178 



THE CIVIL ENGINEER ANDIARCHITECTS JOURNAL. 



[May, 



Fig. S.— Fire Engine, used by the London Fire Brigade. 

 Longitudinal section, — with the Levers turned up for tnivelling. 



this also rentJers the cock somewhat difficult to be opened and shut, if 

 the pressure be great; but as a lever of any length may be used, and 

 the kpy, from its perpeudiculnr position, may be loosened by a blow, 

 this objection is, in a great measure, obviated. 



In figs. 5 and 6, the openings in the street are large enough to admit 

 of the levers for opening the cock to be fixed, that no mistake may 

 occur from the lever being mislaid ; but with those at the British 

 Museum, it was not thought necessary to have fixed levers, as a crow- 

 bar, or anything that could be introduced into the eye of the spanner, 

 would open them. 



On the application of manual pomr to the working of Fire Engines, 



In the application of manual power to the working of fire-engines, 

 the principal object is, to apply the greatest aggregate power to the 

 lightest and smallest machine ; that is, suppose two engines of the 

 same size and weight, the one with space for 20 men to work, throws 

 60 gallons per minute ; the other with space for 30 men, throws 80 

 gallons in the same time ; the latter will be the most useful engine, 

 although each man is not able to do so much work as at the former. 

 The reciprocating motion is generally preferred to the rotary for fire 

 engines. Independent of its being the most advantageous movement, 

 a greater number of men can be employed at an engine of the same 

 size and weight; there is less liability to accident with people unac- 

 quainted with the work, and such as are quite ignorant of either mode 

 of working, work more freely at the reciprocating than the rotary 

 motion. To these reasons may be added, the greater simplicity of 

 the machinery. Various sizes of engines, of different degrees of 

 strength and weight, have been tried, and it is found that a fire engine 

 with two cylinders of 7 inches diameter, and a stroke of 8 inches, can 

 be made sufficiently strong at 17J cwt. If 4 cwt. be added for the 

 hose and tools, it will be found quite as heavy as two fast horses can 

 manage, for a distance under G miles, with five firemen and a driver 

 (figs. 8 and 9). 



This size of engine has been adopted by the Board of Admiralty 

 and the Board of Ordnance, and its use is becoming very general. 

 When engines are made larger, it is seldom that the proper propor- 

 tions are preserved, and they are generally worked with difficulty, and 

 soon fatigue the men at the levers. When a large engine is required 



Fig, 9.— Transverse section. 



in London, two with 7 inch cylinders are worked together by means of 

 a connecting screw, fig. 10, thus making a jet very nearly equal (as 

 9S to 100) to that of an engine with cylinders 10 inches diameter ; 

 any larger size than this cannot be used, as the friction in the hose of 

 24 inches diameter, is so much increased that the jet is comparatively 

 weak ; the hose may of course be enlarged in diameter, but the weight 

 is augmented, and the whole of the machinery is rendered more un- 

 wieldy and less useful. 



Jets. — A great many different shapes of jet have been tried, and 

 that shown in fig. 11 was found to answer best when tried with other 

 forms. The old jet was a continuation in a straight line of the taper 

 of the branch, from the size of the hose screw, to the end of the jet 



i».il'i-^.^~V*3:?'i„ . , 



Fig. 10. 



Pig. 11. 



pipe; this had many inconveniences; the size of the jet could not be 

 increased without making the jet pipe nearly parallel. As the 

 branches were sometimes 7 feet or 8 feet long, in some instances the 

 orifice at the end of the jet pipe was larger than that at the end of the 

 branch. The present form of the jet completely obviates this diffi- 

 culty, as the end of the branch is always li inches diameter. The 

 curve of the nozzle of the present jet is determined by its own size; 

 one-tenth of the difference between the jet to be made and the end of 

 the branch is set up on each side of the diameter of the upper end of 

 the branch, a straight line is then drawn across, and an arc of a circle 

 described on this line, from the extremity of each end of the diameter 

 of the jet, until it meets the top of the branch ; the jet is then con- 

 tinued parallel, the length of its own diameter ; the metal is continued 

 one-eigth of an inch above this, to allow of a hollow being turned out 

 to protect the edge. The rule for determining the size of the jet for 

 inside work is, to " make the diameter of the jet one-eighth of an inch 

 for every inch in the diameter of the cylinder, for each 8 inches of 

 stroke." The branch used in this c^ise is the same size as shown in 

 fig. 11. When it is necessary to throw the water to a greater height, 

 or distance, a jet one-seventh less in area is used, with a branch from 

 4 feet to 5 feet long. 



The usual rate of working an engine, of the size described, is forty 

 strokes of each cylinder per minute, this gives 88 gallons. The num- 

 ber of men required to keep steadily at work for 3 or 4 hours is 26; 

 upwards of 30 men are sometimes put on when a great length of hose 

 is necessary. The lever is in the proportion of 4i to 1. With 40 

 feet of leather hose and a I inch jet, the pressure is 301b. on the square 

 inch ; this gives 10-1 lb. to each man to more a distance of 226 feet in 



