The ''Monosoupape'' (
French for single-valve), was a
rotary engine
The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and i ...
design first introduced in 1913 by
Gnome Engine Company
A gnome is a mythological creature and diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus in the 16th century and later adopted by more recent authors including those of modern fantasy literature. Its character ...
(renamed
Gnome et Rhône
Gnome et Rhône was a major French aircraft engine manufacturer. Between 1914 and 1918 they produced 25,000 of their 9-cylinder Delta and Le Rhône 110 hp (81 kW) rotary designs, while another 75,000 were produced by various licen ...
in 1915). It used a clever arrangement of internal
transfer port
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...
s and a single pushrod-operated exhaust valve to replace the many moving parts found on more conventional rotary engines, and made the ''Monosoupape'' engines some of the most reliable of the era. British aircraft designer
Thomas Sopwith
Sir Thomas Octave Murdoch Sopwith, CBE, Hon FRAeS (18 January 1888 – 27 January 1989) was an English aviation pioneer, businessman and yachtsman.
Early life
Sopwith was born in Kensington, London, on 18 January 1888. He was the eig ...
described the ''Monosoupape'' as "one of the greatest single advances in aviation".
Produced under license in both seven and nine-cylinder versions in large numbers in most industrialized countries including Germany (by
Oberursel
Oberursel (Taunus) () is a town in Germany and part of the Frankfurt Rhein-Main urban area. It is located to the north west of Frankfurt, in the Hochtaunuskreis county. It is the 13th largest town in Hesse. In 2011, the town hosted the 51st Hes ...
), Russia, Italy, Britain and the US. Two differing nine-cylinder versions were produced, the 9B-2 and 9N, with differing
displacements giving the larger displacement 9N version a nearly-cylindrical shaped crankcase, with the 9N also adopting a
dual ignition
Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark plugs and magnetos, are duplicated. Dual ignition is most commonly employed on aero engines,Crane, Dale: ''Dictionary of Aeronautical Terms ...
system for increased flight safety.
2,188 units were produced under license in Britain, with an uprated version later built in Russia and the Soviet Union, two of which flew the Soviet
TsAGI
The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, russian: Центра́льный аэрогидродинами́ческий институ́т, ЦАГИ, Tsentral'nyy Aerogidrodinamicheskiy Institut, ...
-1EA
single lift-rotor helicopter in 1931–32.
Background
Unlike other rotaries, the early Gnome engines like the
Gnome Omega
The Gnome 7 Omega (commonly called the Gnome 50 hp) is a French seven-cylinder, air-cooled aero engine produced by Gnome et Rhône. It was shown at the Paris Aero Salon held in December 1908 and was first flown in 1909. It was the world's ...
,
Lambda
Lambda (}, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed . Lambda gave rise ...
and
Delta
Delta commonly refers to:
* Delta (letter) (Δ or δ), a letter of the Greek alphabet
* River delta, at a river mouth
* D (NATO phonetic alphabet: "Delta")
* Delta Air Lines, US
* Delta variant of SARS-CoV-2 that causes COVID-19
Delta may also re ...
used a unique arrangement of valves in order to eliminate
pushrod
A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) ...
s that operated during the inlet phase of the combustion cycle on more conventional engines. Instead, a single exhaust valve on the
cylinder
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infin ...
head was operated by a pushrod that opened the valve when the pressure dropped at the end of the power stroke. A pressure-operated inlet valve, which was balanced by a counterweight to equalize the centrifugal forces, was placed in the centre of the piston crown, where it opened to allow the fuel–air charge to enter from the engine's central crankcase.
Although ingenious, the system had several drawbacks: the cylinder heads had to be removed to perform maintenance of the intake valves, and to adjust the timing correctly. Fuel economy suffered in comparison to other rotaries because the inlet valves could not be opened and closed at the ideal times.
