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The steam chests are arranged above the cylinders, the valves being driven
by the usual link motion through rocking shafts. The steam pipes are
short, and a single exhaust pipe connects the two cylinders with the con-
densers. The air pumps are provided with two sets of delivery valves, the
upper set delivering air only ; modifications were proposed to improve the
vacuum obtainable with horizontal and other air pumps.

838. Model of engines of H.M.S. "Valiant" (working). (Scale
1 : 18.) Maudslay Collection, 1900. N. 2229.

The " Yaliant " was a wooden-built armour-plated battery ship designed
by the Admiralty and built at Mill wall in 18613. Her dimensions were:
Displacement, 6.364 tons; length (b.p.), 280 -2 ft.; breadth (extreme),
56 33 ft. ; draught, 24 7 ft.

Her engines, by Messrs. Maudslay, Sons and Field, were of the return
connecting-rod type, with a pair of steam- jacketed cylinders 82 in. diam.,
by 48 in. stroke. There were two double-ported slide valves to each cylinder
actuated by the ordinary link motion, but in addition, each cylinder was
provided with an expansion gear designed by Mr. J. Field, in which by a
revolving valve driven at the same speed as the crank-shaft the supply of
steam to the chest could be cut off at any part of the stroke. This gear
could be thrown out of use by a sliding wheel, and the angle of advance of
the revolving valve was made adjustable by the introduction of a coupling
sleeve provided with a helical groove.

There were two jet condensers, arranged opposite the cylinders and each
provided with a long-stroke double-acting air-pump; the feed and other
pumps were driven by an auxiliary engine.

Steam was supplied by six boilers, three on each side of the vessel with
the stokehold amidships.

The screw was of the Maudslay- Griffiths form, 20 ft. diam., with its
pitch adjustable from 22 5 ft. to 27 5 ft. The speed realised on trial was
12 '6 knots, and the power exerted about 3,350 indicated h.p.

839. Model of engines of H.M.S. "Octavia" (working).
(Scale 1 : 16.) Maudslay Collection, 1900. N. 2228.

The " Octavia " was a 51-gun frigate designed by Sir "W. Symonds and
built at Pembroke in 1846-9 ; in 1860 she was converted at Portsmouth
into a screw frigate of 35 guns. Her dimensions were : Tonnage, 3,161
tons; length, 252 "4 ft.; breadth, 52*8 ft.; draught forward, 20'8 ft.;
draught aft, 23 '8 ft.

Her engines, by Messrs. Maudslay, Sons and Field, were of the return
connecting-rod type with three horizontal cylinders abreast, driving cranks
at 120 deg., an arrangement which was claimed to secure a good balance of



270

the moving parts and a nearly uniform turning movement even with a
higher grade of expansion than generally used. The cylinders were 66 in.
diam. by 42 in. stroke, and were steam jacketed ; each had two double-
ported slide valves driven by the gear patented by Mr. Charles Sells in 1859.
The valves were all worked from a valve shaft which carried a single
eccentric for each valve set at a suitable angle of advance for the corre-
sponding crank ; this shaft was driven by four spur wheels carried in an
adjustable frame, by moving which the valve shaft underwent a relative
angular movement which reversed the engine, or would alter the point of
cut off from 25 to 16 of the stroke.

The two condensers were on the opposite side to the cylinders, and the
pumps were driven by two additional rods from each of the two outside
cylinders.

Steam at 20 Ib. pressure was supplied by tubular boilers and was
superheated by passing it through flattened horizontal tubes placed in the
uptake. At the trial in 1861, with a displacement of 2,921 tons and
immersed midship section of 552 sq. ft., the engine made 69 '5 revs, per
min., and indicated 2,265 h.p. with a coal consumption of 2 '25 Ib. per
indicated h.p. per hour and gave a speed of 12 * 25 knots.

840. Model of engines of H.M.S. " Prince Albert " (working).
(Scale 1 : 12.) Lent by Messrs. Humphrys and Tennant,
1869. N. 1310.

