Axial engine
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Axial engines (sometimes known as barrel or Z-crank engines) are a type of
reciprocating engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
with pistons arranged around an output shaft with their axes parallel to the shaft. Barrel refers to the cylindrical shape of the cylinder group (result of the pistons being spaced evenly around the central crankshaft and aligned parallel to the crankshaft axis) whilst the Z-crank alludes to the shape of the crankshaft. The key advantage of the axial design is that the cylinders are arranged in parallel around the output/crank shaft in contrast to radial and inline engines, both types having cylinders at right angles to the shaft. As a result, it is a very compact, cylindrical engine, allowing variation in
compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...
of the engine while running. In a swashplate engine the piston rods stay parallel with the shaft, and piston side-forces that cause excessive wear can be eliminated almost completely. The small-end bearing of a traditional connecting rod, one of the most problematic bearings in a traditional engine, is eliminated. An alternative design, the Rand
cam engine A cam engine is a reciprocating engine where, instead of the conventional crankshaft, the pistons deliver their force to a cam that is then caused to rotate. The output work of the engine is driven by this cam. Cam engines are deeply rooted in his ...
, replaces the plate with one or more
sinusoidal A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in m ...
cam surfaces. Vanes mounted parallel to a shaft mounted inside a cylindrical 'barrel' that are free to sliding up and down ride the sinuous cam, the segments formed by rotor, stator walls and vanes constituting combustion chambers. In effect these spaces serving the same purpose as the cylinders of an axial engine, and the sinuous cam surface acts as the face of the pistons. In other respect this form follows the normal cycles of internal combustion but with burning gas directly imparting a force on the cam surface, translated into a rotational force by timing one or more detonations. This design eliminates the multiple reciprocal pistons, ball joints and swash plate of a conventional 'barrel' engine but crucially depends on effective sealing provided by sliding and rotating surface

In either form the axial or 'barrel' engine can be derived as a
cam engine A cam engine is a reciprocating engine where, instead of the conventional crankshaft, the pistons deliver their force to a cam that is then caused to rotate. The output work of the engine is driven by this cam. Cam engines are deeply rooted in his ...
or Cam engine#Swashplate engine, swashplate or wobble plate engine. (A wobble-plate is similar to a
swash plate A swashplate, also known as slant disk, was invented by Anthony Michell in 1917. It is a mechanical engineering device used to translate the motion of a rotating shaft into reciprocating motion, or vice versa. The working principle is similar to c ...
, in that the pistons press down on the plate in sequence, imparting a lateral moment that is translated into rotary motion. This motion can be simulated by placing a compact disc on a
ball bearing A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...
at its centre and pressing down at progressive places around its circumference. The difference is that while a wobble plate nutates, a swash-plate rotates.) While axial engines are challenging to make practicable at typical engine operating speeds some cam engines have been tested that offer extremely compact size (approximating to a six-inch (150mm) cube) yet producing approximately forty horsepower at c 7000 rpm, useful for light aerial applications. The attraction of lightweight and mechanically simple (far fewer major moving parts, in the form of a rotor plus twelve axial vanes forming twenty-four combustion chambers) engines, even with a finite working life, have obvious application for small unmanned aircraft. (Such a design havin
allegedly been tested
at NAVAIR PSEF in 2003.)


History


Macomber

In 1911 the Macomber Rotary Engine Company of Los Angeles marketed one of the first axial internal-combustion engines, manufactured by the Avis Engine Company of
Allston, Massachusetts Allston is an officially recognized neighborhood within the City of Boston, Massachusetts, United States. It was named after the American painter and poet Washington Allston. It comprises the land covered by the zip code 02134. For the most part ...
. A four-stroke, air-cooled unit, it had seven cylinders and a variable compression ratio, altered by changing the wobble-plate angle and hence the length of piston stroke. It was called a "rotary engine", because the entire engine rotated apart from the end casings. Ignition was supplied by a Bosch
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, ...
directly driven from the cam gears. The
high voltage High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant spec ...
current was then taken to a fixed electrode on the front bearing case, from which the sparks would jump to the spark plugs in the cylinder heads as they passed within 1/16 inch (1.5 mm) from it. According to Macomber's literature, it was "guaranteed not to overheat". The engine was claimed to be able to run at 150 to 1,500 rpm. At the normal speed of 1,000 rpm, it reportedly developed 50 hp. It weighed and it was long by in diameter. Pioneer aviator Charles Francis Walsh flew an aircraft powered by a Macomber engine in May 1911, the "Walsh Silver Dart".