Design
In 1913, Louis Seguin and his brother Laurent (engineers who founded the ''Société Des Moteurs Gnome''
he Gnome motor company
He or HE may refer to:
Language
* He (pronoun), an English pronoun
* He (kana), the romanization of the Japanese kana へ
* He (letter), the fifth letter of many Semitic alphabets
* He (Cyrillic), a letter of the Cyrillic script called ''He'' ...
in 1905) introduced the new ''Monosoupape'' series, which eliminated the inlet valve, replacing it with piston-controlled transfer ports similar to those found in a
two-stroke engine
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of t ...
. Beginning with the power stroke, the
four-stroke
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
engine operated normally until the piston was just about to reach the bottom of its stroke (bottom dead center, or BDC), when the exhaust valve was opened "early". This let the still-hot burnt combustion gases "pop" out of the engine while the piston was still moving down, relieving exhaust pressure and preventing exhaust gases from entering the crankcase. After a small additional amount of travel, the piston uncovered 36 small ports around the base of the cylinder, leading to the
crankcase
In a piston engine, the crankcase is the housing that surrounds the crankshaft. In most modern engines, the crankcase is integrated into the engine block.
Two-stroke engines typically use a crankcase-compression design, resulting in the fuel/a ...
which held additional fuel–air mixture (the ''charge''). No transfer took place at this point since there was no pressure differential; the cylinder was still open to the air and thus at ambient pressure. The overhead valve exhausted directly into the
slipstream
A slipstream is a region behind a moving object in which a wake of fluid (typically air or mustard) is moving at velocities comparable to that of the moving fluid, relative to the ambient fluid through which the object is churning. The term slip ...
since no
exhaust manifold
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' anyand ''feald'' old and refe ...
could be practically fitted to the spinning crankcase and cylinders. The lack of an exhaust manifold also saved weight and prevented excessive gyroscopic forces in flight.
During the exhaust stroke, scavenging occurred as the air moving past the cylinder exterior lowered the pressure inside due to the direct exposure of the exhaust port to the slipstream. The piston continued its exhaust stroke until
top dead center
In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC).
...
(TDC) was reached, but the valve remained open. The piston began to move down on its intake stroke with the valve still open, pulling new air into the cylinder. It remained open until it was two-thirds of the way down, at which point the valve closed and the remainder of the intake stroke greatly reduced the air pressure. When the piston uncovered the transfer ports again, the low pressure in the cylinder drew in the balance of the charge.
The charge was an overly rich mixture of air, which was acquired through the hollow
crankshaft
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
, and fuel that was continuously injected by a fuel nozzle on the end of a fuel line, entering the crankcase through the hollow crankshaft. The nozzle was in the proximity of, and aimed at, the inside base of the cylinder where the transfer ports were located. The fuel nozzle was stationary with the crankshaft, and the cylinders rotated into position in turn. The compression stroke was conventional.
The
spark plug
A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
was installed horizontally into the rear of the cylinder at the top but had no connecting high-voltage wire. An internal-tooth ring gear mounted on the engine drove a stationary
magneto
A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...
mounted on the firewall, whose high-voltage output terminal was in close proximity to the spark plug terminals as they passed by. This arrangement eliminated the need for
distributor
A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
and high-voltage wiring found in conventional
mechanically timed ignition systems. This ring gear also drove the oil pump, which supplied oil to all
bearings, and through hollow pushrods to the rockers and valves and also drove an air pump which pressurized the fuel tank. The later Gnome 9N engines had
dual ignition
Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark plugs and magnetos, are duplicated. Dual ignition is most commonly employed on aero engines,Crane, Dale: ''Dictionary of Aeronautical Terms ...
systems for safety, with twin spark plugs per cylinder which were electrically wired, with the wires routed onto the crankcase and a central pair of magnetos driven by the spinning engine crankcase.
Control
Monosoupapes therefore had a single petrol regulating control used for a limited degree of speed regulation. In early examples, engine speed could be controlled by varying the opening time and extent of the exhaust valves using levers acting on the valve tappet rollers, but this was later abandoned due to causing burning of the valves.
