Gallery opened Sept 2004 |   
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INTRODUCTION
For almost all its history, the preferred valve for the Internal Combustion engine has been the poppet type. (the etymology of the word "poppet" is an interesting study in itself, but a bit off-topic) There are good reasons for this; see the Appendix on the advantages of the poppet valve.
However, many inventors have been attracted by the apparent simplicity and the uniform motion of rotary valves of one kind or another. There is also the tempting prospect of being able to run on inferior fuels because there was no hot exhaust valve always present in the cylinder to trigger pre-ignition. However, as with both steam and IC rotary engines, the simplicity was more apparent than real, and the engineering problems were daunting.
The basic problem, is that the pressures in the cylinder of an internal combustion engine are high, due to both the compression stroke and the explosion of the fuel-air mixture. This produces large forces on the valve system, however it is contrived; the beauty of the poppet valve is that such forces simply push it harder against its seat, and have no effect at all on the valve-actuating mechanism.
However, the geometry of rotary valve systems is inherently different; in the Aspin concept below, the vertical valve cone is pushed up axially against the cylinder head, while the horizontal Cross valve is pressed up against the top half of the bearing surfaces. In both cases this can cause excessive friction and seizure, the root of the problem being that enormous forces are acting on the valve while it is moving.
There were a large number of rotary valve schemes tried, many of which are only known as patents, the practical success or otherwise being lost to history. The first US patents tracked down so far are by Frayer & Howard in 1907 and 1908. Another early patent was in 1911 by Vallillee (Patent 983328) who used a rotating disc. Several other versions by other people were patented later; see the patent list below. In Britain the two systems which gained the most attention were the Aspin vertical rotating valve and the Cross horizontal rotating valve.
Rotary valves were also tried in steam engines, without conspicuous success. See The Paget Locomotive and the Carel engine on the High-Speed Steam Engines page. Not only are rotary valves used in engine design, they have numerous applications including changing the pitch in brass instruments.
This page does not include what are usually called sleeve valves if they do not rotate continuously. The best known reciprocatng sleeve engines were on the Knight principle.
THE CROSSLEY ROTARY VALVE GAS ENGINE: 1886 - 1902
 | Left: Crossley gas engine with rotary valve.
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The tireless researchers of The Museum have obtained this unique personal account of a Crossley rotary valve engine in use in 1903:
"Although the engine was several years old, it would toil away hour after hour with an occasional application of ordinary cylinder oil to the rotor, oil probably of an inferior grade by modern standards. There is no doubt that the rotary feature was in many ways a most reliable device; that is to say, there was never a mechanical failure of any kind. On a few occasions the rotor would show signs of overheating, and in these circumstances all that was necessary to regain normal running was to remove the keep from the rotary member, clean the working surfaces with paraffin, and start up again with a fresh application of clean oil.
The keep is spring loaded and adjustable. The operation of adjusting the spring had to be most carefully carried out. The exact loading needed to be such that at maximum engine load, and when thoroughly warmed up, the valve was just on the point of spitting at each explosion. If the spring load was too light, the oil would be blown out each time the engine fired, and if too heavy, any extra expansion of the rotor due to increase in temperature resulted in so much additional friction that the ill-effects became cumulative and the engine would begin to lose speed. However, in spite of all this, the Crossley product was a practical engineering job, and there are many modern appliances which give far more trouble."
Testimony by Marcus Hunter, in 1946. This account refers to the vertical engine illustrated above; it was used for driving machine tools in a private workshop
The account above is highly revealing. It shows that the Crossley rotary valve engine required almost constant attention, ongoing and critical adjustment of the valve loading, and periodic dismantling.
 | Left: Inside the Crossley rotary valve.
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Since 1988 Crossley has been part of the Rolls-Royce Power Engineering group.
THE FRAYER & HOWARD ROTARY VALVE PATENT: 1907
 | Left: Frayer & Howard rotary valve patent: 1907
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 |  | Far left: Air-cooled engine with Frayer & Howard rotary valve: 1908
The rotary valve is mounted horizontally on top of the four cylinders and is driven through skew gears by the vertical shaft. According to the article, the valve rotated at one-quarter crankshaft speed. When the article appeared, it stated that preparations were being made for by the Ohio Manufacturing Company, and engines from 12 to 40 HP would be available in 60 days. From The Horseless Age for 1 April 1908 |
THE OWEN THOMAS ROTARY VALVE ENGINE: 1909
 | Left: The Owen Thomas engine: 1909
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ROTARY VALVES BECOME THE VOGUE
In the period 1910-1912 there was a remarkable flurry of activity in the field of rotary valves. Engines using them were unveiled by Itala, Castiglione-Bolton, and Darracq in Europe, and by Mead, Reynolds and The Silent Valve Company in the USA. Rotary valves had, to some extent, become the fashion. But they still did not work very well.
THE BALLOT ROTARY VALVE ENGINE: 1910
 | Left: The Ballot engine: 1910
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THE BERLIET ROTARY VALVE ENGINE: 1910
 | Left: The Berliet engine: 1910
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THE COTTEREAU ROTARY VALVE ENGINE: 1910
 | Left: The Cottereau engine: 1910
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THE HENRIOD ROTARY VALVE ENGINE: 1910
 | Left: The Henriod engine: 1910
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UNKNOWN ROTARY VALVE ENGINE: 1910
 | Left: Unknown rotary valve engine: 1910
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THE ROBERT ROTARY VALVE TWO-STROKE AERO ENGINE: 1911
 | Left: The Robert rotary valve 4-X two-stroke aero engine: 1911
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This engine is on display in the Smithsonian Museum.
THE VALLILLEE ROTARY VALVE PATENT: 1911
 | Left: The Vallillee rotary valve patent: 1911
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THE ITALA ROTARY VALVE: 1911
Itala was a car manufacturer based in Turin, Italy from 1904-1935. See Itala in Wikipedia. Water-cooled rotary valves were fitted to models announced at the 1911 Olympia Motor Car Show. At first only a 35 HP model was displayed, but 25 and 50 HP versions were said to be on the way.
 | Left: The Itala rotary valve : 1911
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Rankin Kennedy's "The Book of the Motor Car" published in 1913, had this to say:
"Now for the first time a high-speed multiple cylinder engine without reciprocating parts, is available in a throughly practical form, so well thought out in detail and so beautifully constructed that its possession and use cannot be less satisfactory to the fortunate owner than the contemplation of the design is to the engineering critic." which, quite frankly, is laying it on a bit thick. One can only assume that news of valve troubles had not reached Mr Kennedy before publication.
 | Left: Operating cycle of the Itala rotary valve: 1912
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From 1924 the Itala company was being run in receivership. It was bought by truck maker Officine Metallurgiche di Tortona in 1929, and a few more cars were produced, ending in 1935. After that, what was left of the Itala company was bought by Fiat.
