The larger ships in the navy, and some of the more recent small ones, such
as the new cruisers of the Phaeton class, are fitted with powerful steam
winches of a type made by Messrs. Belliss and Co. These are used for
lifting the pinnaces and torpedo boats.
We give an illustration of one of these winches. The cylinders are 6 in.
in diameter and 10 in. stroke. The barrel is grooved for wire rope, and is
safe to raise the second class steel torpedo boats, weighing nearly 12
tons as lifted. The worm gearing is very carefully cut, so that the work
can be done quietly and safely. With machinery of this kind a boat is soon
put into the water, and as an arrangement is fitted for filling the boat's
boilers with hot water from the ship's boilers, the small craft can be
under way in a very short time from the order being given.
Mr. White is fitting compound engines with outside condensers to boats as
small as 21 ft. long, and we give a view of a pair of compound engines of
a new design, which Messrs. Belliss are making for the boats of this
class. The cylinders are 4 in. and 7 in. in diameter by 5 in. stroke. The
general arrangement is well shown in the engraving. On a trial recently
made, a 25 ft. cutter with this type of engines reached a speed of 7.4
knots.
About three years ago the late Controller of the Navy, Admiral Sir W.
Houston Stewart, wished to ascertain the relative consumption of fuel in
various classes of small vessels. An order was accordingly sent to
Portsmouth, and a series of trials were made. From the official reports of
these we extract the information contained in tables F and G, and we think
the details cannot fail to be of interest to our readers. The run around
the island was made in company with other boats, without stopping, and
observations were taken every half hour. The power given out by the
engines was fairly constant throughout. The distance covered was 56 knots,
and the total amount of fuel consumed, including that required for raising
steam, was 1,218 lb. of coal and 84 lb. of wood. The time taken in raising
steam to 60 lb. pressure was forty-three minutes. The rate of consumption
of fuel is of course not the lowest that could be obtained, as a speed of
over 10 knots is higher than that at which the machinery could be worked
most economically.
[Illustration: STEAM WINCH FOR HOISTING AND LOWERING PINNACLES AND
TORPEDO BOATS.]
The trials afterward made to find the best results that could be obtained
in fuel consumption were rather spoiled by the roughness of the weather on
the day they were made. The same boat was run for 10 miles around the
measured mile buoys in Stokes Bay. The following are some of the results
recorded:
_Table F.--Report of Trials of Engines of H.M. 48 ft.
Twin Screw Steam Pinnace, No. 110._
Date August 4, 1881.
Where tried Round the Isle of
Wight
Draught of water / Forward 3 ft. ½ in.
\ Aft 3 ft. 6½ in.
Average boiler pressure 104.81 lb.
Average pressure in receivers / Starboard 16.27 "
\ Port 16.54 "
Mean air pressure in stokehold 1.4 in. water.
Vacuum in condenser, average 26.72 in.
Weather barometer 30.37 "
Revolutions per minute / Starboard 240.75
\ Port 251.95
lb.
Mean pressure in cylinders / Starboard / High 45.33
| \ Low 16.16
\ Port / High 43.16
\ Low 15.3
Indicated horse-power / Starboard / High 18.20
| \ Low 16.32
| Port / High 18.13
| \ Low 16.17
\ Collective Total 68.82
Speed by log 10.18 knots.
Force of wind One.
Sea Smooth.
Quantity of coal on board 1 ton.
Description Nixon's navigation.
Consumption per indicated horse-power per hour 4.17 lb.
Time under way 5 hrs. 30 min.
_Table G.--Report of Trial of Engines of H.M. 48 ft. Steam Pinnace No.
110._
When tried August 3, 1881.
Where tried Stokes Bay.
Draught / Forward 3 ft. 1 in.
\ Aft 3 ft. 3¼ in.
Average boiler pressure 55.52 lb.
Vacuum 25.12 in.
Weather barometer 30.35 "
Revolutions per minute / starboard 165.54
\ port 161.55
Indicated horse-power[2] / Starboard / High 5.05
| \ Low 5.53
| Port / High 3.75
| \ Low 4.02
\ Collective Total 18.35
Speed of vessel by log (approximate) 7.404
Wind / Force 4 to 5
\ Direction Bow and Quarter.
State of sea Rough.
[Footnote 2: In consequence of the seas breaking over the boat, a large
number of diagrams were destroyed, and, on account of the roughness of the
weather, cards were only taken with the greatest difficulty. The records
of power developed are therefore not put forward as authoritative.]
In connection with this subject it may perhaps be of interest to give
particulars of a French and American steam launch; these we extract from
the United States official report before mentioned.
_Steam Launch of the French Steamer Mouche_.
Length on low water level 27 ft. 10-1/2 in.
Breadth 5 ft. 11 in.
Depth to rabbet of keel 3 ft. 3-1/3 in.
Draught of water aft 2 ft. 1-1/2 in.
Weight of hull and fittings 2,646 lb.
Weight of machinery with water in boiler 3,473 lb.
The boat is built of wood, and coppered. The engine consists of one
non-condensing cylinder, 7-1/2 in. in diameter and 5.9 in. stroke. The
boiler has 4.3 square feet of grate surface. The screw is 21-2/3 in. in
diameter by 43.3 in, pitch. The speed is 7 knots per hour obtained with
245 revolutions per minute, the slip being 19.7 per cent. of the speed.
The United States navy steam cutters built at the Philadelphia navy yard
are of the following dimensions:
Length 27 ft. 7½ in.
Breadth 7 ft. 10 in.
Depth to rabbet of keel 3 ft. 11¾ in.
Displacement (to two feet above rabbet of keel) 5.96 tons.
Weight of hull and fittings 4,675 lb.
" engine 1,240 "
" boiler 3,112 "
" water in boiler and tanks 2,696 "
The engine has a single cylinder 8 in. in diameter and 8 in. stroke of
piston. The screw is four bladed, 4 in. long and 31 in. in diameter by 45
in. pitch. The following is the performance at draught of water 2 feet
above rabbet of keel:
Boiler pressure 90 lb.
Revolutions 353
Speed 7.8 knots.
Indicated horse power. 53
These boats are of 1870 type, but may be taken as typical of a large
number of steam cutters in the United States navy. The naval authorities
have, however, been lately engaged in extensive experiments with compound
condensing engines in small boats, and the results have proved so
conclusively the advantages of the latter system that it will doubtless be
largely adopted in future.--_Engineer._
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