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| A '''parallel twin''',<ref>Fundamentals of automotive engine balance. W. Thomson. Mechanical Engineering Publications, 1978 </ref><ref>The design and tuning of competition engines. Philip Hubert Smith, David N. Wenner. R. Bentley, 1977 - Technology & Engineering </ref> (aka '''straight''', '''inline''', '''transverse''' or '''vertical twin''', or '''straight-two engine''' {{fact|date=June 2012}}) is a two-cylinder ] which has its cylinders arranged side by side. | A '''parallel twin''',<ref>Fundamentals of automotive engine balance. W. Thomson. Mechanical Engineering Publications, 1978 </ref><ref>The design and tuning of competition engines. Philip Hubert Smith, David N. Wenner. R. Bentley, 1977 - Technology & Engineering </ref> (aka '''straight''', '''inline''', '''transverse''' or '''vertical twin''', or '''straight-two engine''' {{fact|date=June 2012}}) is a two-cylinder ] which has its cylinders arranged side by side. | ||
| There are three crankshaft configurations for this engine: 360°, 180°, and the new 270°: | There are three crankshaft configurations for this engine: 360°, 180°, <ref>American bicyclist and motorcyclist, Volume 6. Cycling Press, 1911</ref> and the new 270°: <ref>How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw. Veloce Publishing Ltd, 15 Sep 2012</ref><ref name="feel">American Motorcyclist Dec 2001. P.18</ref> | ||
| * In a 360° engine, both pistons rise and fall together. The dynamic balance is identical to that of a single-cylinder engine, but with twice the number of ignition pulses. | * In a 360° engine, both pistons rise and fall together. The dynamic balance is identical to that of a single-cylinder engine, but with twice the number of ignition pulses. | ||
| * In a 180° engine, one piston rises as the other falls. This gives good primary balance, albeit with a rocking couple; but results in irregular ignition pulses. | * In a 180° engine, one piston rises as the other falls. This gives good primary balance, albeit with a rocking couple; but results in irregular ignition pulses. | ||
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| Unlike ]s, straight or parallel-twin engines do not use a common crank pin for both ]s, each cylinder has its own crank pin. Most vintage British parallel-twin motorcycle engines,<ref>Let's Ride: Sonny Barger's Guide to Motorcycling. Sonny Barger, Darwin Holmstrom. HarperCollins, 8 Jun 2010</ref> such as Triumph, BSA, Norton and Royal Enfield, had two main bearings, the exception being AJS/Machless, which used a third, center main bearing. | Unlike ]s, straight or parallel-twin engines do not use a common crank pin for both ]s, each cylinder has its own crank pin. Most vintage British parallel-twin motorcycle engines,<ref>Let's Ride: Sonny Barger's Guide to Motorcycling. Sonny Barger, Darwin Holmstrom. HarperCollins, 8 Jun 2010</ref> such as Triumph, BSA, Norton and Royal Enfield, had two main bearings, the exception being AJS/Machless, which used a third, center main bearing. | ||
| Honda parallel-twin engines, which began appearing in the late 1950s,<ref>Honda Motorcycles: Everything You Need to Know About Every Honda Motorcycle Ever Built. Doug Mitchel. Krause Publications, 18 Oct 2005</ref><ref>Honda Motorcycles. Aaron Frank. MotorBooks International, 12 Jul 2003 </ref> had four main bearings. Subsequent engines had four or occasionally three main bearings |
Honda parallel-twin engines, which began appearing in the late 1950s,<ref>Honda Motorcycles: Everything You Need to Know About Every Honda Motorcycle Ever Built. Doug Mitchel. Krause Publications, 18 Oct 2005</ref><ref>Honda Motorcycles. Aaron Frank. MotorBooks International, 12 Jul 2003 </ref> had four main ]. Subsequent engines had four or occasionally three main bearings, <ref>Pictorial History of Japanese Motorcycles. Cornelis Vandenheuvel. MBI Publishing Company, 18 Jul 1997 </ref> ball bearings being better than shell bearings for this engine configuration.<ref name="balls" /> Some engines have been built using a more obscure 76° crankshaft for the sake of performance benefits, as proposed by ].<ref>Classic Bike, April 1994</ref><ref>Phil Irving, 1962, as reprinted in Classic Motor Cycle, February 1992</ref> | ||
