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the eccentric rod is connected to the valve by a pin that is very near the
trunnion.

Engines of this type were fitted by Maudslay to the steamboat
" Endeavour," which commenced running between London and Richmond
in May, 1829, and remained on the service till September, 1840. They were
of 20 h.p., and had cylinders 20 in. diam. by 2 ft. stroke, driving paddle-
wheels 10 ft. diam. by 5 ft. wide, at 32 revs, per min. ; the boiler pressure
was 3 5 Ib.

Similar and larger engines were fitted to several other vessels, but the
arrangement was at the time so unpopular that it was practically abandoned.
In 1838 Mr. John Pemi reintroduced it, and considerably improved the
form of the valve chest and gear ; he then constructed many engines of
this type, so that the arrangement is generally known as Penn's oscillating
engine.

812. Model of three-cylinder engine. (Scale 1 : 32.) Con-
tributed by John Scott Russell, F.R.S., 1868. N. 1244.

This arrangement of marine engine, patented by Mr. Scott Russell in
1853, is intended to reduce vibration by securing a nearly uniform turning
effort throughout a revolution, while at the same time forming a oompad
engine which could be used for driving either paddle-wheels or a screw.



257

The feature of the arrangement is the use of three oscillating cylinders,
one vertical, and the other two inclined at 60 deg. to it, all acting on a
single crank-pin ; this is equivalent to three cylinders each at 120 deg., but
is much more compact. The vertical cylinder is directly under the shaft,
and its piston-rod is connected to the crank-pin by a large end to which the
rods of the two other cylinders are pinned, so that all three piston-rods are
connected to this crank-pin.

There are two jet-condensers, with two trunk air-pumps inclined together
and driven from a single crank on the shaft ; this crank partly counter-
balances the main crank. The condensers form a single casting, which
contains the air-pumps. The steam chests are on the steam trunnion side of
each cylinder ; a single pair of eccentrics served for the three slide valves,
but this gear is not shown in the model.

The Egyptian Government yacht " Cleopatra " (see No. 389) was in 1858
fitted with a set of these engines, which had cylinders 40 in. diam. by 4 ft.
stroke, and with 25 Ib. boiler pressure made 42 revs, per min., and indicated
882 h.p. The paddle-wheels were 16 ft. diam., and had feathering floats ;
the average speed was 14 '7 knots.

813. Drawing of engines and boilers of P.S. ''Pacific."
(Scale 1 : 24.) Contributed by John Scott Russell, F.R.S.,
1868. N. 1241.

The " Pacific," an iron ship of 1,469 tons gross register (see No. 201),
was built and engined by Messrs. J. S. Russell & Co. in 1853.

The engines consisted of a pair of oscillating cylinders, 74 in. diam. by
7 ft. stroke, which indicated 1,684 h.p., and weighed 240 tons.

Steam, at a pressure of 18 Ib., was supplied by four box boilers having
in all 1,760 return tubes 6 ft. long by 3 in. diam. Each boiler was 14 -8 ft.
long, 18 ft. wide, and 12 '5 ft. high, and had five furnaces. The total grate
area was 420 sq. ft., and the heating surface 9,507 sq. ft. The weight of the
four boilers was 91 tons, and they carried 69 tons of water. The boiler
room is closed at each end by watertight bulkheads.

The paddle-wheels were 27 ft. diam., and each had 14 feathering floats
10 ft. long by 4 ft. wide. The average speed was 14 knots. She was fitted
with two masts, and the area of canvas was 7,947 sq. ft.

814. Model of paddle engines of the " Great Eastern "
(working). (Scale 1 : 12.) Contributed by Messrs. John
Scott Russell & Co., 1857. Plate IX., No. 1. N. 17.

The steamship " Great Eastern," built at Millwall in 1858, was an iron
ship of the following dimensions : Length, 680 ft. ; breadth, 82 '5 ft. ; depth
at side, 58 ft. ; displacement, 27,384 tons. The vessel was propelled by
paddle-wheels and a screw propeller ; this model represents the engines for
driving the paddle-wheels.

