Steam cylinder

“ The cylinder is the heart and soul of the engine, being the seat and centre of its power. The steam is generated in the boilers, but while it remains there it remains quiescent and inert. The action in which its mighty power is expended, and by means of which all subsequent effects are produced, is the lifting and bringing down of the enormous piston which plays within the cylinder. This piston is a massive metallic disc or plate, fitting the interior of the cylinder by its edges, and rising or falling by the expansive force of the steam, as it is admitted alternatively above and below it. ”

“ The steam, with its store of heat-energy, passes through tortuous pipes and passages to the steam-cylinder of the engine, losing more or less heat on the way, and there expands, driving the piston before it, and losing heat by the [459] transformation of that form of energy while doing mechanical work of equivalent amount. But this steam-cylinder is made of metal, a material which is one of the best conductors of heat, and therefore one of the very worst possible substances with which to inclose anything as subtile and difficult of control as the heat pervading a condensible vapor like steam. ”

“ In the engraved figure of this demonstrative model, one steam cylinder B, is shown, with its steam pipe and valve at A; one end of a cord is attached to the piston B, and passing over the drum wheel D, is attached to the weight X. As condensation ensues, the descent of B, will raise X; and it may be reset for another lift by drawing off the condensed water at E, and readmitting steam.
Here we are required “to make one pound weight” so that it shall be able to raise 100 times its own weight, always bearing in mind—“as high as one falleth.” ”

“ They are of enormous strength, and made with every possible care, and carry from 80 lb. to 100 lb. pressure on the square inch.
It has been found, on the whole, more convenient to expand the steam in two or more cylinders, rather than in one. I quite agree that, as a mere matter of engineering science, there is no reason why the expansion should not take place in a single cylinder, unless it be that a single cylinder is cooled down to an extent which cannot be overcome by jacketing, and which, therefore, destroys a portion of the steam on its entering into the cylinder. ”

“ Our cylinder is to be horizontal, and the steam to work with equal force at each end. The mode by which we obtain (what I take the liberty of terming) a vacuum is, we believe, entirely new; as is also the method of letting the water into it, and throwing it off against the atmosphere without any friction. It is expected that the engine, which is a 12-inch cylinder, will move with a clear force of 11 or 12 cwt., after the frictions are deducted; this force is to act against a wheel of eighteen-inch diameter. ”

“ The exhaust from one cylinder goes into a second larger cylinder. From here after doing work on a piston it discharges into a third still larger cylinder and from that may be led into a fourth cylinder. The cylinders must be progressively larger to allow for the expansion of the steam.
[148]
The ordinary steam engine labors under the disadvantage of having to start and stop its pistons at the end of each stroke. Every body possesses inertia, whether it be moving or at rest. If it be at rest, it takes much more energy to set it in motion than to keep it moving. ”

“ The great bugbear staring the amateur mechanic in the face when he contemplates making a small steam engine is the matter of boring the cylinder. To bore an iron cylinder on a foot lathe is difficult even when the lathe is provided with automatic feed gear, and it is almost impossible with the ordinary light lathe possessed by most amateurs. To bore a brass cylinder is easier, but even this is difficult, and the cylinder, when done, is unsatisfactory on account of the difficulty of adapting a durable piston to it. ”

“ The steam cylinder is shown enlarged in Fig. 160, and is single-acting, being used only to lift the boring rod at each [115] stroke, and the rod is lowered again by releasing the steam from the top side of the piston; the stroke is limited by timber stops both below and above the end of the working beam B.
The boring tool is the part of most importance in the apparatus, and the one that has involved most difficulty in maturing its construction. The points to be aimed at in this are,—simplicity of construction and repairs; the greatest force of blow possible for each unit of striking surface ”

“ Suppose a double-action cylinder, 1-inch bore and 2-inch stroke, is to make one hundred revolutions of the crank per minute, let us see how much steam will be wanted to drive it. The area of the piston is ·785 inch, and each revolution of the crank will require the cylinder to be filled twice—that is, one stroke in each direction. This will take a column of steam ·785 inch in diameter and 4 inches long for each revolution, or 314 cubic inches of steam per minute. If the speed is greater, the quantity of steam must be increased proportionately ”

“ By a cylinder of 10 feet diameter, through which the public would ascend to the top, bored and screwed together, in which a hollow floating sheet-iron piston, with a seat round it, accommodating 25 persons; a steam-engine forces air into the cylinder-column from a blast-cylinder of the same diameter and working 3 feet a second, would raise the floating piston to the top at the same speed, or five or six minutes ascending the whole height ”

“ This system, in which I dispensed with the packing for air-pump buckets of condensing steam-engines, I have also applied to the pistons of the steam cylinders, especially those of high-pressure engines of the smaller vertical construction, the stroke of which is generally short and rapid. Provided the cylinder is bored true, and the piston is carefully fitted, and of a considerable depth in proportion to its diameter, such pistons will be found to perform perfectly all their functions, and with a total absence of friction as a direct result of the absence of packing. ”

“ As it is largely the expansion of the steam that forces the piston from one end of the cylinder to the other this means that a part of the useful force of the steam is wasted in the average single-cylinder engine. ”

“ Suppose live steam issues from a and fills c, directly the cylinder is moved on one side and one of the port-holes comes over the groove e, the steam enters the cylinder and, pressing against the piston, compels the crank to revolve. ”

“ All the other machinery is only to aid the cylinder, and to convey the power to the point where it is wanted to do the work. Thus, the place where the steam exerts its power, and on which the whole movement of the machinery depends, is the cylinder."
Marco observed that a long iron rod, large and solid, and very bright, kept ascending and descending through the top of the cylinder, as if pushed up and drawn down again by some force within. Forester told him that that was the piston rod. ”

