Dugald Clark
Encyclopedia
Sir Dugald Clerk KBE, FRS (1854, Glasgow
– 1932, Ewhurst
, Surrey
) was a Scottish engineer who designed the world's first successful two-stroke engine
in 1878
and patent
ed it in England
in 1881. He was a graduate of Anderson's University in Glasgow (now the University of Strathclyde
), and Yorkshire College, Leeds
(now the University of Leeds
). He formed the intellectual property firm with George Croydon Marks, called Marks & Clerk
.
. Most other sources, including The Encyclopædia Britannica and official documents, list him under Clerk.
Clerk began work on his own engine designs in October 1876. Up to this time the commercial engines available had been the Lenoir
engine from 1860, which worked on a double-acting 2-stroke cycle, but spent half of each stroke drawing gas into the cylinder. The Hugon engine was a slightly improved version, but both were quite inefficient (95 and 85 cubic feet of gas per HP hour respectively), neither used compression. The next commercial engine available (from 1867) was the Otto & Langen
free piston engine, which used atmospheric pressure for the power stroke, and had half the gas consumption of the Lenoir and Hugon engines. It was in May 1876 that Otto developed his engine using the single-acting 4-stroke cycle with compression in the cylinder. Clerk decided to develop an engine using compression, but with the 2-stroke cycle, as he could see benefit to weight and smoothness of operation through having twice as many power strokes.
Clerk initially experimented with engines that "were identical to the Lenoir
in idea, but with separate compression and a novel system of ignition", one of these was exhibited in July 1879. However it was not until the end of 1880 that he succeeded in producing the Clerk engine operating on the 2-stroke cycle, which became the commercial product. Clerk states "The Clerk engine at present in the market was the first to succeed in introducing compression of this type, combined with ignition at every revolution ; many attempts had previously been made by other inventors, including Mr. Otto and the Messrs. Crossley, but all had failed in producing a marketable engine. It is only recently that the Messrs. Crossley have made the Otto engine
in its twin form and so succeeded in getting impulse at every turn."
In "Gas and Oil Engines", Clerk refers to the significant earlier gas engine patents of Barnett
in 1838 and Wright
in 1833.
was patented, immediately recognized to have a significant practical value. Clerk quickly followed with his concept of a two stroke engine of 1880, that would not infringe the Otto's patent (being a four stroke engine).
Clerk describes a Cambell engine as using his cycle, as follows : "It has two cylinders, respectively pump and motor, driven from cranks placed at almost right angles to each other, the pump crank leading. The pump takes in a charge of gas and air, and the motor piston overruns a port in the side of the cylinder at the out-end of its stroke to discharge the exhaust gases. When the pressure in the motor cylinder has fallen to atmosphere, the pump forces its charge into the back cover of the motor cylinder through a check valve, displacing before it the products of combustion through an exhaust port ; the motor piston then returns, compressing the contents of the cylinder into the compression space. The charge is then fired and the piston performs its working stroke. This is the Clerk cycle."
The Clerk engine uses automatic 'poppet' type valves for inlet air and gas (one with spring assistance, one wthout), and a port in the cylinder uncovered by the piston for the exhaust valve. References to a Clerk engine with slide valve may refer to the earlier experiments with a Lenoir
type engine. The ignition is by carrying an external flame, using a modification of a method he developed in 1878.
Most engine designs that pre-dated the Otto engine (and Clerk engine), such as those of de Rivaz
, the Niépce brothers
, Jean Joseph Etienne Lenoir, Samuel Morey
, and others, did use two stroke engines, which were "natural" in the times of steam engine
. Clerk's significant contribution was introducing Otto-styled compression to the two stroke engine, bringing its efficiency up-to-date (for the 1880s). Several manufacturers adopted the Clerk cycle in the short term, though commercial aspects such as patents on the 4-stroke cycle were part of this. Many years later the 2-stroke engine for large capacity diesels using a turbocharger
or supercharger
has become common, for example in ships and railway locomotives. With open crankshafts, and the advantages of higher power to weight ratio, these engines are closely aligned with Dugald Clerk's concepts, and the Clerk Cycle.
. Clerk himself states that "It is not a compressing
pump, and is not intended to compress before introduction into the motor, but merely to exercise force enough to pass the gases through the lift valve into the motor cylinder, and there displace the burnt gases, discharging them into the exhaust pipe." Hence sources recognise it instead as a "pumping cylinder", pointing out that it did not actually compress the fuel-air mixture, it simply moved the fresh mixture to the working cylinder to force out the gasses burnt previously.
in 1894.
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...
