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forward, 4'1 ft.; aft, 4'6 ft.; displacement, 170 tons. Instead of using
frames the hull was built of three layers of planking crossing one another and
nailed together, but separated by felt ; this construction, although strong
and durable, was known as " lath and plaster."

The engines were of the regular side-lever type, constructed by Messrs.
Seaward & Co., of Poplar ; the two cylinders were 40 in. diam. by 3 5 ft.
stroke, and were collectively of 100 h.p. ; steam at 3 5 Ib. pressure was
supplied by flue boilers. The paddle-wheels were 17 '5 ft. diam. with radial
floats 9-16 ft. wide by 1'25 ft. deep; the speed of the " Ruby " was
11 '7 knots, which was '7 knot higher than that of any other Thames
steamer of that day.

The arrangement of these engines was the favourite one, not only for
river boats, but also for ocean-going steamers, and from its introduction,
by the firm of Boulton Watt & Co. prior to 1820, till the general abandonment
of paddle steamers for ocean service in 1860-70, nearly all engineers
constructed such engines. The design is evidently the result of a re-arrange-
ment of the mill engine to suit a limited height, the beam being placed low
down and the connecting-rod working upwards. Such engines worked
efficiently and required very little attention or repair, but their weight was
excessive and the space occupied was very great ; the engines of the " Ruby "
required 18 ft. of the vessel's length, and the total length of the space
occupied by the machinery and boilers was 42 ft., in a vessel only 155 ft.
long.

The engines have two cranks at right angles on the paddle-wheel shaft,
each crank being driven by a connecting-rod attached to the end of a pair
of beams vibrated by a vertical cylinder arranged between their other ends.
The piston-rod crossheads are guided by an interesting modification of
Watt's parallel motion.

The air and feed pumps are driven by a crosshead, working in guides and
moved by side rods, while the condensers are arranged around the gudgeons
or trunnions of the side-levers or beams.

797. Sectional model of side-lever marine engine (working).
(Scale 1 : 8.) Presented by the Institution of Civil
Engineers, 1868. N. 1191.

This shows in detail the arrangement of the type of marine engine
which from 1820 to 1860 was most generally and successfully adopted, being
fitted to most of the sea- going steamers till paddle-wheels were abandoned
for ocean voyages. In the development of this design much was done by
Robert Napier on the Clyde, and this model accurately represents his
regular practice previous to 1845.

To secure a uniform motion, and for other reasons, it was usual to
employ two cylinders driving cranks at right angles ; this model only
indicates one-half of the actual engine. It is, however, a remarkable
property of the arrangement that even with a single cylinder such an engine
can be started from its so-called " dead " centre.

The engine represented had two cylinders, 60 in. diam. by 6 ft. stroke,
and drove a pair of paddle-wheels 24 ft. diam. at 16 revs, per min. The
boiler pressure would be about 15 Ib. above atmosphere, and the indicated
h.p. about 700. The condensers were of the jet type, and were cleared by



251

vertical single-acting air-pumps. The parallel motion, for guiding the
vertically moving rods, is a modification of that of Watt, the " radius-rod '*
and " back-link " having separate points of attachment.

This model, however, if read to a scale of 1 : 9, very closely represents
the engines supplied by Robert Napier in 1840 to the four sister ships
" Britannia " (see No. 183). " Acadia," " Caledonia," and " Columbia," with
which the Cunard line was established. They each had a pair of cylinders
72 -5 in. diam. by 82 in. stroke, and at 16 revs, per min. indicated 740 h.p. ;
the speed was 8 25 knots, with a coal consumption of from 31 to 38 tons
per twenty- four hours.

The finest engines of this type were probably those of the last paddle-
driven Cunarder, the " Scotia," which had two cylinders 100 in. diam.
by 12 ft. stroke. The paddle-wheels were 40 ft. diam., and had floats
11 -5 ft. by 2 ft. Steam at 20 Ib. pressure was supplied by 8 boilers with
40 furnaces, and the speed was 13 '5 knots, with a coal consumption of
160 tons per 24 hours.

Note. The parallel motion levers, the valve gear, and the paddle-
wheel of the model were made in the Museum in 1898 from existing
records.

798. Model of modified side-lever engine (working). (Scale
1 : 16.) Presented by the Institution of Civil Engineers,
1868. N. 1192.

The model represents an arrangement by which the space required for
the side-lever type of marine engine is reduced. Instead of arranging the
pair of cylinders athwartships, they are placed fore-and-aft ; one in the usual
position driving the crank-shaft by a pair of side-levers, and the other
arranged under the crank- shaft, driving directly by side rods. As the crank-
pins driven by the two cylinders are at right angles, the engine exerts a
fairly uniform turning moment, and will start in any position. The portions
of the four-throw crank-shaft are coupled by drag links.