Statax

In 1913 Statax-Motor of
Zürich Zürich () is the list of cities in Switzerland, largest city in Switzerland and the capital of the canton of Zürich. It is located in north-central Switzerland, at the northwestern tip of Lake Zürich. As of January 2020, the municipality has 43 ...
, Switzerland introduced a swashplate engine design. Only a single prototype was produced, which is currently held in the
Science Museum, London The Science Museum is a major museum on Exhibition Road in South Kensington, London. It was founded in 1857 and is one of the city's major tourist attractions, attracting 3.3 million visitors annually in 2019. Like other publicly funded ...
. In 1914 the company moved to London to become the Statax Engine Company and planned on introducing a series of
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 ...
s; a 3-cylinder of 10 hp, a 5-cylinder of 40 hp, a 7-cylinder of 80 hp, and a 10-cylinder of 100 hp. It appears only the 40 hp design was ever produced, which was installed in a Caudron G.II for the British 1914
Aerial Derby The Aerial Derby was an air race in the United Kingdom sponsored by the '' Daily Mail'' in which the competitors flew a circuit around London. It was first held in 1912, with subsequent races in 1913 and 1914. Suspended during the First World Wa ...
but was withdrawn before the flight. Hansen introduced an all-aluminum version of this design in 1922, but it is not clear if they produced it in any quantity. Much improved versions were introduced by Statax's German division in 1929, producing 42 hp in a new
sleeve valve The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve valve engines saw use in a number of pre-World War II luxury cars and in the United States in the Willys-Knight car and light truck. ...
version known as the ''29B''. Greenwood and Raymond of
San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
acquired the patent rights for the US, Canada, and Japan, and planned a 5-cylinder of 100 hp and a 9-cylinder of 350 hp.


Michell

In 1917 Anthony Michell obtained patents for his swashplate engine design. Its unique feature was the means of transferring the load from the pistons to the swashplate, achieved using tilting slipper pads sliding on a film of oil. Another innovation by Michell was his mathematical analysis of the mechanical design, including the mass and motion of the components, so that his engines were in perfect dynamic balance at all speeds. In 1920 Michell established the Crankless Engines Company in Fitzroy (Australia), and produced working prototypes of pumps, compressors, car engines and aero engines, all based on the same basic design. Engine designer
Phil Irving Philip Edward Irving MBE, CEng., FIMechE., MSAE., (1903–1992) was an Australian engineer and author, most famous for the Repco-Brabham Formula One and Vincent motorcycle engines. He also worked at Velocette motorcycles, twice, and drew the en ...
worked for the Crankless Engine Company before his time at HRD. A number of companies obtained a manufacturing license for Michell’s design. The most successful of these was the British company Waller and Son, who produced gas boosters. The largest Michell crankless engine was the XB-4070, a diesel aircraft engine built for the United States Navy. Consisting of 18 pistons, it was rated at 2000 horsepower and weighed 2150 pounds.


John O. Almen

Experimental barrel engines for aircraft use were built and tested by American John O. Almen of
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in the early 1920s, and by the mid-1920s the water-cooled ''Almen A-4'' (18 cylinders, two groups of nine each horizontally-opposed) had passed its
United States Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical r ...
acceptance tests. However, it never entered production, reportedly due to limited funds and the Air Corps' growing emphasis on air-cooled
radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...
s. The A-4 had much smaller frontal area than water-cooled engines of comparable power output, and thereby offered better streamlining possibilities. It was rated at 425 horsepower (317 kW), and weighed only 749 pounds (340 kg), thus giving a power/weight ratio of better than 1:2, a considerable design achievement at the time.


