Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Rotary Engine shopping experience:
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2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Rotary Engine? Wrong! If the Rotary Engine is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Rotary Engine then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
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7. Feedback - happy with your Rotary Engine then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Rotary Engine site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Rotary Engine, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Rotary Engine, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
The
rotary engine was an early type of
internal-combustion engine aircraft engine, used mostly in the years shortly before and during World War I. It is also used in a few
motorcycles and automobile.
In concept, a rotary engine is simple. It is a standard Otto cycle engine, but instead of having an orthodox fixed cylinder block with rotating crankshaft as with the
Radial engine, the crankshaft remains stationary and the entire cylinder block rotates around it. In the most common form, the crankshaft was fixed solidly to an aircraft frame, and the propeller simply bolted onto the front of the cylinder block.
The effect of rotating such a large mass was an inherent large gyroscope flywheel effect, smoothing out the power and reducing vibration. Vibration had been such a serious problem on other conventional piston engine designs that heavy flywheels had to be added. Because the cylinders themselves functioned as a flywheel, rotary piston engines typically had a
power-to-weight ratio advantage over more conventional engines.
Most rotary engines were arranged with the cylinders pointed outwards from a single crankshaft, in the same general form as a radial engine, but there were also rotary boxer engines and even
single cylinder engine rotaries.
History in aircraft
Lawrence Hargrave first developed a rotary engine in 1889 using compressed air, intending for it to be used in powered flight. Weight of materials and lack of quality machining prevented it becoming an effective power unit. Hargrave, Lawrence (1850 – 1915). Australian Dictionary of Biography Online.
The first effective rotaries were built by Stephen Balzer, who was interested in the design for two main reasons:
- In order to generate 100 hp (75 kW) at the low Revolutions per minute at which the engines of the day ran, the pulsation resulting from each combustion stroke was quite large. In order to damp out these pulses, engines needed to mount a large flywheel, which added weight. In the rotary design the engine itself doubled as its own flywheel, thus rotaries could be lighter than similarly sized engines of regular design.
- The cylinders had good airflow over them even when the aircraft in which they were mounted were sitting still, which was an important concern given the alloys they had to work with at the time. Balzer's early engines did not even use cooling-fins, a feature of every other air cooling design, and one that is complex and expensive to manufacture.
Balzer's first designs were ready for use in 1899, at which time they were the most advanced in the world. Other aircraft engines would not catch up in performance for a decade. He then became involved in
Samuel Pierpont Langley's
Aerodrome attempts, which bankrupted him while he tried to make much larger versions.
The next major advance in the design was Louis and Laurent Seguin's Gnome et Rhône series from
1908. This design was developed from a German single-cylinder stationary engine intended for light industrial use, the
Gnom, which the brothers were producing under license from
Motorenfabrik Oberursel. They essentially took several Gnom cylinders and combined them on a common shaft to produce a seven-cylinder rotary, the Gnôme Omega No.1 still exists and is in the collection of the Smithsonian's
National Air and Space Museum. A production version of the Omega then soon reached the aviation market, still as a 7-cylinder 50 hp (37 kW), which soon reached 80 hp (60 kW), and eventually 110 hp (80 kW). The engine was at this later 80 hp (60 kW) standard when World War I started, as the Gnôme Lambda, and the Gnome quickly found itself being used in a large number of aircraft designs. It was so good that it was licensed by a number of companies, including the German Oberursel firm who designed the original Gnom engine. Oberursel was later purchased by Fokker, whose Gnôme Lambda copy was known as the Oberursel U.I. It was not at all uncommon for French Gnômes to meet German versions in combat.
