was suspended between end-springs, in a manner similar to the
suspension of the weigh-bar, the end-springs in this case acting as a pair of hinges
enabling the valve-cover to repose with gentle pressure upon the valve-seat.
To
provide for operation of the auxetophone, the weigh-bar had to be linked to the
valve-cover in such a manner as to allow the opening and closing of the valve
to follow the motion of the gramophone needle. Parsons found that if this link
was a stiff continuous rod fixed at its ends it transmitted vibrations of
high-frequency, including those corresponding to squeaks, scratches, scrapings,
and other intolerable noises. His genius showed itself in devising a link
formed of a rod passing through a partially yielding substance that, while
denying transmission to high-frequency vibrations, gave freedom to pleasant
tones of lower frequency to pass.
As
an alternative, and sometimes as an addition, he provided a small air-piston,
to damp the movements of the link.
In
his early auxetophone, such as he exhibited at the Royal Society and at the
Royal Institution, the weigh-bar formed one piece with the thickened back of
the valve-cover, which carried in a socket the gramophone needle. Pressure
between cover and seat was in this type of valve controlled by a steel wire
soldered at one end to the valve-cover and attached at the other to a fixed
clamp carrying an adjustable eyelet filled with viscous material through which
the end of the wire passed for flexible anchorage.
The
first experiments of Parsons in this direction had for their object the
production of a sound-box for gramophones and phonographs, which at the
beginning of the twentieth century were far from being musical instruments. He
began to study the matter as an engineering problem, to determine the forces
and to discover what characteristics were necessary in the valve to secure
musical results. His first valves, except in essentials, were more or less
roughly made-he used boxwood for the valve-combs, and he moulded many of the
parts out of his favourite constructional material, sealing wax. The boxwood
combs were sawn out with a jewellers' hand-saw. With these primitive means he
satisfied himself that his ideas could be developed and that a loud musical
tone could be obtained.
He
then procured watchmakers' tools and he worked with the care and accuracy that,
by his preliminary investigation, he had decided were necessary for success. To
ensure that the valve tongues were accurately spaced and that the correct
overlaps were being obtained, he made up a measuring microscope. As the result
of experiments with several types of valve, he decided upon one that proved to
be much superior to the others.
To
operate the auxetophone, air filtered by passing through cotton wool and fine
metal gauze was pumped through a tube into a wind-box-which also contained a
fine cotton-wool filter-from which it could only escape through a stationary grid
with narrow openings. This stationary grid, comb, grating, or valve-seat fitted
over an aperture in the wind-box. Above it, a similar grid forming the
valve-cover, was hinged. Whenever this second grid was deflected outwards from
the nearly closed position, it allowed air to pass through the valve-ports. The
mounting had to be such that the valve-cover moved, relatively to its seat, in
a direction substantially normal to it, thus sending out a flat-faced pressure
wave, which passed through an outlet trunk and caused the air in a trumpet to
vibrate.
In
the earliest successful models of this type of auxetophone, the gramophone
needle was fixed into a socket formed integrally with the valve-cover but at
the far side of a torsional weigh-bar support. The needle ran in the groove on
the face of the "record" disc; and the air-valve moved in sympathy
with the waves recorded on the disc.
A
sound-box of this type was also constructed for trial on an
He
also introduced at this time a spring-borne piston, arranged with a passage
that allowed the air-pressure in the wind-box to act on the top of the piston
to give partial balance to the otherwise simple-acting valve. This piston
actuated a wire-spring lever attached to the valve-cover and rendered it
possible to impart to the valve-cover the correct setting in relation to the
valve-seat. In addition, the piston supplied some degree of automatic
correction for slight variations of wind-pressure.
After
he had completed the development of his auxetophone for gramophones and
phonographs, and after the talking-machine patent rights had been sold to the
Gramophone Company, he devoted himself to the application of the devices to
violins, double-bass instruments, 'cellos, and harps. For reasons that were
investigated mathematically by Dr. Johnstone Stoney, the application to violins
was not very successful; but with double-bass instruments the results were
excellent, for the musical quality and the intensity of sound from them were
strikingly enhanced.
When
applying the auxetophone valve to large instruments, Parsons modified the
design by adopting grids of coarse pitch to suit the lower-frequency tones with
which these instruments have to deal. Unfortunately, what Parsons termed the
"boycott by the Musical Fraternity" discouraged him from further
efforts in this direction. His experimental shop was accordingly diverted to
other work.
In
1922-3, when wireless broadcasting became established, the long-neglected
auxetophones were resurrected at Heaton by Mr. A. Q Carnegie, the colleague of
Parsons. Carnegie applied the gramophone type of valve to a magnetic motor
mechanism as a "loudspeaker." The results were superior to any
"loudspeaker" then available. Parsons took interest in these
experiments; but as the master-patents had expired, no monopoly could be
obtained and further experimental work was judged to be likely to be
unremunerative. Carnegie, however, preserved the apparatus, and it is still
used as a "loud-speaker." The experimental valves made by Parsons in
his home workshop with his own hands are, fortunately, in safe keeping at
Heaton.