THE TIPS ROTARY VALVE: 1911
Sometimes it seems as if the history of yet another rotary valve appears every day. Maurice A Tips and his younger brother Ernest Oscar Tips were pioneer Belgian aviators, building their first aircraft in 1909. It was not very satisfactory, and Maurice turned his attention to aero-engines.
 | Left: Tips rotary valve aero-engine: 1911
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Maurice Tips went on to design larger and more complex engines, but all had rotary valves similiar to this arrangement.
THE CASTIGLIONE-BOLTON ROTARY VALVE: 1912
This British rotary valve scheme was put foreward by Castiglione and Bolton. The valve was horizontal, running the length of the engine
 | Left: Castiglione-Bolton rotary valve engine: 1912
The valve had a complex system of inlet and exhaust porting, which connected to the cylinder via a single port in the top of the roughly hemispherical combustion chamber. The view at 7 is of a complete valve for two cylinders.
From the The Automobile Journal Volume 33. Number 7 May 10, 1912, page 46 |
The engine seems to have had little success, as the Castiglione-Bolton team is unknown to Google. It also seems to have escaped the notice of Hunter.
THE DARRACQ-HENRIOD ROTARY VALVE: 1912
The Darracq-Henrold rotary valve engine was a French design, from the well-known car firm of Darracq. According to one source "In 1912 the firm succumbed to the vogue for abolition of the poppet valve with a near disastrous range of rotary valved cars under Henriod patents." which sounds as if things didn't go too well, and also gives a hint as to why so many rotary valves appeared around 1912- it was "the vogue".
In 1912 Darracq produced "systéme Henriod" engines of 2613 cc and 15 HP (uprated to 2951 cc the next year) and a 3969cc version of 20 HP.They were described as Type SS, or 'sans soupapes', meaning without valves- not strictly true, of course. Hunter says, apparently acidly, "'Sans soupapes' is the term which the French give to every engine which has other than poppet-valves." These engines were also described as "completely gutless", presumably due to breathing difficulties, and were prone to seizure. Both profits and Darracq's reputation plummeted, and the debacle seems to have prompted Alexandre Darracq to retire from car manufacture; he sold his company to British financial interests in 1913. Apparently one 1912 SS car is still in existence, but in need of restoration. According to Hunter (p102) only a few engines actually reached customers, so for the effect on the company to be so drastic, their performance must have been truly awful.
The company survived and went on to prosper under British management. This gentleman owned both a rotary-valve Itala and a rotary-valve Darracq.
 | Left: A Darracq four-cylinder engine with rotary valve: 1912
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 | Left: The Darracq rotary valve: 1912
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 | Left: The Darracq rotary valve: 1912
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 | Left: The Darracq rotary valve: 1912
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 | Left: Darracq rotary valve car: 1912
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 | Left: Darracq rotary valve car: 1915
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Charles-Edouard Henriod (the younger brother of Fritz Henriod, who in 1886 made an experimental steam car, and a petrol car in 1893) was Swiss. In 1898 he began making motorcars in Paris. These had a horizontally-opposed air-cooled engine at the front, a three-speed gear system of bevel-gears and pinions, and final drive by side-chains. Over the years Henriod cars became more orthodox, but Charles-Eduoard could not resist the lure of the unconventional. When he stopped making motorcars he designed his rotary-valve system and patented it.
Another licencee of the Henriod patent was Fernand Charron who used it in his Alda cars. It was no more successful than it had been for Darracq. As the French seem wont to say when something is a complete disaster: "It did not give satisfaction."
THE REYNOLDS ROTARY VALVE: 1912
The Reynolds Motor Company was based in Detroit. It originally introduced a four-cylinder four-stroke engine with rotary valves, and following "extended tests in various makes of cars with splendid results" they produced the six-cylinder version seen here.
 | Left: Reynolds rotary valve engine: 1912
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 | Left: The four-cylinder Reynolds engine: 1911
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 | Left: The four-cylinder Reynolds engine: 1912
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 | Left: The four-cylinder Reynolds engine: 1911
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 | Left: The six-cylinder Reynolds engine: 1912
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 | Left: The six-cylinder Reynolds engine: 1912
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The big square box visible in the end-drawing above is labelled "force feed oiler", reinforcing the impression that lubrication was really, really important for these engines.
 | Left: Reynolds engine: 1912
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THE MEAD ROTARY VALVE: 1912
According to the Boston Evening Transcript of 8th March 1913, the Mead rotary valve was the result of seven years of experimental work by Cyrus W Mead, and represented nearly a quarter of a million dollars in expenditure.
 | Left: Mead rotary valve engine: 1912
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 | Left: Mead rotary valve engine: 1912
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 | Left: Mead rotary valve engine: 1912
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THE SILENT VALVE COMPANY: 1912
The Silent Valve Company was based in Connersville, Indiana. The Silent Valve engine was designed by Edwin L Russell, who worked on it for 10 years before achieving something like success. The 'Silent' bit refers to the fact that rotary valves had no tappets to rattle- a common source of noise in early engines.
 | Left: Silent Valve Company engine: 1912
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 | Left: Silent Valve Company engine: 1912
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 | Left: Silent Valve Company engine: 1912
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 | Left: Silent Valve Company engine: 1912
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 | Left: Silent Valve Company engine: 1912
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 | Left: Silent Valve Company engine: 1917
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No more is known about the success of this plan, but it seems very likely that the valves would be prone to seizing.
Google is silent on the Silent Valve Company.
THE CHARTER ROTARY VALVE: 1914
 | Left: Charter straight-eight engine with rotary valve: 1914
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 | Left: Charter rotary valve patent: 1929
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THE SHAW ROTARY VALVE: 1914
The Shaw Motor Company of Chicago exhibited this eight-cylinder rotary-valve engine at the Chicago motor show, reported by Horseless Age in January 1914.
 | Left: Shaw straight-eight engine with rotary valve: 1914
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Searching for the Shaw Motor Company has so far yielded nothing. Looking for patents revealed a James Shaw of Atchison, California, who was granted US patent 1,066,762 for a 'rotary valve' on 8 July 1913. California is a long way from Chicago but everything else looks right; enquiries are proceeding.
