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src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg/220px-Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg/330px-Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg/440px-Douglas_motorcycle_engine%2C_Abergavenny_steam_rally_2012.jpg 2x" data-file-width="4000" data-file-height="3000" /></a><figcaption><a href="/wiki/Douglas_(motorcycles)" title="Douglas (motorcycles)">Douglas</a> 80 Plus motorcycle engine (circa 1950)</figcaption></figure> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"Flat Twin" redirects here. For Soviet radar nicknamed "flat twin", see <a href="/wiki/5N65_radar" title="5N65 radar">5N65 radar</a>.</div> <p>A <b>flat-twin engine</b> is a two-cylinder <a href="/wiki/Internal_combustion_engine" title="Internal combustion engine">internal combustion engine</a> with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the <b>boxer-twin engine</b>, where both pistons move inwards and outwards at the same time. </p><p>The flat-twin design was patented by <a href="/wiki/Karl_Benz" class="mw-redirect" title="Karl Benz">Karl Benz</a> in 1896 and the first production flat-twin engine was used in the <i>Lanchester 8 hp Phaeton</i> car released in 1900. The flat-twin engine was used in several other cars since, however a more common usage is in motorcycles; early models oriented the cylinders in line with the frame, however later models switched to the cylinders being perpendicular to the frame to provide even cooling across both cylinders. </p><p>Flat-twin engines were also used in several aircraft up until the 1930s and in various stationary applications from the 1930s to the 1960s. </p><p>The Australian lawnmower manufacturer Victa also produced a flat-twin engine push mower from August 1975 to 1980 dubbed the ‘Twin 500’, and later the ‘Supreme’. These engines were manufactured in Canada. They are very sought after as only small numbers were produced, most likely due to ignition- and fuel-related problems in early models. In the Supreme (the later model) all these problems were fixed with a rear-domed piston, crankcase mixers and refined ignition system<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (February 2024)">citation needed</span></a></i>]</sup>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Typical_design">Typical design</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=1" title="Edit section: Typical design"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Boxerengineanimation.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Boxerengineanimation.gif/220px-Boxerengineanimation.gif" decoding="async" width="220" height="75" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Boxerengineanimation.gif/330px-Boxerengineanimation.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Boxerengineanimation.gif/440px-Boxerengineanimation.gif 2x" data-file-width="729" data-file-height="249" /></a><figcaption><a href="/wiki/Flat_engine#Boxer_engine" title="Flat engine">Boxer</a> crankshaft configuration</figcaption></figure> <p>Most flat-twin engines use a <a href="/wiki/Flat_engine#Boxer_engine" title="Flat engine">boxer</a> configuration for the <a href="/wiki/Crankshaft" title="Crankshaft">crankshaft</a> and are therefore called "boxer-twin" engines. In a boxer-twin engine, the 180° crankshaft moves the pistons in phase with each other, therefore the forces generated by one piston are cancelled out by the other, resulting in excellent primary balance. The evenly spaced <a href="/wiki/Firing_order" title="Firing order">firing order</a> also assists in reducing vibration. The equal and opposite forces in a boxer-twin engine do however generate a <a href="/wiki/Couple_(mechanics)" title="Couple (mechanics)">rocking couple</a>, due to the offset distance between the pistons along the crankshaft.<sup id="cite_ref-Wilson_1-0" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 27">: 27 </span></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Allumage_2cv.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Allumage_2cv.svg/220px-Allumage_2cv.svg.png" decoding="async" width="220" height="44" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Allumage_2cv.svg/330px-Allumage_2cv.