If
the work of Parsons on the auxetophone had been done twenty years earlier than
it was, his fame would have gone forth to the ends of the earth as a benefactor
in the realm of acoustics and music. If that work had been done twenty years
later than it was, he would have found a remunerative field in wireless broadcasting
and in, "talking-pictures." Genius does not always exhibit discretion
in timing the shot….
In
1906, gramophone
machines were made for the Gramophone Company by the Victor Talking Machine
Company of Camden, United States of America, who also manufactured the
auxetophone and did a great deal of experimental work upon it. The chief
drawback found by them was that the auxetophone was very susceptible to
derangement on account of dust. The pneumatic valve" sound-box," the
cabinet, and some other parts, were manufactured for several years by the
Gramophone Company at Hayes….
It
will thus be seen by those who have taken up subsequently the task of
perfecting vibration instruments for telephony, music, and the gramophone, by
analysis of the energy conditions, that in designing the auxetophone Parsons
was leading the way.
The
theory of the instrument attracted his old friend and tutor Dr. G. Johnstone
Stoney, the famous mathematician and physicist. Parsons explained to him the
fundamental principle involved in the device, and elicited from him the
following letter….”
See
also http://www.angelfire.com/nc3/talkingmachines/auxetophone.html
http://www.dself.dsl.pipex.com/MUSEUM/COMMS/auxetophone/auxetoph.htm
http://www.davidsarnoff.org/vtm-chapter6.htm
[5]
Magnavox started as the
Commercial Wireless and Development Co., a small laboratory in
Peter
Laurits Jensen (1886-1962 )Developed the first commercially available moving coil direct radiator loudspeaker and
the first speaker system designed to
match the first car radio
Peter
Laurits Jensen described as the Danish Edison, and founder of Jensen Car Audio,
came to the
In 1909
Poulsen sold his American patent rights to the Poulsen Wireless Telephone and
Telegraph Company, which reorganized as the Federal Telegraph Company. Jensen
went to
Jensen
discovered the remarkable high fidelity characteristics of the moving coil when
it was applied to the reproduction of sound. Although patented by 1913, it was
two years later when Jensen discovered a revolutionary application for his
ideas. While he was working to develop a telephone receiver, Jensen connected
the telephone ear tubes to a 22'
During
World War I, Jensen and Pridham developed an "antinoise microphone"
that made the human voice audible over the roar of an airplane engine. Magnavox
also won acclaim for a public address system for battleships that Jensen and
Pridham invented. But the company achieved its greatest recognition in 1919,
when President Woodrow Wilson addressed a crowd of 50,000 people and was heard
distinctly with the aid of two Magnavox loudspeakers.
During the
1920's Magnavox moved into the production of phonographs and home radio sets.
Jensen disagreed with Magnavox executives and resigned in 1925. In 1927 he
founded the Jensen Radio Manufacturing Company. Jensen worked to eliminate
distortion and improve fidelity in sound reproduction. In 1943 disputes with financial
backers led once more to his resignation from a firm of his own creation; he
then founded Jensen Industries to manufacture phonograph needles.
Jensen Car
Audio milestones during Jensen's lifetime included the first commercial moving
coil radiator loudspeaker in 1926. In 1930 the first permanent magnet dynamic
loudspeaker, the first commercial compression-driven horn tweeter and the first
molded hi-fi speaker diaphragm were unveiled. The speaker system for the first
car radio produced by Paul Galvin debuted in 1931. In 1936 the bass reflex
enclosed speaker was introduced. 1942 saw the first commercial coaxial two-way
loudspeaker. In 1950 the first Triaxialä three-way unitary loudspeaker hit the
market, and in 1952 the first horn-type super tweeter was launched. The last
development under Jensen's reign was in 1960 when the first flat piston woofer
was introduced. In 1956, the King of Denmark knighted Jensen. The American
Institute of Radio Engineers and the Audio Engineering Society also honored him.
Lewis, W.
David, "Peter L. Jensen and the
Amplification of Sound" in Carroll W. Pursell, Jr., ed. Technology in
[6] For details see chapt IX of Appleyard
[7] “The earliest device for extracting rotary
mechanical energy from a flowing gas stream was the windmill (see above). It
was followed by the smokejack, first sketched by Leonardo da Vinci and
subsequently described in detail by John Wilkins, an English clergyman, in
1648. This device consisted of a number of horizontal sails that were mounted
on a vertical shaft and driven by the hot air rising from a chimney. With the
aid of a simple gearing system the smokejack was used to turn a roasting spit.
Various impulse and
reaction air-turbine drives were developed during the 19th century. These made
use of air, compressed externally by a reciprocating compressor, to drive
rotary drills, saws, and other devices. Many such units are still being used,
but they have little in common with the modern gas-turbine engine, which
includes a compressor, combustion chamber, and turbine to make up a
self-contained prime mover. The first patent to approximate such a system was
issued to John Barber of
Although many devices
were subsequently proposed, the first significant advance was covered in an
1872 patent granted to F. Stolze of