THE SPEEDWELL ROTARY SIX: 1915
According to Motor Age, by the end of 1914 the Speedwell was the only car on the American market with a rotary valve engine, and they were planning to keep it for the 1915 season. This sounds as though it must have been working reasonably well, though it might also have meant that the company was on the brink of bankruptcy and had no money to re-tool a bad design. It also implies that the Shaw rotary valve above did not last out the year.
 | Left: Speedwell in-line six engine: 1915
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 | Left: Operation of Speedwell valve
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 | Left: A Speedwell valve shaft
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The Speedwell Motor Car Company was based in Dayton, Ohio. It appears to have succumbed to the Great Dayton Flood rather than troubles with its rotary valves.
THE MUELLER & SCHULER ROTARY VALVE PATENT: 1914
 | Left: Mueller & Schuler rotary valve patent: 1914
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 | Left: Mueller & Schuler rotary valve patent: 1914
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A GRAPHITE ROTARY VALVE: 1917
This rotary valve system was described in the 1917 August-September issue of La Science et la Vie, a French journal that continues being published today. The article describes a vertical rotary valve made of pure graphite, which would be both resistant to heat and self-lubricating. Unfortunately the article gives no mention of who was putting forward this system, but research is in hand...
 | Left: Vertical rotary valve made of graphite: 1917
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THE GRI ROTARY VALVE: 1920
The Gri (named for its designer, George R Inshaw of Glasgow, 1888-1951) had a 3 HP four-stroke single cylinder which most unusually had a rotary valve and a poppet valve. The motorcycles were built from 1920 to 1922 and were distributed by the company Macrae and Dick of Inverness, Scotland.
 | Left: Hybrid rotary and poppet-valve engine: 1920
As The Motorcycle put it:
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 | Left: Hybrid rotary and poppet-valve engine: 1920
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THE CROSS ROTARY VALVE SYSTEM: 1920-1940
Roland Cross was undoubtedly the great British exponent of the horizontal rotary valve, and he appears to have got nearer to making it work properly than anyone else. Cross began his work on rotary valve engines in 1920. The project lapsed in 1945, squeezed out by the demand for components from his company for conventional aero-engines. He died in 1970.
 | Left: Roland C Cross looking quietly confident
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 | Left: Cross section of an early Cross rotary valve engine
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 | Left: The first Cross rotary valve engine: 1922
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 | Left: Rotary valves applied to a Rhodes car engine: circa 1925
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 | Left: Cross engine with solid rotary valve housing: circa 1930?
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Then came the most significant development. Roland Cross: "Towards the end of 1935 I tried the idea of splitting the valve housing along its horizontal centre-line, holding the top half with four long bolts to the crankcase and allowing the cylinder to float vertically. Under the influence of gas pressure in the cylinder, the valve was thus trapped between two halves of the valve housing. The effect of that modification was remarkable. These engines now had wonderful gase sealing, and the slow pulling rivalled that of the steam engine. Seizure was eliminated (which seems to indicate that seizure was not unknown with the earlier versions- DS) and the bearing metal for the valve was the same metal as that of the cylinder."
 | Left: Cross engine with split rotary valve housing: circa 1935
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 | Left: The Cross rotary valve: circa 1935
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 | Left: The cover of a booklet the Cross company published to publicise their rotary valve system. Date unknown, but some time after 1935
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 | Left: One of the inner pages of the booklet the Cross company published.
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Above: A contemporary display of Cross prototype engines and components at the Sammy Miller Museum in Hampshire
Photograph by Chris Pitt. Used with permission.
Cross evolved a process for the manufacture of high performance piston rings from wire for his rotary valve engine. I am glad to report that the company he founded to make these still exists. See the Cross Manufacturing Company, and look at "history" under the Overview tab. The Cross family continues to be deeply involved, with the third generation continuing the engineering tradition started by their grandfather, working alongside Rodney Cross, surviving son of the founder.
THE MINERVA ROTARY VALVE SYSTEM: 1925
This rotary valve was used by the Minerva Company, who made luxury motorcars in Belgium. There is some more information on the company here; (external link) it says they made Knight double-sleeve valve engines under licence, but strangely fails to mention rotary valves at all. The valve was invented by M. Bournonville, a Belgian engineer; after two years of development work Minerva believed they had an engine that could challenge the Knight sleeve-valve type, and which was of greater reliability than they had seen before. The Minerva-Bournonville rotary valve is mentioned in "Modern Aviation Engines" By Major Victor Page (Norman Henley Publishing Company) in 1929, so it was still live issue at that date.
According to Newton & Steeds:
"It has shown under severe test conditions remarkable reliability and freedom from any tendency to seize up or give trouble through scoring."
Reference: Automobile Engineering Vol XVII No228 1927-5
The rotating valve-block V ran horizontally across the top of the engine, and had ports R which allowed the inlet manifold I and the exhaust manifold E to communicate with the cylinder at the right time. Each valve-block V was pressed against its seating by two segmental saddles, on the top which bore a wedge W through two steel balls to ensure uniform distribution of the pressure; the spring-loading on W could be adjusted by screw and lock-nut S.
This is believed to be a drawing of a Minerva-Bournonville rotary valve engine. Confusingly it appears to have seven cylinders, but what looks like a connecting rod in the centre of the crankshaft is actually a structure supporting a central crankshaft bearing. Minerva made fours, sixes, and straight-eight engines.
For a six-cylinder engine two valve blocks were provided, each serving three cylinders. Because of the multiple ports spaced at 120 degrees, the valves only had to rotate at one-sixth engine speed, which must have reduced problems with wear. Drive was by a double roller chain from a gear-driven countershaft running at one third engine speed.
This shows the valve partially withdrawn from the cylinder block. The two saddles can be seen on top of the block.
Eugene Bournonville was a Belgian minig engineer who made his fortune by inventing the welding torch. Leaving Belgium for Hoboken, New Jersey, he took out a multitude of patents for his rotary valve. In the early 1920s he founded the Bournonville Motors Company, which built the Rotary car with a 5-litre 6-cylinder 60-hp rotary-valve engine.
