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It’s an Akroyd not a Diesel!


The history of technology is full of myths and half-truths about who invented what. One of the real problems is to define exactly what we mean by ‘invented’. For example, do we mean:

  • The first time an idea was suggested?
  • The first time working drawings were produced?
  • The first time a patent was applied for?
  • The first time a patent was actually granted?
  • The first time a working prototype was made?
  • The first time an idea went into production on a limited scale?
  • The first time the concept entered mass production?

In many instances the answer is not clear, and frequently the different milestones can be attributed to different individuals.

However, when it comes to the so-called ‘diesel’ engine there is no doubt or ambiguity at all. Whilst today it is popularly accepted that Rudolph Diesel invented the ‘diesel’ engine that somehow came to bear his name, in truth this is a myth and a great injustice to a brilliant British engineer. The real inventor was Herbert Akroyd Stuart who achieved all the seven milestones listed above years before Rudolph Diesel achieved anything.

Herbert Akroyd Stuart was born in 1864 in Halifax, the son of Charles Stuart, a Scotsman from Paisley. His father established the Bletchley Iron & Tin Plate Works and Herbert, after a short time working as a junior assistant in the Mechanical Engineering Department of the City & Guilds of London Technical College in Finsbury, joined his father’s business in Bletchley. There he started experimenting with oil engines. In 1886, seven years before the German filed his first patent in Berlin, and after four years of experimenting, Akroyd Stuart not only filed his first patent, but also built his first prototype ‘diesel’ engine at the young age of just 22. Dr Diesel’s later patent, filed in 1893 at the Imperial Patent Office in Berlin, was for an engine that burned coal dust rather than oil, and it was not until 1887 that he made his first working prototype. This prototype blew up and nearly killed him. Akroyd Stuart’s engines predated Dr Diesel’s first working example by six years. In addition, Diesel’s design idea was based on the ‘isobaric combustion’ principal which had already been patented in 1874 by an American by the name of George Brayton, so it could be argued that Diesel’s first patent was plagiarised from an earlier invention. However, since the modern diesel does not function on this principal, this is largely irrelevant.

Several experimental engines were built at the Bletchley factory, one of which was installed at the newspaper offices of the Fenny Stratford Times, another went to the waterworks, and a third to the brush factory of Messrs. Cooks. As the quality of the engineering on these engines was poor, George Wailes & Co, Euston Road, London was commissioned to build a subsequent batch of four. Unfortunately there are no known survivors of these early engines.

The seminal patent, #7146 of May 1890, based on research with his early prototypes, described the first proper ‘diesel’ engine in detail. It describes how, after the combustion chamber or vaporiser has been externally heated by a blowlamp....

“the induction stroke which is the first outward stroke, instead of drawing into the cylinder a mixture of hydrocarbon vapour and air, simply draws in pure atmospheric air. The compression or first return stroke compressing this air into the pre-heated vapouriser, and at the desired part of this compression stroke, the supply of liquid hydrocarbon is forced, in a spray form, on to the heated vapouriser which almost instantly changes it into a gas, it combines with the heated air; automatic ignition takes place and propels the piston which forms the working or second outward stroke.”

This system is known as solid injection, and is the principle used by most present-day diesel engines. Although it required the vaporiser to be initially heated, that is exactly the way ‘glow plugs’ in many large modern ‘diesels’ work.  

By 1891 Akroyd realised his engine was ready for proper production, and he granted a licence to Richard Hornsby & Sons of Grantham to build his engines under the title ‘Hornsby Akroyd Patent Oil Engine’. Two of these machines were exhibited at the Royal Agricultural Show in Doncaster in June 1891. They were first sold commercially in May 1892, a year before Diesel even applied for his dubious coal-dust-burning patent. The world’s first successful commercial compression-ignition engine was installed at Fenny Stratford waterworks in July 1892. Shortly afterwards a second engine was installed there. In 1896 the world’s first compression-ignition locomotive was made by Hornsby to Akroyd Stuart’s design, and started work at Woolwich Arsenal. Then, in 1896, also in collaboration with Hornsby, Ackroyd Stuart developed a ‘diesel’ driven tractor, and in 1897 three were built for export to Australia. Hornsby went on to build over 45,000 Hornsby-Akroyd engines, many before Diesel had built even one single engine. They were produced in several formats, horizontal and vertical, stationary and portable, and even in 1903 a ‘V’ engine, a world first for an oil engine. These should really be called the ‘Hornsby-Akroyd’ engine, but unlike Dr Diesel, Akroyd Stuart was a quiet unassuming man who did not seek the limelight.