| ==Automobile use== | ==Automobile use== | ||
| ]<ref>The design and tuning of competition engines. Philip Hubert Smith. R. Bentley, 1963 </ref>]] | ]<ref>The design and tuning of competition engines. Philip Hubert Smith. R. Bentley, 1963 </ref>]] | ||
| In the past, parallel-twin engines have been used in very small cars (e.g. ], ], and ]s such as the ] <ref>The complete handbook of automotive power trains. Jan P. Norbye. Tab Books, 1981</ref> and ], <ref>Popular Science Feb 1975</ref> NSU, <ref>The light car: a technical history of cars with engines of less than 1600 c.c. capacity. Cyril Francis Caunter, Science Museum (Great Britain). H.M.S.O., 1970 </ref> and ]) and in farm equipment, notably by ] <ref>The Art of the John Deere Tractor: Featuring Tractors from the Walter and Bruce Keller Collection. Lee Klancher. Voyageur Press, 13 May 2011</ref> whose large two-cylinder engines were used in their line of farm ]s up until 1960. | In the past, parallel-twin engines have been used in very small cars (e.g. ], ], and ]s such as the ] <ref>The complete handbook of automotive power trains. Jan P. Norbye. Tab Books, 1981</ref> and ], <ref>Popular Science Feb 1975</ref> NSU, <ref>The light car: a technical history of cars with engines of less than 1600 c.c. capacity. Cyril Francis Caunter, Science Museum (Great Britain). H.M.S.O., 1970 </ref><ref>NSU Prim. The Motor, Volume 165. Temple Press Limited, 1983</ref> and ]) and in farm equipment, notably by ] <ref>The Art of the John Deere Tractor: Featuring Tractors from the Walter and Bruce Keller Collection. Lee Klancher. Voyageur Press, 13 May 2011</ref> whose large two-cylinder engines were used in their line of farm ]s up until 1960. | ||
| From 1967 to 1972, Honda produced the ] and its successors N400 and N600 with straight-twin engines in 360 cc, 400 cc, and 600 cc sizes. The ] was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the ] with a rear-mounted, rear-drive 358 cc air-cooled engine. | From 1967 to 1972, Honda produced the ] and its successors N400 and N600 with straight-twin engines in 360 cc, 400 cc, and 600 cc sizes. The ] was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the ] with a rear-mounted, rear-drive 358 cc air-cooled engine. | ||
| Line 46: | Line 46: | ||
| ==Other uses== | ==Other uses== | ||
| Parallel-twins engines are commonly used by the American ATV, <ref>American Motorcyclist Feb 2003</ref> jet ski <ref>Popular Mechanics May 2003. P.116</ref> and snowmobiles <ref>Field & Stream Oct 1972. P. 10</ref> manufacturer Polaris and Japanese manufacturers, |
Parallel-twins engines are commonly used by the American ATV, <ref>American Motorcyclist Feb 2003</ref> jet ski <ref>Popular Mechanics May 2003. P.116</ref> and snowmobiles <ref>Field & Stream Oct 1972. P. 10</ref> manufacturer Polaris and Japanese manufacturers, large ]s such as the ]<ref>Motor Cycle News </ref> and in motorcross sidecar racing. <ref>Off-Road Giants!: Heroes of 1960s Motorcycle Sport. Andy Westlake. Veloce Publishing Ltd, 15 Nov 2008</ref> | ||
| == |
==360° and 180° Crankshaft angle== | ||
| From the 1930s, following the work of ], most British four-stroke parallel twin motorcycles used a ] of 360°, <ref>JAE: the journal of automotive engineering, Volume 2. Institution of Mechanical Engineers (Great Britain). Automobile Division. Automobile Division, Institution of Mechanical Engineers., 1971</ref> which allowed the use of a single carburettor because 180° and 270° twins need twin carburettors, as did an early ] was a copy of the 360° British ]. However, in the 1960s Japanese manufacturers favoured the 180° whose smoothness allowed higher rpm and thus more power. For example, the 1966 Honda 450 cc dohc 180° parallel-twin “Black Bomber" could challenge contemporary British 650 cc 360° twins.<ref>World's Fastest Motorcycles. John Cutts, Michael Scott. Book Sales, 1 Aug 1991</ref><ref>Edward Turner: The Man Behind the Motorcycles. Jeff Clew. Veloce Publishing Ltd, 1 Feb 2007 </ref><ref>Classic superbikes from around the world. Mac McDiarmid. Parragon, 1 Jan 1995 </ref> | |||
