The engine of Newcomen was very wasteful of coal even if there have been many improvements to the engine. James Watt was a man who wanted to know the exactness of things. He studied the Newcomen engine very precise and was astonished on how there was a need of water to be injected to cool down the steam. He recognized that there was a relevant loss of power. Watt made many studies concerning steam pressure, which he used for his great cognition. He recognized that it was useles to cool down the same vessel and heat it again. In his patent, he formulated among other things two principles:
The vessel, which worked by means of steam, had to be as hot as the steam itself.
The vessel where the steam is condensed has to be separated from the cylinder and it has to be as cold as the outside temperature. Watt called it the "condenser."
Watt united these two principles in his first steam engine.
One of the main problems Watt had was not technical related but of financial crisis. So the partnership with Matthew Boulton was very good for him; it made the base of all the inventions James Watt made.
Watt discovered that there was no need to conduct steam during all the time the piston moved up. The natural expansion of steam can be used. The quantity of steam can be reduced to a fourth. Therefore, the piston did not press with the same force all the time, but Watt found out that this problem could be fixed with a fly-wheel.
Watt's second patent described among other things how the natural expansion of steam could be used. He described six ways of providing a regular running of the engine. He also described the double-acting engine in this patent and all the technical details which are necessary to provide a regular running of it. After a while there was also the idea of converting the up and down-movement of the piston into a rotating movement. Unfortunately, there was a patent of a man on this convertion. Watt and Boulton could go round it by inventing some new drivings. The invented i.e. the so called sun-driving. You can look at it in the sketch of the engine of James Watt in 1781, which is located at the bottom of this page: Look at the center of the fly-wheel.
At this time, there was an almost perfect engine. Therefore, the plant Boulton & Watt became famous in the whole world and their machines have been well sold.
Conrad Matschoss - Die Entwicklung der Dampfmaschine
Robert H. Thurston - The growth of the steam-engine (online)
F.Calcagno & S.M. Calizzano - Steam engines (online)
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