“ The now well-known principle of a steam-engine is this: there is a cylinder with its rod fixed to one end of a lever, which is worked by the combined pressure of the atmosphere and the steam upon a piston, a temporary vacuum being made below it by suddenly condensing the steam, which had been let into the cylinder where this piston works, by a jet of cold water thrown into it. ”

“ We have now to notice the double cylinder engine constructed by Woolfs, which will be found, by reference to the diagram in the preceding page, to consist of a high pressure cylinder, connected with a condensing apparatus.
A and B represent the two cylinders, in the larger of which the steam is allowed to expand itself, after passing from the high pressure cylinder B. The steam, which in the first instance is of considerable elasticity, is admitted to the cylinder B, by the tube and valve E, and entering the cylinder above its piston, impels it to the bottom. ”

“ Another mode by which the expansive principle has long been made use of in stationary and marine engines is to allow the steam from the boiler to enter first a smaller cylinder and from that, at the end of the stroke, to pass into a larger one in which, as it expands, it exercises a diminished pressure. This arrangement has been called the compound or double-cylinder engine, and was known to possess certain advantages where high pressure steam was made use of. ”

“ The beam-engine is a peculiarly American type, seldom if ever seen abroad. Fig. 130 is an outline sketch of this engine as built for a steamer plying on the Hudson River. This class of engine is usually adopted in vessels of great length, light draught, and high speed. But one steam-cylinder is commonly used. The cross-head is coupled to one end of the beam by means of a pair of links, and the motion of the opposite end of the beam is transmitted to the crank by a connecting-rod of moderate length. ”

“ If a condenser is not used, then it is simply a compound engine.
Triple and Quadruple Expansion Engines.—Instead of using two cylinders, three, or four, are employed, each succeeding cylinder being larger than the last. As steam expands it loses its pressure, or, stated in another way, whenever it loses pressure it increases in volume. For that reason when steam enters the first cylinder at a pressure of say 250 pounds, it may exhaust therefrom into the next cylinder at a pressure of 175 pounds, with a corresponding increase in volume. ”

“ If you thoroughly understand the working of the steam, you can readily detect any defect in your cylinder or steam chest, by the use of your cylinder cocks. Suppose we try them once. Turn your engine on the forward center, now open the cocks and give the engine the steam pressure. If the steam blows out at the forward cock we know that we have sufficient lead. Now turn back to the back center, and give it steam again; if it blows out the same at this cock, we can conclude that our valve is in its proper position. ”

“ Hence, every reciprocating engine has special valves for this purpose and such valves need rods and cranks (or something equivalent) to operate them. Further, to get the best results the steam must not simply be passed through one cylinder but through several in succession. Engines where the steam goes through only one cylinder are called "simple," where it goes through two they are "compound," where three "triple-expansion," where four "quadruple-expansion." Generally speaking, each cylinder has its own connecting-rod and crank, also its own set of rods, etc., for working its valves. ”

“ If, instead of being allowed to escape without doing any useful work, it was employed to convert a small quantity of water injected into the cylinder into steam, overheating of the cylinder would be prevented, and at the same time this heat would be utilized. Besides the power gained, the use of steam is of value in giving a more sustained pressure on the piston and in lubricating the cylinder. Numerous attempts have been made to realize its advantages, both in hot-air and gas engines, but in most cases with no considerable gain in economy. ”

“ All the cylinders are in a horizontal plane, and usually in two rows, but such rows may be disposed either in horizontal or vertical frames. Floor-space is economized in the latter arrangement, and two or more groups of two rows per group may be provided for. Each cylinder is provided with some type of safety air-valve, which yields to allow air to enter in proportion as the steam is condensed in the cylinder, and so prevents the latter from collapsing. The condensed steam is withdrawn either by means of siphons or revolving scoops, so that the interior may be as dry as possible. ”

“ In the case of a jet condenser part only of the condensed steam goes back to the boiler, the rest going into the sea through the injection discharge pipe.
A steam jacket [61] is an outer casing to a steam cylinder, the space between it and the cylinder being filled with steam direct from the boiler, with the object of preventing condensation of the steam in the engine cylinder. ”

“ In supplying steam from the water compartment to the steam compartment, the inventor intends using a number of small perforations, not amounting in the aggregate to more than about one twentieth the size of the cylinder port, in connection with a number of small valves to be under control of the engineer, so that the amount of steam required can be readily regulated, yet carefully avoiding the possibility of all, when opened to their utmost capacity, forming as large an opening as the valve through which the cylinder is supplied. ”

“ When the steam from one cylinder instead of exhausting into the open air, is passed to a second cylinder, of larger area, and by expanding exerts a pressure on a second piston to aid in the completion of the revolution, the engine is called double expansion or compound, because the steam instead of completing its work in a single operation is afforded a double opportunity for expansion and an increased range of action. In the single cylinder the temperature of the walls is reduced in each revolution to correspond with that of the steam at the exhaust pressure. ”

“ In large engines each cylinder is a separate casting; generally the valve chest is cast with the cylinder, making the whole a rather intricate casting. Cast iron is generally used for cylinders. Cylinders are fitted with liners, a, which form the bearing surface for the piston. The liners are bolted at the lower end to the bottom of the cylinder and the joint at the top is packed. Liners are of cast steel or cast iron; steel is stronger, but cast iron gives a better wearing surface. The space between the cylinder and liner is commonly used as a steam jacket. ”