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Allumage_2cv.svg/440px-Allumage_2cv.svg.png 2x" data-file-width="713" data-file-height="141" /></a><figcaption><a href="/wiki/Wasted_spark" class="mw-redirect" title="Wasted spark">Wasted spark</a> ignition system</figcaption></figure> <p>A commonly used ignition system is <a href="/wiki/Wasted_spark" class="mw-redirect" title="Wasted spark">wasted spark</a>,<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> which is a simple ignition system using a double-ended coil firing both spark plugs on each revolution (i.e. during both the compression and exhaust strokes). This system is distributorless and requires only a single contact breaker and coil for the engine.<sup id="cite_ref-2CVStuff_3-0" class="reference"><a href="#cite_note-2CVStuff-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Crankcase_pressure">Crankcase pressure</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=2" title="Edit section: Crankcase pressure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The boxer-twin configuration can cause pressuring of the <a href="/wiki/Crankcase" title="Crankcase">crankcase</a> during each inward piston stroke and de-pressurisation during each outward piston stroke, since both pistons are moving inwards or outwards at the same time. This crankcase pumping effect (also found on single-cylinder engines and 360° parallel-twin engines) is usually addressed by means of a crankcase breather.<sup id="cite_ref-Cameron_4-0" class="reference"><a href="#cite_note-Cameron-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Citro%C3%ABn_2CV" title="Citroën 2CV">Citroën 2CV</a> boxer-twin engine took advantage of this pumping effect to maintain a partial vacuum inside the crankcase, in order to reduce oil leaks when an oil seal malfunctions. This was achieved by using a <a href="/wiki/Check_valve" title="Check valve">one-way valve</a> (a leather or rubber flap over a hole in the crankcase), to let air escape the crankcase but not enter it.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Applications">Applications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=3" title="Edit section: Applications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Automobiles">Automobiles</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=4" title="Edit section: Automobiles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Citroen_A-series_2CV_602cc_Engine_(18770871302).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg/220px-Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg/330px-Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/73/Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg/440px-Citroen_A-series_2CV_602cc_Engine_%2818770871302%29.jpg 2x" data-file-width="4288" data-file-height="3216" /></a><figcaption><a href="/wiki/Citro%C3%ABn_2CV" title="Citroën 2CV">Citroën 2CV</a> engine (viewed from rear)</figcaption></figure> <p>The beginnings of the flat-twin engine were in 1896, when Karl Benz obtained a patent for the design. A year later, his company <a href="/wiki/Benz_%26_Cie" class="mw-redirect" title="Benz & Cie">Benz & Cie</a> unveiled the first flat-twin engine, a boxer design called the "contra engine".<sup id="cite_ref-English_6-0" class="reference"><a href="#cite_note-English-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>In 1900, The <a href="/wiki/Lanchester_Motor_Company" title="Lanchester Motor Company">Lanchester Engine Company</a> began production of the <i><a href="/wiki/Lanchester_8_hp_Phaeton" title="Lanchester 8 hp Phaeton">Lanchester 8 hp Phaeton</a></i>, which used a flat-twin engine.<sup id="cite_ref-Rogliatti_7-0" class="reference"><a href="#cite_note-Rogliatti-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_8-0" class="reference"><a href="#cite_note-Smith-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> This engine had an unusual design of two counter-rotating crankshafts, with each piston attached to its crankshaft by a thick connecting rod.<sup id="cite_ref-Rogliatti_7-1" class="reference"><a href="#cite_note-Rogliatti-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Each piston was also connected to the other crankshaft by two thinner connecting rods, causing the two pistons to move on the same axis.<sup id="cite_ref-Rogliatti_7-2" class="reference"><a href="#cite_note-Rogliatti-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_8-1" class="reference"><a href="#cite_note-Smith-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> It also had the torque reaction of one crankshaft cancel the torque reaction of the other, cancelling torque reaction in the engine.