The valves are driven by separate loose eccentrics ; no parallel motions
are employed, the crossheads being guided by slides secured to the cylinder
tops ; in most other respects the details resemble those of the common side-
lever arrangement.

799. Photograph of tug-boat engines. Lent by Messrs.
Westgarth, English & Co., 1887. N. 1719.

This represents the engines of the paddle tug " Pendennis," built in 1885.
There is a single cylinder, 25 in. diam. by 42 in. stroke, working the paddle
shaft by means of a half-beam.

This modification of the early side-lever engine is generally considered to
give the most satisfactory type of engine for such paddle vessels.

800. Model of engines of H.M.S. "Gorgon" (working).
(Scale 1 : 24.) Presented by Messrs. Bullivant & Co.,
1902. N. 1874.

The " Gorgon " was a steam frigate designed by Sir "W. Symonds, and
launched at Pembroke in 1837. Her dimensions were : Length, 178 ft. ;
breadth, 37 "5 ft. ; depth, 23 ft. ; draught of water, 13 ft. forward, 14 '5 ft.
aft; tonnage, 1,111 tons. She was built throughout of teak, with the
exception of the main beams, which were of oak.

The engines, by Messrs. Seaward and Capel, of Liniehouse, were the first
direct-acting fixed-cylinder marine engines, and owing to the great saving
in room and weight that they showed when compared with the then almost
universal side-lever engine, they created considerable interest. The substi-
tution of wrought iron columns to cany the upper entablature in place of
the usual heavy cast frames was an additional improvement.

The "Gorgon's" engines had cylinders 64 in. diam. by 5*5 ft. stroke,
and drove paddle-wheels 27 ft. diam. ; the general machinery was 4 ft.



252

below the water-line. Eacli cylinder was carried on a foundation plate
weighing 10 tons, that contained its condenser and hot-well, while also
supporting the air and feed pumps. The piston-rods were guided by a lever
parallel motion of peculiar construction, now known as the " Gorgon "
type ; from a double lever of this motion the pumps were driven. The
eight columns supporting the entablature were 7 in. diam. These engines
were found to weigh 60 tons less than equivalent side-lever engines, but the
chief objection urged against the arrangement was the shortness of the
connecting rods.

Steam was supplied by four tubular boilers with twelve grates and two
stoke-holds. The coal bunkers were arranged around the engines and
boilers, giving a thickness of 8 ft. and a capacity of 400 tons, or 16 days'
consumption at a speed of 7*7 knots. On trial the average speed was
9 8 knots and the fuel consumption one ton of Welsh coal per hour.

801. Model of open-topped cylinder paddle engines (working).
(Scale 1 : 24.) Presented by Messrs. Bullivant & Co., 1902.

N. 1876.

This arrangement of direct-acting marine engine was introduced in 1839
by Messrs. Seaward and Capel, of Limehouse, to avoid the use of the short
connecting-rods seen in the earlier " Gorgon " type, which in other respects
this strongly resembles. One of the first vessels fitted with these " atmo-
spheric " engines was the P.S. " Sapphire," built of iron in 1842 by Messrs.
Ditchbum and Mare. She was 150 ft. long, 19 ft. beam, 4 6 ft. draught,
and was fitted with engines having three cylinders 74 in. diam. by 3 ft.
stroke, supplied with steam at a pressure of 8 Ib. above the atmosphere.
These drove paddle-wheels 16 ft. diam. at about 30 revs, per min. The
" Alliance " and the " Havre," iron vessels built in 1855-6 for the Channel
service, were also fitted with these engines.

The cylinders have no top covers, so that the connecting-rods can be
attached close to the pistons, but each piston has a light rod working in a
guide which the forked end of the connecting-rod clears. The air and feed
pumps are driven by beams rocked by links from the pistons.

The engines in some respects resemble the trunk form subsequently
extensively adopted where space was restricted.

802. Model of double piston-rod engine (working). (Scale
1 : 16). Contributed by Messrs. Maudslay, Sons and Field,
1858. N. 120.

The type of vertical engine in which the crank-shaft is placed a short
distance above the cylinder and is driven by a return connecting-rod from a
crosshead above so as to admit of the use of large cylinders in the limited
height available under a paddle shaft appears to have been first introduced
in 1837 by Messrs. G. Forrester & Co. of Liverpool, for the P.S. "Rainbow."
In this engine the piston rod was extended upward to form a kite- shaped
loop within which the crank and connecting-rod could work.