Heraclio Alfaro

Heraclio Alfaro Fournier Heraclio Alfaro Fournier (September 20, 1893 – October 8, 1962) was an aviation pioneer, aeronautical engineer, and member of the Early Birds of Aviation. Early life Born in Vitoria, Spain, Heraclio was the son of Juan Bautista Alfaro and gran ...
was a Spanish aviator who was
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ed at the age of 18 by
King Alfonso XIII Alfonso XIII (17 May 1886 – 28 February 1941), also known as El Africano or the African, was King of Spain from 17 May 1886 to 14 April 1931, when the Second Spanish Republic was proclaimed. He was a monarch from birth as his father, Alf ...
of Spain for designing, building, and flying Spain's first airplane. He developed a barrel engine for aircraft use which was later produced by the
Indian Motocycle Manufacturing Company Indian Motorcycle (or ''Indian'') is an American brand of motorcycles owned and produced by American automotive manufacturer Polaris Inc.sleeve valve The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve valve engines saw use in a number of pre-World War II luxury cars and in the United States in the Willys-Knight car and light truck. ...
system based on a rotating cylinder head, a design that never entered production on any engine. It was later developed further for use in the Doman helicopter by Stephen duPont, son of the president of the Indian Motorcycle Company, who had been one of Alfaro's students at
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...
.


Bristol

The Bristol Axial Engine of the mid-1930s was designed by Charles Benjamin Redrup for the
Bristol Tramways and Carriage Company The Bristol Omnibus Company was a dominant bus operator in Bristol, and was one of the oldest bus companies in the United Kingdom. It ran buses over a wide area of Gloucestershire, Somerset, Wiltshire and neighbouring counties. History ...
; it was a 7-litre, 9-cylinder, wobble-plate type engine. It was originally conceived as a power unit for buses, possibly because its compact format would allow it to be installed beneath the vehicle's floor. The engine had a single rotary valve to control induction and exhaust. Several variants were used in Bristol buses during the late 1930s, the engine going through several versions from RR1 to RR4, which had a power output of 145 hp at 2900 rpm. Development was halted in 1936 following a change of management at the Bristol company.


Wooler

Perhaps the most refined of the designs was the British
Wooler Wooler ( ) is a small town in Northumberland, England. It lies on the edge of the Northumberland National Park, near the Cheviot Hills. It is a popular base for walkers and is referred to as the "Gateway to the Cheviots". As well as many shops ...
wobble-plate engine of 1947. This 6-cylinder engine was designed by John Wooler, better known as a motorcycle engine designer, for aircraft use. It was similar to the Bristol axial engine but had two wobble-plates, driven by 12 opposed pistons in 6 cylinders. The engine is often incorrectly referred to as a swashplate engine. A single example is preserved in the Aeroplane Gallery of the Science Museum, London.


H.L.F. Trebert

Some small barrel engines were produced by th
H.L.F. Trebert Engine Works
of
Rochester, New York Rochester () is a City (New York), city in the U.S. state of New York (state), New York, the county seat, seat of Monroe County, New York, Monroe County, and the fourth-most populous in the state after New York City, Buffalo, New York, Buffalo, ...
for marine usage.


Present day


Dyna-Cam

The Dyna-Cam engine originally came from a design by the Blazer brothers, two
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
engineers in the brass era automotive industry who worked for
Studebaker Studebaker was an American wagon and automobile manufacturer based in South Bend, Indiana, with a building at 1600 Broadway, Times Square, Midtown Manhattan, New York City. Founded in 1852 and incorporated in 1868 as the Studebaker Brothers M ...
in 1916. They sold the rights to Karl Herrmann, Studebaker's head of engineering, who developed the concept over many years, eventually taking out US patent 2237989 in 1941. It has 6 double-ended pistons working in 6 cylinders, and its 12 combustion chambers are fired every revolution of the drive shaft. The pistons drive a sine-shaped cam, as opposed to a swashplate or wobble-plate, hence its name. In 1961, at the age of 80, Herrmann sold the rights to one of his employees, Edward Palmer, who set up the Dyna-Cam Engine Corp. along with son Dennis. Edward's son Dennis and daughter Pat then helped get the engine installed in a
Piper Arrow The Piper PA-28 Cherokee is a family of two-seat or four-seat light aircraft built by Piper Aircraft and designed for flight training, air taxi and personal use.Plane and Pilot: ''1978 Aircraft Directory'', pages 62–64. Werner & Werner Corp, ...
airplane. The engine was flown for about 700 hours from 1987 through 1991. Their longest-life engine ran for nearly 4000 hours before overhaul. Dyna-Cam opened a research and development facility about 1993 and won many various awards from NASA, the United States Navy, the United States Marine Corps, California Energy Commission, Air Quality Management District, and Los Angeles Regional Technology Alliance for different variations of the same Dyna-Cam engine. About 40 prototype engines were built by the Herrmann Group and another 25 built by the Dyna-Cam Group since they acquired the engine and opened their shop. A new patent was granted to Dennis Palmer and Edward Palmer, first in 1985 and then several more around 2000 to Dennis Palmer. In 2003 the assets of the Dyna-Cam Engine Corporation were acquired by Aero-Marine Corporation, who changed their name to Axial Vector Engine Corporation. Axial Vector then totally re-designed the cam engine. Axial Vector's new engine, like many of the others on this list, suffers from the "put in everything" problem, including
piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical s ...
valves and ignition, ceramic cylinder liners with no piston rings, and a variety of other advanced features. It has little similarity to the original Herrmann and Dyna-Cam engines, since the Dyna-Cam engine used conventional valves, piston rings, accessories, had no unproven ceramic materials and actually flew in an aircraft and also powered a "Eliminator"
ski boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...
for over four years.