The picture shows a four-cylinder prototype. It can just be discerned that there is something unusual about the top of the engine.
The relationship between the Bournonville Motors Company and the Minerva company is not currently clear. The Minerva company suffered in the financial crisis of the early 1930s. It was restructured as Société Nouvelle Minerva but in 1934 merged with the other major Belgian car-maker Imperia.
THE PEACEY ROTARY VALVE: 1926
The Reverend William Howell Peacey of Cheltenham was a remarkable man. Having built a successful steam car with a flash boiler and a 3-cylinder rotary-valve (of course!) single-acting steam engine under the floorboards, he went on to develop a rotary-valve IC engine. Although Peacey was a clergyman and not a trained engineer, this apparently worked well until the boiler blew up at a pressure of 1,750 PSI; flash boilers hold little water so all concerned survived. There are more details here.
The Peacy valve consisted of a vertical funnel-shaped rotor, with segments cut out to act as valve ports. It had some similarities to the later Aspin rotary valve. The valve was fitted to a Blackburne engine. After the WW1 Blackburne became a major supplier of engines to motor cycle manufacturers, including the Cotton company.
Peacey obtained US patent 1,709,036 in March 1926.
Source: “Cotton Pickins” the journal of the Cotton Owners & Enthusiasts Club, Sept 2020. Used by permission.
Oil was fed from the oil pump to the rotating valve spindle, which had a spiral groove on its lower part which pumped oil down between the valve cone and the cylinder head. The valvegear and its drivetrain were fully enclosed to prevent loss of oil.
Source: “Cotton Pickins” the journal of the Cotton Owners & Enthusiasts Club, Sept 2020. Used by permission.
The Peacey valve was driven by a pair of gears mounted in a flat case. The vertical shaft was driven from the crankshaft by a helical gear.
Source: “Cotton Pickins” the journal of the Cotton Owners & Enthusiasts Club, Sept 2020. Used by permission.
This shows the vertical shaft driven from the crankshaft by a helical gear. The transverse shaft comes out of the rectangular box at the top, which probably contained another pair of helical gears.
Source: “Cotton Pickins” the journal of the Cotton Owners & Enthusiasts Club, Sept 2020. Used by permission.
This shows the top of a Peacey valve engine, with the driving gear in the centre.
Summary of US patent 1,709,036 for the Peacey valve.
Peacey also did a rotary valve conversion of a Sunbeam engine, shown here, but this time the rotary valve was mounted at right-angles to the piston and the combustion chamber (which resembles 1/4 of an orange) is to one side of the head.
I am informed that "...it did thousands of miles on tests at the hands of Bob Peacey- we have his log books! The castings are of a very high standard for a one-off prototype."
Peacey seems to have had much better results than other rotary-valve exponents, and it is a question why his designs were not developed further.
Image kindly provided by the Cotton Owners & Enthusiasts Club.
THE SCHEEL ROTARY VALVE
The rotary valve head on this engine was invented by the American Herbert Scheel who at one time worked for Louis Chevrolet.The head had a horizontal valve with ports in it, very much like the Minerva valve just above. There is more information at the Museum Of American Speed website. Ford Model-A engine were used with the head replaced by the rotary valve version.
The cover on the left holds the chain drive to the horizontal valve. Its shape suggests that the two sprockets were the same size and the valve therefore rotated at crankshaft speed.
Here the horizontal valve is driven by a shaft and bevel gears; they are of equal size so this confirms that the valve rotated at crankshaft speed.
I hope the text in the ad is just about readable. "Greatly increased efficiency and economy" are just two of the claims.
THE ERNST ROTARY VALVE: 1940s?
I know it says don't reproduce, (thank you Dr Malthus) but the site gives no way to contact its owners, and indeed does not even tell you where Larchmont is.
But it is now confirmed the inventor was Otto Ernst, a dental surgeon from Larchmont, New York. He obtained the following patents for his invention (all with the same content): US1083812, CA152393, GB191321530, DE282325 and FR463107. They are all from the early 1910s, therefore contemporary with the Mead valve, which was installed in the Speedwell car. The springs visible on the top of the engine in the photograph are indeed part of the valve-sealing mechanism.
It may have been designed by a dentist, but this looks like a pretty workmanlike job to me.
There are clearly two rotary valves running horizontally across the top of the cylinder block, coupled with a pair of spur gears and driven from the crankshaft by the vertical chain. Looking at the sprocket sizes, it appears that the valves rotated at half crankshaft speed. The five pairs of springs visible on the top of the engine in the photograph are part of the valve-sealing mechanism. It seems unlikely this is five-cylinder engine; four is much more probable.
The other horizontal chain probably drove the water-pump and magneto.
THE ASPIN ROTARY VALVE SYSTEM: 1933-1977
Aspin's first experimental engine was a 250cc machine, based on a Rudge 250cc motorcycle engine. It was built in 1933. Aspin claimed that it produced 18 bhp at 7500 rpm, 31 bhp at 10,000 rpm, and was capable of a maximum speed of 14,000 rpm. It used a 14:1 compression ratio, implying great resistance to pre-ignition, given the low-octane petrol of the time, and this was ascribed to the absence of a hot exhaust poppet valve in the cylinder.
An Aspin modified Velocette 350cc engine was tested without much success by the Velocette factory in Birmingham in 1936.
By 1939 Aspin had decide it was necessary to liquid-cool the valve rotor to prevent distortion. This change did not greatly reduce the heating problems but it did require the spark-plug to be moved away from its central location, and it was placed at the side of the cylinder, placed so the rotating valve uncovered it at the right time for ignition. The valve rotor at this point was made of case-hardened nickel steel, rotating in an aluminium-bronze housing. Performance was once again claimed to be exceptionally good, but lubrication problems persisted, and the engine required careful warming up since heavy-footed use when cold would be certain to cause seizure of the valve rotor.
At some point Aspin tried a variable-speed drive to the rotor, ie changing speed during the combustion cycle but still in sync with the crankshaft; the idea being that the rotor would be moving relatively slowly during the high-friction parts of the cycle. It does not appear to have been a success, and would certainly have added complications to what is (in principle) a beautifully simple design.
In 1944 the magazine Autocar tested a family car with a four-cylinder Aspin engine.