In 1839 Joseph Maudslay and Joshua Field patented the arrangement,
shown in the model, in which two piston rods and a return connecting-rod to
a crank, which just clears the top of the cylinder, are used. The piston rods
are both on the same side of the crank which is consequently off the centre
line, thereby increasing the maximum obliquity of the connecting-rod and
causing considerable difference in the times of the two strokes. This led to
the neglect of the arrangement but not until several engines of 70 h.p. with
cylinders 4 ft. diam. by 3 ft. stroke had been built for service on. the river
Rhone. The air and feed pumps were worked by a sway beam rocked by
the crosshead.

The engine is interesting in that it shows the original form of the
arrangement, subsequently adopted extensively when placed horizontally,
known as the return connecting-rod engine.



253

803. Model of quadruple piston-rod engine (working).
Received 1902. N. 2283.

This shows the improved arrangement of engine (see No. 802) patented
in 1842 by David Napier of Millwall. He adopted four piston rods which
allowed the axes of the cylinder and of the crank shaft to be in one plane,
thus giving a symmetrical and satisfactory engine. Napier built many of
his four piston-rod engines which became very popular on the Clyde
for vessels of shallow draught, owing to their reduced length as compared
with those having side levers ; on account of the height of their guides
above deck, they became generally known as " steeple " engines.

The model, which was in use for driving a small boat, has a pair of
cylinders 4 5 in. diam. by 5 3 in. stroke, each with four piston-rods and a
return connecting rod, driving cranks at right angles. The valve chests are
arranged for long D slide valves, worked by weigh-shafts and gabs from
loose eccentrics on the crank- shaft. The condenser is of the jet type, formed
in the bed plate, and is cleared by a diagonal air pump 3 in. diam. by 3 in.
stroke, worked by an intermediate crank in the shaft, and there is a plunger
feed pump, 6 in. diam, and 1 5 in. stroke driven by an eccentric at one end
of the crank- shaft.

804. Model of double piston-rod engine (working). (Scale
1 : 8.) Maudslay Collection, 1900. N. 2220.

The arrangement here shown is an improvement on Napier's steeple
engine (see No. 803) in that while sharing its symmetrical arrangement, only
two piston rods are required.

The cylinder is placed vertically some distance below the crank-shaft,
and through its upper cover pass two piston rods, one on either side of the
crank-shaft, united above by a crosshead which slides on vertical cylindrical
guides. From this crosshead descends the connecting-rod to the crank-shaft
while the vertical air, feed and bilge pumps are driven by beams worked by
links from, the main crosshead. The steam is distributed by a locomotive-
type slide valve which is driven by link motion ; in this case, however, the
link is shifted by a hand wheel and pinion gearing into teeth on the link, the
short travel of which would not seriously interfere with the movements of
the attendant in reversing or "linking up."

The model represents generally several engines of 30 h.p. with single
cylinders 32 in. diam. by 3 5 ft. stroke which were built in 1850 to the
order of the Hon. East India Company for shallow- draught river steamers.

805. Model of direct-acting paddle engine (working).
(Scale 1 : 16.) Contributed by J. Seaward, Esq., 1860.

N. 326.

This is an arrangement of paddle engine in which, by the use of what
may be termed " return piston rods," a long connecting- rod is accommo-
dated in a limited height. The cylinder has a single piston rod, terminating
in a four-armed crosshead, from which four rods pass downwards to two
short cross pieces that are guided by side-levers controlled by a " Gorgon "
parallel motion. From these cross pieces a forked connecting-rod extends
upward to the crank-shaft above. The air and feed pumps are worked
by a crosshead moved by prolongations of the side-levers ; the condenser is
arranged in the framing and between the cylinder and air puinp. The
upper entablature is connected with the cylinder by turned columns and
inclined stays that give a generally light appearance.

This arrangement of engine, which it is stated was fitted to several tug
boats, gives a flexibility in the machine that was of advantage in the early
days of marine machinery ; but the number of working parts is great, and
careless adjustment can cause considerable trouble with so many connecting
Jinks.



254

806. Model of direct-acting paddle engines (working);
(Scale 1 : 12.) Contributed by Messrs. Ravenhill, Salkekt
& Co., 1859. N. 320.

This arrangement of paddle-wheel engine was patented in 1841 by
Mr. Joseph Miller as an improvement on the side-lever type, and was fitted
in several vessels. Its merit consisted chiefly in the reduction in the amount
of space required, the length being but little more than the diameter of the
cylinders, which were arranged vertically under the crank-shaft, with the
two air-pumps between them.