The "Prince Albert" is a coast defence armour-plated turret ship,
designed under the superintendence of Capt. C. P. Coles and built in 1864
at Poplar. She is constructed of iron and has the following dimensions :
Displacement, 3,687 tons; length, 240 ft. ; beam, 48 ft. ; depth, 25 25 ft. ;
draught forward, 17 7 ft. ; draught aft, 19 8 ft. ; area of immersed midship
section, 760 sq. ft.

The engines, which were constructed by Messrs. Humphrys and Tennant,
are of the horizontal direct-acting type, with two cylinders each 72 in. diam.
by 3 ft. stroke, and are remarkable for the shortness of their connecting-rods,
which are only 63 ins. long, or 3 5 times the crank radius. The piston rods
are exceptionally stiff, and the connecting-rods have forked ends with the
pins fast in them. The slide valves are double-ported and cut off at two-
thirds of the stroke in full gear ; they are worked by the usual shifting link
motion direct from the crank-shaft, but the link is of the bar construction,
which, although more simple than the usual slotted link, involves the use of
a special cylindrical joint to transmit the motion to the valve spindle.

There is a condenser of the jet type, to which the steam from the two
cylinders is conveyed by a single central exhaust pipe. The sea water from
the wings enters the condenser through a long slotted pipe which breaks up
the jets, and the exhaust steam is distributed by a diaphragm plate. There
are two double-acting piston air pumps, 22 '5 in. diam., within the condenser,
and two similar feed or bilge pumps 7 * 6 in. diam. These pumps are driven
by two rods directly from each piston, and so have a uniform stroke of 3 ft.

The central portion of the engine framing is in one piece, and has three
vertical hollow box projections forming pedestals for the crank-shaft bearings,
while it also carries the slipper guides for the crossheads ; the outer bearings
for the crank-shaft are stayed to the upper parts of the cylinders by turned
wrought-iron struts.

Steam at 24 Ib. pressure was supplied by four boilers of the high
rectangular multitubular type arranged in one stokehold. The engines
indicated 2,128 h.p. at 61 revs, per min., and drove a propeller 17 ft. diam.,
21 ft. pitch, and 2 -5 ft. long.

841. Model of engines of H.M.S. " Monarch " (working).

(Scale 1 : 8.) Lent by Messrs. Humphrys and Tennant,

1869. N. 1309.

H.M.S. " Monarch " was built at Chatham in 1868, and was the first

sea-going turret ship. Her dimensions are : Displacement, 8,000 tons j



271

length, 330 ft. ; beam, 57 5 ft. ; depth, 36 ft. ; immersed midship section,
1,200 sq. ft. ; draught, 24 ft.

The model represents the pair of single horizontal engines, constructed
by Messrs. Humphrys and Tennant, with steam-jacketed cylinders 120 in.
diam. and 4*5 ft. stroke. Each piston has four piston-rods and drives the
crank- shaft by a return connecting-rod from a crosshead that works in
guides formed upon the condenser. The valve gear is of the shifting link
type, and with the other valves is controlled from a bridge arranged above
the crank- shaft. The crank-shaft is 22 in. diam. and the propeller shaft
18 in. diam.

The condensers are of the surface type, with over 17,000 tubes each
6 ft. long, and have a cooling surface of 16,500 sq. ft. To reduce weight
the bodies of the condensers are of wrought iron and the tops of cast brass.
The air and circulating pumps are driven directly by rods attached to the
pistons and passing through glands in the cylinder covers ; the feed pump
plungers are connected directly to the crossheads. The condenser tubes are
of copper, and the circulating water passes outside them, two features that
are now seldom seen.

The engines indicated 7,800 h.p., made 64 revs, per min. with a boiler
pressure of 31 lb., and drove a two-bladed Griffiths' propeller 23 3 ft. diam. and
26 3 ft. pitch, weighing 22 tons, that gave the vessel a speed of 14* 9 knots.