They were designed and constructed by Messrs. John Scott Russell &
Co., and were of the oscillating type, of 1,000 nominal h.p., but indicated
3,411 h.p. ; the weight of the engines was 836 tons. The cylinders, four
in number, were 74 in. diam. by 14 ft. stroke, and the mean number of
revolutions was 10- 75. Two of the cylinders drove one crank, and the other
two a crank at right angles, on a built-up paddle shaft. There were two
air-pumps, driven by a single crank on the intermediate length of the paddle
shaft, and there were two independent condensers, reversing gears, &c., so
that each paddle-wheel was driven by a complete double cylinder engine
that could be run alone if required. The cylinders were inclined at a mean
angle of 22 5 deg. from the vertical, and on opposite sides, so that a fairly
uniform turning moment was obtained with a single pair. The condensers
were of the jet type, arranged under the shaft and between each pair of
cylinders. The vacuum maintained was 25*5 in. The slide valves were of
the gridiron form, with back relief frames ; to reduce the length of the
steam passages, the two ends of each cylinder were supplied by separate
valves.

u 6773. it



258

Steam at 24 Ib. pressure was supplied to the paddle engines by four
double-ended tubular boilers of the rectangular or box type, each 17 '5 ft.
long, 17-75 ft. wide, and 13 '75 ft. high, with 40 furnaces and 4,500 sq. ft.
of heating surface. Each boiler weighed 50 tons, and carried about 40 tons
of water.

The original paddle-wheels were 56 ft. diam., and weighed 90 tons
each. The paddle shafts were connected to the engine shaft by powerful
friction clutches, so arranged that each could by gearing be released or
closed as occasion required ; the elaborate power-driven disconnecting gear
shown on the model was, however, never actually fitted. These wheels
were destroyed during a gale in 1861 ; the new ones fitted were much
stronger, and only 50 ft. diam., while the floats were also narrower; these
wheels were on the ship when she was broken up.

The calculated speed of the vessel, with both screw and paddle-wheels
working, was 15 knots ; a special trial of the ship under paddles alone gave
a speed of 7 '25 knots.

For a description of the screw engines of this vessel, see No. 831, and
of the vessel itself, No. 213.

[N.B. The two balance weights on the model were added in 1895, when
it was first shown in motion and did not exist in the actual engines.]

815. Model of engines of P.S. " Mersey " (working). (Scale
1 : 12.) Maudslay Collection, 1900. N. 2226.

The " Mersey" was built of iron in 1859 at Millwall by Messrs. Samuda
Bros., for the West Indian Mail service. Her registered dimensions were :
Tonnage, gross 1,001, net 729 tons; length, 260-4 ft.; breadth, 30-2 ft. ;
depth, 16 2 ft. ; mean draught, 18 5 ft.

Her engines were of the oscillating type, patented by Joseph Maudslay
in 1827, and had two cylinders 60 in. diam. by 5 ft. stroke. Steam was
admitted to the outer trunnion of each, and passed by a belt to the steam
chest where it was distributed by two slide valves, the exhaust passing by
the inner trunnion into the condenser. The slide valves were worked by
rocking levers driven by a sweep which was moved between vertical guides
by a loose eccentric reversing gear ; the hand movement of the valves when
necessary was accomplished by a rack and pinion arrangement. The
condenser was between the cylinders, and the two diagonal air-pumps were
worked by an intermediate crank in the main shaft ; the two feed and bilge
pumps on each side of the engine were worked by a single eccentric for
each pair, and the driving platform was arranged above one of the air-
pumps. The upper framing was tied to the engine bed by eight inclined
wrought iron columns.

Steam at 20 Ib. pressure was supplied by four tubular boilers, and the
coal capacity was sufficient for 12 days' consumption ; at 30 revs, per min.
of the engine the speed of the vessel was 11 -5 knots.

