The Sun.
London, England, 1864-03-03 00:00:00

Trial of Twin-screw Steamers,

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Two very interesting trials of steam vessels pro-
pelled on the tevin‘ecrew principle took place on
the Thames during the past week. The vessels and
their engines were constructed by Messrs. J. and
W. Dudgeon, iron ship-builders and engineers, of
Cubit town yard and London street, City. On
Tuesday a small vessel, the Experiment, built to
order for the Admiralty for service at Ascension,
made her official trial, in Long Reach, under the
supervision of Mr. John Dinnen, Admiralty Inspec •
for of Machinery Afloat, and the results were
highly satisfactory. The Experiment is only fitted
with engines of 20-horse power nominal, but in her
two runs over the measured mile she realised 7.659
knots against the tide and 10.909 knots with the
tide. Off Barking she took in tow a deep-laden
schooner of 200 tons and towed her to the West
India Decks against tide at the rate of 5.1 knots.
The Experiment is the first vessel fitted with twin
screws in her Majesty's navy. Her engines are
horizontal direct-acting high-pressure, and drive
two three-bladed propellers, having a diameter of
3ft. Sin. and a pitch of 7ft. 4in.
The second vessel, named the Edith, tried on
S iturday, is of a larger description than the Expe-
riment. She has been built for commercial pur-
poses, and is intended to cross the Atlantic. Her
principal dimensions are :—Length, 175 ft ; breadth,
25ft. ; depth, 151 feet; draught of water, aft, 9ft.
Gin, ; forward, Eft. Gin. Her engine-power is 200-
horse nominal, and the cylinders have a diameter
of 34in., with a 21in. stroke. The weight of the
engines, with shafting, tubes, and propellers, is 64
tons, and that of the boilers 35 tons. The propellers,
each driven by its own independent engine, have
each three blades of the common form, With a dia-
meter of Bft. Gin., a pitch of 16ft., and a length on
line of keel of 2ft, 4in.
The Edith left Gravesend at noon for Long Reach,
with a large party on board, including Mr. E. J.
Reed, Chief Constructor of the Navy; Rear-Admi-
ral Sir Edward Belcher, K.C.8.; Mr. John Dinnen,
Inspector of Machinery Afloat to the Admiralty ;
Captains Symonds and Selwyn, R.N., &c. On
arriving in Long Reach, a run was taken over the
measured mile each way, with and against the tide,
the ship realising under the latter circumstances a
speed of 11.803 knots, and with the tide 15 knots,
the mean of the two runs being 13-401 knots, which
was considered highly satisfactory. Her engines
averaged 100 revolutions under 281 b. of steam pres-
sure, and with a vacuum of 251 inches.
The vessel's course was next kept down the river
to obtain space for putting her through several
manoeuvres under steam, so as to exhibit the powers
of twin screws in relation to military purposes. On
reaching the position required the experiments were
prefaced by mrking two complete circles with both
screws going ahead, starting with the vessel's head
upon tide. The first circle was made in 4 min. 10
sec., and the second in 3 min. 57 sec. The subse-
quent experiments, relating more entirely to mili-
tary purposes, were commenced by starting from a
state of rest with the starboard engine going astern
and the port ahead, the helm being hard sport. The
vessel turned a complete circle under these circum.
stances, with her own centre as the pivot, in 3 min.
29 sec., the mean revolutions of the engines being
84. The circle being completed, the engines were
suddenly reversed to opposite directions, and their
action upon the vessel was instantaneous, the
revolving motion of the ship being checked and
changed to the opposite direction with the
greatest ease and nicety. The mannsuvre was
repeated several times, and the vessel thus repre-
sented a revolving battery mounted with monster
ordnance, too heavy for training upon any given
object by ordinary appliances. The hull became the
carriage for such heavy guns, and trained them upon
any given point by revolving under the action of
the screws alone. This part of the day's experiments
was watched with very great interest, and gate the
liveliest satisfaction by the clear manner in which
it demonstrated the value of the twin-screw princi-
ple for military purposes.
The ship's course was next laid at full speed, both
screws going ahead up the river, the supposition
being that the vessel was carrying out hostile mea-
sures in the presence of an enemy, and that it sud-
denly became necessary to altogether alter the
vessel's course and retrace her path down the river.
Tile time was taken from the order " Hard over"
being given by the pilot, and in 1 min. 40 sec. the
Edith was in a straight course in the required op-
posite direction. Continuing her course thus, the
port engine was next stopped, and with the star-
board continuing to go ahead the helm was put
over, and a full circle made in 4 min. 31 sec., the
revolutions of the engines being 79. This brought
the day's experiments to a conclusion, and the Edith
returned up the river for her destined outfitting
berth in the West India Docks, passing the mea-
sured mile in Long Reach, with a small drain of
flood tide in her favour, at the rate of 14.884 knots,
and making the distance from Gravesend to Black-
well, 21 miles, in 59 minutes, one of the quickest
runs on record.

It may be interesting to state here that the first
twin-screw vessel built by Messrs. Dudgeon, the
Flora, was some time after her launch purchased
for the Southern States of America, ran the block-
ade successfully nine times, is now the property of
the Confederate Government, and is doing seryite
as such on the Wilmington River.