Instead of the ordinary thin plate,which is usually suspended below the furnace, for the purpose of receiving the falling cinders, Mr. Melling employs a shallow tank containing three or four inches depth of water, supplied from the tender by means of a pipe and stop-cock. The falling cinders, and the radiating heat from the furnace, consequently heat the water in the tank, which, being returned into the tender, raises the temperature of the water therein, and effects an important saving of fuel. To render this operation self-acting, the boiler is furnished with a ball valve, loaded with 50lbs. on the square inch, so that at such pressure the steam will escape and pass into the water tank, and become condensed. By this arrangement, the boiler may be always supplied with water at or near the boiling point.
Buffers are strong elastic cushions, placed at each end of the carriage, connected with a system of springs, to deaden the effects of concussion. They are variously constructed.
The following Fig. 1 represents a side elevation of one of the Dublin and Kingstown railway carriages, with Mr. Bergin's invention applied to the same. Fig. 2 is a plan of the under part of the same, the body being removed, a a represents a slight frame, made of two similar plates of iron, screwed to each other about three inches apart, and resting upon turned bearings in the centres of the axles. A wrought-iron tube b b, about three inches in diameter, the entire length of the carnage, and extending about two feet beyond each end, is supported on this frame by rollers, which allows the tube to be moved thereon lengthways with facility. On this tube is placed, at either end, within the frame of the carriage, about four feet of helical springs c c, of graduated strengths; one end of each of these sets of springs abuts against a strong collar d, fixed to the tube b, and the other end against a small box of iron attached to the frame, and furnished with one of the bearing rollers before mentioned, also with two friction-rollers resting against the inner side of the carriage-frame end. To each extremity of the tube b b is attached a buffer-headff, by means of a rod of iron passing through the tube, and connected to the buffer-heads by screwed nuts sunken below their surfaces.
At the back of each buffer-head is a cross-bar g, to which, by chains and hooks, the carriages are attached together. This apparatus lies loosely on the axles, and is perfectly independent of the frame-work of the carriage, which is sustained by springs in the usual manner; and there are long vertical slots made in the framing, through which the buffing-tube passes, which permits the frame to rise or fall, according to the pressure of the load thereon, without affecting the height of the buffing apparatus above the road. The action is as follows: - The train being moved in the direction of the arrow, the locomotive power is applied to the cross-bar g, and draws forward the central tube b, thereby compressing the springs c c between the collar d d and the friction roller box, which rests against the end of the carriage frame, without moving the latter, until the elastic force of the compressed springs becomes sufficient to overcome the resistance presented by the friction of the carriage and load. The carriage then begins to move forward, so slowly as almost to be imperceptible to persons seated within; the second and each succeeding carriage in the train is by similar means brought from a state of rest into motion.
In case of one carriage running against another, the resistance is offered by the furthest end; the effect being to drive the tube b forward, compressing the springs at the opposite end from which the concussion is given, and the carriage will be but little affected by the blow, until the elasticity communicated to the springs by compression overpowers the resistance of the carriage, which then begins to move, actuated by a force just sufficient to start it. The coiled springs have a range of action of about two feet, beginning to be compressed by a force equal to about twenty pounds, and presenting a total resistance to entire compression of upwards of two tons. A spring of this strength, the patentee states, has been found suitable for carriages weighing, when loaded, about four tons. It will be observed, that the entire resistance to the action of the springs is on the ends of the carriage frame: the middle of each is armed with a strong plate of iron, about fifteen inches square, through which pas3 the tension rods, h h, Fig. 2, to the outer angles of the opposite ends of the frame; consequently, the rods receive the entire force of the springs.
The springs at either end of each carriage act totally independent of those at the other end, and of all the carriages in the train, except that to which they are attached; each has, therefore, to bear only its own share of the resistance of the entire train, the sum of which is made up of the separate resistances of all the springs acted upon.