| Many small motorcycles of less than 250 cc use a 360° crankshaft as the vibration issue was less significant; examples includes Honda's CB92, CB160, CA72, CA77s, and CM185. Larger twins over 500 cc, such as the Yamaha's XS650 and TX750, have used 360° crankshafts, but such parallel twins tend to feature balance shafts. The Honda CB-series in the 250 to 500 cc range used 180° crankshafts. Both the 1973 Yamaha TX500 and the 1977 Suzuki GS400 featured a 180° crankshaft and a balance shaft, while the 1974 Kawasaki KZ400 used a 360° crankshaft and a balance shaft. | Many small motorcycles of less than 250 cc use a 360° crankshaft as the vibration issue was less significant; examples includes Honda's CB92, CB160, CA72, CA77s, and CM185. Larger twins over 500 cc, such as the Yamaha's XS650 and TX750, have used 360° crankshafts, but such parallel twins tend to feature balance shafts.<ref name="balls">Pictorial History of Japanese Motorcycles. Cornelis Vandenheuvel. MBI Publishing Company, 18 Jul 1997</ref> The Honda CB-series in the 250 to 500 cc range used 180° crankshafts. Both the 1973 Yamaha TX500 and the 1977 Suzuki GS400 featured a 180° crankshaft and a balance shaft, while the 1974 Kawasaki KZ400 used a 360° crankshaft and a balance shaft. | ||
| A 180° crankshaft engine suffers fewer pumping losses than a 360° twin, as displacement in the crankcase stays roughly constant. However, a 180° engine requires a separate ignition system, points or otherwise, for each cylinder. The 360° twins can have a single ignition system for both cylinders, with a ] on each cylinder's exhaust stroke. The ] parallel twin motorcycle is a 360° design. Inherent vibration in the BMW F800 means its engine is limited to 9,000 rpm. BMW reduced the vibration using a third "vestigial" connecting rod to act as a counterbalance.<ref>BMW Motorcycles. Darwin Holmstrom, Brian J. Nelson. MotorBooks International, 4 Dec 2009 </ref> | A 180° crankshaft engine suffers fewer pumping losses than a 360° twin, as displacement in the crankcase stays roughly constant. However, a 180° engine requires a separate ignition system, points or otherwise, for each cylinder. The 360° twins can have a single ignition system for both cylinders, with a ] on each cylinder's exhaust stroke. The ] parallel twin motorcycle is a 360° design. Inherent vibration in the BMW F800 means its engine is limited to 9,000 rpm. BMW reduced the vibration using a third "vestigial" connecting rod to act as a counterbalance.<ref>BMW Motorcycles. Darwin Holmstrom, Brian J. Nelson. MotorBooks International, 4 Dec 2009 </ref> | ||
| Line 57: | Line 57: | ||
| In ]s, the crank angle is generally 180° with a working cycle every 180°. Such an engine will produce fewer vibrations. An exception is the ], which featured a 360° crankshaft. The Yankee's configuration, which featured separate combustion chambers for the two cylinders, should not be confused with that of a ]. | In ]s, the crank angle is generally 180° with a working cycle every 180°. Such an engine will produce fewer vibrations. An exception is the ], which featured a 360° crankshaft. The Yankee's configuration, which featured separate combustion chambers for the two cylinders, should not be confused with that of a ]. | ||
| == |
==270° Crankshaft angle== | ||
| A modern development of the parallel-twin engine is the 270° crank, <ref>Cycle world, Volume 46. CBS Publications, 2007</ref><ref>How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw. Veloce Publishing Ltd, 15 Sep 2012 </ref> which imitates the sound and feel of a 90° V-twin |
A modern development of the parallel-twin engine is the 270° crank, <ref>Cycle world, Volume 46. CBS Publications, 2007</ref><ref>How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw. Veloce Publishing Ltd, 15 Sep 2012 </ref> which imitates the sound and feel of a 90° V-twin <ref name="feel" /> but requires a balance shaft to reduce vibration. Effectively, the 270° crank is a compromise which allows a more regular firing pattern than a 180° crank and less vibration than a 360° crank. Just like a 90° V-twin, both pistons in 270° engine are never stationary thereby aiding crankshaft ]. | ||
| ==References== | ==References== | ||
Revision as of 11:11, 29 June 2012
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A parallel twin, (aka straight, inline, transverse or vertical twin, or straight-two engine ) is a two-cylinder piston engine which has its cylinders arranged side by side.
