Sunday 18 September 2022

Locomotive Steam Engine

James Watt’s steam engine was a big improvement over the Newcomen steam engine. The timing of the James Watt’s improvements were impeccable, coming along when the Cotton Revolution was well under way. Improvements in metallurgy were critical. Watt’s business partnership was with Boulton excellent.

The invention of crank shafts and sun-and-planet gears, which converted the linear motion of the steam driven pistons into rotary motions which powered wheels, textile looms, and grain mills, made the steam engine the prime mover of the Industrial Revolution.

But the next stage of evolution, the emergence of the locomotive steam engine, took nearly fifty years after Watt’s improvements and innovations. James Watt himself planned a road based locomotive, and his assistant Murdoch designed a model, but they never built one. Three people played key roles in the emergence of the locomotive steam engine and the railways: Richard Trevithick; George Stephenson and Robert Stephenson.

Richard Trevithick 
Pic: Wikipedia

Richard Trevithick

Richard Trevithick grew up in Cornwall, full of coal mines, the district of England where most of James Watt engines were installed in the first few years. Unlike James Watt, he had no fear of high pressure steam.

He conceived the boldest, most imaginative changes to the steam engine. But he had to wait until 1800 when James Watt’s patent, extended by Parliament, expired. Boulton and Watt’s phenomenal success, fame, and global recognition, especially among the aristocrats of England, worked against Trevithick, a commoner from lower classes. But his advantage was that neither science nor technology respects reputations; only society does.

First Trevithick realized that the condenser itself was not necessary. This alone was quite revolutionary. The right amount of steam pressure is sufficient to run the engine, if it was higher than atmospheric pressure. In fact, he was working for the DingDong mine, and trying to help them avoid paying royalties to Boulton & Watt – when he had this epiphany. He built a engine running at 30 psi, three times the pressure in Watt’s engines. The higher pressure meant a smaller, lighter engine, with a power-to-weight ratio sufficient to power its own locomotion.

Second, he put the furnace inside the boiler. Just the sheer audacity of this design is mind-boggling – but taken for granted once it was accomplished. Tubes ran inside the boiler, heating all the water around them, rather than just heating a vessel from the bottom, as is still mostly common in cooking. He made the boiler horizontal rather than vertical which suits this model of heating so well. Excess steam was let out with a blast pipe, since the condenser was eliminated. A safety valve was added.

Another major design change was that the piston and its cylinder were tilted, at a 45 degree angle. The tilted operated a set of wheels via a crankshaft. Basically, the whole engine was a boiler fitted on to wheel-based chassis.

These seem to be the most radical alteration in design of any major mechanical device, until the advent of turbines nearly a century later. Several things helped Trevithick : first a much better understanding of heat, steam, flow etc. Second, there were incremental improvements in metallurgy, which allowed for stronger cast iron cylinders which could withstand higher steam pressure without exploding.

Puffing Devil
Pic: Industrial revelations - Youtube

Trevithick built a steam locomotive for the road, in 1801, called the Puffing Devil, which featured all these innovations. It had a successful road test, with a few people. But it was hard to steer, fell into a gully, and left unattended, the furnace still boiling water, exploded when it all the water boiled off. He later built another vehicle for the road called London Carriage, but it also had a lever-steering, and no one wanted to buy it.

He patented this high pressure steam engine in 1802. He sold it as a stationary engine, powering a water pump and operated at 145 pounds per square inch (PSI) compared to around 10psi for Watt’s engines. One of these engines exploded, killing four people, and James Watt called for hanging Trevithick for killing them. But it was shown that it was operator error, not a design problem. Trevithick added a second safety valve, which would open and quench the furnace with water, shutting it down, if the pressure exceeded danger levels.

In 1802,  Trevithick also built a steam locomotive that ran on rails, called the Penny Darren. It successfully carried cargo and passenger wagons for 15 km, at a slow speed of about 4kmph. Historians consider this the first steam locomotive train. But the engine was too heavy for the cast iron rails, which broke.

Trevithick's Penny Darren steam locomotive
Pic: Industrial Revelations - Youtube

Trevithick spent the rest of his life building stationary engines, and several other experimental devices, but none of them brought him the commercial success that Newcomen and Watt got from their engines. He spent some years building engines for mining in South America, but returned to England when war broke out. He died almost a pauper, and was only recognized for his contributions and honored after his death.