The Gnôme (and its copies) had a number of features that made it unique, even among the rotaries. Notably, the fuel was mixed and sprayed into the center of the engine through a hollow crankshaft, and then into the cylinders through the piston itself, a single valve on the top of the piston let the mixture in when opened. The valves were counter balanced so that only a small force was needed to open them, and releasing the force closed the valve without any springs. The center of the engine is normally where the oil would be, and the fuel would wash it away. To fix this, the oil was mixed in liberal quantities with the fuel, and the engine spewed smoke due to burning oil. Castor oil was the lubricant of choice, its gum-forming tendency being irrelevant in a total-loss lubrication system. An unfortunate side-effect was that World War I pilots inhaled and swallowed a considerable amount of the oil during flight, leading to persistent
diarrhoea. Finally, the Gnôme had no throttle or
carburetor. Since the fuel was being sprayed into the spinning engine, the motion alone was enough to mix the fuel fairly well. Of course with no throttle, the engine was either on or off, so something as simple as reducing power for landing required the pilot to cut the ignition. "Blipping" the engine on and off gave the characteristic sputtering sound as though the engine was nearly stalling, though it did not stall as quickly as conventional engines due to its great rotational inertia.
Throughout the early period of the war, the
power-to-weight ratio of the rotaries remained ahead of that of their competition. They were used almost universally in fighter aircraft, while traditional water cooled designs were used on larger aircraft. The engines had a number of disadvantages, notably very poor fuel consumption, partially because the engine was always "full throttle", and also because the valve timing was often less than ideal. The rotating mass of the engine also made it, in effect, a large
gyroscope, which resulted in tricky handling. The
Sopwith Camel, for example, was known to turn very nimbly to the right, but rather sluggishly to the left. Nevertheless, rotaries maintained their edge through a series of small upgrades, and many newer designs continued to use them.
A few of the nine cylinder rotaries managed to accomplish a partial "throttle" functionality by switching off either three or six cylinders (or other numbers of them), instead of all nine of them, when the "coupe switch" was depressed to cut the spark. It is believed that both German and Allied WW I rotaries had this ability, as some surviving documentation regarding the
Fokker Eindecker shows a rotary selector switch to cut out a selected number of cylinders on its rotary engine. The Gnôme
Monosoupape engine series of engines is known to have this sort of switching available to it, and has been demonstrated long after WW I by a 160 hp Monosoupape powered reproduction Sopwith Camel at
Old Rhinebeck Aerodrome while in flight in the 1990s.
As the war progressed, aircraft designers demanded ever-increasing amounts of power. Inline engines were able to meet this demand by improving their RPM, as more "bangs per minute" meant more power delivered. Improvements in valve timing, ignition systems and lighter materials made these higher RPM possible, and by the end of the war the average engine had increased from 1,200 RPM to 2,000. However the rotary was not able to use the same "trick," due to the drag of the cylinders through the air as they spun. For instance, if an early-war model of 1,200 RPM increased to only 1,400, the drag on the cylinders increased 36%, as air drag increases with the square of velocity. At lower speeds the drag could simply be ignored, but as speeds increased the rotary was putting more and more power into spinning the engine, and less into spinning the propeller.
One clever attempt to rescue the design was made by
Siemens AG. The crankcase and cylinders spun counterclockwise at 900 RPM while the crankshaft spun clockwise at the same speed. This was achieved by the use of bevel gearing at the rear of the crankcase, resulting in the Siemens-Halske Sh.III, running at 1800 RPM with little net torque. It was also apparently the only rotary engine to use a normal carburetor that could be controlled by a conventional throttle, just as in an in-line engine. Used on the
Siemens-Schuckert D.IV fighter, the new engine created what is considered by many to be the best
fighter aircraft of the war.
One new rotary powered aircraft, Fokker's own Fokker D.VIII, was designed at least in part to provide some use for their Oberursel factory's backlog of now-useless Oberursel Ur.II 110 hp engines, themselves clones of the Le Rhône 9J rotary. By the time the war ended, the rotary engine had become obsolete, and on the whole it disappeared from use quite quickly. The British Royal Air Force probably used rotary engines for longer than most other operators - the post-war standard fighter, the
Sopwith Snipe used the
Bentley BR2 rotary, and the standard trainer, the
Avro 504K, had a universal mounting to allow several types of low powered rotary, of which there was a large surplus supply. The cheapness of war-surplus engines had to be balanced against their poor
fuel economy, and the expense of their total loss lubrication system.
By the mid twenties rotaries had been more or less completely displaced even in British service, largely by the new generation of air-cooled radial engines.