So where does this leave Rudolph Diesel, who didn’t even build built his first working engine, albeit one that blew up, until 1897? It was a copy of someone else’s design, it didn’t run on oil, it used an ignition cycle quite different from the modern ‘diesel’ engine, and it wasn’t in fact until 1898 that he was able to exhibit a successful oil-burning engine at the Paris Exhibition Fair. And this was a gargantuan vertical monstrosity with a ten-foot (three metre) long cylinder, a real contrast to the much more elegant and compact Hornsby-Ackroyd design. Diesel was an arrogant, self-promoting, person but also an odd and unstable character, having several nervous breakdowns and suffering from paranoia. On 29 September 1913 Diesel boarded the SS Dresden ferry to cross the English Channel. Some time during the night he fell overboard, and his body was ultimately found in the Scheldt River on 18 October. Various rumours abound, one that he committed suicide because he was riddled with debt.

But Akroyd Stuart’s fame does not end with the engine itself. He built the first ever ‘diesel’ car and the first ever ‘diesel’ locomotive. He supplied the ‘diesel’ engines to illuminate the Statue of Liberty, and also provided the ‘diesel’ engine which generated electricity for Marconi’s landmark radio transmission across the Atlantic Ocean. In addition, in collaboration with Hornsby, he invented what we now call the ‘caterpillar tractor’ (yes, also ‘diesel’ powered) of which over 500 were built. The tracked vehicle was designed for towing large guns and was produced between 1915 and 1918. However, in what might be seen as a serious error of business judgment, he sold the rights to the Holt Tractor Co, which became Caterpillar, at the end of the war as he saw no commercial prospects for his idea!

Akroyd Stuart was a private, self-effacing, very polite man by all contemporary accounts. He never married, and so had no direct descendents to support his cause for recognition. He moved to Australia in 1900 and set up a new company of Sanders & Stuart with his brother Charles. He died of throat cancer in 1927 in Perth Australia, and his body was returned to England and buried in Halifax. In his old age he was quite bitter that his legitimate claim to have invented the ‘diesel’ engine was not recognised, whilst the self-publicising Rudolph Diesel managed to grab the headlines for something he did not invent, but just copied.

Having made quite significant money from his invention of the ‘diesel’ engine, and the Hornsby licence to manufacture it, and with no family to support, Akroyd Stuart made substantial donations to the universities of Western Australia and Nottingham, as well as the Institution of Mechanical Engineers, the Royal Aeronautical Society, and the Institute of Marine Engineers to help establish his claim. Income from the bequests is still used to support the Herbert Akroyd Stuart lectures on the origin and development of heavy oil engines. Modern oil engines use Akroyd Stuart’s method of oil-spray injection with constant volume burning, in preference to Diesel’s method of air-blast injection with constant pressure burning, a technology which is now dead.

It is time this English engineering genius is finally credited with the invention of what we have all come to refer to as the ‘diesel’ engine. It is not the ‘diesel’ engine, it is the Hornsby-Akroyd engine. And overall Herbert Akroyd Stuart was a genius of an engineer easily ranking alongside Sir Frank Whittle, Isambard Kingdom Brunel, George & Robert Stephenson and other such giants in the Hall of Fame of British technology. It is time we recognised his contribution to society.

There is a rather ironic footnote to the true story of the ‘diesel’ engine. The first two production engines, 101 and 102, worked at the Great Brickhill Water Works until 1923, when No 101 was purchased by a Bletchley timber merchant. In 1939 it was returned to Hornsbys for restoration, and then preserved as a museum piece. It was kept in the entrance to the R&D Department at Ruston-Paxman Diesels in Lincoln. But since the Ruston-Paxman business was taken over by the German M.A.N. Group it is now believed to have been shipped to Germany, ironically the home of Rudolph Diesel who claimed falsely to have invented this type of engine. I think Herbert Akroyd Stewart would have rather approved of that!

Hornsby Oil Engine 5hp 1908

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