Steam was supplied by boilers possessing 21,000 sq. ft. of heating surface
and 770 sq. ft. of grate area.

The " Monarch " was subsequently refitted with modern vertical three-
stage expansion engines.

842. Model of single-trunk screw engines (working). (Scale
1 : 12.) Presented by J. K. Rennie, Esq., 1876. N, 1413.

This type of trunk engine was introduced by Messrs. J. and G. Rennie,
who fitted them to many vessels both naval and mercantile ; the arrange-
ment was found most suitable for powers of from 60 to 400 h.p. The
model closely resembles the engines of H.M.S. " Reindeer," a wooden sloop,
built in 1860 to the following dimensions : Displacement, 1,365 tons ;
length, 185 -lft. ; breadth, 33 -2 ft.; mean draught, 14-8 ft.; her speed
was 10 6 knots.

The " Reindeer's " engines had cylinders 44 - 5 in. diam., which, allowing
for the trunk, is equivalent to a diameter of 41 5 in. ; the stroke was 24 in.
The cylinders were placed at opposite corners one on each side of the crank-
shaft, with their respective air pumps and condensers beside them ; each air
pump was driven from the crank pin of the other engine. The cylinders
and air pumps had single-ended trunks that admitted the use of connecting
rods 2 5 times the length of the stroke. The bearing of the connecting-rod
at the bottom of the steam trunks was 6 in. diam., as large as could be got
in ; it could be tightened whilst in motion by means of a steel bar within
the connecting-rod abutting at one end upon the bearing and at the outer end
against a cotter set up by a screw. The air pump trunks were single-acting
plungers ; the feed and bilge pumps were driven by lateral projections from
them.

The chief advantages claimed for these engines were : the short and
direct connection of the cylinders with their respective condensers, the small
space occupied, and the balancing of the parts.

843. Model of engines of S.S. "Carnatic" (working). (Scale
1 : 8.) Lent by the Peninsular and Oriental Steam
Navigation Co., 1878. N. 1501.

The " Carnatic " was built by Messrs. Saniuda Bros, at Poplar in 1863
for the P. & O. service. She was of 2,800 tons displacement, 285 ft. long
(b.p.), 38 ft. in breadth, 28 ft. deep, and had an immersed midship section of
548 sq. ft.

The engines, made by Messrs. Humphrys and Tennant, were of the
direct-acting, inverted, two-stage expansion type, with two high-pressure



272

cylinders 43 in. diam., and two low-pressure cylinders 96 in. diain., with a
common stroke of 3 ft. The standards contained the surface condensers,
and the two low-pressure cylinders bolted together formed a girder con-
necting them and supporting their high-pressure cylinders, which were
arranged tandem-wise above them. The cylinders were steam-jacketed, and
each had its own slide valve, but only two sets of link motion were employed.
The links were of the bar type, and were reversed by gearing from a central
platform ; the weight of each pair of valves was counterbalanced by weighted
levers.

The air pumps were worked by rods direct from the low-pressure pistons,
and it is stated that they served also as feed pumps for the boiler, but the
circulation water was forced by a centrifugal pump driven by a separate
engine.

Steam at 26 Ib. pressure was supplied by boilers of Messrs. Lamb and
Summers' sheet flue type, and was somewhat superheated in copper
superheaters.

The propeller was a two-bladed screw 16 ft. diain. by 23 ft. pitch ; the
mean speed on trial was 13 '9 knots with 2,442 indicated h.p., and the coal
consumption under 2 Ib. per indicated h.p. per hour.

844. Model of engines of S.S. " A. Lopez " (working).
(Scale 1 : 4.) Made by Messrs. W. Denny and Bros.
Received 1871. N. 1195.

This represents the engines of the Cadiz and Havana mail steamer
" A. Lopez," built and engined at Dumbarton in 1865. Her dimensions
are : Displacement, 2,665 tons ; length, 270 ft. ; beam, 38 ft. ; depth,
27 ft. ; midship section, 492 sq. ft.