Two arrangements of paddle-wheels are shown in this model, one having
fixed and the other feathering floats.

816. Model of engines of P.S. " Leinster " (working). (Scale
1 : 8.) Lent by Messrs. Ravenhill, Hodgson & Co., 1869.

N. 1307.

The " Leinster " is one of the four iron vessels that were built in 1860
for the mail service between Holyhead and Kingstown. She is 343 ft. long,
35 ft. beam, 19 ft deep, and of 1,467 tons gross register, with a draught
of 13 ft., and an iiainersed midship section of 336 sq. ft. (see No. 217).

The engines consist of a pair of oscillating cylinders, 98 in. diam. by
78 in. stroke, placed immediately underneath the paddle-shaft. There
are two valve-boxes to each cylinder, arranged on opposite sides of the
trunnions so that their weights balance each other. Each pair of valves is
worked by a single loose eccentric, driving a sliding rod whose lower end
is provided with a curved slot in which slide two blocks connected with
the valve rods ; by this arrangement the motion of the valves is made



259

independent of the oscillation of the cylinders. To reverse the position
of the valves, a rack and pinion gear worked by a large hand-wheel is
provided, by which, after the valve gear has been released, the valves can
be moved so as to reverse the motion, the loose eccentric in the mean-
time stopping till it is caught by the second driver, which will then continue
the motion for reversed running when the gear is again engaged. The
condenser is placed between the cylinders, and contains the two air-pumps,
which are inclined and worked by an intermediate crank on the paddle-
shaft, an arrangement patented in 1841 by Mr. Joseph Miller. The feed
and bilge pumps are placed in the comers of the foundation frames, and
their plungers are directly moved by brackets attached to the cylinders.
Each cylinder weighed when finished upwards of 20 tons, and the condenser
22 tons.

The original boilers supplied steam at 20 Ib. pressure ; they were
multitubular and eight in number, four being placed forward of and four
abaft the engines, arranged in pairs- with their backs against the sides of
the vessel so as to allow the furnaces to be stoked from the middle line.
They were 9 -25 ft. long by 18 ft. wide, and 12 '25 ft. high; the total number
of furnaces was 40; there were 4,176 tubes in the boilers, 677 sq. ft. of
grate area, and 16,800 sq. ft. of heating surface.

The paddle-wheels are of the usual feathering construction (see No. 955),
and 32 ft. diam. ; each has 14 floats 12 ft. long by 5 ft. wide.

On the trial trips with a boiler pressure of 20 Ib. the engines made
25 -5 revs, per min. and indicated 4,751 h.p., while the speed of the ship
was 17 '8 knots. The average speed in all weathers during the first six
months of the service was 15 5 knots.

817. Model of high-pressure oscillating engine for paddle
launch. (Scale 1 : 8.) Presented by A. T. Home, Esq.,
1894. N. 2037.

This shows a pair of cylinders, 9 in. diam. by 14 in. stroke, working an
overhead crank shaft carrying two paddle-wheels 6 ft. diam. The valve
motion is of the usual loose eccentric arrangement, fitted with a gab and
lever gear for hand working when reversing. In larger engines of this type
an air-pump and condenser are arranged between the two cylinders, while in
the largest examples rack and pinion gear is added to enable the engineer to
move the heavy valves when reversing.

818. Model of beam engine of an American river steamer
(working). (Scale 1 : 16.) Made in the Museum, 1906.
Plate IX., No. 2. N. 2428.

The type of engine represented was developed and perfected by Robert
L. Stevens in the United States about 1822. It has been used chiefly in the
Eastern States and especially for the paddle steamers on the Hudson river
and on Long Island Sound.

The model shows an engine built in 1884 by the Pusey and Jones
Company of Wilmington, U.S.A. ; a similar engine was built from the same
drawings in 1896, very little change having been made in the design during
the interval.

