Hornsby-Akroyd 20 hp Oil Traction
Engine (serial no. 12359, built 1896)
at Onslow Park Rally, Shropshire,
England in 2005.
Hornsby-Akroyd
Richard Hornsby & Sons of Grantham, Lincs. built a range of steam traction and portable engines during the 19th century and were one of the best-known engineering firms in the UK. In 1896 they constructed Britain's first tractor, based around an Akroyd Stuart 20 hp single-cylinder horizontal oil engine. This tractor was known as the Hornsby-Akroyd Patent Safety Oil Traction Engine, and in 1897 it was awarded the Silver Medal of the Royal Agricultural Society of England. One tractor was sold in the UK and three were later exported to Australia, where one still survives today. The original tractor from 1896 was later returned to factory and fitted with crawler tracks, with one such tracklayer being sent to the Yukon region of Canada in 1909. Unfortunately the military potential of this machine, the predeccesor of the tank, was not recognized by the British government; Hornsby subsequently sold the tracklayer patents to the Holt company of the USA shortly before the First World War. Following the sales of the 20 hp oil tractors to Australia, Hornsby had plans to build a 32 hp oil tractor, but there is no evidence that any of these were ever produced.
The Hornsby-Akroyd oil engine was the first successful design of internal combustion engine using 'heavy oil' as a fuel. It was the first to use a separate vaporizing combustion chamber and is the forerunner of all hot-bulb engines.
Early internal combustion engines were quite successful running on gaseous and light petroleum fuels. However, due to the dangerous nature of gasoline and light petroleum fuel, legal restrictions were placed on their transportation and storage. Heavier petroleum fuels, such as kerosene, were quite prevalent, as they were used for lighting. However, heavier oils posed specific problems when used in internal combustion engines.
Oil used for engine fuel must be turned to a vapor state and remain in that state during compression. Furthermore, the combustion of the fuel must be powerful, regular, and complete, to avoid deposits that will clog the valves and working parts of the engine.
Early oil enginesThe earliest mention of an oil engine was by Robert Street, in his English patent no. 1983 of 1794. The earliest working engine was built by Julius Hock, of Vienna, in 1870. Hock's was a non-compression engine, not unlike that of Étienne Lenoir.
Others made refinements to the oil engine; William Dent Priestman, George Brayton and Emile Capitaine are some of the more notable. However, it was Herbert Akroyd Stuart's design that was the most successful.
Herbert Akroyd Stuart
Hornsby portable engine
Akroyd Stuart's first prototype engines were built in 1886. In 1890, in collaboration with Charles Richard Binney, he filed Patent 7146 for Richard Hornsby and Sons of Grantham, Lincolnshire, England. The patent was entitled entitled: "Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air".
Stuart's oil engine design was simple, reliable and economical. It had a comparatively low compression ratio, so that the temperature of the air compressed in the combustion chamber at the end of the compression stroke was not high enough to initiate combustion. Combustion instead took place in a separated combustion chamber, the "vaporizer" (also called the "hot bulb") mounted on the cylinder head, into which fuel was sprayed. It was connected to the cylinder by a narrow passage and was heated either by the cylinder's coolant or by exhaust gases while running; an external flame such as a blowtorch was used for starting. Self-ignition occurred from contact between the fuel-air mixture and the hot walls of the vaporizer.
The Stuart engine is of four cycle design. During the intake stroke, fresh air is inducted into the cylinder through a mechanically operated intake valve. Simultaneously, oil is injected into the vaporizer. The vapor of the oil is almost entirely confined to the vaporizer chamber. This cloud of hot oil vapor is too rich to support combustion. On the compression stroke of the piston, the fresh air is forced through the narrow neck and into the vaporizer. Just as compression is completed, the mixture is just right to support combustion and ignition occurs.
By contracting the bulb to a very narrow neck where it attached to the cylinder, a high degree of turbulence was set up as the ignited gases flashed through the neck into the cylinder, where combustion was completed. As the engine's load increased, so did the temperature of the bulb, causing the ignition period to advance; to counteract pre-ignition, water was dripped into the air intake.
First production oil engine
Vaporizing Oil Engine
Akroyd-Stuart's engines were built from June 26, 1891 by Richard Hornsby and Sons, a large manufacturer of steam engines and agricultural equipment, as the Hornsby Akroyd Patent Oil Engine under licence and were first sold commercially on July 8, 1892. It was the first internal combustion engine to use a pressurised fuel injection system. The engine was hugely successful. During the period from 1891 through 1905, a total of 32,417 engines were produced.
