, Bridgnorth, about 1804, and illustrated after being rescued ; from
Scientific American Supplement, Vol. XIX, No. 470, 3 January 1885. This engine is on view at the
Science Museum (London). As his experience grew, he realised that improvements in
boiler technology now permitted the safe production of high-pressure steam, which could move a
piston in a steam engine on its own account, instead of using near-atmospheric pressure, in a condensing engine. He was not the first to think of so-called "strong steam" or steam of about .
William Murdoch had developed and demonstrated a model steam carriage in 1784 and
demonstrated it to Trevithick at his request in 1794. In fact, Trevithick lived next door to Murdoch in Redruth in 1797 and 1798.
Oliver Evans in the U.S. had also concerned himself with the concept, but there is no indication that Trevithick knew of his ideas. Independently of this,
Arthur Woolf was experimenting with higher pressures whilst working as the Chief Engineer of the Griffin Brewery (proprietors Meux and Reid). This was an engine designed by Hornblower and Maberly, and the proprietors were looking to have the best steam engine in London. Around 1796, Woolf believed he could save substantial amounts of coal consumption. According to his son Francis, Trevithick was the first to make high-pressure steam work in England in 1799, although other sources say he had invented his first high-pressure engine by 1797. Not only would a high-pressure steam engine eliminate the condenser, but it would allow the use of a smaller cylinder, saving space and weight. He reasoned that his engine could now be lighter, more compact, and small enough to carry its own weight even with a carriage attached (this did not use the
expansion of the steam, so-called "expansive working" came later).
Early experiments Trevithick began building his first models of high-pressure (meaning a few
atmospheres) steam engines – one stationary one and then one attached to a road carriage. A
double-acting cylinder was used, with steam distribution by means of a
four-way valve. Exhaust steam was vented via a vertical pipe or
chimney straight into the atmosphere, thus avoiding a condenser and any possible infringements of Watt's patent. The
linear motion was directly converted into circular motion via a
crank instead of using a more cumbersome beam.
Puffing Devil and running on Trevithick's day 2017 Trevithick built a full-size steam road locomotive in 1801, on a site near present-day Fore Street in Camborne. (A steam wagon built in 1770 by
Nicolas-Joseph Cugnot may have an earlier claim.) Trevithick named his carriage
Puffing Devil and on
Christmas Eve that year, he demonstrated it by successfully carrying six passengers up Fore Street and then continuing on up Camborne Hill, from Camborne Cross, to the nearby village of
Beacon. His cousin and associate,
Andrew Vivian, steered the machine. It inspired the popular Cornish folk song "
Camborne Hill". During further tests, Trevithick's locomotive broke down three days later after passing over a gully in the road. The vehicle was left under some shelter with the fire still burning whilst the operators retired to a nearby
public house for a meal of roast goose and drinks. The boiler went dry, overheating the engine destroying it in a fire. Trevithick did not see this caused by a design flaw, but rather operator error. In 1802 Trevithick took out a patent for his high-pressure steam engine. To prove his ideas, he built a stationary engine at the
Coalbrookdale Company's works in
Shropshire in 1802, forcing water to a measured height to measure the
work done. The engine ran at forty piston strokes a minute, with an unprecedented boiler pressure of .
Coalbrookdale Locomotive In 1802 the
Coalbrookdale Company in
Shropshire built a rail locomotive for him, but little is known about it, including whether or not it actually ran. The death of a company workman in an accident involving the engine is said to have caused the company to not proceed to running it on their existing railway. To date, the only known information about it comes from a drawing preserved at the
Science Museum, London, together with a letter written by Trevithick to his friend
Davies Giddy. The design incorporated a single horizontal
cylinder enclosed in a return-flue
boiler. A
flywheel drove the wheels on one side through
spur gears, and the
axles were mounted directly on the boiler, with no frame. On the drawing, the piston-rod, guide-bars and cross-head are located directly above the firebox door, thus making the engine extremely dangerous to fire while moving. Furthermore, the first drawing by Daniel Shute indicates that the locomotive ran on a
plateway with a
track gauge of . This drawing was used as the basis of all images and replicas of the later "Pen-y-darren" locomotive, as no plans for that locomotive survived.
London Steam Carriage , by Trevithick and Vivian, demonstrated in London in 1803 The
Puffing Devil was unable to maintain sufficient steam pressure for long periods, and would have been of little practical use. He built another steam-powered road vehicle in 1803 dubbed the
London Steam Carriage, which attracted much attention from the public and press that year when he drove it in London from
Holborn to
Paddington and back. It was uncomfortable for passengers and proved more expensive to run than a horse-drawn carriage, and was abandoned. In 1831, Trevithick gave evidence to a
Parliamentary select committee on steam carriages.