The engine shown has two gallows frames, built up of heavy timbers
having cross frames and diagonals, the whole structure being tied and braced
by bolts, keys, and timber knees. Two wrought iron box girder keelsons
with cast iron crowns support the frames which are secured to them by iron
shoes and gusset plates. The cylinder, 3 ft. diarn. by 9 ft. stroke, with
condenser beneath, is placed between the feet of the forward legs of the
gallows frames, webs cast on the cylinder and condenser sides being bolted
to the frames. The crank- shaft has outer and inner bearings on each side
of the paddle-wheels and bearings near the crank. The paddle-wheel is
keyed to the shaft by three sets of keys.

B 2



260

The valve gear for this type of engine is of great interest. It was
patented by Mr. Francis B. Stevens in 1841 in the United States, and has
been generally adopted there. In front of the cylinder are two vertical
cylindrical valve chambers with flaring tops. Box castings connected with
the top and bottom of these chambers contain the valve seats for the two
upper and the two lower valves. At each end of the cylinder is a steam and
exhaust valve ; the valve chests are connected by the hollow columns. The
left-hand column is the steam chamber, connecting the upper and lower
steam valves, and the right is the exhaust, connecting the upper and lower
exhaust valves, this latter being connected with the condenser; copper
diaphragms at the upper ends of the columns allow for expansion. The
valves are of the double beat disc type. There is one eccentric for the steam
valves and one for the exhaust valves, the use of two eccentrics being one of
the essentials in the Stevens cut-off. The eccentric rods drive two horizontal
rocking shafts on which are keyed four curved arms called " wipers." These
wipers operate four " toes " on vertical lifter rods connected with the valves.
Springs on the lifter rods assist gravity to make the toes follow the move-
ments of the wipers steadily. The wipers for the exhaust valves are only
just long enough to give the requisite lead and lift, while they are so arranged
on the shaft that as the down stroke of one rod is completed, the up stroke
of the other rod is commenced. The admission valves require no lead, and
the steam wipers are so arranged that a brief interval elapses between the
shutting of one valve and the opening of the opposite one. Below the
rocking shafts are placed stops called " gags." The Stevens cut-off is not
adjustable, and can only be varied by these gags. When they are in use the
steam valve is operated by the exhaust, and steam is used for practically the
full stroke. The power is kept up temporarily in this way when encountering
heavy ice or in other cases of special necessity. Hand gear is fitted below
the gags, consisting of a trip-shaft having toes and wipers similar to the
rocking shaft. Stripper rods, worked by a foot lever, throw the eccentric
rods out of gear when working by hand. The hand- wheels shown operate
the injection valves. Steam for engines of this type was supplied by a single
cylindrical return-flue boiler, placed forward of the engine, and tested to a
pressure of 65 Ib. per sq. in.

The paddle-wheels for this engine are of simple construction. Each
wheel is 24 83 ft. diam. , and has three sets of radial spokes. Each set of
spokes has two concentric rings of iron, and near the centre one of wood.
Iron straps with T-ends connect the two iron rings at equal intervals between
the spokes. The straps and spokes cany 20 wooden floats, 6'5 ft. long,
secured by U-shaped bolts or staples. The six floats nearest the line of
dead centres are made narrower than the remainder for greater ease in
starting.

The ship structure shows details of a typical boat, of moderate dimen-
sions, as used for cargo and passenger service. Many of these vessels are
built entirely of wood, but in the present example the hull is of iron and the
remaining upper works of wood ; this arrangement provides a structure of
increased longitudinal strength and thus dispenses with the huge " hog-
frames" or fore-and-aft trusses which are conspicuous features of the
wooden-built vessels. Special wooden trusses, however, are used to give local
support to the paddle boxes and to the outer shaft bearings on each side ;
the main truss and " spring beam " are carried upon diagonal struts and
plate-brackets attached to the ship's side, and receive supplementary support
from diagonal suspension rods attached to upright square masts or king-
posts which are in turn tied together in pairs forward of and abaft the
paddle-shaft. A central trunk or casing, extending from the main deck to
the skylight, encloses the upper parts of the machinery, and the weight of
this trunk and adjacent super-structure is distributed by two tiers of pillars
placed between the main deck and the side keelsons.