In the 1960's an Aspin-converted 8.6 litre Leyland lorry engine was used to power a bus operated by The Northern Ireland bus company. At this point Aspin was using a lead-beryllium coating on the rotors to reduce friction. The bus ran successfully for an unknown period, recorded only as "many thousands of miles" until oil consumption abruptly climbed as the special coating on the valve rotors wore off. No further testing was done so the results cannot have been too impressive.
Aspin developed his rotary valve concept over more than thirty years, and there is not space here to trace the detailed evolution of his ideas. In essence, Aspin could build an engine with high oil consumption and good reliability, or with normal oil use but having a distressing tendency for the rotary valves to seize up solid. He never resolved this problem, and many others also failed.
Aspin's last rotary valve patent was taken out in 1977 (US 4033317) and I believe he died shortly afterwards.
There is a very fine site on the Aspin valve and its engines here.
THE FROEDE ROTARY VALVE: 1950s.
The detailed design of the rotary valve was done by Felix Wankel, building on his valve designs for the Daimler-Benz’s DB601, a 33.4-liter V-12 for military aircraft, and later the Junkers KM8 torpedo engine. The engine is tilted over to the left, and the piston is shown at TDC. The rotary valve was driven at a constant 1/4 of crankshaft speed. Although initially successful in racing, it was not repeated, probably due to the demise of NSU.
In 1936 Felix Wankel joined the Deutschen Versuchsanstalt Für Luftfahrt (German Experimental Institute for Aviation), designing rotary valves for Daimler-Benz’s DB601, a 33.4-liter (2,020 cu. in.) V-12 aeroengine, and later the Junkers KM8 torpedo engine. See the next section for more on Wankel and rotary valves.
Later NSU introduced the famous Wankel rotary IC engine, but its poor reliability and short service life finished off the company and NSU was absorbed by Audi.
FELIX WANKEL AND ROTARY VALVES: 1935-1950s.
Felix Wankel, the originator of the famous rotary engine, was involved from 1930 to 1945 in the development of a rotary disc valves for use in aircraft and torpedo engines. His primary expertise was in the difficult business of sealing. During this time he worked at BMW, DVL, Daimler-Benz, Lilienthal and Junker Aircraft.
Various sources state that he was involved in developing the "Daimler-Benz DB601 V-12 rotary disk valve aircraft engine" but other sources say that this engine had four conventional poppet valves. This mystery currently remains unresolved. He certainly worked on the Junkers Jumo KM8 torpedo engine, which had to fit into a cylindrical casing that had no room for conventional valvegear. The short working life of a torpedo engine meant that rapid wear of the rotary valve disc was not an issue.
The disc valve is visible on the right side of the engine, just above the piston.
The KM8 engine had eight liquid-cooled cylinders of 90mm bore by 85mm, stroke arranged as a V-8 with a 90deg angle. The total swept volume was 4.34 litres and the compression ratio was 6.6 to 1. Output was 275 HP at 3650 rpm. It ran on a mixture of petrol, oxygen, and its own exhaust gas- the latter presumably to dilute the oxygen to a manageable content.
There is more info on the KM8 engine here. It was a`Closed Cycle' (Kreislauf cucle) engine using petrol and oxygen diluted with exhaust gas for propulsion of submarines and torpedoes; the exhaust was cooled by sea-water before mixing with the petrol and oxygen. When pressure built up in the system some of the gas was released through a relief valve.
A production order for 100 engines was issued towards the end of WW2 but was never completed. A prototype was examined by British and American intelligence engineers, who concluded it was "a progressive trend in automotive development." It would appear they were wrong.
The disc valves are fitted between upper and lower cylinder heads. They had teeth on their periphery, and formed two gear trains without the need for idlers or extra gearwheels. The train of valve discs was driven by bevel gears from the crankshaft, with splined connections to allow valve timing to be altered.
In 1951 NSU became interested in Wankel's rotary engine project, and he joined them. It seems very likely he was involved in the design of the Froede rotary valve shown above.
THE MELLORS ROTARY VALVE SYSTEM: 1940s.
The Mellors rotary valve system had two conical valves, one for inlet and one for exhaust. They moved not continuously but in 90-degree steps, driven by a maltese-cross mechanism. When stationary the valves were pressed against their housing by helical springs and so were cooled. Just before each movement they were lifted a few thou from their seatings by a face cam. The valve was thus able to turn freely, and then was released back to its rest position when it stopped.
It appears that the valve drive shaft at the bottom of this picture rotates once per cycle, ie at half crankshaft speed. The maltese cross mechanism would have been subjected to some severe accelerations, and I am not too sure how well this would have worked at high rpm.
Note the hinged sections and the two little levers at the top. This may have been a method of applying sealing forces to the valves, but I suspect it might have been a misinterpretation of the two levers that lifted the valves when they were due to turn.
Ted Ambrose Mellors was an international motor cycle racer; he became European Champion in 1938. He designed and patented his rotary valve system in the early 1940's, during WW2. See Patent 559830, March 1944.
He died in 1946:
see Ted Mellors Biographical Notes (External site)
The two bolted-down covers on the side of the cylinder head show the valve locations.
A close-up of the maltese-cross mechanism. The two maltese crosses marked A are driven by pins on opposite sides of the central disc B.
THE NORTON ROTARY VALVE ENGINE: 1950s
The Manx engine was based on a square-500 design. The cylindrical valve at the top is driven by bevel gears from a vertical shaft, which is driven from another vertical shaft via two small pinions. The second vertical shaft is driven by bevel gears from the crankshaft. The mystery of why two vertical shafts were used has been solved by Jean-François Depau, who points out that in his book "Built For Speed", John Griffith writes: "As the head is wider than that of a "Manx" unit, the vertical shaft of the bevel drive had to be stepped out to reach the end of the rotor. A virtue was made of this necessity by installing a gear-type oil pump at the "step", so that the drive went in on one shaft of the pump and out on the other."
This book was published by Temple Press, second impression in 1965. John Griffith was a journalist in the 1950's, writing for Motor Cycling magazine. His specialty was road testing the motorcycles of the day, but he had a special interest in historic racing motorcycles.
The Manx engine began its life with a 35 BHP output, which was developed to 47 BHP. There were problems with valve seizure due to uneven expansion of the head assembly. In 1954 Norton policy towards racing changed and the project was shelved.
