Full steam ahead

The story of Newcomen's steam engine and its influence today.

Thomas Newcomen lived through the Glorious Revolution of 1688 and fired another revolution of his own in 1712.

It was a period of enormous upheaval; Catholic James II was pushed from the throne by the Protestant partnership of William III of Orange and Mary II, and religious beliefs struggled to contain the advancement of science.

English forests were stripped for fuel faster than they could grow, and seekers of mineral wealth bored deep into the hills and well below the water line. It was a crisis of inundation. Mines in Tyneside, Cornwall, Staffordshire and Warwickshire had been abandoned as horse-powered pumps reached the limit of their capabilities.

Not that the solution to these problems was out of reach - turning heat into mechanical movement via steam had been known for a thousand years or more - but technology was incapable of building cylinders of sufficient tolerance to contain direct-drive high-pressure steam, and a few critical gaps in scientific knowledge had yet to be plugged.

In 1698, Modbury-born Thomas Savery patented 'the miner's friend' for "raising water by the impellent force of fire". His machine, which gained only limited success, forced water up and through a non-return valve using the pressure of steam. The steam then cooled and condensed, forming a vacuum which subsequently lifted, via suction and through another non-return valve, more water to start the cycle once more.

But Savery's invention was limited. The maximum suction lift was determined by atmospheric pressure (about 33ft at sea level, though with losses Savery probably achieved less), and the boilers of the day were capable of maintaining only a low pressure, adding perhaps 20 more feet via the forcing lift.

Technical limitations

Philosopher, scientist and Church of England rector, John Theopholus Desaguliers, wrote of an episode (Experimental Philosophy 1744) when Savery tried to increase the forcing pressure: "Its heat was so great that it would melt common soft solder, and its strength so great as to blow open several of the joints of his machine."

So what could an ironmonger from Dartmouth, Newcomen, and John Calley, local plumber and glazier, bring to these needy times? Newcomen biographers, LTC Rolt and JS Allen in 'The Steam Engine of Thomas Newcomen', say: "Newcomen and Calley had to be adept at every variety of metal work in iron, brass, copper, tin and lead. Add to this that Newcomen was a member of a respected family with a long background of world trading and it is possible to appreciate how the two men possessed precisely the right combination of commercial ability and practical, versatile craftsmanship, which was required to bring the steam engine to a successful birth."

Newcomen had visited south-west tin mines and was probably aware of Savery's work. Savery's patent - regarded by many as extremely wide-ranging - meant a commercial relationship was inevitable.

And so it was, in 1712 at Coneygree Coal Works near Dudley Castle in Staffordshire, Newcomen erected the first 'Newcomen engine' under the Savery patent, improving the performance of Savery's original contraption and finally beginning the practical exploitation of steam power.

"The machine made 12 strokes a minute and delivered ten English Gallons a stroke. The mine was 51 yards or 25½ fathoms deep," wrote Marten Triewald, engineer and founder of the Swedish Academy of Sciences, in a contemporary account.

Newcomen's engine consisted of an open-ended cylinder in which a piston moved up and down. The piston was connected via chains to one end of a rocking beam, and on the other end were pump rods that went down into the mine. On the upstroke the piston moved up in the cylinder drawing in steam from a boiler below. At the very top of the stroke, cold water was injected into the cylinder, condensing the steam and forming a vacuum into which the piston was forced by atmospheric pressure. Finally, the piston was raised by the overbalancing weight of the pump rods on the far end of the beam.

Market leading

How Newcomen was inspired to inject cold water into the cylinder to speed up condensation is a matter of some conjecture. His early cylinders were wrapped in a water-cooled jacket to accelerate the natural process, but this would still have achieved a derisory cycle time.

The success of the first engine was the start of a rapid programme of commissioning considered remarkable. By 1733 (four years after Newcomen's death), some 110 engines existed worldwide, most in England, but at least a dozen in Europe. At the turn of the century, over 1,400 Newcomen engines had been built, and even after James Watt invented the separate condensing chamber, massively increasing the efficiency of such engines, the Newcomen version retained its market leading position.

But the machine was horribly inefficient. Its engine was expensive to run and lease; in 1714, an engine at Woods Colliery, near Hawarden, paid out one-third share of the profits of the mine in fees!

Continued innovation

Pressure to improve was probably considerable, and from 1712 onwards the machine continued to develop. It was possible in the early engines for the piston to draw so much steam from the top of the boiler that the water went off the boil and halted the engine.

This was due to a limitation in the design of Newcomen's boilers, as witnessed by Triewald. "It is evident that the invertors do not know that the boiler must be given a suitable shape. Neither did they know that the flames should be allowed to play all around the side of the boiler as well as on the bottom." When suitable boilers were introduced, the working rate doubled to 15 or 16 strokes a minute.

Newcomen also added valves to remove water that accumulated in the cylinder. This was later recycled to the boiler introducing a significant saving in fuel costs. In addition, air introduced with the steam was expelled via a 'snifting valve'. Without this, air built-up in the cylinder eventually causing the engine to lose power and stop by 'wind-logging'.

Through this evolutionary improvement, Newcomen's engines became a bedrock of the Industrial Revolution and inspired two centuries of steam engineers.

Today, a full-sized coal-fired replica of the 1712 engine, inaugurated in 1989, runs at the Black Country Museum at Dudley, and not 200 yards from Newcomen's birth place in Dartmouth, the Newcomen Memorial Engine stands in the tourist information office.

These are fitting memorials, though it is perhaps surprising his achievements have not fired the public's imagination as well as some of his successors, such as Watt or Stevenson. Then again, navigating one revolution only to kick start another with "one of the strategic innovations in world history and the single greatest act of synthesis in the ensuing history of the steam engine," (as the plaque commemorating the Dartmouth Engine puts it) is probably enough pressure for any man.

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