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24. Organ blower (working). Received 1897.

This is a water-pressure engine designed for working the bellows supply-
ing air to an organ, but the cylinder in its action resembles the steam cylinder
of a direct-acting steam pump. The supply of water is controlled by a valve
connected with the air reservoir, so that the speed of working is automatically
adjusted to the consumption of wind.

The blower shown has a cylinder 5 -5 in. diam. by 10 in. stroke, and is fitted
with a valve gear patented by Mr. D. Joy in 1874. The piston-rod is directly
attached to the bellows, but has on it a tappet which reverses the distributing
slide valve on the completion of each stroke. This slide valve is of the piston
type, but is in reality two valves combined in one, for by its sliding motion
the valve acts as the main slide valve, while by a rotary motion through
20 deg. it acts as a plug valve which does duty as the auxiliary valve. The
plug is in the middle of the length of the piston slide, and by its motion lets
the water to and from the ends of the chest of the piston valve, so causing the
sliding motion of this valve. The rotation of the valve is performed by two
inclined horns, secured to the valve-rod and moved by the tappet on the
piston-rod. A simple tappet moving a single slide valve will not work at a slow
speed without assistance, and it is for this reason that some form of auxiliary
valve is almost invariably introduced. A sectional drawing further illustrates
the construction. M.2971.

25. Water motor with oscillating cylinder (working). Lent
by Messrs. W. H. Bailey & Co., 1894.

This is a small example of Haag's high-pressure water motor, for pressures
up to 300 Ib. per sq. in. These motors are frequently used in mine workings,
ths witter for driving being obtained from the delivery pipe of the main
pumping engine, and the motor discharging its exhaust water into the mine
sump.

The cylinder of the engine oscillates on two hollow trunnions, closed at the
outer ends, the hollow spaces within each trunnion being divided into two
compartments, one of which on each side communicates with either end of tho
cylinder. Two slots cut longitudinally in the trunnion serve for ports for
admission and exhaust of the water, one slot giving admission to each end of
the cylinder. In the lower part of each bearing there are three ports, a wide
one in the middle leading to the exhaust pipe, and a narrower one on each side
of this communicating with the supply pipe. The oscillation of the cylinder
causes the ports in the trunnions to slide over those in the bearings, so open-
ing up each end of the cylinder to exhaust or pressure alternately, just as in
the case of an ordinary slide valve. The supply and exhaust pipes are each
fitted with an air vessel to prevent shocks in the pipes.

This motor has a cylinder 2'5 in. diain. by 4 in. stroke, and when making
100 rev. per min. under a pressure of 150 Ib. gives off 1 brake h.p. Larger
sizes are made up to those having 9 in. cylinders, which, running at 50 rev.
per min., exert 24 brake h.p. under 150 Ib. pressure. M.2566

26. Water-pressure motor (working). Lent by the Glenfiekl
Co., 1896.

This is an example of Wilson's water motor for pressures up to 200 Ib.
per sq. in. ; such motors are intended for driving small quick-running
machinery, dental drills, ventilator fans, etc.

The two cylinders are double-acting, fixed with their axes at right angles
to each other and working by connecting rods a crankpin common to both.
One eccentric actuates both valves which are of the solid piston type. To
prevent shock at the reversal points a small conical-seated relief valve is fitted
to each water passage opening into the valve chamber, the pressure there
keeping them closed under normal conditions. The supply and exhaust
passages are cast with the framing connecting the two cylinders.

. This motor has cylinders T25 in. diam. by 1'5 in. stroke, and when running
at 200 rev. per min. under a pressure of 150 Ib. exerts about 0*3 brake h.p.

M.2965.



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27. Hydraulic motor, in section. Made by the Hydraulic
Engineering Co., 1888.

This is a small motor on Brotherhood's system with three single-acting
cylinders inclined at 120 deg. to one another, and having trunk pistons with
cup -leather packing. The connect big rods are always under compression and
are ball-jointed at the piston end, while at the other extremity they each
embrace 90 deg. of the crankpin. The water is distributed by a rotating
disc valve (shown separately in section) which has an opening from the outside
for pressure, while the exhaust passes through the spindle ; the port face is of
lignum vitse.