Tragedy at Greenwich Also in 1803, one of Trevithick's stationary pumping engines in use at
Greenwich exploded, killing four men. Although Trevithick considered the explosion to be caused by careless operation rather than design error, the incident was heavily exploited by
James Watt and
Matthew Boulton (
competitors and promoters of low-pressure engines) who highlighted the perceived risks of using high-pressure steam. Trevithick's response was to incorporate two
safety valves into future designs, only one of which could be adjusted by the operator. The adjustable valve comprised a disc covering a small hole at the top of the boiler above the water level in the steam chest. The
force exerted by the steam
pressure was equalised by an opposite force created by a weight attached to a pivoted lever. The position of the weight on the lever was adjustable thus allowing the operator to set the maximum steam pressure. Trevithick also added a
fusible plug of lead, positioned in the boiler just below the minimum safe water level. Under normal operation the water temperature could not exceed that of
boiling water and kept the lead below its melting point. If the water ran low, it exposed the lead plug, and the cooling effect of the water was lost. The temperature would then rise sufficiently to melt the lead, releasing steam into the fire, reducing the boiler pressure and providing an audible alarm in sufficient time for the operator to damp the fire, and let the boiler cool before damage could occur. He also introduced the hydraulic testing of boilers, and the use of a
mercury manometer to indicate the pressure.
"Pen-y-Darren" locomotive , Swansea. In 1802 Trevithick built one of his high-pressure steam engines to drive a
hammer at the
Penydarren Ironworks in
Merthyr Tydfil,
Mid Glamorgan. With the assistance of Rees Jones, an employee of the iron works, and under the supervision of Samuel Homfray, the proprietor, Trevithick mounted the engine on wheels and turned it into a locomotive. In 1803, Trevithick sold the patents for his locomotives to
Samuel Homfray. Homfray was so impressed with Trevithick's locomotive that he made a bet of 500
guineas with another ironmaster,
Richard Crawshay, that Trevithick's steam locomotive could haul ten
tons of iron along the
Merthyr Tramroad from
Penydarren () to
Abercynon (), a distance of . On 21 February 1804, amid great interest from the public, it successfully carried 10 tons of iron, five wagons and 70 men the full distance in 4 hours and 5 minutes, at an average speed of approximately . As well as Homfray, Crawshay and the passengers, other witnesses included
Mr. Giddy, a respected patron of Trevithick, and an "engineer from the Government". The engineer from the government was probably a safety inspector, who would have been particularly interested in the boiler's ability to withstand high steam pressures. The configuration of the Pen-y-Darren engine differed from the Coalbrookdale engine. The cylinder was moved to the other end of the boiler so that the fire door was out of the way of the moving parts, which involved putting the crankshaft at the chimney end. The locomotive comprised a
boiler with a single
return flue mounted on a four-wheel frame. At one end, a single
cylinder with very long stroke was mounted partly in the boiler, and a
piston rod crosshead ran out along a slidebar. There was only one cylinder, which was coupled to a large
flywheel mounted on one side. The
rotational inertia of the flywheel would even out the movement that was transmitted to a central
cog-wheel that in turn was connected to the driving wheels. It used a high-pressure cylinder without a condenser. The exhaust steam was sent up the chimney, which assisted the draught through the fire, further increasing the engine's efficiency. Despite heavy scepticism it had been shown that, provided that the
gradient was sufficiently gentle, it was possible to successfully haul heavy carriages along a smooth iron road using just the adhesive weight of a suitably heavy and powerful steam locomotive. Trevithick's example was likely the first to do so; however, the locomotive broke some of the tramroad's short cast iron
plates because they were only meant to support the lighter axle load of horse-drawn wagons. Consequently, the tramroad returned to horse power after the initial test run. The engine was placed on blocks and reverted to its original
stationary job of driving hammers. A full-scale working reconstruction of the Pen-y-darren locomotive was commissioned in 1981 and delivered to the
Welsh Industrial and Maritime Museum in Cardiff. When that closed, the locomotive was moved to the
National Waterfront Museum in Swansea. Several times a year, it is run on a length of railway outside the museum.
"Newcastle" locomotive Christopher Blackett, proprietor of the
Wylam colliery near Newcastle, heard of the success in Wales and wrote to Trevithick asking for locomotive designs. These were sent to Trevithick's agent John Whitfield at Gateshead, who in 1804 built what was likely the first locomotive to have flanged wheels. Blackett used wooden rails for his tramway, and once again Trevithick's machine was too heavy for its track.
Catch Me Who Can In 1808 Trevithick publicised his steam railway locomotive expertise by building a new locomotive called
Catch Me Who Can, built for him by
John Hazledine and
John Urpeth Rastrick at
Bridgnorth in
Shropshire, and named by
Davies Giddy's daughter. The configuration differed from the previous locomotives in that the cylinder was mounted vertically and drove a pair of wheels directly without a flywheel or gearing. Admission to the "steam circus" was one
shilling including a ride and was intended to show that rail travel was faster than by horse. This venture also suffered from weak tracks and public interest was limited. Trevithick was disappointed by the response and designed no more railway locomotives. It was not until 1812 that twin-cylinder steam locomotives, built by
Matthew Murray in
Holbeck,
Leeds successfully started replacing horses for hauling coal wagons on the
edge railed,
rack and pinion Middleton Railway from
Middleton colliery to
Leeds,
West Yorkshire. ==Engineering projects==