George Stephenson

Where Trevithick failed, George Stephenson, ten years his junior, a coal worker and self-taught mechanical engineer, succeeded, barely a few years later.  Illiterate until the age of 18, he attended night school to learn to read and write, to add to all his practical knowledge. Wagons running on wooden and cast-iron rails, usually pulled by horses, had become popular over several years. Inspired by Trevithick several others built high pressure steam locomotive, to replace horses, including Stephenson, in 1814. He built several locomotives, all of which eventually damaged the rails by their weight. Stephenson came up with some innovations like steam springs, and using more wheels, to distribute weight. In the meanwhile, iron smiths had developed wrought iron, which had lower carbon content than cast iron, was tougher and more malleable.

In 1821, Stephenson was hired to build the 40km Stockton-Darlington railway line, to carry horse drawn wagons. He convinced the director, Edward Pease, to use a steam locomotive instead, running on wrought iron rails. The Stephenson engine was a slightly improved version of the Trevithick engine, featuring horizontal boiler, internal furnace, water tubes, tilted pistons and blast tube.

His son Robert Stephenson, built an engine called Locomotion, which hauled a coal wagons for 14 km in 2 hours. The successful run inspired another the commissioning of a railway line between the much larger industrial city of Manchester, hub of the cotton industry, and the harbour town of Liverpool, a distance of 97km. The biggest challenge now was building a railway line over varied terrain including marshes and peat bogs, and George Stephenson took on this challenge.

Robert Stephenson's "Rocket"
Pic: Wikipedia

The directors of the LMR railway line arranged a competition among five different locomotive engines, in 1829, one of which “Rocket”,  was built by Robert Stephenson, son of George. It was the only one that completed the run, so it won. It became the model for all future railway locomotive engines. This success, launched an era of building railway lines, carrying both cargo and passengers, first across England, then in several European countries, launching a total revolution in the field of transportation.

The Stephensons found the financial success and fame, that sadly eluded Trevithick whose innovations were the basis of the railway revolution.

Economic and Social Impact

Railway lines were built all across Europe, then the USA, and in India in the next few decades. The cost of transporting goods dropped precipitously. The time for travel across land also dramatically reduced from days to hours. In parallel, steam powered boats, then ships, made ocean voyages cheaper, safer and more predictable; and cost of shipping goods across the world also dropped spectacularly. The great benefits in manufacturing, powered by stationary steam engines, now could reach all corners of the world, thanks to locomotive steam engines.

It also had downsides. Vast numbers of artisanal workers, especially weavers in Europe and later India, lost their livelihoods or became poorer, as the couldn’t compete with loom produced textiles. But the number of manufactured goods increased dramatically, making necessities out of luxuries.

The political consequence was Britain’s ascent as an unprecedented global industrial, technological, military, economic and hence political, superpower. The nineteenth century was truly the century of steam power, which continued well into the twentieth century, even decades after the invention of electrical, deisel and oil powered engines, and later turbines.



Industrial Revelations : Youtube series

ThoughtCo website

Related Links

James Watt's Steam Engine

Charles Parsons and Steam turbines

Essays on Inventors and Discoverers

Monday 5 September 2022

James Watt and the Steam Engine

We have heard the fabulous story that young James Watt watched a water boil in a tea kettle, which rattled the kettle’s lid and struck James by the power of steam. This childhood experience, the story goes, inspired him to invent the steam engine as an adult. It is indeed a marvelous fable, ranking with Newton’s apple.

But why didn’t a Chinese James Watt invent the same steam engine, long before the English one? After all the Chinese have been boiling tea for a thousand years before England. Why not a Tamil boy or girl watching idli being steamed? Same water. Or someone in Sumeria or Egypt?


It turns out, even James Watt was not the first Englishman to work on a steam engine. The Royal Society of England records a Frenchman Denis Papin, who claimed to have run a steam powered boat on a French river, with recommendations from Gregory Leibniz and Christian Huygens. Some drawings of Papin survive, but nothing else. Some historians say that Isaac Newton, a fierce rival of Leibniz was then President of the Society, and ignored Papin because of his Leibniz connection. Curiously, neither Newton nor most scientists of the society, showed much interest in either Papin’s engine or even about heat as worthy of scientific study.

