Part 12 (1/2)
”To Oliver Evans,” says Dr. Ernest Alban, the distinguished German engineer, ”was it reserved to show the true value of a long-known principle, and to establish thereon a new and more simple method of applying the power of steam--a method that will remain an eternal memorial to its introducer.” Dr. Alban here refers to the earliest permanently successful introduction of the non-condensing high-pressure steam-engine.
OLIVER EVANS, one of the most ingenious mechanics that America has ever produced, was born at Newport, Del., in 1755 or 1756, the son of people in very humble circ.u.mstances.
[Ill.u.s.tration: Oliver Evans.]
He was, in his youth, apprenticed to a wheelwright, and soon exhibited great mechanical talent and a strong desire to acquire knowledge. His attention was, at an early period, drawn to the possible application of the power of steam to useful purposes by the boyish pranks of one of his comrades, who, placing a small quant.i.ty of water in a gun-barrel, and ramming down a tight wad, put the barrel in the fire of a blacksmith's forge. The loud report which accompanied the expulsion of the wad was an evidence to young Evans of great and (as he supposed) previously undiscovered power.
Subsequently meeting with a description of a Newcomen engine, he at once noticed that the elastic force of confined steam was not there utilized. He then designed the non-condensing engine, in which the power was derived exclusively from the tension of high-pressure steam, and proposed its application to the propulsion of carriages.
About the year 1780, Evans joined his brothers, who were millers by occupation, and at once employed his inventive talent in improving the details of mill-work, and with such success as to reduce the cost of attendance one-half, and also to increase the fineness of the flour made. He proved himself a very expert millwright.
In 1786 he applied to the Pennsylvania Legislature for a patent for the application of the steam-engine to driving mills, and to the steam-carriage, but was refused it. In 1800 or 1801, Evans, after consultation with Professor Robert Patterson, of the University of Pennsylvania, and getting his approval of the plans, commenced the construction of a steam-carriage to be driven by a non-condensing engine. He soon concluded, however, that it would be a better scheme, pecuniarily, to adapt his engine, which was novel in form and of small first cost, to driving mills; and he accordingly changed his plans, and built an engine of 6 inches diameter of cylinder and 18 inches stroke of piston, which he applied with perfect success to driving a plaster-mill.
This engine, which he called the ”Columbian Engine,” was of a peculiar form, as seen in Fig. 46. The beam is supported at one end by a rocking column; at the other, it is attached directly to the piston-rod, while the crank lies beneath the beam, the connecting-rod, 1, being attached to the latter at the extreme end. The head of the piston-rod is compelled to rise and fall in a vertical line by the ”Evans's parallelogram”--a kind of parallel-motion very similar to one of those designed by Watt. In the sketch (Fig. 46), 2 is the crank, 3 the valve-motion, 4 the steam-pipe from the boiler, _E_, 5 6 7 the feed-pipe leading from the pump, _F_. _A_ is the boiler. The flame from the fire on the grate, _H_, pa.s.ses under the boiler between brick walls, and back through a central flue to the chimney, _I_.
[Ill.u.s.tration: FIG. 46.--Evans's Non-condensing Engine, 1800.]
Subsequently, Evans continued to extend the applications of his engine and to perfect its details; and, others following in his track, the non-condensing engine is to-day fulfilling the predictions which he made 70 years ago, when he said:
”I have no doubt that my engines will propel boats against the current of the Mississippi, and wagons on turnpike roads, with great profit....”
”The time will come when people will travel in stages moved by steam-engines from one city to another, almost as fast as birds can fly, 15 or 20 miles an hour.... A carriage will start from Was.h.i.+ngton in the morning, the pa.s.sengers will breakfast at Baltimore, dine at Philadelphia, and sup in New York the same day....
”Engines will drive boats 10 or 12 miles an hour, and there will be hundreds of steamers running on the Mississippi, as predicted years ago.”[45]
[45] Evans's prediction is less remarkable than that of Darwin, elsewhere quoted.
In 1804, Evans applied one of his engines in the transportation of a large flat-bottomed craft, built on an order of the Board of Health of Philadelphia, for use in clearing some of the docks along the water-front of the city. Mounting it on wheels, he placed in it one of his 5-horse power engines, and named the odd machine (Fig. 47) ”Oruktor Amphibolis.” This steam dredging-machine, weighing about 40,000 pounds, was then propelled very slowly from the works, up Market Street, around to the Water-Works, and then launched into the Schuylkill. The engine was then applied to the paddle-wheel at the stern, and drove the craft down the river to its confluence with the Delaware.
