THE EMERGENCE OF THE STEAM THRESHING ENGINE

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.