Flat-twin engine: Difference between revisions
Wasted spark ignition system, well suited to the flat-twin engine |
We don't need to know that a company that once made washing machines but is now part of Whirlpool once used a flat-twin engine (when? nowheret mentioned in Maytag article). |
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[[File:Blackjack Avion-engine.jpg|thumb|Blackjack Avion displaying the cylinders of its [[Citroën 2CV]] engine]] |
[[File:Blackjack Avion-engine.jpg|thumb|Blackjack Avion displaying the cylinders of its [[Citroën 2CV]] engine]] |
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Flat-twin engines were used in several [[economy car]]s, including the [[Citroën 2CV]], the [[Panhard Dyna X]] and [[Panhard Dyna Z|Dyna Z]], Steyr-[[Puch 500]], [[DAF Daffodil]], [[BMW 600]], several [[Jowett]] cars between World Wars I and II, and the [[Toyota Publica]] and [[Toyota Sport 800]]. Flat-twin engines were also used in several early cars, including the [[Ford Motor Company|Ford]] 1903-04 [[Ford Model A (1903–1904)|Model A]], [[Ford Model C|Model C]] and [[Ford Model F|Model F]]. |
Flat-twin engines were used in several [[economy car]]s, including the [[Citroën 2CV]], the [[Panhard Dyna X]] and [[Panhard Dyna Z|Dyna Z]], Steyr-[[Puch 500]], [[DAF Daffodil]], [[BMW 600]], several [[Jowett]] cars between World Wars I and II, and the [[Toyota Publica]] and [[Toyota Sport 800]]. Flat-twin engines were also used in several early cars, including the [[Ford Motor Company|Ford]] 1903-04 [[Ford Model A (1903–1904)|Model A]], [[Ford Model C|Model C]] and [[Ford Model F|Model F]]. |
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==Other uses== |
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[[Maytag]] used its Model 72 flat-twin engines to power washing machines.<ref name=MaytagClub37>{{Cite web| url = http://www.maytagclub.com/page-37.htm| title = Maytag Multi-Motor Engines| accessdate = 2009-01-08| publisher = Maytag Collector's club}}</ref><ref name=MaytagWasher>{{Cite web| url = http://www.herculesengines.com/Maytag/Default.htm| title = Maytag Engine-Driven Wringer Washer| accessdate = 2009-01-08| last = Kinney| first = Keith| date = 2007-02-27| work = [http://www.herculesengines.com/Default.htm Old Iron and Other Americana: The collections of the Kinney family]| publisher= }}</ref>{{-}} |
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==Ignition systems== |
==Ignition systems== |
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Revision as of 16:07, 27 December 2010
A flat-twin is a two cylinder internal combustion engine with the cylinders arranged on opposite sides of the crankshaft. It is part of the class of flat engines, sub-type "boxer", and shares most characteristics of those engines.
Motorcycle use
BMW Motorrad manufactures a number of flat-twin engine motorcycles,[1][2] as do Ural and Dnepr. The geometry gives good primary balance, but there is an unbalanced moment on the crankshaft caused by the pistons being offset from each other.[2]
Engine alignment
Cylinders along frame
The earliest flat-twin motorcycles, including Douglas in the United Kingdom, Helios of Germany, and Harley-Davidson of the United States, had their cylinders aligned along the frame, and therefore with the crankshaft running transverse to the frame.[2][3] [4] This position allowed the use of a conventional motorcycle drivetrain by belt or chain to the rear wheel.[3][5] Another advantage of this layout is that it has a low centre of gravity.[5] However, in this layout, the front cylinder is more heavily cooled than the rear cylinder,[3][5] and the wheelbase tends to be excessive due to the length of the engine. The wheelbase can be reduced by placing the transmission above the rear cylinder, as done on some Douglas motorcycles.[5]
Cylinders across frame
In 1919, ABC introduced a motorcycle with a flat-twin engine with the cylinders across the frame, and therefore with the crankshaft running longitudinally when referenced to the frame. To accommodate chain drive, the ABC used a bevel drive at the gearbox to change the direction of the drive through ninety degrees.[6] The 1923 BMW R32 used a similar engine position with a drive shaft using bevel gears to power the rear axle.[2]
This position allowed both cylinders to protrude into the airflow, providing excellent air cooling for each cylinder.[2][5] The Harley-Davidson XA, which used a flat-twin engine with the cylinders across the frame, maintained an oil temperature 100 °F (56 °C) cooler than a Harley-Davidson WLA with a V-twin with the cylinders in line with the frame.[7]
Many motorcyclists appreciate the way the cylinders in this layout provide protection to the rider in the event of a collision or fall, and keeps their feet warm in cold weather.[2][5]
A disadvantage of this layout is that it exposes the cylinders and valve covers to the danger of collision damage.[2][5] Longitudinal crankshaft mounting is also associated with a torque reaction that tends to twist the motorcycle to one side on sharp acceleration or when opening the throttle in neutral and in the opposite direction on sharp deceleration. Many modern motorcycle manufacturers correct for this effect by rotating flywheels or alternators in the opposite direction to that of the crankshaft.[8][9]
Automotive use
Flat-twin engines were used in several economy cars, including the Citroën 2CV, the Panhard Dyna X and Dyna Z, Steyr-Puch 500, DAF Daffodil, BMW 600, several Jowett cars between World Wars I and II, and the Toyota Publica and Toyota Sport 800. Flat-twin engines were also used in several early cars, including the Ford 1903-04 Model A, Model C and Model F.