The example has cylinders 1-75 in. diam. by 2-5 in. stroke. It gives 2 brake
h.p. at 105 rev. with 7 gal. of water per min. at 750 Ib. pressure, or
2-5 brake h.p. at 87 rev. with 5'75 gal. at 1,050 Ib. pressure. K.497.

28. Hydraulic engine. Lent by the Glenfield Co., 1896.

This is a small example of a three-cylinder water-pressure engine, suitable
for pressures up to 1,000 ib. per sq. in.

The three cylinders are cast together, their axes radiating at 120 deg. to
one another, and they are always open at their inner ends to the crank chamber.
The pistons are packed with cupped leathers and are hollowed out to receive
the spherical ends of the thrust bars by which motion is given to the crank.
The pressure is always on the outer end of the piston, so that the thrust bars
are in compression and take up their own wear. The water is admitted and
exhausted by means of a circular disc valve driven by a stem fi*om the crank-
pin and working on a face which in the case of the larger engines is made of
lignum vitae. Water is admitted at the side of the valve chamber and exhausts
by the centre of the valve.

This example has cylinders 1 in. diam. by 1*5 in. stroke, and when running
at 250 rev. per min. with 600 Ib. pressure gives off about 0*75 brake h.p.

M.2965.

29. Hydraulic swash-plate engine (working). Lent by
Messrs. Sir W. G. Armstrong, Whitworth & Co., Ltd., 1910.

This is a type of engine in which a shaft, having an oblique disc or swash-
plate fixed to it, is caused to rotate by the successive pressures upon the disc
of a number of pistons, working in cylinders arranged in a circle, with their
axes parallel with the shaft. Such an engine may have a large number of
cylinders compactly arranged and gives a very uniform torque.

The small example shown has 16 cylinders bored horizontally in a single
casting; the pistons are packed with cup leathers and bear against the
rounded ends of the piston-rods. The outer ends of the rods are ball-shaped
and are held in a circular ring which bears against the swash-plate, ball bear-
ings being interposed to reduce the friction, The ring is controlled by two
diametrically opposite pins which slide in horizontal slots attached to the bed-
plate of the engine. The end thrust is taken by a row of balls placed between
the back of the swash-plate and a fixed disc which is surrounded by an outer
casing formed in one with the driving shaft.

The valve gear is of the simplified form patented by Mr. F. G. D. Johnston
and Sir W. G. Armstrong, "Whitworth & Co. in 1908. A single rotary valve
is used, placed behind the cylinder and having five inlet and five exhaust
ports disposed in a circle ; the valve seat has 16 cylinder ports symmetrically
arranged and these are connected with the cylinders in a particular order.
This arrangement besides reducing the number of ports in the valve, and
therefore its size, also requires that the valve shall rotate at only one-fifth of
the speed of the main shaft, this reduction being effected by means of
epicyclic gearing. The valve opens and closes the cylinder ports at the ends of
the stroke, and eight cylinders are working while the remainder are exhausting.
The engine may be reversed by interchanging the inlet and exhaust pipes.

The cylinders are 0*75 in. diam. and the water pressure is 1,000 Ib. per
sq. in. A full-size sectional drawing is also shown. M.3796,



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30. Tidal motor. Contributed by Richard Roberts, Esq.,



This apparatus, patented by Mr. Roberts in 1848, is shown arranged for
clock-winding, or doing lighthouse work, by tidal energy.

The machine is erected over a tank or well to which the tide has access ;
into this hangs a weight and also a float, connected by a chain that passes
over a sprocket wheel on the overhead shaft, then round a loose wheel on the
framing and back over another sprocket wheel. These wheels are connected
with the shaft by ratchet and pawl mechanism, which causes both upward and
downward movements of the float chain to rotate the shaft, always in one
direction. The power so obtained will cease for a while during the turn of
the tide, and therefore, when continuous motion is required, an additional
mechanism is added. On the end of the intermittently rotated shaft is a
sprocket wheel, and on the shaft to be continuously rotated, which is in line
with it, is another sprocket wheel ; over the two wheels hangs an endless chain,
in the loops of which are two weighted sheaves, one of which is much the
heavier, the difference being the driving weight. When the tidal motion is
rapid the excess power is stored by lifting the weight, while, when the tidal
movement stops, this weight gives off its stored energy in descending, and so
keeps the driving shaft in motion. The weighted sheaves are connected by a
hanging chain which prevents the inequalities in the effort which would other-
wise arise from the varying length of chain on the driving side. Inv. 1858- J).



