Popular Science Monthly/Volume 12/March 1878/The Growth of the Steam-Engine V
|THE GROWTH OF THE STEAM-ENGINE.|||
93. The prize gained by Fulton was, however, most closely contested by Colonel John Stevens, of Hoboken, who has been already mentioned in connection with the early history of railroads, and who had been, since 1791, engaged in similar experiments.
In 1789 he had petitioned the Legislature of the State of New York for an act similar to that granted Livingston, and stated that his plans were complete, and on paper.
In 1804, while Fulton was in Europe, Stevens had completed a steamboat (Fig. 53) sixty-eight feet long and fourteen feet beam, which combined novelties and merits of design in a manner that was
the best possible evidence of remarkable inventive talent, as well as of the most perfect appreciation of the nature of the problem which he had proposed to himself to solve.
The machinery of this interesting vessel is carefully preserved among the collections of the Stevens Institute of Technology. Its boiler, shown in section, in Fig. 54, is of what is now known as the water tubular variety. The inventor says in his specifications: "The principle of this invention consists of forming a boiler by means of a system or combination of small vessels, instead of using, as is the common mode, one large one: the relative strength of the materials of which these vessels are composed increasing in proportion to the diminution of capacity." The steamboat boiler of 1804 was built to bear a working pressure of over fifty pounds to the square
inch, at a time when the usual pressures were from four to seven pounds. It consists of two sets of tubes, closed at one end by solid plugs, and at their opposite extremities screwed into a stayed water and steam reservoir, which was strengthened by hoops. The whole of the lower portion was inclosed in a jacket of iron lined with non-conducting material. The fire was built at one end, in a furnace inclosed in this jacket. The furnace-gases passed among the tubes, down under the body of the boiler, up among the opposite set of tubes, and thence to the smoke-pipe. In another form, as applied to a locomotive in 1825, the tubes were set vertically in a double circle surrounding the fire.
The engine (Fig. 55) was a direct-acting, high-pressure condensing engine of ten inches diameter of cylinder, two feet stroke of piston, and drove a screw of four blades, and of a form which, even to-day, appears quite good. The hub and one blade of this screw are still preserved. The whole is a most remarkable piece of early engineering. The use of such a boiler seventy years ago is even more remarkable than the adoption of the screw-propeller in such excellent proportions thirty years before the labors of Smith and of Ericsson brought the screw into general use. We have, in this strikingly original combination, as good evidence of the existence of unusual engineering talent, in this fellow-countryman of ours, as we found of his political and statesman-like ability in those efforts to forward the introduction of railways already described.
Colonel Stevens designed a peculiar form of iron-clad in the year 1812, which has been since reproduced by no less distinguished and successful an engineer than the late John Elder, of Glasgow, Scotland. It consisted of a saucer-shaped hull, carrying a heavy battery and plated with iron of ample thickness to resist the shot fired from the heaviest ordnance then known. This vessel was secured to a swivel, and was anchored in the channel to be defended. A set of screw-propellers driven by steam-engines and situated beneath the vessel, where they were safe against injury by shot, were so arranged as to permit the vessel to be rapidly revolved about its centre. As each gun was brought into line of fire it was discharged, and was then reloaded before coming around again. This was probably the earliest embodiment of the now well-established "Monitor" principle.
This great engineer and inventor was therefore far in advance of his time. The sectional steam-boiler only just becoming a standard type; high-pressure steam with condensation has just become generally adopted; the screw only came in use forty years later, when Ericsson, Smith, and Woodcroft, came forward with it, and twin-screws
are hardly yet familiar to engineers. The revolving battery protected by iron plating is another of what are generally considered recent devices; and the peculiar Stevens revolving ship is reproduced by Elder sixty years later.