The bearing for the vertical drive shaft can be seen at top right.
THE DUNSTAN ROTARY VALVE: 1957
The Dunstan rotary valve was introduced by South Australian engineer David Dunstan in 1957. It was a horizontal valve running across the tops of the cylinder-heads, and was applied to a Holden grey six-cylinder engine, which in unmodified form gave only 60hp at 3800rpm, from its 2163 cc.
This picture shows the top of the valve housing.
This shows the parts used to modify the standard engine. The rotary valve lies across the page in the upper half of the picture.
David Dunstan displays the parts of his rotary valve. The valve itself is bottom right; it looks like a substantial piece of metal.
The machine with dials next to him is probably a dynamometer for engine-testing.
Dunstan died in 1958 and interest in the idea appears to have then faded.
THE ZIMMERMAN ROTARY VALVE: 1959
In the mid-fifties Merritt Zimmerman developed a horizontal valve, that in 1959 was applied to a 250cc V-twin engine that reliably produced 39.5 bhp at 9000 rpm, giving
158 bhp/litre, rather impressive at a time when poppet valve engines struggled to reach 100 bhp/litre. The engine was installed in a motorcycle that raced regularly in US enduros and scrambles. Zimmerman took out two patents on the valve but resisted efforts to persuade him to the engine for production, for reasons currently unknow.
The diagram is taken from Zimmerman's first patent and is a section through a four-cylinder engine. The horizontal rotary valve 52 was rotated by skew helical gears on a a horizontal shaft 108 running the length of the engine, which was driven from the crankshaft by what appears to be a toothed belt. (Toothed belts were first used in a car engine in 1954, so no anachronism here) This shaft ran at crankshaft speed. The item 38 is the oil filler pipe.
Zimmerman's 1972 patent runs to 21 pages and I'm not going to pretend I've read it all yet. In short, what Zimmerman claimed was a lubrication metering system that adapted itself to the load on the engine, and some form of self-adjustment in the valve so it would fit properly with low friction at various temperatures. Judging by the results, these ideas were effective.
Zimmerman also took out US patent 5,052,349 in 1991 so clearly his work on rotary valves was no passing interest.
Thanks to the Cotton Owners & Enthusiasts Club for drawing this valve to my attention.
Source: US patent 3,871,340 of 1972.
THE ALPHA ROTARY VALVE ENGINE: 1962
It is heartening to report that Alpha Bearings are still very much in business.
THE QUEENS UNIVERSITY BELFAST (QUB) ROTARY VALVE: 1967
The QUB 250cc twin cylinder two-stroke rotary valve engine was devised by Gordon Blair, M Johnston and others at Queens University Belfast in June 1967.
The inlet valve was cylindrical, admitting the charge to the underneath of the piston, from where it was transferred to the top of the piston and ignited; there were conventional exhaust ports. The valve was therefore not exposed to high pressure on the power stroke.
A 250cc water cooled twin cylinder engine with the new valve was designed and built from scratch, and first road tested on a motorcycle in 1969.
Dynamometer tests showed a very steep power increase above 9000 rpm with an abrupt drop above 11000 rpm. Maximum power was 45 BHP.
This drawing gives details of the rotary inlet valve.
The motorcycle was raced twice in 1969, but failed both times due to small-end bearing failure.
More information can be found at the Yorkshire Ferret,
Thanks to Paul Burke for bringing this engine to my attention.
THE DEANE ROTARY VALVE: 1971
The Deane spherical valve was devised by William Ronald Deane, Harry Bishop and Charles Beard of Victoria, Australia.
The Deane Rotary valve used a spherical steel rotor fitted with piston-style sealing rings. It turned at one-quarter crankshaft speed in the cylinder head.
Despite considerable publicity, the project was unable to attract financial backing.
Deane was issued US patent 3,730,161 filed 28 May 1971
THE ESSO-CROSS ROTARY VALVE ENGINE: 1975
The Esso-Cross rotary valve engine was a joint project between Esso and the Cross Manufacturing Company of Bath. This was after the death of Roland Cross in 1970. Its two radical feature were the rotary valves and an eccentric crank system much the same as that patented by Charles Parsons (of turbine fame) for his epicyclic steam engine in 1877.
The stated engine capacity was 1606 cc (98 cu in) from which it was hope to ultimately get 145 HP. The compression ratio was a high 10.5:1, designed to exploit the absence of exhaust-valve hotspots given by the Cross rotary valves.
The same reaction-bridge arrangement invented by Roland Cross around 1935 was used to control the loading on the rotary valves.
This arrangement eliminates the connecting rods of a conventional engine. It was also supposed to reduce the number of heavily-loaded bearings from 13 to 5, and eliminate side-forces on the pistons.
How it moved.
Animation by Bill Todd. Another stunning bit of work.
The convoluted path of the chain drive for the four rotary valves can be seen. I think there are two separate chains, each driving two valves.
At the time of the Popular Science report in July 1975 the engine was said to have run for 75 hours at the Esso Research Centre in Abingdon, developing 69 HP at 5500 rpm. Quite a long way short of the hoped-for 145 HP.
It is absolutely usual for wildly optimistic claims to be made for new IC engine concepts. One of many is that the new engine will be able to successfully run on low-octane fuel using a high compression-ratio. Given the earlier successes of the Cross rotary, this claim seems more plausible here than is usually the case. Strangely, this intriguing project appears to have dropped completely out of sight, despite the claim by Stephen Baker (an Esso research engineer working on the project) that it had aroused "considerable commercial interest". The Popular Science article of 1975 is the only reference known to Google.
THE LOTUS ROTARY VALVE TWO-STROKE ENGINE: 1991.
This two-stroke engine was of the "uniflow" type, with exhaust ports uncovered as the piston moves down.
Because there is no dedicated exhaust stroke, scavenge air is blown in to clear the exhaust gases out of the cylinder by an external compressor, and then the fuel/air mixture is admitted.
The rotary bearing was of the Cross or horizontal type, rotated by a toothed belt at crankshaft speed as this is a two-stroke. By rotating the stator inside the valve, the inlet timing and the relative duration of scavenge air and mixture admission phases could be altered.
It was commented at the time that the uniflow operation should avoid the overheating and lubrication problems of other rotary valves which handled exhaust gases as well as induction. However, as far as I can see the rotary valve here is still subjected to the full combustion pressures, and I wonder how this was tackled.