Use in cars and motorcycles
Although the rotary engines were mostly used in aircraft, there were also a few cars and motorcycles with rotary engines. The most famous motorcycle (probably because of winning many races) is the
Megola motorcycle with a radial rotary engine inside the front wheel. Another motorcycle with a radial rotary engine was the
Redrup Radial, which had a rotating 3 cylinder engine in its frame.
In
1904, the Barry engine was built in Wales, a rotating 2 cylinder boxer engine inside a motorcycle frame, weighing 6.5 kg. In the
1940s Cyril Pullin developed the
Powerwheel, a wheel with rotating
single cylinder engine,
clutch and
drum brake inside the hub but it never went into serial production.
Cars with rotary engines were built (among others) by American companies
Adams-Farwell,
Bailey (car),
Balzer and Intrepid.
Other rotary engines
Besides the configuration described in this article with cylinders moving around a fixed crankshaft, several other very different engine designs can also be described as rotary engines. The most notable pistonless rotary engine, the Wankel engine has also been used in cars (notably by NSU in the NSU Ro 80 and by Mazda in cars such as the RX-7 and
RX-8), as well as in some experimental aviation applications.
Difference between rotary and radial engines
There has been some confusion when comparing Rotary engines and
Radial engines. When looked at from the outside, both Rotary and Radial engines look strikingly similar.
The difference between these two engines is that Radial engines have pistons that move in a reciprocating fashion that cause the crankshaft to rotate. In rotary engines however, the crankshaft does not rotate. Instead, the cylinders that accommodate the reciprocating pistons will rotate around the crankshaft.
In aviation, planes that use Radial engines have their propellers connected in one way or another to the crankshaft while the cylinders and crankcase are mounted on the airframe. Planes that use Rotary engines however, have their propellers connected to the cylinders and crankcase while the "crankshaft" is mounted onto the airframe.
An external difference is that radial engine cylinders are usually finned for cooling, whereas rotary engine cylinders are often not finned, as the cooling is sufficient without the extra expense and complexity of construction.
Notes and references
See also
External links
- Animation of Gnome Rotary in action
- Ray Williams' operable miniature rotary engine website
- A rotary engine that runs solely on compressed air
- New York Rotary Association New York's Biggest Rotary Engine Auto Club
- History of the Rotary Engine from 1588 Onward
- Gif animation of a rotary engine
The
rotary engine was an early type of
internal-combustion engine aircraft engine, used mostly in the years shortly before and during
World War I. It is also used in a few motorcycles and
automobile.
In concept, a rotary engine is simple. It is a standard Otto cycle engine, but instead of having an orthodox fixed
cylinder block with rotating crankshaft as with the
Radial engine, the crankshaft remains stationary and the entire cylinder block rotates around it. In the most common form, the crankshaft was fixed solidly to an aircraft frame, and the propeller simply bolted onto the front of the cylinder block.
The effect of rotating such a large mass was an inherent large
gyroscope flywheel effect, smoothing out the power and reducing vibration. Vibration had been such a serious problem on other conventional piston engine designs that heavy flywheels had to be added. Because the cylinders themselves functioned as a flywheel, rotary piston engines typically had a power-to-weight ratio advantage over more conventional engines.
Most rotary engines were arranged with the cylinders pointed outwards from a single crankshaft, in the same general form as a
radial engine, but there were also rotary
boxer engines and even
single cylinder engine rotaries.
History in aircraft
Lawrence Hargrave first developed a rotary engine in 1889 using compressed air, intending for it to be used in powered flight. Weight of materials and lack of quality machining prevented it becoming an effective power unit. Hargrave, Lawrence (1850 – 1915). Australian Dictionary of Biography Online.
The first effective rotaries were built by
Stephen Balzer, who was interested in the design for two main reasons:
- In order to generate 100 hp (75 kW) at the low Revolutions per minute at which the engines of the day ran, the pulsation resulting from each combustion stroke was quite large. In order to damp out these pulses, engines needed to mount a large flywheel, which added weight. In the rotary design the engine itself doubled as its own flywheel, thus rotaries could be lighter than similarly sized engines of regular design.
- The cylinders had good airflow over them even when the aircraft in which they were mounted were sitting still, which was an important concern given the alloys they had to work with at the time. Balzer's early engines did not even use cooling-fins, a feature of every other air cooling design, and one that is complex and expensive to manufacture.