A model of the little steamer built in 1804 is preserved in the lecture-room of the department of mechanical engineering at the Stevens Institute of Technology, and the machinery itself (Fig. 55), the high-pressure "section" or "safety" tubular boiler as it would be called to-day, the high-pressure condensing engine with rotating valves, and with twin-screw propellers, is given a place of honor in the model-room or museum, where it contrasts singularly with the mechanism contributed to the collection by manufacturers and inventors of our own time.
94. The first of Stevens's boats performed so well that he immediately
built another one, using the same engine as before, but employing a larger boiler, and propelling the vessel by twin-screws (Fig. 56), the latter being another instance of his use of a device brought forward long afterward as new, and since frequently adopted. This boat was sufficiently successful to indicate the probability of making steam-navigation a commercial success, and Stevens, assisted by his sons, built a boat which he named the Phœnix, and made the first trial in 1807, just too late to anticipate Fulton. This boat was driven by paddle-wheels.
The Phœnix, shut out of the waters of the State of New York by the monopoly held by Fulton and Livingston, was placed for a time on a route between Hoboken and New Brunswick; and then, anticipating a better pecuniary return, it was concluded to send her to Philadelphia to ply on the Delaware.
At that time, no canal offered the opportunity to make an inland passage, and, in June, 1808, Robert L. Stevens, a son of John, started with Captain Bunker to make the passage by sea.
Although meeting a gale of wind, he arrived at Philadelphia safely, having been the first to trust himself on the open sea in a vessel relying entirely upon steam-power.
95. From this time forward the Messrs. Stevens, father and sons, continued to construct steam-vessels.
After Fulton and Stevens had led the way, steam-navigation was introduced very rapidly on both sides the ocean, and on the Mississippi the number of boats set afloat was soon large enough to fulfill Evans's prediction that the navigation of that river would become a steam-navigation.
Except in Stevens's earlier boats, and in the boats plying on the Western rivers, all steamers were then propelled, as they are still, by condensing engines. The instrument of propulsion was also, even in Stevens's own boats after his earlier experiments, the paddle-wheel. The use of the screw did not become general, even in deep water, until within the last twenty years.
96. The steam-engine in most general use for sea-going ships when the introduction of the screw compelled its withdrawal, with the paddle-wheel which it drove, was that shown in Fig. 57, which represents the side-lever engine of the steamer Pacific, as designed by Charles W. Copeland.
In the sketch, A is the steam-cylinder; B C the side-rods, or links, connecting the cross-head in the piston-rod with the end-centres
D, of the side-lever D E F, which vibrates about the main centre E, like the overhead beams. A cross-tail at G is connected with the side-lever and with the connecting-rod G H, which latter communicates motion to the crank I J, turning the main shaft J. The air-pump and condenser are seen at O M. This engine was one of the earliest and best examples of the type, and perhaps the first ever fitted with a framing of wrought-iron.
97. After the experiments of Stevens, we find no evidence of the use of the screw, although schemes were proposed and various forms were even patented, until about 1836.
In 1836 Francis P. Smith, an English farmer, who had become interested in the subject, experimented with a screw made of wood, and fitted in a boat built with funds furnished by a Mr. Wright, a London banker. He exhibited it on the Thames and on the Paddington Canal for several months. In February, 1837, by an accident, a part of the screw-blade was broken off, and the improved performance of the boat called attention to the advisability of determining its best proportions.
In 1837 Smith exhibited his courage and his faith in the reliability of his little steamer by making a coasting-voyage in quite heavy weather, and the performance of his vessel was such as to fully justify the confidence felt in it by its designer.
The British Admiralty soon had its attention called to the performance of this vessel, and to the very excellent results attained by the Archimedes, a vessel of 237 tons burden, which was built by Smith and his coadjutors in 1838, and tried in 1839, attaining a speed of eight knots an hour. By the performance of the Archimedes, the advantages of screw-propulsion, especially for naval purposes, were rendered so evident that the British Government built its first screw-vessel, the Rattler, and Brunel adopted the screw in the iron steamer Great Britain, which had been designed originally as a paddle-steamer.