There are three crankshaft configurations for this engine: 360°, 180°, and the new 270°:
- In a 360° engine, both pistons rise and fall together. The dynamic balance is identical to that of a single-cylinder engine, but with twice the number of ignition pulses.
- In a 180° engine, one piston rises as the other falls. This gives good primary balance, albeit with a rocking couple; but results in irregular ignition pulses.
- In a 270° engine, one piston follows a quarter of a turn behind the other. This is a compromise between the first two types, yielding results similar to a V-twin.
Unlike V-twins, straight or parallel-twin engines do not use a common crank pin for both connecting rods, each cylinder has its own crank pin. Most vintage British parallel-twin motorcycle engines, such as Triumph, BSA, Norton and Royal Enfield, had two main bearings, the exception being AJS/Machless, which used a third, center main bearing.
Honda parallel-twin engines, which began appearing in the late 1950s, had four main bearings. Subsequent engines had four or occasionally three main bearings, ball bearings being better than shell bearings for this engine configuration. Some engines have been built using a more obscure 76° crankshaft for the sake of performance benefits, as proposed by Phil Irving.
Automobile use
In the past, parallel-twin engines have been used in very small cars (e.g. Microcars, "light" cars, and city cars such as the Fiat 500 and 126, NSU, and Mitsubishi Minica) and in farm equipment, notably by John Deere whose large two-cylinder engines were used in their line of farm tractors up until 1960.
From 1967 to 1972, Honda produced the N360 and its successors N400 and N600 with straight-twin engines in 360 cc, 400 cc, and 600 cc sizes. The Z600 was produced from 1970 to 1972. From 1958 to 1971, Subaru produced the 360 with a rear-mounted, rear-drive 358 cc air-cooled engine.
Current production cars that use an inline twin engine include the Tata Nano, which has a 623 cc engine, the Fiat 500 TwinAir, which has a turbocharged 875 cc engine, and the VW Up, which uses a parallel-twin turbodiesel.
Ferrari briefly tested a two-cylinder engine for Formula One use in the 1950s, designed by Aurelio Lampredi.
Motorcycle use
The motorcycle world generally refers to these engines as "parallel twins" or "vertical twins", and the term "straight-two" is obsolete. "Parallel twin" refers to an engine which has its crankshaft mounted transversely across the frame; and the term "inline twin" refers to exclusively to an engine with its crankshaft mounted inline with the frame, such as the Sunbeam S7. In four-stroke designs, the parallel twin is usually vertical or near vertical. One exception is the only parallel-twin to win a 500cc Grand Prix, the supercharged AJS E-90 Porcupine which featured nearly horizontal cylinders.
Edward Turner's 1937 Triumph Speed Twin started a trend, and up to the mid-1970s four-stroke parallel-twins were the most common type of British motorcycles, being produced by Triumph, BSA, Norton, Ariel, Matchless and AJS. Italian, German and USA manufacturers have also made parallel-twins. BMW and Japanese manufacturers still make them, particularly for middleweight bikes. American made parallel-twins included the 1949 440 cc Indian Scout and the 1950 500 cc Indian Warrior.
Although the rise in popularity of the large V-twin motorcycle has seen the parallel twin fall out of favour, the latter retains these advantages over the former:
- A parallel twin is cheaper to make, having only one cylinder block and one cylinder head.