When the Lotus project was reported in the press, it was said to be in "the early stages" of development, and no performance figures were given. I can find no further reference to it anywhere, and it is far from certain that even a prototype engine was built.
Interest in two-stroke engines fell away as emission standards became tighter in the 1990's.
UNIDENTIFIED ROTARY VALVE ENGINE: 19??
We would be very glad if someone could indentify it or provide any information at all.
The valve cover on top and the camshaft drive cover at the right do not seem to match the rest of the engine. This is likely to be an experimental conversion.
There appears to be a standard inlet/exhaust manifold arrangement, except that the upper flange (presumed to be the inlet) seems to have too small an aperture for normal operation. The upper dual pipe is probably the inlet for water-cooling.
The general opinion of my correspondents is that the lower 'pipe' on the side of the crankcase is an engine mounting.
The engine from the other side, showing four spark plugs, the one on the right being broken.
The pipe between the spark plugs is probably the outlet for water-cooling. The lower 'pipe' is probably the corresponding engine mounting.
The camshaft drive cover shows a chain drive inside, though puzzlingly this does not extend up to the camshaft. There is presumably a second chain drive inside that is not visible.
The drive cover appears to have been once fitted with with a celluloid window to allow observation of the working parts, but only the edges of it remain.
THE COATES ROTARY VALVE SYSTEM
Here is apparently a contemporary development: The Coates Spherical Rotary Valve System; one of the Coates patents is in the table below. Judging by the website alone, they seem to be serious about what they're doing.
The Coates website claims that the use of this valve "has permitted elimination of both oil lubrication and cooling water flow in the upper portion of the cylinder head." which seems somewhat out of line with the experiences of Aspin and Cross. It is probably significant that the Coates valve, which, if the website is to be believed works, is horizontal like that of Cross rather than vertical like the less successful Aspin.
But... it seems it was a scam. If you read through this rather long document (Thanks to Will Poundstone for providing that link) it emerges that there were a whole load of financial shenanigans and Mr Coates ended up in jail when he was arrested for mail fraud. However, there were certainly prototypes built, which were tested by Harley-Davidson. In November 1991, Harley notified Coates that it was discontinuing testing of the Coates prototype engines because of mechanical durability problems; no surprise there. Coates also lied about his engines meeting EPA emissions standards.
The Coates website still exists and was apparently updated in 2022.
OTHER ROTARY VALVE SYSTEMS
These are rotary valves about which little is known.
The Brown rotary valve was developed by J & E Brown of Wednesbury, Staffordshire. It first appeared in 1938, fitted to a modified 490cc Norton motorcycle. It emerged again after WW2, and was highly praised in The Motor Cycle for Oct 16, 1947. A conversion kit for overhead cam Nortons was planned but apparently never appeared, and the Brown Valve faded from view.
John Anelay introduced a spherical rotary valve system in 1955. So far no more information has been found on this.
The Museum of American Speed located in Lincoln, Nebraska, has two rotary-valve engines on display; a Reynolds and a Scheel rotary valve head.
The Crosley Rotary-Valve Midget engine.Crosley was a USA manufacturer of sub-compact cars and should not be confused with Crossley.
A Ford Model-A conversion by Scheel Motors Corp.
ROTARY VALVE SYSTEMS NOW
A contemporary concept is the PatRoVa rotary valve. Like the Cross design it balances out the forces acting on the rotating valve.
From 2002 to 2004 the Australian developer Bishop Innovation and Mercedes-Ilmor were testing a Formula-1 V10 engine with rotary valves. Bishop Innovations' patent for the rotary valve engine was bought by BRV Pty Ltd, owned by Tony Wallis, one of the valves original designers. There are some biographical info on Tony Wallis here.
The technology uses a horizontal valve on top of the cylinder and is very similar to the Cross rotary valve above, one of the few that had some success. It is not at present clear what was new and patentable.
From European patent EP 1,792,058 B1 granted 29 Dec 2010. See also US patent 7,584,741 Sept 2009.
It is clear that we have not yet heard the last of rotary valves in IC engines.
ROTATING CYLINDER ENGINES
One advantage claimed is that the absence of a hot exhaust valve in the cylinder gives greater freedom from detonation, allowing the engine to be run on kerosene (JP8) with a high compression ratio and hence good efficiency.
The version shown here is for model aeroplane propulsion. The cylinder (green) is geared to the crankshaft through bevel gears (purple) carrying a valve port around with it. The propellor is fastened to the head of the cylinder, and this axial format gives a small cross-sectional area and consequently reduced aerodynamic drag. Note that the finned cylinder jacket and the exhaust system do not rotate.
The concept is being extended to one-cylinder engines for scooters, mopeds and motorcycles. For more info see RCV Engines.
ROTARY VALVE PATENTS.
Here is a small and so far very incomplete list of rotary valve patents in the USA. Dates are when the patent was granted.
Left: The Minerva-Bournonville rotary valve
From The Motor Vehicle by Newton & Steeds, pub Iliffe, date unknown but certainly post-1921, p71
Left: The Minerva-Bournonville engine
The Japan Society of Mechanical Engineers
Left: The Minerva-Bournonville valve
The Japan Society of Mechanical Engineers
Left: Prototype Rotary car with Bournonville valve engine
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Peacey rotary valve: 1926
Left: The Scheel rotary valve: 1928
Left: The Scheel US patent, granted 1928
Left: Scheel advert: date unknown
This rotary valve engine was apparently invented by Dr Ernst, (floreat 1900-1950?) a Larchmont dentist who lived at 149 Beach Avenue. The invention was found on the website of the Larchmont Historical Society.
Left: The Ernst rotary valve engine: date is guesswork
This rotary valve concept by Frank Aspin has a conical vertical valve rotating above the cylinder. The Aspin is probably the best-known rotary valve after the Cross, but it seems to have suffered significantly more technical difficulties.
Left: One version of the Aspin rotary valve. Note the conical thrust bearing C, intended to absorb the upward thrust of high pressures in the cylinder. This version has no rotor cooling.
All these figures were startlingly high for the engine technology of the time, and it appears that they were greeted with some disbelief. A recurring theme in the Aspin story is impressive claims for performance, without backing from independent testing.
Walter Froede was the head of the German company NSU's motorcycle racing program; at the time, NSU was the largest builder of motorcycles in the world.