But in 1698, a patent was filed by an Englishman Thomas Savery, for a “fire-engine” – that is, a boiler of water heated by a coal-fired furnace. The steam produced pushed a metal piston up. This piston was attached to a lever, at whose other arm was suspended a bucket which was lowered into a coal mine. Coal mines often filled up with ground water, which prevented mining. When the bucket filled with water from the coal, the boiler was cooled by splashing cold water on it. This cooled the boiler and the steam, which condensed and the steam pressure, which had driven up the piston, fell. Atmospheric pressure then lowered the piston, and the connected lever pulled up the bucket full of water. Today we call this a pump – but since it was powered by heating water, the popular name was fire engine. Several Savery engines sold for around 150 to 200 pounds. This was the first effective steam engine : but since the actual work of lifting the water was done by atmospheric pressure rather than the steam, historians call Savery’s engine an “atmospheric engine.”

Newcomen's Steam engine:
Pic from: Michael de Greasley's Youtube video

Savery had a fourteen year patent, which was extended to 35 years, until 1733. A generation later, in 1712, Thomas Newcomen, another Englishman, made some improvements to the Savery engine, paying a license fee to Savery’s heirs. His Newcomen engine, was also an atmospheric engine, but it was safer, could stand higher heat and steam pressure, and could pump up water from 150 feet rather than the thirty feet of Savery’s engine. So it was popular among coal and other miners, who paid a royalty of about 450 pounds a year to operate a Newcomen engine. 

Mathematical Instruments

James Watt, was born far north of the British island, in Scotland, in 1735 (after Savery’s patent had expired, and Newcomen engines became popular). He went to school, where he was taught mathematics and astronomy, which he loved more than Greek and Latin, which were also part of his education. When he turned eighteen, Watt traveled to London, to learn some skills as an apprentice. Carnegie says that it was a twelve day travel by walk or horse carriage; quite hazardous; and the whole village met in church to pray for such travelers’ welfare.

Watt joined John Morgan of Cornhill road, a maker of mathematical instruments. These were navigational instruments like the compass, the telescope, the quadrant, the geared watch; mercantile instruments like brass scales, rulers; surveying instruments like theodolites, etc. Watt was described as  “having a fortune at his fingers’ ends”; that is mechanically very talented; and he was a quick learner. After a couple of years, he returned to Glasgow to set up a  shop selling such devices. But he wasn’t very successful. He expanded to repairing musical instruments like fiddles and pianos, and fishing equipment and surveying tools.

Early experiments at Glasgow

He had made friends with some academics at the University of Glasgow and was allowed to perform some experiments there. The university had a model version of a Newcomen engine, which had broken down, and even Watt’s efforts couldn't fix it. The model was sent to London for repair, but a curious Watt built a similar model himself, using a vial as a boiler and hollow canes as tubes. He observed that the engine wasted a lot of heat, alternately cooling and heating the cylinder. Experimenting a little more, he discovered Latent Heat.

Latent heat is the property of water, whereby when it reaches its boiling point, it doesn’t immediately turn to steam, but continues to absorb heat without any sensible (measurable) change in temperature. After absorbing this heat for a while some of the water turns into steam. The heated steam has much more thermal energy than water at the same temperature (five times, as Watt found out).

Excited, he met Professor Joseph Black of the university, and explained what he had discovered. An amused Black, showed Watt that he had discovered the same phenomenon a few years earlier. They gained a mutual respect for each other.

External Condenser

Believing Watt could improve the Newcomen engine, a local businessmen, John Roebuck formed a partnership, investing a thousand pounds for Watt’s research. The understanding was that, when Watt finally made a better engine, Roebuck would get two thirds  of the revenue as the financier.

Watt’s first great insight was about the inefficiency of alternatively heating and cooling the cylinder, to get mechanical work out of it. In 1769, he added an external condenser to the engine, which received the piped off excess steam. This vastly increased the efficiency of the engine. Several mine owners bought this engine from Watt.

But, then Roebuck went bankrupt. And Watt stopped working further on improvements to the engine.

An Era of Canals

Watt spent several years working as a surveyor, putting his mathematical skills to use. He surveyed several canals, designed bridges, and docks and piers. He surveyed the Monkland, Clyde, Forth, Caledonian and Perth canals, receiving about 400 for the last of these. He designed a bridge over the river Clyde for which he was paid 37 pounds.