98. Simultaneously with Smith, Captain John Ericsson was engaged in the same project.
He patented, July, 1836, a propeller which was found at the first trial to be of such good form and proportions as to give excellent results.
His first vessel was the Francis B. Ogden, named after the United States consul at Liverpool, who had lent the inventor valuable aid in his work. The boat was forty-five feet long, eight feet beam, and drew three feet of water. It attained a speed of ten miles an hour, and towed an American packet-ship, the Toronto, four and a half miles an hour on the Thames. This was a splendid success.
Ericsson built several screw-boats, and finally, meeting Captain Robert F. Stockton, of the United States Navy, that gentleman was so fully convinced of the merits of Ericsson's plans that he ordered an iron vessel of seventy feet length and ten feet beam, with engines of fifty-horse power.
The trial of the Stockton, in 1839, was eminently satisfactory. The vessel was sent to America under sail, and the designer was soon induced to follow her to this country, where his later achievements are well known.
The engines of the Stockton were direct-acting, the first examples of engines coupled directly to the crank-shaft without intermediate gearing, that we meet with after that of John Stevens.
99. Soon after Ericsson arrived in the United States, he obtained an opportunity to design a screw-steamer for the United States Navy, the Princeton, and, at about the same time, the English and French Governments had screw-steamers built from his plans, or from those of his agent in England, the Count de Posen.
In these ships—the Amphion and the Pomone—the first horizontal, direct-acting engines ever built were used. They were fitted with double-acting air-pumps, having canvas valves and other novel features.
From 1840 the screw gained favor rapidly, and finally began to displace the paddle for deep-water navigation. Progress in this direction was at first somewhat slow.
In 1840, and during the following ten years, many experiments were instituted between the performance of screw and paddle steamers without definitely settling engineering practice.
100. The reason was, probably, that the introduction of the rapidly-revolving screw, in place of the slow-moving paddle-wheel, necessitated a complete revolution in the design of their steam-engines. And the unavoidable change from the heavy, long-stroked, low-speed engines, previously in use, to the light engines, with small cylinders and high piston-speed, called for by the new system of propulsion, was one that necessarily occurred slowly, and was accompanied by its share of those engineering blunders and accidents that invariably take place during such periods of transition.
Engineers had first to learn to design such engines as should be reliable under the then novel conditions of screw-propulsion, and their experience could only be gained through the occurrence of many mishaps and costly failures. The best proportions of engines and screws for a given ship were determined only by long experience, although great assistance was derived from the extensive series of experiments made on the French steamer Pelican. It also became necessary to train up a body of engine-drivers who should be capable of managing these new engines, for they required the exercise of a then unprecedented amount of care and skill. Finally, with the accomplishment of these two requisites to success, must simultaneously occur the enlightenment of the public, professional as well as non-professional, in regard to their advantages.
Thus it happens that it is only very recently that the screw has
attained its proper place as an instrument of propulsion, and has only now driven the paddle-wheel almost out of use, except in shoal water.
Now our large screw-steamers are of higher speed than any paddle-steamers on the ocean, sometimes crossing the Atlantic from New York to Queenstown in a week, making their passages with wonderful regularity, and developing their power at far less cost than the old side-wheel steamers. This increased economy is due, not only to the use of a more efficient propelling instrument, but, perhaps in even a higher degree, to the economy which has followed as a consequence of the accompanying changes in structure of the steam-engine driving it.
101. The earliest clays of screw propulsion witnessed the use of steam of ten or fifteen pounds' pressure, in a geared engine using jet condensation, and giving a horse-power at an expense of, perhaps, seven or eight pounds of coal per hour.
A little later came direct-acting engines with jet condensation, and steam at twenty pounds' pressure, costing about five or six pounds per horse-power per hour. The steam-pressure rose a little higher with the use of greater expansion, and the economy of fuel was further increased. The introduction of the surface-condenser, which began to be generally adopted some ten or fifteen years ago, brought down the cost of power to between three and four pounds in the better class of engines.