For the general appearance of a completed vessel of this type see
No. 189.

The principal dimensions of the vessel are : Length, 160 ft. ; depth at side,
8 ft. ; draught, 4'5 ft. ; breadth of hull, 28 ft. ; breadth over guards, 48 ft.



261

819. Model of engines of P.S. " Princesse Henriette " (working).
(Scale 1 : 12.) Constructed by Messrs. Denny & Co. Re-
ceived 1899. N. 2181.

The " Princesse Henriette " and " Princesse Josephine " are sister ships,
built and engined at Dumbarton in 1888, for the Dover and Ostend service
of the Belgian Government. They are constructed of steel, and have the
following dimensions : Length, 300 ft. ; beam, 38 ft. ; depth, 13 '5 ft. ; gross
register, 1,099 tons.

The engines are of the two- stage expansion, surface-condensing type, with
the cylinders arranged diagonally, or inclining upwards to the crank-shaft, a
construction that is now very generally followed in high speed paddle steamers.
The high-pressure cylinder is 59 in. diam., the low-pressure 104 in., and
the stroke of each is 6 ft. The high-pressure slide valve is of the piston
construction, while that of the low-pressure is a flat double-ported slide ; in
each case the valve rods extend through the chests both back and front.
Each valve is driven by Walschaerts single eccentric gear (see No. 854), with
the eccentric set at right angles to the crank, the lead, which is constant,
l>e ing given by a lever connected with the main crosshead ; the engine is
linked up and reversed by altering the position of the end of the valve
rod in a rocking quadrant worked by the eccentric. The valve gears are
simultaneously controlled from a shaft that is moved by Brown's steam
reversing gear (see No. 873). The condenser is cylindrical in form, with the
shell made of steel plate; there are two vertical air-pumps, 34 in. diam., by
2 ft. stroke, worked by bell-cranks from the high and low pressure crossheads
respectively. The cooling water is circulated by a pair of centrifugal pumps,
and the boiler feed is supplied by Weir's automatic pumps, but these
independently driven pumps are not shown in the model.

To keep down the weight of the engines, the pistons, entablatures, and
ties are made of cast steel, while the air-pumps and the condenser ends are
of brass. The framing for the engine-bed and its incorporation with that of
the ship are shown in the model, from which it will be seen that four specially
deep web frames are provided under the line of the crank- shaft, and that the
depth of the longitudinal girders is also increased at this locality.

The paddle-wheels are of the usual feathering type, 24 ft. diam., by
13 ' 5 ft. wide, and have each nine steel floats with concave faces. The star
centres of the feathering gear are fixed to the paddle-box beams, but as these
beams are not shown on the model, the centres are here supported by brackets.

Steam is supplied by six boilers worked at 120 Ib. pressure ; on trial the
engines indicated 7,000 h.p. at 50 revs, per min., and gave the ship the speed
of 21 2 knots.



SCREW ENGINES.

820. Model of engines of S.S. "Great Britain" (working).
(Scale 1 : 12.) Presented by Messrs. Gibbs, Bright & Co.,
1862. Plate IX., No. 3. N. 330.

The " Great Britain," built at Bristol in 1839-43, was the first large iron
ship and the first screw steamer to cross the Atlantic. She was 289 ft. in
length, 50 5 ft. beam, 32 5 ft. deep, and on a draught of 18 ft. displaced
3,618 tons (see No. 187).

The hull, engines, and boilers, designed by Mr. I. K. Brunei, were at that
time considered so large that no contractor could be found willing to
undertake their construction, and the Great Western Steamship Co. therefore
resolved to undertake the work themselves.