Balzer's first designs were ready for use in 1899, at which time they were the most advanced in the world. Other aircraft engines would not catch up in performance for a decade. He then became involved in Samuel Pierpont Langley's
Aerodrome attempts, which bankrupted him while he tried to make much larger versions.
The next major advance in the design was Louis and Laurent Seguin's
Gnome et Rhône series from 1908. This design was developed from a German single-cylinder stationary engine intended for light industrial use, the
Gnom, which the brothers were producing under license from Motorenfabrik Oberursel. They essentially took several Gnom cylinders and combined them on a common shaft to produce a seven-cylinder rotary, the Gnôme Omega No.1 still exists and is in the collection of the Smithsonian's National Air and Space Museum. A production version of the Omega then soon reached the aviation market, still as a 7-cylinder 50 hp (37 kW), which soon reached 80 hp (60 kW), and eventually 110 hp (80 kW). The engine was at this later 80 hp (60 kW) standard when World War I started, as the Gnôme Lambda, and the Gnome quickly found itself being used in a large number of aircraft designs. It was so good that it was licensed by a number of companies, including the German Oberursel firm who designed the original Gnom engine. Oberursel was later purchased by
Fokker, whose Gnôme Lambda copy was known as the Oberursel U.I. It was not at all uncommon for French Gnômes to meet German versions in combat.
The Gnôme (and its copies) had a number of features that made it unique, even among the rotaries. Notably, the fuel was mixed and sprayed into the center of the engine through a hollow crankshaft, and then into the cylinders through the piston itself, a single valve on the top of the piston let the mixture in when opened. The valves were counter balanced so that only a small force was needed to open them, and releasing the force closed the valve without any springs. The center of the engine is normally where the oil would be, and the fuel would wash it away. To fix this, the oil was mixed in liberal quantities with the fuel, and the engine spewed smoke due to burning oil. Castor oil was the lubricant of choice, its gum-forming tendency being irrelevant in a total-loss lubrication system. An unfortunate side-effect was that World War I pilots inhaled and swallowed a considerable amount of the oil during flight, leading to persistent
diarrhoea. Finally, the Gnôme had no throttle or carburetor. Since the fuel was being sprayed into the spinning engine, the motion alone was enough to mix the fuel fairly well. Of course with no throttle, the engine was either on or off, so something as simple as reducing power for landing required the pilot to cut the ignition. "Blipping" the engine on and off gave the characteristic sputtering sound as though the engine was nearly stalling, though it did not stall as quickly as conventional engines due to its great rotational inertia.
Throughout the early period of the war, the power-to-weight ratio of the rotaries remained ahead of that of their competition. They were used almost universally in fighter aircraft, while traditional water cooled designs were used on larger aircraft. The engines had a number of disadvantages, notably very poor fuel consumption, partially because the engine was always "full throttle", and also because the valve timing was often less than ideal. The rotating mass of the engine also made it, in effect, a large gyroscope, which resulted in tricky handling. The Sopwith Camel, for example, was known to turn very nimbly to the right, but rather sluggishly to the left. Nevertheless, rotaries maintained their edge through a series of small upgrades, and many newer designs continued to use them.
A few of the nine cylinder rotaries managed to accomplish a partial "throttle" functionality by switching off either three or six cylinders (or other numbers of them), instead of all nine of them, when the "coupe switch" was depressed to cut the spark. It is believed that both German and Allied WW I rotaries had this ability, as some surviving documentation regarding the Fokker Eindecker shows a rotary selector switch to cut out a selected number of cylinders on its rotary engine. The Gnôme Monosoupape engine series of engines is known to have this sort of switching available to it, and has been demonstrated long after WW I by a 160 hp Monosoupape powered reproduction Sopwith Camel at Old Rhinebeck Aerodrome while in flight in the 1990s.