Left: Froede rotary valve in a 125cc racing motorcycle engine. Valve rotor coloured pink.
Left: Froede rotary valve in a 250cc racing motorcycle engine: 1956
Left: Cross-section of a Junkers Jumo KM8 disc-valve engine, enclosed in its torpedo casing.
Above: Longitudinal section through one cylinder bank of a Junkers Jumo KM8 disc-valve engine.
Left: The Mellors maltese-cross valve drive system.
The use of the maltese-cross or Geneva mechanism was first suggested by Mueller in a 1914 rotary valve patent.
Left: The Mellors valves in cross-section.
Left: The Mellors rotary valve system fitted to a 250cc New Imperial engine.
Left: Mellors' prototype rotary valve engine today.
Image kindly provided by John Wood.
Joe Craig, Norton development engineer, spent two and a half years working on a horizontal rotary valve proposed by Laurie Bond. (The originator of the Bond three-wheeler) The valve design closely followed Cross technology.
There were the usual problems with lubrication, sealing, and plug fouling, and the resulting engine, called the Manx, (a reference to TT racing) was less powerful than the standard version. Definitely not a success.
Left: The Norton Rotary cylinder head fitted to a Manx Norton motorcycle engine
Image kindly provided by John Wood.
Left: The Norton Rotary cylinder head seen from the underneath
Image kindly provided by John Wood.
Left: The Dunstan rotary valve
Image from Wheels 1957
Left: The Dunstan rotary valve
Image from Wheels 1957
Left: The Dunstan rotary valve
Image from Wheels 1957
Left: The Zimmerman rotary valve: 1959
Assigned to Tetrahedron Associates Incorporated.
In the early Sixties, Alpha Bearings of Dudley in the West Midlands produced an engine in which the flywheel acted as a rotary valve. All I know about it comes from the very informative website here so I will send you straight there.
Left: The The QUB two-stroke rotary valve engine: 1967
Left: The The QUB two-stroke rotary valve engine: 1967
Left: The Deane spherical rotary valve: how it works
Left: The Esso-Cross rotary valve engine from the exhaust side
Popular Science July 1975
Left: The Esso-Cross eccentric crank system for the rotary valve engine
Popular Science July 1975
Left: The Esso-Cross rotary valve engine
Left: The Esso-Cross rotary valve engine from the induction side. Each stub pipe leads to the centre of a rotary valve, and had an SU carburettor attached
Popular Science July 1975
In the early 1990's several manufacturers were investigating supercharged two-stroke engines as the way forward. Since a two-stroke has one firing stroke per crankshaft revolution as opposed to one every other revolution, the power-to-weight ratio is potentially much better. The engineering challenges involved in making an engine that can compete with the conventional four-stroke are, however, severe.
Left: The Lotus two-stroke Rotary valve project: 1991
Left: End view of the Lotus two-stroke Rotary valve.
Photographs of this four-cylinder rotary valve engine were sent to me by David Ziegler, a researcher for the Smith Collection, of The Museum of American Speed located in Lincoln, Nebraska.
Left: Unidentified rotary valve engine
Left: Unidentified rotary valve engine
Left: Unidentified rotary valve engine
Left: Coates rotary valve engine
Rotary valve systems have not disappeared; it seems that nothing technological ever does.
Left: Bishop Innovation rotary valve: from the patent
A related technology is the rotating-cylinder-valve engine, in which not just a valve assembly, but the whole cylinder rotates. This has been introduced for 4-stroke operation by RCV Engines Ltd, a UK-based company.
Left: Cross-section of an RCV model engine.
Some British rotary valve patents. (not a complete list) Dates are when the patent was granted.
Patent No
Date
Name
Valve type
136 334
Dec 1919
Musures
Horizontal rotary valve
151 994
Apr 1922
Tebaldi
Horizontal rotary valve
158 269
Jan 1921
Dennison
Horizontal rotary valve
168 841
Sept 1921
Francis
Horizontal rotary valve
171 822
Dec 1921
Stoner
Vertical rotary valve
173 877
Jan 1922
Acher
Horizontal rotary valve
.
246 687
Feb 1926
Cross
Horizontal rotary valve
The first Cross patent
259 400
Oct 1926
Cross
Horizontal rotary valve
268 937
April 1927
Peacey
Vertical rotary valve
373 660
June 1932
Cross
Horizontal
408 756
April 1934
Cross
Horizontal
411 010
May 1934
Cross
Horizontal
448 368
June 1936
Cross
Horizontal rotary valve
463 412
Mar 1937
Aspin
Vertical rotary valve
The first Aspin patent
559 830
Mar 1944
Mellors
Horizontal
570 286
Jun 1945
Aspin
Vertical
570 354
July 1945
Aspin
Vertical
.
872 216
July 1961
Aspin
Vertical
Patent No
Date
Name
Valve type
908 656
Sept 1907
Frayer & Howard
Horizontal transverse
908 657
Aug 1908
Frayer
Explosive engine
921 264
May 1909
Mead
Horizontal longitudinal
924 382
June 1909
Reynolds
Vertical rotary valve
983 328
Feb 1911
Vallillee
Vertical
1 007 040
Oct 1911
Mead
Horizontal longitudinal
1 154 647
Sept 1915
Mead
Horizontal longitudinal
1 098 679
1914
Mueller
Vertical
1 159 482
1915
English
Vertical
1 427 726
Aug 1922
Echard
Vertical rotary valve
1 539 041
May 1925
Crawford
Vertical rotary valve
1 718 755
June 1929
Charter
Gas engine
2 129 024
Sept 1938
Reynolds
Horizontal longitudinal
2 283 594
May 1942
Aspin
Vertical rotary valve
As British patent 463 412
Some more recent US patents:
4 008 694
Feb 1977
Monn
Horizontal rotary valve
4 404 934
Sep 1983
Asaka et al
Horizontal rotary valve
4 658 776
Apr 1987
Coman
4 773 364
Sep 1988
Hansen
Vertical rotary valve
4 788 945
Dec 1988
Negre
4 852 532
Aug 1989
Bishop
Horizontal rotary valve
4 944 261
Jul 1990
Coates
Horizontal rotary valve
5 000 136
Mar 1991
Hansen
Vertical rotary valve
5 052 349
Oct 1991
Buelna
5 490 485
Feb 1996