Instead, a blip switch was used, which cut out the ignition when pressed. This was used sparingly to avoid fouling the spark plugs, since it was only safe to be used when the fuel supply was also cut. The later 160 CV output 9N subtype also featured an unusual method of functioning with its integral dual-ignition setup, that allowed output values of one-half, one-quarter and one-eighth power levels to be achieved through use of the coupe-switch and a special five-position rotary switch that selected which of the trio of alternate power levels would be selected when the coupe-switch was depressed, allowing it to cut out all spark voltage to all nine cylinders, at evenly spaced intervals to achieve the multiple levels of power reduction. The airworthy reproduction Fokker D.VIII parasol monoplane fighter at Old Rhinebeck Aerodrome, uniquely powered with a Gnome 9N, often demonstrates the use of its Gnome 9N's four-level output capability in both ground runs and in flight.
Lubrication
![Sopwith Tabloid RAFM](https://upload.wikimedia.org/wikipedia/commons/8/80/Sopwith_Tabloid_RAFM.jpg)
The lubrication system, as with all rotary engines, was a total-loss type in which
castor oil
Castor oil is a vegetable oil pressed from castor beans.
It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about ...
was pumped into the fuel–air mix. Castor oil was used because it did not readily dissolve into the fuel, and because it offered lubrication qualities superior to other available oils. Over two gallons of castor oil were sprayed into the air during each hour of engine operation. This explains why most rotaries were fitted with cowls, with the lowermost quarter omitted to direct the spray of castor oil away from the pilot. Unburnt castor oil from the engine had a laxative effect on the pilot if ingested.
Because the entire engine rotated, it had to be precisely balanced, requiring precision machining of all parts. As a result, ''Monosoupapes'' were extremely expensive to build, the models costing $4,000 in 1916 (approx. $89,000 in 2017 dollars). However, they used less lubricating oil and weighed slightly less than the earlier two-valve engines.
Variants
;Gnome Monosoupape 7 Type A
:(1916) seven-cylinder rotary engine, .
Bore and
stroke
A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
: .
;Gnome Monosoupape 9 Type B-2
:(1916) nine-cylinder rotary engine, . Bore and stroke: .
;Gnome Monosoupape 11 Type C
:An 11 cylinder version
;Gnome Monosoupape 9 Type N
:(1917) nine-cylinder rotary engine, larger diameter crankcase than the B-2, 150 or 160 hp (112 or 119 kW), increasing capacity to . Bore and stroke: .
;Gnome Monosoupape 9 Type R
:180 hp nine-cylinder rotary engine, development of 9N with same stroke.
Applications
''List from Lumsden.''
Monosoupape 7 Type A
*
Avro 504
The Avro 504 was a First World War biplane aircraft made by the Avro aircraft company and under licence by others. Production during the war totalled 8,970 and continued for almost 20 years, making it the most-produced aircraft of any kind tha ...
*
Avro 511
*
Bristol-Coanda G.B.75
*
Sopwith Pup
The Sopwith Pup is a British single-seater biplane fighter aircraft built by the Sopwith Aviation Company. It entered service with the Royal Naval Air Service and the Royal Flying Corps in the autumn of 1916. With pleasant flying characteristi ...
Monosoupape 9 Type B
*
Avro 504
The Avro 504 was a First World War biplane aircraft made by the Avro aircraft company and under licence by others. Production during the war totalled 8,970 and continued for almost 20 years, making it the most-produced aircraft of any kind tha ...
*
Airco DH.2
*
Airco DH.5
The Airco DH.5 was a British First World War single-seat biplane fighter aircraft. It was designed and manufactured at British aviation company Airco. Development was led by aircraft designer Geoffrey de Havilland as a replacement for the obs ...
*
Blackburn Scout
*
Blackburn Twin Blackburn
The Blackburn TB (for "Twin Blackburn") was a long-range twin-engined anti-Zeppelin seaplane. It was Blackburn's first multi-engine aircraft to fly.
