Newcomen engines

Wliile not nearly as sophisticated as later engines, the quantity of Newcomen engines built vastly exceeded the hundreds of Watt engines, with the more primitive types often used as substitutes for the newer, far more expensive versions. 

Newcomen engines continued to operate, especially in collieries, almost to the end of the eighteenth centuiy. Yet they, too, were wasteful. The way was open for a great advance, James Watt s invention in 1768 of the sepai atc condenser. Next to the driving cylinder stood another cylinder, exhausted and permanently cold. When the inoincnt for the down-stroke came, a valve opened, the steam rushed over and condensed the valve then closed and the cycle was repeated. The driving cylinder stayed permanently hot. 

Both the Newcomen and the Papin pumps derived most of their power from this atmospheric force rather than from steam pressure. Newcomen engines consumed perhaps 32 pounds of coal each hour per horsepower developed, about 1 percent of the energy that burning coal emits. 

I will... recall your attention to that in which the invention did consist in order to shew you in what it does not consist. It did consist in an attention to the chemical principles and properties of steam by which the causes of the defects in Newcomens Engine as well as the remedies were suggested...9... 

The Newcomen Engine is then depicted as a largely inadvertent solution to some of the problems with Savery s engine. In particular, the advantage that the cylinder... 

In the slightly fuller treatment of the history of Watt s improvements which he gave in his Manual of the Steam Engine, Rankine again gave prominence to the model Newcomen engine and described Watt s procedure as follows ... 

So Rankine has Watt moving smoothly from the puzzle of the model Newcomen engine to experiments, to data, to principles, and thence to specification of the improved engine. Once again history is cast in the mould of the ideals of engineering science practice. 

So Watt was on the hunt for sources of waste. He knew that in the Newcomen engine the cylinder had to be re-heated at each stroke, that is, a large... 

On the workings of the Newcomen Engine see R. L. Hills, Power from Steam A History of the Stationary Steam Engine (1989 Cambridge Cambridge University Press, 1993), pp. 20-30. 

Watt did not, of course, invent the steam engine, but prior to his time the old Newcomen engine was used exclusively as a steam pump it was slow. 

Fifty years after the event, he described what took place so vividly that it still has a ring of actuality about It. He was originally trained and practiced as an Instrument maker, particularly of surveying Instruments. But In 1764, he was asked to repair — note, only to repair — an already existing Newcomen engine. This he did, and to most other engineers, no problems would have arisen. But to young Watt, there was a problem — a "state of discomfort." For we find him a year later, in 1765, as... 

The simplest steam engine is a cylinder with a movable piston. Water in the piston is heated by an external flame until it turns to steam, which expands and moves the piston out. When the heat source is removed, steam condenses, and the piston moves back into the vacuum. This simple design was improved by Thomas Newcomen, who added a jet of cold water to cool the steam. The Newcomen engine became the standard model until it was improved in the 1700s by a Scottish instrument maker, James Watt. 

Double-acting Watt steam engine from the late 18tb century within a few years of its introduction, Watt s steam engine ousted all existing Newcomen engines because of its far better thermal efficiency. 

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