20

STATIONARY STEAM ENGINES.

The earliest known record of the employment of steam as a
motive agent is that of Hero of Alexandria, a philosophical
writer who flourished, it is now believed, about 50 A.D. He left
several treatises on mechanical subjects which are interesting as
records of the knowledge of his time ; of these, the best known
is his compilation on " Pneumatics," in which he describes the
ceolipile, or reaction steam engine, and a steam jet supporting a
light ball (see No. 81) ; the first of these is said to have been used
practically during succeeding centuries, but was never more than
a toy owing to its inefficiency. A few proposals for using high
pressure steam that bore fruit much later are met with in philo-
sophical writings up to the middle of the seventeenth century
(see Nos. 32 and 33).

It was at this time, however, that the important discovery
was made that the atmosphere was a fluid possessed of weight,
the pressure due to which could be excluded at will from the
interior of a closed vessel so as to obtain a vacuum (see No. 34),
facts destined to have a most important bearing on the develop-
ment of the steam engine. The means for obtaining this vacuum
were found in the adaptation for the purpose of the common
syringe or the bucket pump. The properties of the air pump
and the experiments that could be made with it became widely
known, but it was some years before it was realised that the
converse was also true, i.e.., that if a vacuum could be obtained
readily below the bucket or piston, then the pressure of the
atmosphere could be utilised for doing mechanical work. Acting
on this idea, Huygens in 1678-9 exploded a charge of gun-
powder in the bottom of a vertical cylinder. The greater part
of the air and of the gaseous products were expelled through
non-return valves; the cooling of the remaining gases produced
a partial vacuum below a piston which then descending owing
to atmospheric pressure, doing work by means of a cord over a
pulley. Papin, in 1690, demonstrated the suitability of steam
for producing the vacuum (see No. 36), but was no nearer solving
the problem of how to repeat at frequent intervals this recipro-
cating motion by causing differences in pressure behind the piston.

In the meantime the idea of raising water by the direct
pressure of steam upon its surface in a closed vessel had re-
ceived attention. The introduction of an apparatus combining
not only this principle but also that of the reduction of pressure
resulting from the condensation of steam in the same vessel,
together with valves and cocks which enabled the operations to
be repeated indefinitely, was embodied in a remarkable manner
in a practical machine for raising water, patented and constructed
in 1698 by Thomas Savery (b. 1650, d. 1715) and known as the
" fire engine " (see No. 37). Whether Savery was indebted in any
way to the labours of the Marquis of Worcester (see No. 35) and
others, we do not know, but it may safely be said that he was
the first to utilise fuel as a practical means of performing
mechanical work. Already there existed a great sphere for the
employment of such an engine in the drainage of mines ; Savery
appears to have erected several engines for this purpose, but
their range was limited by the materials and methods of boiler



21

construction then known, to a maximum lift of about 80 ft. ;
hence a mine of even moderate depth would require a number of
engines at intervals, one delivering into the sump of another.
This drawback, and the danger of* explosion owing to the lack
of a safety valve, greatly restricted the employment of the
engine, so that it was in positions demanding only a single lift
(see No. 88) that we find it to have been used.

Meanwhile, after many years' work Thomas Newconien
(b. 1GG3, d. 1729), assisted by John Cawley (d. 1717), both of Dart-
mouth, who had been following in Papin's steps, had succeeded
prior to 1712 in perfecting the atmospheric engine, from which
the growth of the modern steam engine can be clearly and con-
tinuously traced. However much Newcomen was indebted to
the work of his predecessors, the atmospheric engine must be
regarded as so much in advance of anything which had gone
before as to be practically anew invention. Newcomen adopted
a separate vessel in which to generate the steam ; furthermore,
lie hit upon the idea of injecting cold water into the cylinder in
order to effect a speedy vacuum under the piston, but had, in
consequence, to overcome the further difficulties caused by the
condensed water and the air carried in along with the steam and
water ; lastly, to enable the machine to regulate and repeat its
movements automatically, Newcomen provided valve gear. The
engine thus equipped was applied to work a lifting or bucket
pump by means of a lever or wooden beam (see No. 41). This
and the vertical position of the cylinder necessitated by the
water packing were features that survived for many years
after the conditions that rendered them necessary had ceased to
exist. As Savery's patent was sufficiently general to cover
Newcomen's invention, although quite different in principle, and
as it had been extended for twenty-one years, i.e., till 1733, the
inventors appear to have come to an understanding, for we find
that the invention of the latter was exploited under the patent
of the former.