Covaxe

United Kingdom company Covaxe Limited (known as FairDiesel Limited up until 2017) is designing two-stroke Diesel opposed piston barrel engines that use non-sinusoidal cams, for industrial applications and aviation use. Their engine designs range from a 2-cylinder, 80 mm bore to 32-cylinder, 160 mm bore.


Duke Engines

New Zealand company Duke Engines started in 1993 has created several different engines and installed one in a car in 1999. The engine runs a 5-cylinder, 3 litre, 4-stroke internal combustion engine platform with its unique axial arrangement, which is in its third generation. Due to a valveless design, Duke engine loses less energy between the power strokes. Current prototypes of Duke's engines claim to match characteristics of conventional internal combustion engines but with fewer parts and 30% lighter. This goes in the direction of developing a more efficient engine. During development the Duke has been tested at
MAHLE Powertrain MAHLE Powertrain Ltd is the wholly owned engineering services division of MAHLE GmbH. With its headquarters in Northampton, UK and sister company in Plymouth, Michigan, United States the company specialises in the design, development and tes ...
in the United Kingdom and in the United States; test results show that it has multi-fuel capabilities. The Duke engine's benefits of lightness and compactness should render this design ideal for motorcycles engines; and these benefits might make the powerplant suitable for light aircraft as well. (There is little data on whether the Duke engine is smooth; the mainshaft has a large counterweight attached).


Cylindrical Energy Module

The Cylindrical Energy Module (CEM) is a sine-wave swashplate engine that can also be used as a standalone pump, powered by an external source. The rotating swashplate rotor assembly is moved back and forth with the help of piston drive pins, which follow a stationary
sinusoidal A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in m ...
cam track that encircles the rotor assembly.


Applications

*The most well-known application is in
torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...
es, where the cylindrical shape is desirable. The modern
Mark 48 torpedo The Mark 48 and its improved Advanced Capability (ADCAP) variant are American heavyweight submarine-launched torpedoes. They were designed to sink deep-diving nuclear-powered submarines and high-performance surface ships. History The Mark 48 wa ...
is powered by a 500 hp swashplate engine geared to a
pump-jet A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller (axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of both ...
propulsor. It is fueled by Otto fuel II, a
monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...
that requires no oxygen supply and can propel the torpedo at up to (74.56 mph). *Other applications include pneumatic and hydraulic motors,
hydrostatic transmission A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. T ...
s such as
Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda has been the world's largest motorcycle manufacturer since 1959, reaching a product ...
's Hondamatic CVT, and
air conditioner Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
pumps. Also, some
Stirling engine A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the ''working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work. More specif ...
s use a swashplate arrangement, ''e.g.'', Stirling Thermal Motors' STM 4-120 engine.


See also

*
Axial piston pump An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a ''cylinder block''. It can be used as a stand-alone pump, a hydraulic motor or an automotive air conditioning compressor. Description ...


Notes


References

* *


External links


Barrel Engine - Part 2 ''Flight'' December 1941
{{Authority control Engine technology Piston engines