– 1932, Ewhurst
Ewhurst, Surrey
Ewhurst is a small village in the English county of Surrey.Ewhurst is located between Cranleigh and Shere which is around five miles to the north. Ewhurst has many well-known legends as members of the village, such as Eric Clapton, who is known to play at the Church of England church in Ewhurst...
, Surrey
Surrey
Surrey is a county in the South East of England and is one of the Home Counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of...
) was a Scottish engineer who designed the world's first successful two-stroke engine
in 1878
and patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
ed it in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
in 1881. He was a graduate of Anderson's University in Glasgow (now the University of Strathclyde
University of Strathclyde
The University of Strathclyde , Glasgow, Scotland, is Glasgow's second university by age, founded in 1796, and receiving its Royal Charter in 1964 as the UK's first technological university...
), and Yorkshire College, Leeds
Leeds
Leeds is a city and metropolitan borough in West Yorkshire, England. In 2001 Leeds' main urban subdivision had a population of 443,247, while the entire city has a population of 798,800 , making it the 30th-most populous city in the European Union.Leeds is the cultural, financial and commercial...
(now the University of Leeds
University of Leeds
The University of Leeds is a British Redbrick university located in the city of Leeds, West Yorkshire, England...
). He formed the intellectual property firm with George Croydon Marks, called Marks & Clerk
Marks & Clerk
Marks & Clerk is an international firm of patent and trade mark attorneys with an associated intellectual property law firm Marks & Clerk Solicitors...
.
Name
Clerk's name is also rendered as Clark in the archive of his works in the University of GlasgowUniversity of Glasgow
The University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...
. Most other sources, including The Encyclopædia Britannica and official documents, list him under Clerk.
Clerk's work on the internal combustion engine
Dugald Clerk was the author of a comprehensive book covering the development of the oil and gas engine from its early inception, and including details of his own work in this area. The first edition was produced in 1886, and the notes here are taken from the 7th edition, revised and updated up to 1896.Clerk began work on his own engine designs in October 1876. Up to this time the commercial engines available had been the Lenoir
Etienne Lenoir
-Sources:* Georgano, G.N. Cars: Early and Vintage 1886-1930. London: Grange-Universal, 1990 . ISBN 0-9509620-3-1....
engine from 1860, which worked on a double-acting 2-stroke cycle, but spent half of each stroke drawing gas into the cylinder. The Hugon engine was a slightly improved version, but both were quite inefficient (95 and 85 cubic feet of gas per HP hour respectively), neither used compression. The next commercial engine available (from 1867) was the Otto & Langen
Otto engine
-Otto Engine Types:There are three types of internal combustion engines designed by German inventors Nikolaus August Otto and his partner Eugen Langen. They are the 1862 compression engine, which failed, the 1864 atmospheric engine, and the engine known today as the "Gasoline Engine", the Otto...
free piston engine, which used atmospheric pressure for the power stroke, and had half the gas consumption of the Lenoir and Hugon engines. It was in May 1876 that Otto developed his engine using the single-acting 4-stroke cycle with compression in the cylinder. Clerk decided to develop an engine using compression, but with the 2-stroke cycle, as he could see benefit to weight and smoothness of operation through having twice as many power strokes.
Clerk initially experimented with engines that "were identical to the Lenoir
Etienne Lenoir
-Sources:* Georgano, G.N. Cars: Early and Vintage 1886-1930. London: Grange-Universal, 1990 . ISBN 0-9509620-3-1....
in idea, but with separate compression and a novel system of ignition", one of these was exhibited in July 1879. However it was not until the end of 1880 that he succeeded in producing the Clerk engine operating on the 2-stroke cycle, which became the commercial product. Clerk states "The Clerk engine at present in the market was the first to succeed in introducing compression of this type, combined with ignition at every revolution ; many attempts had previously been made by other inventors, including Mr. Otto and the Messrs. Crossley, but all had failed in producing a marketable engine. It is only recently that the Messrs. Crossley have made the Otto engine
Otto engine
-Otto Engine Types:There are three types of internal combustion engines designed by German inventors Nikolaus August Otto and his partner Eugen Langen. They are the 1862 compression engine, which failed, the 1864 atmospheric engine, and the engine known today as the "Gasoline Engine", the Otto...
in its twin form and so succeeded in getting impulse at every turn."
In "Gas and Oil Engines", Clerk refers to the significant earlier gas engine patents of Barnett
William Barnett
William Barnett may refer to:* William Barnett , British engineer* William Barnett , American politician and soldier* William Barnett , current Mayor of Cadillac, Michigan* William A...
in 1838 and Wright
Lemuel Wellman Wright
- Name :Lemuel Wellman Wright is the name recorded in the British patent index for the patents listed below, however some texts use Lemuel Willman Wright to refer to the author of the same patents, and there are contemporary references to an American from Massachusetts, Lemuel William Wright, who...
in 1833.