Horse drawn Boats

It was the age of canals in England. Catching up to Europe, India, China and other countries which had developed intricate networks of canals over the centuries, England built several new canals for transport. One of the wettest countries in the world, it was blessed with several perennial rivers and streams. Connecting these with canals was quite profitable for landowners, especially owners of coal and iron mines. Transporting by water was far cheaper than transporting by muddy roads over uneven terrain. Horses walking alongside the canals could pull more loads on water than on land.

Matthew Boulton

Boulton was a maker of “toys” – by which was meant decorative cups and jars, plated jewellery, silver plates, candlesticks, buttons, buckles, mirrors – things sold by “fancy stores” in every street corner in India today. He had a manufactory at Soho, near Birmingham, an area rich in coal, which had developed an ironwork industry. The factory was mainly water powered.

In his times, France was considered superior to England at manufacturing these “toys”. Often, Boulton shipped good from his factory across the English channel and then had them return, pretending the goods were imported from France. This was an effective business tactic. He soon drew wealthy and reputable customers, including the best advertisers possible – the English royal family. When princes George (later king) and Edward bought swords from Boulton, his reputation, and business, soared. He even attracted the attention of Princess Catherine of Russia, who declared his products superior to those of France.

Reduced summer time water flows in the streams powering his mills, convinced Boulton to buy a Watt engine to pump water into a lake to supply his factory. After seeing Watt’s external condenser engine, Boulton realized not only could it renew his water supply, a better steam engine may replace it and power his factory. Cashing in on a debt that Roebuck owed him, Boulton took over from Roebuck as a business partner for Watt and persuaded him to move to Birmingham and work on improving the engine.

James Watt was lucky to get such a good and influential friend. He had great faith in Watt as an inventor and spoke in praise of him to whomever listened. Catherine of Russia listened, and agreed, and offered Watt five thousand pounds to move to Russia and continue his investigations. It took an alarmed Boulton all his persuasive powers to keep Watt in England.

Industrial Success

One major problem was the reliability of cylinder to operate under the higher pressure and heat of steam. An iron-master John Wilkinson, invented a boring machine, with which he made stronger cannons. Boulton introduced him to Watt, who began using Wilkinson’s cylinders for his steam engine. Wilkinson was not only a supplier, he was also one of the first customers of Watt’s engines, which he used for blowing machines, forge hammers and other metal works.

The first Watt engines were popular among mine owners, who cancelled orders for Newcomen engines. These engines were not manufactured, but assembled on location from assembled parts constructed on site under Watt’s personal supervision. Most of the parts and even the tools were handcrafted by smiths. Alcoholism, the lack of engineers, absenteeism were major problems for their business. Some others began copying the design without paying Watt a patent fee.

Boulton and Watt offered a business model, based on the far superior efficiency of the Watt engine over the Newcomen engine. Most of the money was saved on coal used to power the engine. The mine owners were charged one-third of the estimated savings on coal – for example, if a Watt engine used 400 tonnes of coal compared to an earlier Newcomen engine which used 1000 tonnes, the customers had to pay the cost of 200 tonnes (one third of the cost of 600 tonnes of coal they saved). This led to a lot of bargaining disputes and negotiations, all of which Watt was personally averse to. Fortunately, Boulton’s excellent business skills came into play.

Boulton got the patent extended for twenty years, from 1775 to 1800, by an act of Parliament. This ensured no other company could make or sell a steam engine with an external condenser. So inefficient Newcomen engines continued to be sold. This also prevented innovations and experiments with high pressure engines, which Watt detested as potentially deadly.

Boulton realized that the steam engine had a limited market as  a pump, with only a linear action; if the pistons linear movement could be converted to a rotary motion, whole new industries would buy the engine. A competitor, Pickard, had developed a crank-shaft to do just that, but wanted to cross-license it with the external condenser. Watt refused. He instead invented a sun-and-planet gear, an alternative mechanism that turned linear into rotary motion, in 1781. He sold an engine with this rotary mechanism to Whitbread’s brewery, which replaced horses with Watt’s engines to grind corn. Boulton proposed that brewers pay for one-third of the horses that breweries replaced – if the Watt engine replaced eighteen horses, they received annual fees equivalent to the cost of maintaining six horses. This was also the beginning of the practice of rating engine power in number of horses : or horsepower.