- Both cylinders can have the exhaust pipe exiting at the front, in the cool air stream.
- Siting of ancillaries (air-filter, carburetters, ignition etc.) is simpler.
- This simpler layout can potentially make maintenance access easier.
- The parallel twin is both lighter and shorter, allowing a lighter frame and shorter wheelbase.
- The motorcycle's centre of gravity can be sited optimally, i.e. lower and further forward.
- Provided a 270° crank is used, a parallel twin can simulate the "feel" of a V-twin.
Other uses
Parallel-twins engines are commonly used by the American ATV, jet ski and snowmobiles manufacturer Polaris and Japanese manufacturers, large scooters such as the Yamaha TMAX and in motorcross sidecar racing.
360° and 180° Crankshaft angle
From the 1930s, following the work of Val Page, most British four-stroke parallel twin motorcycles used a crank angle of 360°, which allowed the use of a single carburettor because 180° and 270° twins need twin carburettors, as did an early Meguro was a copy of the 360° British BSA A7. However, in the 1960s Japanese manufacturers favoured the 180° whose smoothness allowed higher rpm and thus more power. For example, the 1966 Honda 450 cc dohc 180° parallel-twin “Black Bomber" could challenge contemporary British 650 cc 360° twins.
Many small motorcycles of less than 250 cc use a 360° crankshaft as the vibration issue was less significant; examples includes Honda's CB92, CB160, CA72, CA77s, and CM185. Larger twins over 500 cc, such as the Yamaha's XS650 and TX750, have used 360° crankshafts, but such parallel twins tend to feature balance shafts. The Honda CB-series in the 250 to 500 cc range used 180° crankshafts. Both the 1973 Yamaha TX500 and the 1977 Suzuki GS400 featured a 180° crankshaft and a balance shaft, while the 1974 Kawasaki KZ400 used a 360° crankshaft and a balance shaft.
A 180° crankshaft engine suffers fewer pumping losses than a 360° twin, as displacement in the crankcase stays roughly constant. However, a 180° engine requires a separate ignition system, points or otherwise, for each cylinder. The 360° twins can have a single ignition system for both cylinders, with a wasted spark on each cylinder's exhaust stroke. The BMW F800 parallel twin motorcycle is a 360° design. Inherent vibration in the BMW F800 means its engine is limited to 9,000 rpm. BMW reduced the vibration using a third "vestigial" connecting rod to act as a counterbalance.
In two-stroke engines, the crank angle is generally 180° with a working cycle every 180°. Such an engine will produce fewer vibrations. An exception is the Yankee, which featured a 360° crankshaft. The Yankee's configuration, which featured separate combustion chambers for the two cylinders, should not be confused with that of a split-single.
270° Crankshaft angle
A modern development of the parallel-twin engine is the 270° crank, which imitates the sound and feel of a 90° V-twin but requires a balance shaft to reduce vibration. Effectively, the 270° crank is a compromise which allows a more regular firing pattern than a 180° crank and less vibration than a 360° crank. Just like a 90° V-twin, both pistons in 270° engine are never stationary thereby aiding crankshaft momentum.