The engines are of the inverted vertical type, with two cylinders 66 in.
diam. by 3' 5 ft. stroke, acting on cranks at right angles. Each piston has
two piston-rods connected to a long crosshead working between guides, an
arrangement that slightly reduces the total height of the engine. Steam is
distributed by slide valves and link motion reversing gear, but on the back
of each main slide is a "cut-off" plate driven by a separate eccentric, with
a link for varying the travel. By the link motion the periods of exhaust
are adjusted, while the "back cut-off" plate gives an independent control
of the steam supply so as to permit of any desired degree of expansion.
Friction of the main slide is reduced by a relief frame carried in the steam
chest cover and making a steamtight joint on the back of the valve, so
reducing the unbalanced area ; the weight of the valve is counterbalanced
by a small piston at the top of the valve rod, working in a cylinder on the
steam chest.

The condenser is of the surface type, with horizontal tubes giving a
cooling surface of 3,488 sq. ft., and is arranged between the two engines.
The air, circulating, feed, and bilge pumps are driven directly from the
crossheads ; to balance the loads each is in duplicate, and both engines are
complete and independent. The pumps are vertical and have solid pistons,
the portions above the pistons acting as air pumps and those below as
circulating pumps, but the feed and bilge pumps have simple plungers.
The valve boxes are arranged in the condensers with external doors, and
have removable grids provided with rubber disc valves. Circulating water
enters the pumps through two pipes at the engine base, and after passing
through the tubes of the condenser is delivered overboard by a large pipe
at the back of the engines. The exhaust steam passes through pockets
round the cylinders into the top of the condensers, and the feed pumps
draw from a hot- well in the bottom of the condenser. Provision is made
however, for working it as a jet condenser should the surface condensing
arrangements break down.

On trial the engines indicated 1,427 h.p. at 45 '5 revs, per min., with a
boiler pressure of 18 Ib. and a vacuum of 24 in. The speed was 13 '3 knots,
with a mean draught of 17 ft.



273

[N.B. The model would exert about 15 h. p., but is now running light under
low pressure air with one cylinder only, and drives the other marine models
in the gallery by a shaft beneath the floor. A fly-wheel has been added to
give the momentum that the screw propeller provides in the actual engines.]

845. Model of engines of H.M.S. "Northumberland"
(working). (Scale 1 : 12.) Received 1903. - Plate IX.,
No. 8. N. 2325.

H.M.S. " Northumberland " (see No. 96) is an iron-built sea-going
armourclad of 26 guns, designed by the Admiralty and completed in 1865-8
at the Millwall Ironworks. Her dimensions are : Displacement, 10,780
tons; length (b.p.), 400'2 ft.; extreme breadth, 59 '3 ft.; mean draught,
27 '2 ft.

She and one sister ship, H.M.S. " Minotaur," were fitted by Messrs. John
Penn and Sons with horizontal trunk engines, as represented in this model,
while the other sister ship, H.M.S. " Agincourt," was fitted by Messrs.
Maudslay, Sons and Field with the horizontal return connecting-rod engines
represented, to the same scale, in the adjacent model No. 846. Both con-
structions enabled the engines to be placed completely below the water-
line, and therefore out of the reach of shot, the more modern arrangement
with vertical cylinders only becoming possible in warships after the
protective power of inclined armour had been demonstrated.

The single-trunk engine had been patented in 1784 by Watt, and also
subsequently by others, but the double-trunk construction, by which equality
of piston area was attained and the engine adapted for horizontal working,
was first patented in 1845 by John Penn, who successfully introduced and
extensively fitted it for driving screw propellers. The arrangement gave
a light and compact engine, without piston rod or guides, and the thrust of
the connecting-rod, when steaming ahead, materially reduced the down-
ward pressure due to the weight of the piston. On the other hand, the
cooling losses due to the surfaces of the trunks were serious and inconvenient,
the gland friction was excessive, and the bearing at the small end of the
connecting-rod was almost inaccessible.

