THE EMERGENCE OF THE STEAM THRESHING ENGINE

Steam engine

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Princeton, Wisconsin 54968

A person is taught a heap of nonsense in a lifetime, much of it on supposedly good authority. In school you were probably taught that Watt invented the steam engine. Now there is some truth in this statement, but it is far from the whole truth. Yet your teacher probably never stopped to question the assertion, and it is unlikely you did either. What you should have been taught was that the steam engine emerged from the sweat and work of Watt and many other men, most of whom have received little, if any, public acclaim.

James Watt (b. 1736-d.l819) did not make the first devise for harnessing steam power. Centuries before Watt, the Greeks had devised simple models; and later steam power had been used to open and close cathedral doors. Robert H. Thurston, one of the best known authorities on the steam engine, described the state of the steam engine of 1700 in these terms:

'Every essential fact and every vital principle had been learned, and every one of the needed mechanical combinations had been successfully effected. It was only requisite that an inventor should appear, capable of perceiving that these known facts and combinations of mechanism, properly illustrated in a working machine would present to the world its greatest physical blessing.' (Robert H. Thurston, A History of the Growth of the Steam Engine, 1878, p. 56.)

The man who effected the combinations of which Thurston wrote was Thomas Newcomen, a blacksmith of Deptford, England. About 1705 Newcomen built an engine that functioned by means of a rocker arm situated above a cylinder in such a way that it could activate a water pump used to remove water from the mines of Britain. The cylinder set upright above the boiler and was open at its upper end. Steam entered the cylinder from below, and when the pressure was great enough the piston would rise within the cylinder. When the piston reached the top of the cylinder a jet of cold water was sprayed into the cylinder reducing the pressure and creating a vacuum. This caused the atmospheric pressure to depress the cylinder so that the cycle could be repeated. As a consequence of the use of both steam and atmospheric pressure, these kinds of engines were sometimes called atmospheric steam engines.

At first a Newcomen engine could make six to eight strokes per minute. With improvement some engines reached as many as a dozen strokes per minute. There was no flywheel, no governor, and steam was applied to only one side of the piston. The earlier boilers were made of copper. Subsequently sheet iron was used. The steam space within the boiler was about 8 to 10 times the capacity of the cylinder. It was a simple machine but it had several characteristics of later steam engines.

Others set out to improve Newcomen's engine. For example, a gentleman by the name of Smeaton discarded the rocker arm for a pulley and chain arrangement, and built a portable engine that he mounted upon a wooden frame, thus enabling the engine to work wherever needed. But it remained for James Watt to make certain major changes in the Newcomen engine as a result of a series of carefully controlled experiments.

Watt began experimenting with a model of the Newcomen engine while working in a laboratory at the University of Glasgow, Scotland. One of the first things he did was to make a new boiler. He built it so that he could measure the amount of water evaporated and the quantity of steam used per stroke of the piston. Almost immediately he discovered that only a very small quantity of steam was needed to heat a relatively large quantity of water. This led him to measure the relative weight of steam and water in the cylinder when condensation took place at the time of the down stroke of the piston. This in turn caused him to see the importance of economizing on the use of steam. The economy seemed desirable not only because of the improvement it would bring in steam power, but for financial reasons as well. The cost of fuel at points distant from the sources of coal made the operation of steam engines very expensive because there were no railroads at that time. To secure this economy, Watt made a boiler with a wooden jacket as Smeaton had done before him. He increased the flues and insulated the pipes through which the steam passed. Then he realized that he was concentrating his efforts at the wrong point. It was the cylinder that was the main culprit. Made of brass it was both a good conductor and an excellent radiator of heat. Moreover, the necessity for cooling the cylinder with each stroke was extremely wasteful of steam. Furthermore, he saw that the imperfect method of condensing steam led to a loss of power because of the pressure of vapor beneath the piston as it traveled down the cylinder. Among his most significant findings were that about three-fourths of the steam was wasted, and that about four times as much water was needed in the Newcomen than would suffice to condense a cylinder full of steam. This led Watt to see that it was necessary to find some new means to keep the cylinder hot as the steam entered it.