At about the same time, this change to surface-condensation helping greatly to overcome the troubles arising from boiler-incrustation, which had checked the rise in steam-pressure above about twenty-five pounds, and, it being at the same time learned by engineers that the deposit of the scale and sulphate of lime in the marine boiler was determined by temperature rather than by the degree of concentration, and that all the lime entering the boiler was deposited at the pressure just mentioned, a sudden advance took place.
Careful design, good workmanship, and skillful management, made the surface-condenser an efficient apparatus, and, the dangers of incrustation being thus lessened, the movement toward higher pressures recommenced and progressed so rapidly that, now, seventy-five pounds per square inch is very usual, and two hundred and fifty pounds has been attained in marine engines built by the Messrs. Perkins, who are said to have reached the remarkable economy of a horse-power for each pound of combustible consumed in the boiler.
102. These high pressures, and the greater expansion of the steam, have, in turn, produced another revolution in engine-construction.
It has at last become generally known, as was seen by well-informed and scientific engineers long ago, that one of the most serious losses of heat, and consequently of power, in the steam-engine, when expansion is carried to a considerable extent, occurs in consequence of condensation and the deposition of moisture upon the interior of the cylinder, which moisture, when the exhaust takes place, carries, by its reëvaporation, large quantities of heat into the condenser, without deriving any power from it.
The steam-jacket furnishes one means of reducing the amount of this loss by keeping up the temperature of the interior of the cylinder, and thus preventing, in some degree, this deposition, and by reëvaporating this moisture during expansion, and thus deriving useful effect from heat so expended before the exhaust-valve opens, and it is thrown unutilized into the condenser.
James Watt, therefore, applied the steam-jacket more wisely than he knew, for this matter was not, in his time, understood. Indeed, he gave up its use, thinking it could have no possible economical value, but the consequent falling off in the duty of the engine induced him to restore it, and we still find it on the Cornish engine of to-day.
103. This loss is also, in some degree, prevented, by dividing the expansive working of the steam among two or more cylinders, as in the compound or Woolf system described in the preceding lectures.
Here the heat wasted in either cylinder is less, in consequence of the lessened range of temperature, and that lost by one cylinder is carried into the second, and then, to some extent, utilized.
The amount of saving effected by these means is quite considerable—so great, in fact, as to have produced a complete revolution in engineering practice in the construction of marine engines by the best-known builders.
They have, under the lead of John Elder, adopted the Woolf engine, which had, in earlier times, with lower steam, less expansion, and less intelligent engineering, proved apparently a failure.
104. To-day, nearly all sea-going steamers are fitted with such engines having surface-condensers, and with tubular boilers, which are fitted, frequently, with superheaters. One of the best examples of these steamers, the City of Peking, a screw-steamer built by Roach
for the Pacific Mail Company, is a vessel of 5,000 tons. There are two pairs of compound-engines, having cylinders of 51 and 88 inches diameter, and 42 feet stroke of piston. The crank-shafts are 18 inches in diameter. Steam is carried at 60 pounds, and is expanded nine times. The boilers are ten in number, cylindrical in form, and with cylindrical flues; they are 13 feet in diameter, 102 feet long, with shells of iron 16 inch thick, and have 520 feet of grate-surface, 16,500 square feet of heating-surface, and 1,600 square feet of superheating-surface. The smoke-funnels, or stacks, are 82 feet in diameter and 70 feet high.
Fig. 60 shows a section of the simplest and the least costly form of compound-engine, as it is now built on the Clyde, in Great Britain, and in the United States, on the Delaware.
Here, the cranks Y Z are coupled at an angle of ninety degrees, only two cylinders, A B, being used, and an awkward distribution of pressure is avoided by having a considerable volume of steam-pipe, or by a steam-reservoir, O P, between the two cylinders.