Clerk cycle
In 1877 the Otto cycleOtto cycle
An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....
was patented, immediately recognized to have a significant practical value. Clerk quickly followed with his concept of a two stroke engine of 1880, that would not infringe the Otto's patent (being a four stroke engine).
Clerk describes a Cambell engine as using his cycle, as follows : "It has two cylinders, respectively pump and motor, driven from cranks placed at almost right angles to each other, the pump crank leading. The pump takes in a charge of gas and air, and the motor piston overruns a port in the side of the cylinder at the out-end of its stroke to discharge the exhaust gases. When the pressure in the motor cylinder has fallen to atmosphere, the pump forces its charge into the back cover of the motor cylinder through a check valve, displacing before it the products of combustion through an exhaust port ; the motor piston then returns, compressing the contents of the cylinder into the compression space. The charge is then fired and the piston performs its working stroke. This is the Clerk cycle."
The Clerk engine uses automatic 'poppet' type valves for inlet air and gas (one with spring assistance, one wthout), and a port in the cylinder uncovered by the piston for the exhaust valve. References to a Clerk engine with slide valve may refer to the earlier experiments with a Lenoir
Etienne Lenoir
-Sources:* Georgano, G.N. Cars: Early and Vintage 1886-1930. London: Grange-Universal, 1990 . ISBN 0-9509620-3-1....
type engine. The ignition is by carrying an external flame, using a modification of a method he developed in 1878.
Most engine designs that pre-dated the Otto engine (and Clerk engine), such as those of de Rivaz
De Rivaz engine
The de Rivaz engine was a pioneering reciprocating engine designed and developed from 1804 by the Franco-Swiss inventor Isaac de Rivaz. The engine has a claim to be the world's first internal combustion engine and contained some features of modern engines including spark ignition and the use of...
, the Niépce brothers
Pyréolophore
The Pyréolophore was probably the world's first internal combustion engine. It was invented in the early 19th century in Chalon-sur-Saône, France, by the Niépce brothers: Nicéphore Niépce and his brother Claude....
, Jean Joseph Etienne Lenoir, Samuel Morey
Samuel Morey
Samuel Morey was an American inventor, who worked on early internal combustion engines and was a pioneer in steamships who accumulated a total of 20 patents.-Early life:...
, and others, did use two stroke engines, which were "natural" in the times of steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
. Clerk's significant contribution was introducing Otto-styled compression to the two stroke engine, bringing its efficiency up-to-date (for the 1880s). Several manufacturers adopted the Clerk cycle in the short term, though commercial aspects such as patents on the 4-stroke cycle were part of this. Many years later the 2-stroke engine for large capacity diesels using a turbocharger
Turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
or supercharger
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
has become common, for example in ships and railway locomotives. With open crankshafts, and the advantages of higher power to weight ratio, these engines are closely aligned with Dugald Clerk's concepts, and the Clerk Cycle.
Pumping cylinder vs supercharger
Clerk's engine was made of two cylinders - one working cylinder and an additional cylinder to charge the cylinder, expelling the exhaust through a port uncovered by the piston. Some sources consider this additional cylinder the world's first superchargerSupercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
. Clerk himself states that "It is not a compressing
pump, and is not intended to compress before introduction into the motor, but merely to exercise force enough to pass the gases through the lift valve into the motor cylinder, and there displace the burnt gases, discharging them into the exhaust pipe." Hence sources recognise it instead as a "pumping cylinder", pointing out that it did not actually compress the fuel-air mixture, it simply moved the fresh mixture to the working cylinder to force out the gasses burnt previously.
Clerk's engine vs modern two-stroke engine
Clerk's original design did not allow the construction of smaller engines, as it required the aforementioned additional pumping cylinder for each working cylinder. The crucial simplification of the concept, that made possible small yet powerful two stroke engines for mass markets, was patented by Joseph DayJoseph Day
Joseph Day trained as an engineer at the School of Practical Engineering at Crystal Palace in London, began work at Stothert & Pitt in Bath, and in 1889 designed the two-stroke engine as it is widely-known today , the Valve-less Two-Stroke Engine...
in 1894.
- Joseph Day, design of a three-port two-stroke engine
- Nash, design of a two-port two-stroke engine
- Robson, design of a two-stroke engine with under-piston scavenge
- Fielding, design of a uniflow two-stroke engine