The model shows the original propelling machinery of the ship, which
consisted of four direct-acting cylinders, each 88 in. diam. and 72 in. stroke,
with their axes inclined 33 deg. to the vertical, each pair working on an
overhanging crank-pin.

The cylinders were placed low down in the ship, resting on cast iron
base-plates bolted to girders which were riveted to the ship's frames ; the



262

crank-shaft was supported in bearings on two massive A-shaped frames,
made of hard wood and iron plating, placed athwartship and firmly secured
to the beams at each deck level.

In the middle of the crank-shaft was a drum 18*25 ft. diam., and 38 in.
wide, connected with a drum directly below it on the propeller shaft, by four
sets of flat pitch chains. These chains, of 24 sq. in. section and 7 tons
weight, had teeth on their undersides engaging with teak and lignum vitse
blocks on the peripheries of the large and small drums, the propeller shaft
making 53 revs, and the crank-shaft 18 revs, per min. respectively. The
slide valves were of the piston type, 20 in. diam., each actuated by a single
loose eccentric, which by a geared rim could be moved by manual power
when disengaged for reversing.

The condensers were of wrought iron, 12 ft. long, 8 ft. wide, and 5 ft.
deep, placed amidships between the cylinders ; in these were placed the
air-pumps, 45 5 in. diam. and 72 in. stroke, worked from the main crank-pins.
The feed and bilge pumps were actuated by a lever parallel motion from the
crosshead of the air-pump.

The propeller shafting was in three lengths ; on the first, 28 25 ft. long
and 16 in. diam., was fixed the chain drum, 6 ft. diam. ; the second length
was 61*66 ft. long and 30 in. diam., built up of two thicknesses of boiler
plate riveted together with countersunk rivets ; the third length, on which
was fixed the propeller, was 25 -5 ft. long, and 17 in. diam. at the journals.
The thrust bearing was simply a steel plate 2 ft. diam., against which pressed
a gun-metal plate of the same diam. fixed to the end of the shaft. A stream
of water was found to give sufficient lubrication.

The screw propeller, adopted after numerous experiments, was 15 5 ft.
diam. and 25 ft. pitch, with six blades 6 in. thick (not with four blades as
shown on the model), the whole being built up and riveted together (see
No. 986).

Steam was supplied by a double-ended boiler, consisting of a large shell
34 ft. long, 31 ft. wide, and 21 66 ft. high, with rounded top, divided
longitudinally into three distinct and independent compartments, each
provided with four furnaces at the forward and four at the after end, giving
a total of 360 sq. ft. of grate area. The boiler was earned on ten plate-
girders, the middle ones 3 25 ft. deep amidships, running the whole length
of the ship. The funnel was 8 ft. diam., and round its base was a feed-
water heater.

The nominal b.p. was 1,000, but at the normal speed of 18 revs, per
rnin. and a boiler pressure of 5 Ib. per sq. in., nearly 2,000 h.p. could be
indicated, and a speed of over 12 knots obtained.

821. Model of disc engine (working). Woodcroft Bequest,
1903. N. 56.

This form of steam-engine was patented by Messrs. Taylor and Davies
in 1836-8 and has been repeatedly tried since, both on land and at sea.

The chamber which acts as the cylinder is bounded laterally by a zone
of a sphere and endwise by a pair of cones, the apices of which coincide with
the centre of the sphere. The piston is a ball which forms a joint on which
it turns. From the ball, and perpendicular to the disc, projects a rod, the
further end of which is socketed in a crank plate attached to the driven
shait. A wedge-shaped partition is fixed across the upper part of the
chamber, and a corresponding slot is made in the disc. The partition and
the disc divide the chamber into four cells, two of which immediately on one
side of the partition are always expanding and the other two contracting as



Online LibraryScience Museum (Great Britain)Catalogue of the naval and marine engineering collection in the ... museum .. → online text (page 36 of 58)