Richard Trevithick - High pressure steam engine: Monaco Patents

The first engineer to use steam power for railroad cargo hauling was Richard Trevithick. Trevithick was a Redruth-born Cornishman by birth. Naturally talented in mechanics, his father assigned him to work with Watt's assistant, Murdoch, who was overseeing the construction of pumping engines in Cornwall. From that brilliant and accomplished engineer, young Trevithick most likely picked up the knowledge and skills that, when combined with his natural talent, entrepreneurship, and industry, allowed him to complete the work that he was entrusted with. He was quickly given responsibility for setting up and overseeing huge pumping engines.

Trevithick moved into the steam engine building business later on with another engineer named Edward Bull, who actively participated in the fight against the Boulton & Watt patents with the Hornblowers and other others. Their firm was forced out of business when the lawsuits established the validity of Watt's patent.

Trevithick formed a cooperation with a family member who was a skilled mechanic named Andrew Vivian. They collaborated to create and patent the steam carriage. For use on the Welsh Pen-y-darran road, Trevithick finished building a "locomotive" engine in February 1804. This engine had an Oliver Evans-inspired cylindrical flue-boiler (A), a single steam cylinder (B) positioned vertically within the steam space of the boiler (A), and extremely long connecting rods (D) connected to its cross-head at E, which drove the outside cranks (L) on the engine's rear axle. Braces going to the other end of the boiler held the guide bars (I) in place. There was no attempt to condense the exhaust steam that was released into the smoke pipe. The steam pressure used was 40 pounds per square inch (2.8 bar), but Trevithick had already built numerous non-condensing engines with pressures ranging from 50 to 145 pounds (3.4 - 10 bar). [1]

James Watt opposed the use of high pressure in steam engines for the entirety of his life because he was aware of the risks involved. His own account states that one or two years before receiving the Newcomen's engine model in winter 1763/1764, he experimented with a Papin's digester. He used a syringe with a one-third-inch (appr. 0.85cm) diameter connected to Papin's digester and was able to lift a 15-pound weight. This corresponds to a pressure of 15 pounds divided by (1/6)² ∗ π = 172 psi, almost 12 bar. James Watt relinquished the idea of constructing a machine upon this principle because of the risks of bursting the boiler and the perceived difficulty of making the joints tight. He had however described this principle in the 4th aspect of his 1769 patent and again in the specification of his 1784 patent with a mode of applying it to the moving of wheel carriages. [2]

James Watt probably saved many lives by using his patents to block the development of high-pressure steam engines, when metal processing was poor. Even 100 years later, when metal processing had considerably improved one boiler explosion occurred every week, one person was killed, and two injured, more or less, by a boiler explosion every four days. [3]

------------------

[1] Robert H. Thurston, A History of the Growth of the Steam-Engine, 1886, available as part of the Gutenberg project EBook #35916,

[2] Robison, footnate page 113.

[3] Hugh Mason M.P. (1882, pp 1348-1355] cited in Endress+Hauser Flowtec AG, CH-4153 Reinach/BL, Steam Handbook page 9