The following table shows the law according to which the elasticity of the air will act on the surface of the water in the air vessel : For a complete and detailed account of Newsham's fire engine, see Desaguliers' -Experimental Philosophy, vol. ii. p. 505.
20. Description of another Fire Engine.
This fire engine, which is now in use, is constructed on the principle of some of the pumps proposed by Ramelli, and which we shall describe in the next section. It is represented in Fig. 4, and is wrought by the levers LL. The interior mechanism is shown in Fig. 3, where CD is the piston working tight in the cylindrical barrel EFD, and moved by the levers LL. When the piston CD is in the position shown in Fig. 3, the water ascending the main M, rises through the valve v, and enters by the opening A the barrel ED. The motion of the piston CD from D to A then closes the valve v, and forces the water between 1) and E up through the valve x into the air ves sel at W. When CD quits the side B of the barrel, the water follows it, rushing in through the valve y, and the aperture B, and when CD returns again towards B, it forms up this water through the valve z into the air vessel, as it cannot return towards M by the valve y, which closes on the return of CD towards B.
21. Description of Sellers f.5" Pennock's Rivettcd Hose. and other Fire Apparatus.
The hose, or flexible pipes for fire engines, were former ly made by sewing the edges together with waxed thread, which being soon rotted by the oil used for the preserva tion of the leather, rendered the seams insecure, and al ways liable to burst, while, from various causes, such hose were never durable, nor could they be relied on to sustain much pressure. To remedy these obvious defects, Messrs. A. L. Pennock and J. Sellers, of Philadelphia, to whom the improvement is patented, devised and carried into per manently successful operation a mode of R1VETTING 110SE, and in connexion with S. and C. Sellers, arc manufactu rers of that and other improvements in fire machinery.
According to their method, the edges of the leather to be held together are lapped about three quarters of an inch for single rivetted, and one inch for double rivetted hose; and through both thicknesses, formed by this overlapping, rivets are passed, having their heads on the inside of the hose, while over their externally projecting stems burrs are placed and firmly secured by the hammer, in the usual way. The principal or longitudinal seam is formed with a
single or double row of rivets, according to the strength required; the connecting seams by which different pieces of leather are joined, to form one length or section of hose, are united diagonally by a double row of rivets, so as to produce a spiral line. These seams are represented in Plate CCCCLXXI. No. I. Fig. 5, and in No. II. Fig. 2.
The rivets and burrs are made of the same material, which is iron, well tinned, tutanag, or wrought copper, the two latter being used for salt water. By having the rivets and burrs of the same material, the necessary galvanic ac tion is avoided, which would prove injurious both to the metals and leather. To obtain a water-tight and suffici ently flexible seam, with a single row of rivets, about twenty-two are to be used for a foot of hose, and should be of such a size that the burrs and heads shall be nearly touching. When a double row is desired, about thirty two rivets, for the same extent, are inserted.
Should a rivet break, it is replaced by the aid of the in strument termed anvil, No. II. Fig. 3, which is a flat bar of iron, having a socket at one end for the attachment of a pole, both being sufficiently small to be passed into the hose. On this bar there is a forked spring, which receives and holds the rivet, with its head resting flat on the anvil, and the stem pointing upwards, in which position it is conveyed within the hose by means of the pole, to the place it is in tended to occupy. The rivet is now pushed through the leather by pressing on the hose from without, and a burr is slightly driven on the projecting stem; the pole is now withdrawn far enough to extricate the head of the rivet from the spring, and the burr is finally driven tight and se curely rivetted down. Similar repairs may be made, when the anvil is not at hand, by making an opening in the seam large enough to allow the introduction of the hand, not merely to replace the rivet that has been broken, but those taken out to form the opening. Rivets are then inserted, and secured in the usual manner of making the hose.