It is scarcely possible to over-estimate the importance of the
Newcomen engine, which in practically its original condition
remained for upwards of sixty years the only economical and
powerful agent for draining mines. So rapid was its adoption
that Sineaton found that down to 1769 nearly 100 engines had
been built in the Northern colliery districts and about half that
number in Cornwall.

In 1763-4 James Watt (b. 1736, d. 1819), while engaged in
repairing a working model of Newcomen.'s engine, found the con-
sumption of steam to be much greater than he had imagined,
and was thus led to make experiments and careful measurements
of the temperature, pressure, and volume of steam, and also of
the quantity of water required for its condensation. By these
investigations he discovered that the chief waste in the engine
arose from the cooling of the cylinder and piston surfaces by
the water-spray used to condense the steam ; this led in 1765 to
his brilliant invention of the separate condenser, an improve-
ment which at once halved the fuel consumption of the engine.
The use of a snifting valve being impracticable, Watt devised



22

the air pump to clear out both air and water from the condenser.
He then covered in the top of the cylinder to exclude the cool-
ing action of the air and exposed it to steam from the boiler.
He thus produced the single-acting beam pumping engine, a
machine which is employed yet with economical results for
raising water (see No. 615). These improvements were secured
to Watt by patent in 1769, which was extended in 1775 for a
period of twenty-five years at the time when he entered into
partnership for a like period with Matthew Boulton.

The next step was to employ the engine for obtaining
rotatory motion, and Watt, with several others, proposed to use
the oscillating motion of the beam to drive a flywheel shaft by
the intervention of a crank and connecting-rod. Watt, however,
was forestalled in this application by a patent taken out in 1780,
so he was obliged to resort to other means, and in his specification
of 1781 described several arrangements for obtaining rotatory
motion from a rocking beam including the "sun and planet"
gear, with which all his mill engines were fitted till the crank
patent expired. To obtain regular reciprocation from the single-
acting engines, a weight equivalent to half the load of the piston
was at first fixed on the connecting-rod or at its end of the
beam (see No. 73), but it soon became evident that by making
the cylinder double-acting, not only was the power of the engine
doubled, but greater regularity in its speed was obtainable.
This change, however, prohibited the use of the hitherto flexible
connection, by chain and arch head, between the piston-rod and
its end of the engine beam, but the difficulty was completely
surmounted by Watt's introduction of the parallel motion bear-
ing his name, which he stated to have been of all his inventions
the one with which he was most proud. These improvements
were patented in 1782 & 1784, and the first engine embodying
them was made in 1784. From this time onwards the engine
ceased to be exclusively an apparatus for raising water, and
entered the much wider field of industrial employment.

The reduction in steam consumption resulting from cutting
off the supply early in the stroke, and allowing the completion
of the stroke to be performed by the steam while expanding,
was discovered by Watt in 1769, and practically carried out at
Soho in 1776, but he did not patent the invention till 1782.

The great success which attended the introduction of Boulton
and Watt's engines stimulated other inventors (see No. 100).
Among these was Jonathan Hornblower, who in 1781 patented
and introduced the compound single-acting engine for pumping ;
the high-pressure cylinder was placed between the low-pressure
cylinder and the beam centre. With the low boiler pressure in
use at the period it proved -less economical than the simple
engine, and, as it embodied the separate condenser, was an
infringement of Watt's patent.

To the last Watt was satisfied with having perfected the
steam engine in its original form of a vacuum apparatus.
Although he had experimented with high-pressure steam as
early as 1761-2, and had included its use in his patent of 1769,
he consistently opposed its introduction and restricted himself



23

to pressures of not more than 1 or 2 Ib. above the atmosphere,
owing to the risk of explosion with boilers as then constructed.
Immediately after 1800, the date of expiration of his patent, an
advance began which is still continuing at the present day. The
vacuum has become of relatively less importance, and in the
case of the high-pressure engine is dispensed with altogether.
One of the first to advocate and introduce the latter was
Richard Trevithick (b. 1771, d. 1833), who patented in 1802 a
semi-portable engine of this type (see No. 109) ; his application
of it to the locomotive engine (see p. 87) was, however, its most
important development.

