The Stoker's Catechism

by W. J. Connor

36. Question.—How is the accumulator started working?

Answer.—The engines are started pumping into the ram and cylinder, whose drain-cocks have previously been opened, and air and water issues from them; when the air has escaped they are shut off, and then the great mass of iron and steel begins to tremble and totter and moves upwards and upwards, and on nearing the limit of its journey the top of the accumulator lifts a projecting lever which has a small chain attached to it, the bottom end of the chain is attached to the steam throttle valve, and when the chain is pulled up at the top the steam is shut off at the throttle-valve and the engine stops, but will start as soon as any water is taken from the accumulator.

37. Question.—Is there any similarity in terms used in hydraulic work and steam boiler work?

Answer.—There are several terms common to hydraulics and steam; the steam boiler might be called an accumulator of power; there is a slide-valve in hydraulics as in the steam engine, to admit the power and to allow the exhaust to escape; there are stop-valves and intermediate valves in hydraulics, as in steam pipes, also air-vessels in each: there are suction and delivery pipes and valves in each, and relieve valves also in each; there is a cylinder in each in which the power is concentrated; there are reversing levers in a hydraulic crane, as in a steam crane.

38. Question.—Who invented the atmospheric engine, and how was it constructed?

Answer.—Savory, a mining agent, invented the first method, which he called an engine, of drawing water up from a well by means of a vacuum which he happened accidentally to discover a method to create, and the pressure of the atmospheric combined with it. He procured a real steam boiler with a safety valve and gauge cocks and erected two vessels in which to create a vacuum; a suction pipe from the bottom of each vessel led down into a well beneath the vessels, and a valve that opened upwards was on the end of each pipe. When about to start work, steam from the boiler was turned into one of the vessels, and kept on until it was as hot as the boiler itself, while a drain cock was kept open the while, and when air and water had been forced out of the vessel steam was shut off, and water from a tank above the vessel was allowed to flow on it, which soon made a vacuum inside the vessel, and water was sucked up through the valves opening upwards and delivered into a tank placed for the purpose. While this performance was in progress, the other vessel was being charged with steam to repeat the performance, etc. This is the extent as far as I know of Savory's claim to be the inventor of the atmospheric engine.

39. Question.—Who was the real inventor then?

Answer.—Newcomen and his partner Cawly adopted a working beam, that is, a beam working on a centre or trunnion. At one end of the beam was the pump, at the other was an iron cylinder with an iron piston in it; both ends of the beam were arched or sexton-shaped, and had a chain on each, one connected to the pump rod, the other to the piston rod. When about to start work, the piston being up near the top of the cylinder, steam was let in under it and a jet of water was let in which soon condensed the steam and created a vacuum within the cylinder, and the piston was drawn down to the bottom and the pump drawn up with its load of water; and a counter weight was attached to the pump-rod to always bring the piston to the top of the cylinder after each descent. This is a very brief description of this atmospheric engine; there were now only two cocks to open and close—the steam cock and water cock, and the engine only required a boy for this purpose, but the boy himself added a share in this engine. In order to have a relief from the monotony of opening and shutting the cocks alternately, he tied strings to the handles and then connected to the working beam in such a manner that the cocks were opened and closed exactly at the nick of time; this caused the engine to work far more regularly and to do twice the work it had done previously, the boy's name was Humphrey Potter.

40. Question.—What did James Watt do in connection with the atmospheric engine?

Answer.—Watt being a mathematical instrument maker, was requested to repair an old engine used by some students of Glasgow University; having finished the repairs, and in working this model (the best type of the atmospheric engine), he found and proved by many and various experiments, that an enormous waste of fuel was absolutely necessary in working the engine; he found great difficulty in keeping the air from entering the cylinder, and the cylinder top was so exposed to the atmosphere that the steam was much condensed when it entered the cylinder, and he came to the conclusion to put a cover on the top of the cylinder, and allow the piston-rod to play in a hole in the cover with a gland and stuffing box, and to press down the piston with steam instead of the atmosphere. This engine was no longer atmospheric, it was a real steam engine, the first ever seen or constructed, for steam was used to create the vacuum, and steam was used to work the piston; but this was only the beginning of his great improvements. This engine though suitable for the purpose of pumping water, was totally unsuitable for continuous rotary motion, the steam acting only on the downward stroke after the piston had been pulled up to the top of the cylinder by means of the additional weight fixed on the pump end of the beam. He devised a method to admit steam under the piston as well as above it, but the flexible chains although suitable for the down stroke of the piston were powerless in the up stroke, they would hang listless and useless. This being so, he determined to get rid of the chains at both ends of the beam, and also both arched ends, and substitute a ridged connection at both ends of the beam. He put an iron connecting rod from the end of the beam to the pump rod, and the other end of the beam was connected to the piston rod by a crosshead; to this engine he attached that grand appendage the "Parallel Motion" which is the pride of the beam engine up to to-day. He devised the improvement of the separate condenser for the exhaust steam, instead of the jet of water under the piston. He invented the crank for his engine, also the sun and planet motion, also the throttle valve, also the counter to indicate the number of revolutions the engine had performed, also the "Cut off," the steam moving the piston by expansion when it was cut off at one-third the length of the cylinder, and thus saving two-thirds of the steam and a more uniform rate of speed.