Ignition systems
Flat-twin engines are well suited to the wasted spark ignition system, a distributor-less ignition system using a double-ended coil firing both spark plugs on each revolution, that is, on both the compression stroke and the exhaust stroke. This system requires only a single contact breaker and single coil to run two cylinders.[10]
See also
References
- ^ "BMW Motorrad USA - Bikes". http://www.bmwmotorcycles.com/. Archived from the original on 2008-08-22. Retrieved 2008-12-22.
{{cite web}}: External link in|work= - ^ a b c d e f g Wilson, Hugo (1995). "The A-Z of Motorcycles". The Encyclopedia of the Motorcycle (in UK English). London: Dorling Kindersley. pp. 26–32, 51. ISBN 0 7513 0206 6.
{{cite book}}: CS1 maint: unrecognized language (link) - ^ a b c Norbye, Jan P. (1984). "The Origins of BMW: From Flying Machines to Driving Machines". BMW - Bavaria's Driving Machines. New York, NY, USA: Beekman House. pp. 14–17. ISBN 0-517-42464-9.
- ^ Mitchel, Doug (1997). "The Early Years (1903-1928)". Harley-Davidson Chronicle. Lincolnwood, Illinois, USA: Publications International. pp. 44–45. ISBN 0-7853-2514-X.
{{cite book}}: Cite has empty unknown parameters:|month=and|lastauthoramp=(help) - ^ a b c d e f g Willoughby, Vic (1977) [1975]. "Douglas". Classic Motorcycles (Third impression ed.). The Hamlyn Publishing Group. p. 23. ISBN 0600318702.
{{cite book}}: Cite has empty unknown parameters:|lastauthoramp=and|separator=(help) - ^ Wilson, H. The Encyclopedia of the Motorcycle p. 10 Dorling-Kindersley Limited, 1995 ISBN 0 7513 0206 6
- ^ AMA Motorcycle Hall of Fame Museum: 1942 Harley-Davidson XA
- ^ Friedman, Art; Trevitt, Andrew; Cherney, Andrew; Elvidge, Jamie; Brasfield, Evans (2000). "Sport Cruisers Comparison - Seven Sport-Cruiser Motorcycles". Motorcycle Cruiser. Source Interlink Media. "Take a Spin" section, paragraph 4. Retrieved 2010-09-10.
Though the Valkyrie also has a longitudinal crankshaft, this torque reaction has been eliminated by making some of the components, such as the alternator, spin the opposite direction of the engine.
{{cite web}}: Cite has empty unknown parameter:|separator=(help); External link in|work=|month=ignored (help) - ^ Battisson, Stephen (1997). "Developing the V6 - Taming The Beast". The Laverda V6. Stephen Battisson. p. 3. Retrieved 2010-09-10.
By arranging the rest of the engine internals to rotate in the opposite direction to the crankshaft their forces are cancelled out without having to resort to the weight, complexity and friction associated with two crankshafts.
{{cite web}}: Cite has empty unknown parameter:|separator=(help); External link in|work= - ^ 2CV Stuff: A Series Ignition System