The condensers, which surrounded the air-pumps, connected the two
cylinders, the whole being bolted together so that no foundation plate was
required, the cylinders only being fastened down to the sleepers or keelson
of the vessel. The bearings for the crank-shaft were carried in a cast-iron
frame supported on wrought-iron columns fixed to the cylinders. The
piston rods were guided by vertical slide bars fixed to the cylinder covers,
and supported by the framing ; the air-pump rods were similarly guided.
The slide-valves were of the long D type, and were actuated by eccentrics
on the crank-shaft giving motion to rocking -shafts above the valve chests.
The feed and bilge pumps were worked by a bell-crank driven from one of
the air-pump crank pins.

807. Model of engines of H.M.S. "Retribution" (working).
(Scale 1 : 24.) Contributed by Messrs. Maudslay, Sons
and Field, 1858. N. 121-2.

The paddle frigate " Retribution " was designed by Sir W. Symonds,
and launched at Chatham in 1844. Her dimensions were : Tonnage, 1,641
tons ; length, 220 ft. ; breadth, 40 -5 ft. ; depth, 26 3 ft. She carried 10
guns.

The model represents one of the pair of double-cylinder, or " Siamese "
engines, by which the paddle-wheels were driven. The arrangement was
patented in 1839 by Messrs. J. Maudslay and J. Field, as a means by which
a long cylinder could be fitted in the limited height available in a paddle
ship.

Each engine consisted of two vertical cylinders, 72 in. diam., 8 ft. stroke,
placed fore-and-aft under the paddle shaft. The two piston rods were
attached to a double crosshead of T shape, which worked in guides between
the two cylinders, while between them swung the connecting-rod joining
the crosshead with the overhead crank ; in this way a connecting-rod of
ample length was provided for. The air and feed pumps were driven by a
pair of levers connected to the main crosshead. Steam was supplied at
a pressure of 7 Ib. per sq. in., by four flue-boilers, and the engines made
13 revs, per min.

The portion of the paddle-wheel shown has the float cut into three strips,
arranged as in the " cycloidal " paddle-wheel (see No. 937).

808. Model of engines of H.M.S. " Devastation " (working).
(Scale 1 : 16). Maudslay Collection, 1900. Plate VIII.,
No. 7. N. 2217.

The " Devastation " was a wooden-built paddle frigate, constructed at
Chatham during 1840-4 to the following dimensions : B.o.m.. 1,058 tons ;
length, 220 ft. ; breadth, 40 ft. ; depth, 26 ft.

The engines were of the twin cylinder or " Siamese " type.

The engines represented had four vertical cylinders each 54 in. diam..
by 6 ft. stroke, arranged in pairs and working on two cranks at right angles
in the paddle-shaft. The crosshead for each pair returned between the
two cylinders and was there controlled by guides, while the connecting-
rod extended from this lower end, between the two plates forming the
crosshead, to its crank pin. There was a single steam, chest and a long
piston slide valve for each pair of cylinders ; the valves were each actuated



255

through a rocking-shaft by a loose eccentric, while rack- and -pinion gears
were added for moving the valves by hand when the gabs were disengaged
while reversing. Each pair of cylinders had its own jet condenser, which
formed also a base plate, and by means of side levers drove its air and feed
pumps which were all arranged vertically. The model shows also the
bearers, platforms and columns of the engines, together with the framing
of the hull and paddle boxes.

Between 1840-6 nine vessels for H.M. Navy were fitted with these
engines, and within 10 years from their introduction 55 sets, representing
a total of 48,000 h.p., were supplied for driving paddle-wheels.

809. Model of engines of " Princess Alice " (working).
(Scale 1 : 16.) Maudslay Collection, 1900. N. 2218.

The "Princess Alice" was a paddle vessel, built of iron by Messrs.
Ditchburn and Mare in 1843 at Blackwall for the Admiralty's channel packet
service between Calais and Dover. Her dimensions were : B.o.m., 270 tons ;
length, 144 ft. ; breadth, 20 -1 ft. ; depth, 10'9 ft. ; mean draught, 6 -5 ft.

Her engines were of the .annular type, patented by Joseph Maudslay in
1841 and a development of his twin cylinder arrangement ; although more
compact they were less easily constructed and, therefore, less extensively
adopted than those having twin cylinders.

Each of the two cylinders was 43 in. diam. by 3 5 f t. stroke, but through
the centre was a hollow column, so that the piston was annular and had
two rods. These rods were secured to a double plate crosshead of T shape,
the tail of which worked within the central column and at its lower
extremity received the small end of the connecting-rod, the big end of
which was attached to the crank of the paddle-shaft above. The upper end
of the crosshead was also guided, and sufficient clearance was allowed in
the central column to permit of the swing of the connecting-rod ; the valve
gear and the pumps were all arranged as in the twin cylinder engines.