The valves, y y, are set like those of an ordinary engine, the peculiarity being that the steam exhausted by the one cylinder, A, is used again in the second and larger one, B. In this combination, the expansion is generally carried to about six times, the pressure of steam in the boiler being usually between sixty and seventy-five pounds per square inch.
105. The revolution by which the screw has superseded the paddle-wheel elsewhere, has not taken place in our shallow American rivers, where there is not depth enough for the screw.
In the West, boats are driven by the horizontal high-pressure engine usually, as in the days of Oliver Evans, and retain their peculiarities of construction. Some of the Mississippi steamboats (Fig. 61) make the trip from St. Louis to New Orleans—about 1,200 miles—in four days, and can make, in still water, more than twenty miles an hour.
In the East, we have a form of engine which is distinctively known as the American steamboat-engine. It is shown in Fig. 62.
This engine is recognized throughout the engineering world as one of the most complete and thoroughly perfected of known types of steam-engine.
106. This peculiarly effective and easy-working engine, and the equally peculiar vessel (Fig. 63) which is usually impelled by it, are, in all their peculiarities, characteristically American.
The "skeleton-beam," which is one of the prominent features, was first used by Robert L. Stevens on the ferry-boat Hoboken, in 1822.
The valve-gear is usually that known as the "Stevens valve-gear." It was invented by Messrs. Robert L. and Francis B. Stevens, in 1841. The "gallows-frame" took its present form in the hands of Messrs. Stevens. The hull of the Phoenix had hollow water-lines sixty-five years ago, and this important characteristic of modern vessels is, therefore, an American improvement.
The North America (Fig. 64) was built in 1827. The hull was stiffened by the "hog-frame," now as distinctive a characteristic of the vessel as are the gallows-frame and the skeleton-beam of the engine.
This engine is not usually quite as economical in fuel as are the screw-engines last described; but it has the advantages—which are so extremely important in the shallow, flexible hulls of our river-boats —of being the easiest working and least easily injured, by "getting out of line," of all known forms of engines.
The British and Continental engineers also still retain the paddle-wheel in some of the steamers plying in their narrower and more
closely-crowded rivers and harbors, in consequence of the greater facility which it gives for manœuvring.
107. The magnitude of our modern steamships excites the wonder and admiration of even the people of our own time. There is certainly no creation of art that can be grander in appearance than a transatlantic steamer, a hundred and fifty yards in length, and weighing, with her stores, 5,000 or 6,000 tons, as she starts on her voyage, moved by engines more than equal in power to the united strength of 5,000 horses. Nothing can more thoroughly awaken a feeling of awe than the sight of immense structures like the great modern iron-clads (Fig. 65), vessels having a total weight of 8,000 to 10,000 tons,
and propelled by steam-engines of 8,000 or 10,000 horse-power, carrying guns whose shot penetrate solid iron fifteen inches thick, and having a power of impact, when steaming moderately, sufficient to raise 35,000 tons a foot high.
108. Far more huge than the Monarch among the iron-clads even is that prematurely-built monster, the Great Eastern (Fig. 66), more than the eighth of a mile (680 feet) long, of 84 feet beam, and drawing thirty feet of water at load-draught, when the weight of ship and contents amounts to over 25,000 tons. This great vessel
is driven by steam-engines of 10,000 horse-power, turning huge paddle-wheels 56 feet in diameter, and a screw-propeller having a diameter of 24 feet.
109. We are evidently fulfilling at least a part of that well-known poetical prophecy which Darwin wrote in the early days of the steam-engine, and possibly before Watt had told him of the great advance which had been produced by his inventive genius:
Drag the slow barge, or drive the rapid car;
Or, on wide-waving wings expanded, bear
The flying chariot through the fields of air."
- An abstract of "A History of the Growth of the Steam-Engine," to be published by D. Appleton & Co.
- These cuts are fac-similes of steel engravings made for Stevens.