How to accomplish this occupied Watt's mind as he took a walk one Sunday afternoon. Everything fell into place in a matter of minutes. He described the experience thusly:

'I had entered the Green by the gate at the foot of Charlotte Street.......I was thinking upon the engines at the time, and had gone as far as the herd's house, when the idea came into my mind, that as steam was an elastic body, it would rush into a vacuum, and, if communication were made between the cylinder and an exhausted vessel, it would rush into it, and might be condensed without cooling the cylinder. I then saw that I must get rid of the condensed steam and injected water if I used a jet, as in Newcomen's engine. Two ways of doing this occurred to me: I had not walked further than the Golf-house, when the whole thing was arranged in my mind.' (J. G. Crowther, Scientists of the Industrial Revolution, 1963, p. 123.)

The very next morning Watt began experimental tests that eventually proved successful. He then started building engines, seeking improvements as he went along. He encountered a certain amount of difficulty, however, because of the lack of skilled workmen and the crude tools that had to be used. Consequently, parts did not always fit well. On one occasion he is said to have been pleased that a certain cylinder only lacked about three-eights of an inch of being round.

Watt's work led him to a number of important refinements. A governor and a 'sun and planet gear' that turned a flywheel were added. These imparted a smoothness to the functioning of the engine. A major improvement was the closing of the cylinder and the application of steam to both sides of the piston. This marked the end of the atmospheric steam engine and the birth of the modern steam engine.

The economies Watt was able to realize in the use of steam and in fuel were important in and of themselves. But these engines were still quite large and very inefficient. It is difficult to imagine the size of some of the engines that Watt built. One was said to have covered an enormous area, weighed 37 tons, but it produced only 7 HP. P. S. Rose of North Dakota Agricultural College estimated that the steam threshing engines of 1908 were only about 10 to 20% efficient. Watt's were even less so. (Professor P. S. Rose, 'Thresher's School of Modern Methods, 'The American Thresher-man,' September, 1908, p. 24.) But the development of the 'sun and planet gear' (soon replaced by the crank) and the flywheel made possible the application of steam to new purposes. Among the things that could now be done was driving a crude threshing machine by means of a belt.

In 1812, seven years before Watt died, Richard Trevithick (b. 1771-d. 1833) built a 'farmer's engine' for Sir Christopher Hawkins of Trewithen, England which was used to drive a threshing machine. (L.C.T. Rolt, The Cornish Giant: The Story of Richard Trevithick, Father of the Steam Locomotive, p. 128). The 'farmer's engine' had a horizontal boiler that was about 7' long; and it was mounted on a wooden frame. The cylinder was embedded in the front end of the boiler while the flywheel was supported by a large frame at the front of the boiler. One author described the construction in these words: 'It must not be forgotten, in comparing these antiques with modern productions; that they were made before the days of machines. The plates were bent on the anvil, and all the finishing and fitting were either done with the hammer and chisel, or the file.....' The writer continued by saying, 'The plates of the boiler are about one-half inch thick; flanges being hammered to get good joints. The boiler is 4' 6' diameter and the internal flue us 27' diameter.....'The writer then pointed out that there were two important improvements in this engine;'......the placing of the cylinder......(within the body of the boiler) and the plate in front of the furnace. The latter was to lessen the amount of smoke. The coals formed a kind of door through which the air slowly passed. They were gradually pushed back and then replaced by more, the bright fire within the furnace burning up the smoke from the smoldering coals upon the iron plate in front of the furnace.' Speaking of the flywheel he wrote that it '........has a V groove in it to take a rope about 1' in diameter.' (W. J. Blackmure, 'The First Threshing Engine and Its Builder.' The American Threshermen, February, 1908, p. 26-27.)

There is really no way of telling whether this was the very first threshing engine. What is important is that the inventors were now on their way to developing what eventually became the steam threshing engines of the late 19th and early 20th centuries; and the knowledge acquired at the time of Watt and Trevithick became generally disseminated and led to the building of simpler, stronger and more efficient and durable engines. The years that followed, especially those after 1850, were marked not so much by a change of standard types as a gradual refinement through the operation of the principle of the 'Survival of the fittest.'

Steam power came into its own on the American farm about 1885. Already, however, the seeds of its eventual demise were being planted. Nicolas August Otto, a German engineer, and his partner, Langen, made an improved free piston gas engine which they exhibited at the Paris Exhibition in 1867. Just 10 years later Otto and Langen incorporated Alphonse Bean de Rochas' principle of the four cycle engine into their gas engine. This proved to function rather effectively. In another 40 years, that is about 1918, steam power was already being gradually replaced by gasoline power because of the influences of World War I and the efforts of men like Henry Ford. Those ingenious inventors, men like Newcomen, Watt and Trevithick, could not have dreamed of these eventualities in their most fanciful moments.