Design and development
The first attacks by German bombing airships on the United Kingdom in ...
*
Blackburn Triplane
*
Bristol-Coanda T.B.8
The Bristol T.B.8, or Bristol-Coanda T.B.8 was an early British biplane built by the Bristol Aeroplane Company and designed by the Romanian Henri Coandă. Fifty four Bristol T.B.8s were built, being mainly used as a trainer. A small number of B ...
*
Bristol Scout
The Bristol Scout was a single-seat rotary-engined biplane originally designed as a racing aircraft. Like similar fast, light aircraft of the period it was used by the RNAS and the RFC as a "scout", or fast reconnaissance type. It was one of t ...
*
FBA Type B
The FBA Type A and the similar Type B and C were a family of reconnaissance flying boats produced in France prior to and during World War I.
Development
All three were unequal-span pusher biplane flying boats with a single step hull with a ...
Flying boat
*
Nieuport IV
The Nieuport IV was a French-built sporting, training and reconnaissance monoplane of the early 1910s.
Design and development
Societe Anonyme des Etablissements Nieuport was formed in 1909 by Édouard Nieuport. The Nieuport IV was a developm ...
*
Royal Aircraft Factory B.E.8
The Royal Aircraft Factory B.E.8 was a British two-seat single-engined general purpose biplane of the First World War, designed by John Kenworthy at the Royal Aircraft Factory in 1913.Hare 1990, p. 171. Small numbers were used by the Royal Fly ...
*
Royal Aircraft Factory F.E.8
The Royal Aircraft Factory F.E.8 was a British single-seat fighter of the First World War designed at the Royal Aircraft Factory. It could not escape the drag penalty imposed by its tail structure and was no match for the Albatros fighters of ...
*
Short S.80
The Short S.80 was an early British floatplane built by Short Brothers for Frank McClean to undertake an aerial expedition up the Nile to investigate the cataracts between Aswan and Khartoum. After a successful flight to Khartoum it was returned ...
*
Short Type C
*
Sopwith Sociable
The Sopwith Sociable (or sometimes Churchill or TweenieRobertson 1970, p. 211.) was a British single-engined two-seat tractor configuration biplane designed and built by Sopwith for the Royal Naval Air Service.
Design and development
The Soc ...
*
Sopwith Type 807 Folder Seaplane
*
Sopwith Two-Seat Scout
*
Sopwith Schneider
The Sopwith Tabloid and Sopwith Schneider (floatplane) were British biplanes, originally designed as sports aircraft and later adapted for military use. They were among the first successful types to be built by the Sopwith Aviation Company. The ...
*
Sopwith Pup
The Sopwith Pup is a British single-seater biplane fighter aircraft built by the Sopwith Aviation Company. It entered service with the Royal Naval Air Service and the Royal Flying Corps in the autumn of 1916. With pleasant flying characteristi ...
*
Sopwith F.1 Camel
*
Vickers Gunbus
The Vickers F.B.5 (Fighting Biplane 5) (known as the "Gunbus") was a British two-seat pusher military biplane of the First World War. Armed with a single .303 in (7.7 mm) Lewis gun operated by the observer in the front of the ...
(FB.2, 3, 5, 6 and 7)
*
Vickers F.B.12
The Vickers F.B.12 was a biplane pusher fighter aircraft developed during World War I by Vickers Limited. The failure of the engine for which it was designed, and the obsolescence of the pusher configuration, resulted in its remaining an expe ...
*
Vickers F.B 19 Bullet
The Vickers F.B.19 was a British single-seat fighting scout of the First World War, developed from the Barnwell Bullet prototype, and sometimes known as the Vickers Bullet. It served with the Royal Flying Corps and the Imperial Russian Air ...
