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.
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 lb.|
|Mean air pressure in stokehold||1.4 in. water.|
|Vacuum in condenser, average||26.72 in.|
|Weather barometer||30.37 in.|
|Revolutions per minute||Starboard||240.75|
|Mean pressure in cylinders||Starboard||High||45.33 lb.|
|Indicated horse-power||Starboard||High||18.20 lb.|
|Collective Total||68.82 lb.|
|Speed by log||10.18 knots.|
|Force of wind||One.|
|Quantity of coal on board||1 ton.|
|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.|
|Weather barometer||30.35 in.|
|Revolutions per minute||starboard||165.54|
|Speed of vessel by log (approximate)||7.404|
|Wind||Force||4 to 5|
|Direction||Bow and Quarter.|
|State of sea||Rough.|
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. 10½ in.|
|Breadth||5 ft. 11 in.|
|Depth to rabbet of keel||3 ft. 3⅓ in.|
|Draught of water aft||2 ft. 1½ 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, 7½ in. in diameter and 5.9 in. stroke. The boiler has 4.3 square feet of grate surface. The screw is 21⅔ 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.|
|Weight of engine||1,240 lb.|
|Weight of boiler||3,112 lb.|
|Weight of water in boiler and tanks||2,696 lb.|
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.|
|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.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.