The engines represented have two simple cylinders, 112 in. diam. by
52 in. stroke, but from the front and back of the pistons extend trunks
41 in. diam. which reduce the areas to those of cylinders of 104 in. diam.
The gudgeons to which the small ends of the connecting-rods are attached
are on the pistons, and the large ends of the connecting-rods act on balanced
cranks set at right angles, the internal diameter of the trunks being such as
just to permit of the full swing of the connecting-rods. The two condensers
are of the jet type, and are arranged close together on the opposite side to
the steam cylinders ; the horizontal double-acting air-pumps for clearing
them are directly driven by a rod from each piston, passing through a gland
in the cylinder cover. Another rod from each piston similarly drives the
feed and bilge pumps, which are arranged with the condensers.

Steam is distributed to each cylinder by a large double-ported slide
valve, fitted with a circular relief-frame and worked by the usual shifting-
link motion. An early steam cut-off is provided for by a large gridiron
expansion valve, arranged above the steam chest and actuated by a separate
eccentric through a link by which the point of cut-off can be varied ; this
arrangement includes the steam chest in the clearance space until the
link-motion gives a second cut-off, the diagram obtained consequently being
what is known as "broken-backed."

The propeller was a 4-bladed Mangin screw, 24 ft. diam., whose pitch
could be varied from 22-5 ft. to 28 '5 ft., but was set at 25 '5 ft.

Steam, at 25 Ib. pressure was supplied by 10 tubular boilers, each having
four furnaces ; the total heating surface was 23,040 sq. ft., and the grate
area 956 sq. ft. At the sea trials the engines made 58 -4 revs, per min., and
indicated 6,545 h.p., which gave the vessel a speed of 14 -1 knots. With
half boiler power the revs, were 47 * 6, the indicated h.p. 3,213, and the
speed 11 7 knots.

u 6773. s



274

The base of this model shows the general arrangement of engine seatings
and adjacent ship-structure. The former consists of three large transverse
box-girders combined with three smaller fore-and-aft girders, the whole
being well secured to the ship's main frames. These latter illustrate details
of the single-plate frames with joggled and stapled angle-bars used in early
iron-built warships. A complete inner skin was fitted in the way of engine
and boiler rooms. Additional structural features of this class of vessel are
shown (see No. 658).

846. Model of engines of H.M.S. "Agincourt" (working).
(Scale 1 : 12.) Maudslay Collection, 1900. ' N. 2230.

The " Agincourt " is an armour-plated cruiser designed by the Admiralty
and built of iron in 1868 by Messrs. Laird Bros, at Birkenhead. She is a
sister ship to the " Northumberland " (see No. 96), and her dimensions
are : Displacement, 10,600 tons ; length (b.p.), 400 ft. ; breadth (extreme),
59 -4ft. ; draught, 27 -75 ft.

The engines, by Messrs. Maudslay, Sons and Field, are of the horizontal
return-connecting-rod type and have a pair of cylinders 91 in. diam., by
54 in. stroke, fitted with steam jackets. To reduce the friction of the
several glands, the nuts of each are connected by worm-gearing so as to
ensure alignment while tightening up.

The slide valves are actuated by the ordinary reversing link motion
controlled by screw gearing from the platform, but the weight of the links
is supported by counterbalancing levers. Each cylinder has an expansion
valye, of the revolving cylindrical type introduced by Mr. J. Field, fitted
where the steam pipe enters its steam chest. By this the supply of steam
is cut off independently of the link motion, but the steam chest for the time
becomes part of the cylinder clearance space. These rotary expansion
valves are driven by spur gearing from the crank- shaft and at the same
speed, but in each connection there is introduced a sliding sleeve with a
helical groove by which the point of cut-off can be altered ; there is also a
disengaging clutch. (Another arrangement of this expansion gear is seen
in the engines of H.M.S. " Yaliant," see No. 838).

Opposite to the cylinders are the two condensers which are of the jet
type. The two air pumps are horizontal, double acting, and driven directly
by a separate rod from each piston ; between them are the crosshead guides
and above is the driving platform.