As the war progressed, aircraft designers demanded ever-increasing amounts of power. Inline engines were able to meet this demand by improving their RPM, as more "bangs per minute" meant more power delivered. Improvements in valve timing, ignition systems and lighter materials made these higher RPM possible, and by the end of the war the average engine had increased from 1,200 RPM to 2,000. However the rotary was not able to use the same "trick," due to the drag of the cylinders through the air as they spun. For instance, if an early-war model of 1,200 RPM increased to only 1,400, the drag on the cylinders increased 36%, as air drag increases with the square of velocity. At lower speeds the drag could simply be ignored, but as speeds increased the rotary was putting more and more power into spinning the engine, and less into spinning the propeller.
One clever attempt to rescue the design was made by Siemens AG. The crankcase and cylinders spun counterclockwise at 900 RPM while the crankshaft spun clockwise at the same speed. This was achieved by the use of bevel gearing at the rear of the crankcase, resulting in the Siemens-Halske Sh.III, running at 1800 RPM with little net torque. It was also apparently the only rotary engine to use a normal carburetor that could be controlled by a conventional throttle, just as in an in-line engine. Used on the
Siemens-Schuckert D.IV fighter, the new engine created what is considered by many to be the best
fighter aircraft of the war.
One new rotary powered aircraft, Fokker's own Fokker D.VIII, was designed at least in part to provide some use for their Oberursel factory's backlog of now-useless
Oberursel Ur.II 110 hp engines, themselves clones of the
Le Rhône 9J rotary. By the time the war ended, the rotary engine had become obsolete, and on the whole it disappeared from use quite quickly. The British
Royal Air Force probably used rotary engines for longer than most other operators - the post-war standard fighter, the Sopwith Snipe used the Bentley BR2 rotary, and the standard trainer, the Avro 504K, had a universal mounting to allow several types of low powered rotary, of which there was a large surplus supply. The cheapness of war-surplus engines had to be balanced against their poor fuel economy, and the expense of their total loss lubrication system.
By the mid twenties rotaries had been more or less completely displaced even in British service, largely by the new generation of air-cooled radial engines.
Use in cars and motorcycles
Although the rotary engines were mostly used in aircraft, there were also a few cars and motorcycles with rotary engines. The most famous motorcycle (probably because of winning many races) is the Megola motorcycle with a radial rotary engine inside the front wheel. Another motorcycle with a radial rotary engine was the
Redrup Radial, which had a rotating 3 cylinder engine in its frame.
In 1904, the Barry engine was built in Wales, a rotating 2 cylinder
boxer engine inside a motorcycle frame, weighing 6.5 kg. In the 1940s Cyril Pullin developed the
Powerwheel, a wheel with rotating
single cylinder engine,
clutch and
drum brake inside the hub but it never went into serial production.
Cars with rotary engines were built (among others) by American companies
Adams-Farwell, Bailey (car), Balzer and Intrepid.
Other rotary engines
Besides the configuration described in this article with cylinders moving around a fixed crankshaft, several other very different engine designs can also be described as rotary engines. The most notable pistonless rotary engine, the
Wankel engine has also been used in cars (notably by NSU in the NSU Ro 80 and by
Mazda in cars such as the
RX-7 and RX-8), as well as in some experimental aviation applications.
Difference between rotary and radial engines
There has been some confusion when comparing Rotary engines and Radial engines. When looked at from the outside, both Rotary and Radial engines look strikingly similar.
The difference between these two engines is that Radial engines have pistons that move in a reciprocating fashion that cause the crankshaft to rotate. In rotary engines however, the crankshaft does not rotate. Instead, the cylinders that accommodate the reciprocating pistons will rotate around the crankshaft.
In aviation, planes that use Radial engines have their propellers connected in one way or another to the crankshaft while the cylinders and crankcase are mounted on the airframe. Planes that use Rotary engines however, have their propellers connected to the cylinders and crankcase while the "crankshaft" is mounted onto the airframe.
An external difference is that radial engine cylinders are usually finned for cooling, whereas rotary engine cylinders are often not finned, as the cooling is sufficient without the extra expense and complexity of construction.
Notes and references
See also
External links
- Animation of Gnome Rotary in action
- Ray Williams' operable miniature rotary engine website
- A rotary engine that runs solely on compressed air
- New York Rotary Association New York's Biggest Rotary Engine Auto Club
- History of the Rotary Engine from 1588 Onward
- Gif animation of a rotary engine
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