About 1800 also commenced the introduction of self-contained
engines of low power, which should be more compact than the
established beam type (see No. 103) ; this has gradually led up to
the direct acting engine, which, although adopted in 1801 by
Symington in the horizontal form, was slow in attaining recog-
nition, but has now superseded the indirect type.

In 1804 Arthur Wool! (b. 1766, d. 1837) reintroduced the
compound engine, and by expanding the steam from six to nine
times was able to demonstrate its superiority in economy over
the simple engine, owing to the reduction of temperature range
and consequent losses in each cylinder ; with increased pressures
and temperatures the principle has been extended since with
great advantage to engines in which the steam is used succes-
sively in three, four, or even five cylinders.

The demand which arose about 1880 for engines for driving
dynamo-electric machinery resulted not only in the improvement
of the existing type of slow-running engines (see No. 130) but
also in the development of a new type of high-speed or quick
revolution engines for direct driving (see No. 131), necessitating
attention to such problems as balancing rotating, and recipro-
cating parts, the use of better constructional materials to keep
down weight, closer governing, and forced lubrication. With
this advance and with researches into the thermodynamics of
the steam engine, Peter William Willans (b. 1851, d. 1892) is
closely associated.

The economy resulting from the use of superheated steam by
diminishing cylinder condensation losses was known early in the
19th century, but is now carried to greater temperatures than
formerly, e.g., Schmidt has employed 150 deg. C. of superheat.
The difficulties of lubrication have been got over by the use of
mineral oil and of packing by the use of soft metals for pistons
and glands.

The advantages of obtaining rotatory motion from steam
without the intervention of reciprocating parts are so great
that ever since the time of Watt (see No. 133) much attention
has been paid to the subject, resulting in the discovery of many
new mechanisms. Within a chamber enclosing the shaft to be
driven some abutment on which an- unbalanced pressure can be
exerted will usually be found ; in many rotatory engines, however,
reiprocating motion will be found to exist also. The excessive
weight for the power developed has confined these engines, where
successful, to low powers only.



24

The steam turbine, which has been developed practically
within the last three decadefi, is also a rotary engine and
shares its advantages, but differs both from it and the recipro-
cating type in that the working fluid acts, not by pressure, but
by change of momentum. The simplest form, analogous to the
impulse water wheel, consisting of a jet of steam acting on the
vanes of a wheel, is very old (see No. 33) but inefficient. With
a plain orifice there is considerable loss in converting the heat
energy of the steam into kinetic energy. By using a diverging
nozzle, Dr. C. G. P. de Laval (b. 1845, d. 1913) in 1889 was able
practically to eliminate this loss. To obtain efficiency the vanes
should travel at about half the speed of the fluid of the jet-, and
as this velocity is very great (e.g., a difference of pressure of
200 Ib. per sq. in. gives a velocity of 4,000 ft. per sec.), special
arrangements and reduction by gearing to obtain practical shaft
speeds were necessitated (see No. 144). To avoid exceeding
these ordinary limits of speed, the Hon. Sir Charles A. Parsons
in 1884 arranged side by side on the shaft a number of axial
or parallel flow turbines in each of which a part of the pressure
energy of the steam was converted efficiently into kinetic
energy, the velocity resulting at each step being within desired
limits (see No. 143). The condensing type introduced in 1891
demonstrated that the turbine could equal in efficiency and even
surpass at high powers the reciprocating engine. The success of
the Parsons turbine has resulted in the design of other successful
types in which the number of wheels has been reduced without
necessitating excessive shaft speeds. The chief of these are
the Curtis and Rateau turbines (see Nos. 146 and 147), while a
combined type, in which the earlier stages of a Parsons turbine
are replaced by a Curtis wheel, is much favoured (see Nos. 149
and 152). Most steam turbines are of the axial flow type, but
a few are of the tangential or radial flow types (see No. 154).
The size of turbines has increased rapidly, some recent



Online LibraryVictoria and Albert MuseumCatalogue of the mechanical engineering collection in the science division of the Victoria and Albert museum, South Kensington → online text (page 3 of 71)