References
- Fundamentals of automotive engine balance. W. Thomson. Mechanical Engineering Publications, 1978
- The design and tuning of competition engines. Philip Hubert Smith, David N. Wenner. R. Bentley, 1977 - Technology & Engineering
- American bicyclist and motorcyclist, Volume 6. Cycling Press, 1911
- How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw. Veloce Publishing Ltd, 15 Sep 2012
- ^ American Motorcyclist Dec 2001. P.18
- Let's Ride: Sonny Barger's Guide to Motorcycling. Sonny Barger, Darwin Holmstrom. HarperCollins, 8 Jun 2010
- Honda Motorcycles: Everything You Need to Know About Every Honda Motorcycle Ever Built. Doug Mitchel. Krause Publications, 18 Oct 2005
- Honda Motorcycles. Aaron Frank. MotorBooks International, 12 Jul 2003
- Pictorial History of Japanese Motorcycles. Cornelis Vandenheuvel. MBI Publishing Company, 18 Jul 1997
- ^ Pictorial History of Japanese Motorcycles. Cornelis Vandenheuvel. MBI Publishing Company, 18 Jul 1997
- Classic Bike, April 1994
- Phil Irving, 1962, as reprinted in Classic Motor Cycle, February 1992
- The design and tuning of competition engines. Philip Hubert Smith. R. Bentley, 1963
- The complete handbook of automotive power trains. Jan P. Norbye. Tab Books, 1981
- Popular Science Feb 1975
- The light car: a technical history of cars with engines of less than 1600 c.c. capacity. Cyril Francis Caunter, Science Museum (Great Britain). H.M.S.O., 1970
- NSU Prim. The Motor, Volume 165. Temple Press Limited, 1983
- The Art of the John Deere Tractor: Featuring Tractors from the Walter and Bruce Keller Collection. Lee Klancher. Voyageur Press, 13 May 2011
- World's cheapest car launched: Tata Nano, Autocar,
- air-2-cylinder-engine-makes-the-500-pure-fun/ "Fiat's TwinAir 2-cylinder engine makes the 500 pure fun". autoblog.com. Retrieved 2010-08-01.
{{cite web}}: Check|url=value (help); Cite has empty unknown parameter:|1=(help) - Volkswagen reveals four new Up city cars, The Telegraph, 03 Feb 2012
- American Motorcyclist, Jul 1965
- Modern Motorcycle Technology: How Every Part of Your Motorcycle Works. Massimo Clarke. MotorBooks International, 17 Apr 2010
- The Art of BMW: 85 Years of Motorcycling Excellence. Peter Gantriis, Henry Von Wartenberg. MotorBooks International, 15 Sep 2008
- Pictorial History of Japanese Motorcycles. Cornelis Vandenheuvel. MBI Publishing Company, 18 Jul 1997
- Modern Motorcycle Technology. Edward Abdo. Cengage Learning, 3 Jan 2012
- American Motorcyclist, Dec 2004
- The Illustrated Directory of Motorcycles. Mirco De Cet. MotorBooks International, 13 Feb 2003
- The BSA Bantam Bible: All Models 1948 to 1971. Peter Henshaw. Veloce Publishing Ltd, 15 Jun 2008
- ^ 365 Motorcycles You Must Ride, Dain Gingerelli, Charles Everitt, James Manning Michels. MBI Publishing Company, 10 Jan 2011
- Triumph: A Century of Passion and Power. Lindsay Brooke. MotorBooks International, 5 Jan 2003
- Parallel Universe. American Motorcyclist Dec 2004. P.13
- Modern Motorcycle Technology: How Every Part of Your Motorcycle Works. Massimo Clarke. MotorBooks International, 17 Apr 2010
- Walneck's Classic Cycle Trader, February 1987
- Fast Bike magazine August 1995 page 21
- American Motorcyclist Feb 2003
- Popular Mechanics May 2003. P.116
- Field & Stream Oct 1972. P. 10
- Motor Cycle News Yamaha T-Max (2001-2011)
- Off-Road Giants!: Heroes of 1960s Motorcycle Sport. Andy Westlake. Veloce Publishing Ltd, 15 Nov 2008
- JAE: the journal of automotive engineering, Volume 2. Institution of Mechanical Engineers (Great Britain). Automobile Division. Automobile Division, Institution of Mechanical Engineers., 1971
- World's Fastest Motorcycles. John Cutts, Michael Scott. Book Sales, 1 Aug 1991
- Edward Turner: The Man Behind the Motorcycles. Jeff Clew. Veloce Publishing Ltd, 1 Feb 2007
- Classic superbikes from around the world. Mac McDiarmid. Parragon, 1 Jan 1995
- BMW Motorcycles. Darwin Holmstrom, Brian J. Nelson. MotorBooks International, 4 Dec 2009
- Cycle world, Volume 46. CBS Publications, 2007
- How Your Motorcycle Works: Your Guide to the Components & Systems of Modern Motorcycles. Peter Henshaw. Veloce Publishing Ltd, 15 Sep 2012
External links
- A detailed analysis of the effect of different crankshaft offset angles on the engine balance of a straight twin engine.
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