The engines represented were supplied with steam at 16 Ib. pressure
and drove a pair of feathering paddle-wheels 18 ft. diam., which gave the
vessel a speed of 12 5 knots.

810. Models of engines of P.S. "Helen McGregor" (one
working). (Scales 1 : 24 and 1 : 12.) Contributed by
Messrs. G. Forrester & Co, 1860 and 1869. N. 328 and 1312.

The " Helen McGregor " was built by Mr. John Laird, at Birkenhead,
in 1843, for the Hull and Hamburg trade. Her dimensions were :
Length, 180 ft. ; breadth, 26 ft. ; depth, 15 ft. ; register, 573 tons, and she
was at the time one of the largest vessels of her class.

The engines, by Messrs. Gr. Forrester & Co., consisted of two inverted
cylinders, 42 in. diam. by 4' 5 ft. stroke, carried by four wrought iron
columns, which also connected the foundation plate with the entablature
and crank-shaft pedestals above. The cylinders were placed athwartship
with their stuffing boxes at a sufficient height from the bottom to allow of
the crosshead, which connected the two piston-rods, working below them.
This crosshead was guided by a lever parallel motion, and from it the
power was transmitted to a crank in the paddle-wheel shaft, by a connecting-
rod that swung in the space between the two cylinders. The parallel
motion contained a strong vibrating frame of cast iron, which prevented
cross-winding ; the motion served also to work the air-pump as well as the
feed, bilge, and brine pumps. To shorten the steam ports, each cylinder
had its own slide valve, but these were connected and worked by a single
eccentric. The condenser was placed immediately beneath the slide-valve
chest, and was connected with the air-pump by a passage in the foundation
plate ; the capacity of the condenser, including the passage to the air-pump,
was 44 cub. ft. The air-pump was 33 5 in. diam. by 2 375 ft. stroke ; the
hot- well had a capacity of 36 cub. ft., and the waste water from it was
discharged by an overflow pipe through the side of the vessel.



256

Steam was supplied at a pressure of 3 75 Ib. by tubular boilers ; the
paddle-wheels, which were 23 -5 ft. diarn., made 23 -5 revs, per min.

It was estimated that these engines and their boilers saved 25 ft. in
length when compared with the space required by the then general side-lever
engine and box boiler. The smaller model shows a section of the hull with
the engines in position.

811. Maudslay's original oscillating paddle engine. Con-
tributed by Joseph Maudslay, Esq., 1857. N. 112.

This construction of marine engine, patented by Joseph Maudslay in
1827, has been very extensively adopted in paddle ships, although originally
the prejudice against it was very strong. The advantages of the plan are,
that it is compact and enables large cylinders to be placed in a limited
height, while, at the same time, the stresses are taken almost entirely by
the engine frame. Oscillating cylinders had been proposed by Murdock as
early as 1785 (see Catalogue of Mechanical Engineering Collection), and in
1822 Aaron Manby built and fitted an iron ship of the same name, 120 ft.
long, 18 ft. beam, and 3'5 ft. draught, with such engines of 80 h.p., by
which she steamed in cargo from London to Paris, where she arrived on
June 12th, 1822 ; she was the first iron ship to make a sea voyage, and
for several years continued plying between Paris and Havre. Maudslay,
however, appears to have independently adopted the arrangement, and to
have been the first to provide such engines with an efficient valve gear, and
so make them as economical as those with fixed cylinders.

The engine shown has a pair of oscillating cylinders 6'1 in. diam. by
8*5 in. stroke, acting directly on the crank-shaft above; the condenser
is arranged between the cylinders, and contains the air-pump, which is
driven by an intermediate crank on the shaft. The engine is erected on a
cast-iron bed-plate, upon which are A frames that at the top carry the
crank-shaft bearings, and lower down the bearings for the cylinder
trunnions ; the central trunnions communicate directly with the condenser,
while the outside ones are connected with the steam-pipe, tightness in both
cases being secured by packed glands. The piston rods pass through glands
in the top covers, which have long bushes to resist the wear due to the
swaying of the cylinders. The valves ai'e of the D type, and are contained
in a chest on the exhaust side of each cylinder ; the steam is brought to the
chest from the other trunnion by a belt round the cylinder. Each valve is
driven by a separate eccentric on the crank shaft, and the eccentric rod is
provided with a disengaging catch, so that the slide valve can be moved by
hand when desired ; to reduce the irregularities due to the oscillating motion,



Online LibraryScience Museum (Great Britain)Catalogue of the naval and marine engineering collection in the ... museum .. → online text (page 35 of 58)