Meanwhile Watt worked on other improvements. In 1781, he also developed a double acting engine, where the steam operated on both ends of the cylinder. In 1782, he developed a compound engine, where two engines combined their power.

He also developed  a steam pressure indicator, which measured and showed the pressure of the active steam, making the operation much safer. An ingenious invention, in 1788 was the centrifugal governor, (originally invented by Huygens), which regulated the rate of steam and rotary action, so that it would neither slow down nor speed up much, but maintain a somewhat constant speed. A steam throttle was useful in actually controlling the amount of steam flowing, and controlling the speed of the rotary engine.

Sun and Planet gear
Pic: Wikipedia

With these significant improvements, other industries also bought the Watt engine. The textile industry which had mechanised looms; the metal forging industry; and mills. Boulton himself employed them later in minting coins. Competitors and patent infringements and fighting over dues were a constant problem. Boulton and Watt lost a lot of potential revenue, but eventually became rich and reputed men, because of their machine.

Prime Mover

The steam engine is a prime mover, which replaced human, animal and water power in a vast number of industries, with. It changed the world in a way that perhaps no other invention before or after has done. The stationary atmospheric engine became a stationary steam engine, slowly expanding into new industries. Then it evolved into a more compact engine, capable of moving itself – a locomotive engine. Finally steam power was adapted to operate turbines.

It was quite gradual; it evolved over two centuries, before diesel petrol and electric engines began to replace steam engines as major prime movers in several industries.

Boulton conscious of its significance and impact, declared: “I sell, sir, what all men desire: power.”

James Watt, inventor extraordinary

Watt was not just an practical mechanic and industrial inventor; he had extraordinary scientific skills as witnessed by his independent discovery of Latent Heat. Humphrey Davy said that Watt “was distinguished as a natural philosopher and chemist; his inventions demonstrate his profound knowledge of those sciences, and that peculiar characteristic of genius, the union of them for practical application."      

Watt invented a copying machine which soaked an original document or drawing in a chemical and could transfer it to another sheet of paper. He didn’t sell many, but some of them were in use for over a hundred years. He improved the gas lamp; invented an unfinished arithmetical machine; and even built a sculpture copying machine.

Carnegie says Watt, continuing on extraordinary discoveries of Joseph Priestley and Antoine Lavoisier, discovered that water was a compound of flammable air and dephlogisiticated air – independently also discovered by Cavendish. But his name is strongly associated with the steam engine, all other discoveries pale in comparison.

Lunar Society

Boulton was not only a business partner for Watt. He was a personal friend and intellectual compatriot. When Watt lost his first wife, and contemplated marrying another lady, her family objected. Boulton wrote a recommendation letter to Watt’s prospective father-in-law lauding his friend’s virtues.

Boulton had met the ingenious American scientist Benjamin Franklin, the Scottish philosopher and economist Adam Smith, a medical doctor Erasmus Darwin (grandfather of Charles), the chemist and clergyman Joseph Priestley and businessman and potter Josiah Wedgwood. He brought them all together at his Birmingham mansion, on full moon nights, discussing science, inventions and discoveries. They called themselves the Lunar Society. They have been called the Founding Fathers of the Industrial Revolution.

Watt eventually died in 1819, a few years after Boulton. Neither of them saw the emergence of the railways, though Watt apparently once journeyed on a paddleboat powered by steam engine. The British magazine “Chemist” paid him a fitting tribute:

“Different from other public benefactors by never having made or pretended to make it his goal to benefit the public. This unpretending man conferred more benefit to the world, than all those who for centuries made it their special business to look after public welfare.”

There are statues to Watt in London, Manchester and Birmingham. The watt was adopted as a unit of power, in 1889, by the British Association for the advancement of Science. The Bank of England issued a ₤50 currency note with images of Watt and Boulton in 2009.


1.       James Watt: A Biography, by Andew Carnegie

2.       Creating the Twentieth Century, by Vaclav Smil

3.       Industrial Revelations : Youtube series

4.       The Lunar Society, by Jenny Uglow

5.       Wikipedia

6.       Other videos, internet

Related Links

James Watt's Steam Engine - my lecture at Varahamihira Science Forum

Charles Parsons - Inventor of Steam Turbines

Inventors and Discoverers - my blogs