* helicopter (licence-built as M-2)
Monosoupape 9 Type N
*
Nieuport 28
The Nieuport 28 C.1, a French biplane fighter aircraft flown during World War I, was built by Nieuport and designed by Gustave Delage. Owing its lineage to the successful line of sesquiplane fighters that included the Nieuport 17, the Nieu ...
*
Sopwith Camel
The Sopwith Camel is a British First World War single-seat biplane fighter aircraft that was introduced on the Western Front in 1917. It was developed by the Sopwith Aviation Company as a successor to the Sopwith Pup and became one of the b ...
*
Morane-Saulnier AI
The Morane-Saulnier AI (also Type AI) was a French parasol-wing fighter aircraft produced by Morane-Saulnier during World War I.
Development and design
The AI was developed as a refinement of the Morane-Saulnier Type N concept, and was intended ...
*
Orenco B
Engines on display
* A nine-cylinder Monosoupape engine is on public display at the
Royal Air Force Museum London
The Royal Air Force Museum London (also commonly known as the RAF Museum) is located on the former Hendon Aerodrome. It includes five buildings and hangars showing the history of aviation and the Royal Air Force. It is part of the Royal Air Forc ...
.
* A nine-cylinder Monosoupape engine is on public display at the
Aerospace Museum of California
The Aerospace Museum of California is a private non-profit aviation museum located in North Highlands, California, outside of Sacramento, California, on the grounds of the former McClellan Air Force Base. The museum has a 4.5-acre outdoor Air Park ...
.
* A seven-cylinder Monosoupape engine is on display at
Solent Sky
Solent Sky is an aviation museum in Southampton, Hampshire, previously known as Southampton Hall of Aviation.
It depicts the history of aviation in Southampton, the Solent area and Hampshire. There is special focus on the Supermarine aircraft c ...
.
* One Monosoupape built by
Peter Hooker
Peter Hooker Limited owned an engineering business originally established in 1827 and carried on under the name Messrs Peter Hooker
*Peter Hooker (1817-1902) Printer's Engineer and inventor (Obituary, page 260, ''The British Printer'', vol. 15, Mac ...
- England is on display at the
Museo Nacional de Aeronáutica -
Morón,
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
. It is used during exhibitions to explain the rotary engines systems as it shows its operative internal parts.
* There is a restored B-2 Monosoupape on display at the
New England Air Museum
The New England Air Museum (NEAM) is an American aerospace museum located adjacent to Bradley International Airport in Windsor Locks, Connecticut. The museum consists of three display hangars with additional storage and restoration hangars. Its c ...
, Bradley Int'l Airport, Windsor Locks, CT, USA.
* TAVAS in Australia have two. http://www.tavas.com.au/rotary-engine.php Both for exhibition in flying aircraft.
* A restored Monosoupape 9 Type N is on display in the
Reynolds-Alberta Museum
The Reynolds-Alberta Museum is an agricultural, industrial, and transportation museum in Wetaskiwin, Alberta, Canada. The museum is situated on an property containing the main museum building, an aviation display hangar, and its storage facility. ...
.
* An original (unrestored) running nine-cylinder Monosoupape engine is on public display at the South Australian Aviation Museum in South Australia. A video of it running can be found at https://www.saam.org.au/engines.html
Specifications (Monosoupape 9 Type B-2)
See also
References
Citations
*
Bibliography
* Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. .
External links
Rattling of a Gnome engineGround run of a rare 100 hp ''Monosoupape'' in AustraliaYouTube video of 100 hp Gnome ''Monosoupape'' demonstrationModern reproduction Fokker D VIII powered with 160 hp Gnome MonosoupapeNew Zealand-built (21st century) reproduction Type 9B-2 100 hp Monosoupape runningClassic Aero Machining Service/CAMS Reproduction Gnôme Type 9B-2 ''Monosoupape'' reproduction engine development videoComputer video of how the 100 CV Type 9B-2 Monosooupape Goes Together
{{Aircraft piston engine components
1910s aircraft piston engines
Monosoupape
Rotary aircraft piston engines