On trial, in 1865, the engines exerted 6,667 indicated h.p. at full boiler
power, which gave the vessel a speed of 15 '48 knots.

The engine bearers and local ship- structure are represented by the base
of the model. A combination of three transverse box- girders with five
longitudinal girders is used for the former while the latter consists of the
heavy plate-framing which was generally adopted before the introduction of
bracket-framing and watertight double-bottoms. The inner skin-plating
extends only to the first longitudinal on each side of the middle line.
Additional structural features of this class of vessel are shown (see No. 658).

847. Drawing of engines of S.S. " Edinburgh Castle."
(Scale 1 : 12.) Presented by Messrs. R. Napier and Sons,
1874. N. 1376.

This vessel was built and engined by Messrs. Napier and Sons in 1872
for the Cape Mail Service. She is an iron vessel of the following dimen-
sions : Gross register, 2,624 tons ; length, 335 -3 ft. ; beam, 37 '7 ft. ;
depth, 28 -2 ft.

The engines represented are of the inverted two-stage expansion type,
with cylinders 44 in. and 72 in. diam., by 42 in. stroke, and were supplied
with steam at 63 Ib. pressure. The high-pressure cylinder has its steam
jacket formed by the insertion of a liner, but the low-pressure cylinder has
its jacket cast with it. The piston of the latter has a separate rod by which
steam is admitted to the piston jacket. The high-pressure valve has a back



275

cut-off expansion valve, worked by a separate eccentric, and has the pressure
on the back reduced by Dawe's relief arrangement (see Mechanical Engi-
neering Collection). The low-pressure valve has a back cut-off plate, which
is stationary but can be adjusted in position.

848. Model of engines of S.S. "Britannic" (working). (Scale
1 : 12.) Maudslay Collection, 1900. Plate X., Nos. 1 & 2.

N. 2231.

The " Britannic " is a four-masted barque, built of iron at Belfast in
1874, by Messrs. Harland and Wolff, for the White Star Line. Her registered
dimensions are : Tonnage, 3,152 tons net, 5,004 tons gross ; length, 455 ft. ;
breadth, 45 2 f t. ; depth to main deck, 33 7 ft.

The engines, by Messrs. Maudslay, Sons and Field, are of the inverted
two-stage expansion type, with two high-pressure cylinders 48 in. diam.,
and two low-pressure cylinders 83 in. diam., arranged in tandem pairs
with the high-pressure cylinders at the top ; the common stroke is 60 in.
Between the tandem cylinders is an open distance piece by which access is
obtained to the intermediate glands. The main slide valves of each set are
moved by a single valve rod worked by the usual link-motion, but on the
back of each high-pressure slide valve is an expansion valve worked by a
separate eccentric and provided with an arrangement by which the cut-off
of each can be simultaneously adjusted. The link-motion is fitted with a
screw reversing gear assisted by a steam cylinder. Both engines exhaust
into a single surface condenser, which is cylindrical in form and is arranged
behind them. There are two vertical air pumps and duplicate feed pumps
driven by levers from the crossheads, but the circulation is performed by a
centrifugal pump independently driven by a pair of vertical steam cylinders.
The details of the pumps and their valve boxes are clearly shown in the
model. The various steam and exhaust pipes are of copper and are provided
with a form of bellows expansion joint to give some flexibility under the
stresses due to unequal temperatures.

Steam at 70 Ib. pressure was supplied by eight oval boilers, fired at each end
and possessing a total heating surface of 19,500 sq. ft, while they contained
2,423 tubes. The engines indicated 4,971 h.p. and drove a screw 23*5 ft.
diam., with a pitch increasing from 28 ft. to 31 5 ft. The first voyage from
'Queenstown to Sandy Hook took 7 days 20 hrs., with an average speed of
13 knots.

The after part of the screw shaft was originally fitted with a universal



Online LibraryScience Museum (Great Britain)Catalogue of the naval and marine engineering collection in the ... museum .. → online text (page 38 of 58)