[Ill.u.s.tration: FIG. 47.--Evans's ”Oruktor Amphibolis,” 1804.]
In September of the same year, Evans laid before the Lancaster Turnpike Company a statement of the estimated expenses and profits of steam-transportation on the common road, a.s.suming the size of the carriage used to be sufficient for transporting 100 barrels of flour 50 miles in 24 hours, and placed in compet.i.tion with 10 wagons drawn by 5 horses each.
In the sketch above given of the ”Oruktor Amphibolis,” the engine is seen to resemble that previously described. The wheel, _A_, is driven by a rod depending from the end of a beam, _B' B_, the other end of which is supported at _E_ by the frame, _E F G_. The body of the machine is carried on wheels, _K K_, driven by belts, _M M_, from the pulley on the shaft carrying _A_. The paddle-wheel is seen at _W_.
Evans had some time previously sent Joseph Sampson to England with copies of his plans, and by him they were shown to Trevithick, Vivian, and other British engineers.
Among other devices, the now familiar Cornish boiler, having a single internal flue, and the Lancas.h.i.+re boiler, having a pair of internal flues, were planned and used by Evans.
At about the time that he was engaged on his steam dredging-machine, Evans communicated with Messrs. McKeever & Valcourt, who contracted with him to build an engine for a steam-vessel to ply between New Orleans and Natchez on the Mississippi, the hull of the vessel to be built on the river, and the machinery to be sent to the first-named city to be set up in the boat. Financial difficulties and low water combined to prevent the completion of the steamer, and the engine was set at work driving a saw-mill, where, until the mill was destroyed by fire, it sawed lumber at the rate of 250 feet of boards per hour.
Evans never succeeded in accomplis.h.i.+ng in America as great a success as had rewarded Watt in Great Britain; but he continued to build steam-engines to the end of his life, April 19, 1819, and was succeeded by his sons-in-law, James Rush and David Muhlenberg.
He exhibited equal intelligence and ingenuity in perfecting the processes of milling, and in effecting improvements in his own business, that of the millwright. When but twenty-four years old, he invented a machine for making the wire teeth used in cotton and woolen cards, turning them out at the rate of 3,000 per minute. A little later he invented a card-setting machine, which cut the wire from the reel, bent the teeth, and inserted them. In milling, he invented a whole series of machines and attachments, including the elevator, the ”conveyor,” the ”hopper-box,” the ”drill,” and the ”descender,” and enabled the miller to make finer flour, gaining over 20 pounds to the barrel, and to do this at half the former cost of attendance. The introduction of his improvements into Ellicott's mills, near Baltimore, where 325 barrels of flour were made per day, was calculated to have saved nearly $5,000 per year in cost of labor, and over $30,000 by increasing the production. He wrote ”The Young Steam-Engineer's Guide,” and a work which remained standard many years after his death, ”The Young Millwright's Guide.” Less fortunate than his transatlantic rival, he was nevertheless equally deserving of fame. He has sometimes been called ”The Watt of America.”
The application of steam to locomotion on the common road was much more successful in Great Britain than in the United States. As early as 1786, William Symmington, subsequently more successful in his efforts to introduce steam for marine propulsion, a.s.sisted by his father, made a working model of a steam-carriage, which did not, however, lead to important results.
In 1802, Richard Trevithick, a pupil of Murdoch's, who afterward became well known in connection with the introduction of railroads, made a model steam-carriage, which was patented in the same year. The model may still be seen in the Patent Museum at South Kensington.[46]
[46] _See_ ”Life of Trevithick.”
In this engine, high-pressure steam was employed, and the condenser was dispensed with. The boiler was of the form devised by Evans, and was subsequently generally used in Cornwall, where it was called the ”Trevithick Boiler.” The engine had but one cylinder, and the piston-rod drove a ”cross-tail,” working in guides, which was connected with a ”cross-head” on the opposite side of the shaft by two ”side-rods.” The connecting-rod was attached to the cross-head and the crank, ”returning” toward the cylinder as the shaft lay between the latter and the cross-head. This was probably the first example of the now common ”return connecting-rod engine.” The connection between the crank-shaft and the wheels of the carriage was effected by gearing.
The valve-gear and the feed-pumps were worked from the engine-shaft.