<sup id="cite_ref-Rogliatti_7-3" class="reference"><a href="#cite_note-Rogliatti-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Lanchester used this engine design until 1904.<sup id="cite_ref-Smith_8-2" class="reference"><a href="#cite_note-Smith-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Other early uses of flat-twin engines were 1903-04 <a href="/wiki/Ford_Model_A_(1903%E2%80%931904)" class="mw-redirect" title="Ford Model A (1903–1904)">Ford Model A</a>, the 1904-1905 <a href="/wiki/Ford_Model_C" title="Ford Model C">Ford Model C</a>, the 1905-1906 <a href="/wiki/Ford_Model_F" title="Ford Model F">Ford Model F</a>.<sup id="cite_ref-Kimes_9-0" class="reference"><a href="#cite_note-Kimes-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Brooke_10-0" class="reference"><a href="#cite_note-Brooke-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Pages: 38–44">: 38–44 </span></sup> and several <a href="/wiki/Jowett_Cars" title="Jowett Cars">Jowett Cars</a> models from 1910 to 1937.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Culshaw&Horrobin_12-0" class="reference"><a href="#cite_note-Culshaw&Horrobin-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Pages: 188–189">: 188–189 </span></sup> </p><p>The <a href="/wiki/Citro%C3%ABn_2CV" title="Citroën 2CV">Citroën 2CV</a>, produced from 1948 to 1990, was one of the first front-wheel drive cars to use a flat engine. The 2CV was powered by an air-cooled boxer-twin engine. Also in 1948, the <a href="/wiki/Panhard_Dyna_X" title="Panhard Dyna X">Panhard Dyna X</a> was released with front-wheel drive and an air-cooled boxer-twin engine. Other cars following World War II using boxer-twin engines were the 1945-1954 <a href="/wiki/Jowett_Bradford" title="Jowett Bradford">Jowett Bradford</a> van,<sup id="cite_ref-Culshaw&Horrobin_12-1" class="reference"><a href="#cite_note-Culshaw&Horrobin-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 373">: 373 </span></sup>, the 1961-1976 <a href="/wiki/DAF_Daffodil" title="DAF Daffodil">DAF Daffodil</a>, the 1961-1978 <a href="/wiki/Toyota_Publica" title="Toyota Publica">Toyota Publica</a>, the 1965-1969 <a href="/wiki/Toyota_Sports_800" title="Toyota Sports 800">Toyota Sports 800</a> sportscar and several front-wheel drive models from <a href="/wiki/Citro%C3%ABn" title="Citroën">Citroën</a> and <a href="/wiki/Panhard" title="Panhard">Panhard</a>. Several rear-engined cars were also produced with boxer-twin engines originally designed for motorcycles, such as the 1957-1975 <a href="/wiki/Puch_500" title="Puch 500">Puch 500</a>, the 1957-1959 <a href="/wiki/BMW_600" title="BMW 600">BMW 600</a> and the 1959-1965 <a href="/wiki/BMW_700" title="BMW 700">BMW 700</a>. The Brazilian manufacturer <a href="/wiki/Gurgel" title="Gurgel">Gurgel Motores</a> used an in-house developed water-cooled boxer-twin engine (Enertron engine) and the Volkswagen air-cooled boxer-four in several models from 1988 to 1994. </p><p>The <a href="/wiki/Toyota_U_engine" title="Toyota U engine">Toyota U engine</a> was an air-cooled flat-twin engine produced from 1961 to 1976. Introduced in the <a href="/wiki/Toyota_Publica" title="Toyota Publica">Toyota Publica</a> subcompact car, the U engine was also used in the <a href="/wiki/Toyota_MiniAce" title="Toyota MiniAce">Toyota MiniAce</a> small commercial vehicle and the <a href="/wiki/Toyota_Sports_800" title="Toyota Sports 800">Toyota Sports 800</a> sports car. </p> <div class="mw-heading mw-heading3"><h3 id="Motorcycles">Motorcycles</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=5" title="Edit section: Motorcycles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading4"><h4 id="Transverse_mounting">Transverse mounting</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=6" title="Edit section: Transverse mounting"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Flat_twin_Douglas_1912_N_3.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Flat_twin_Douglas_1912_N_3.jpg/220px-Flat_twin_Douglas_1912_N_3.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Flat_twin_Douglas_1912_N_3.jpg/330px-Flat_twin_Douglas_1912_N_3.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Flat_twin_Douglas_1912_N_3.jpg/440px-Flat_twin_Douglas_1912_N_3.jpg 2x" data-file-width="640" data-file-height="480" /></a><figcaption>1912 <a href="/wiki/Douglas_(motorcycles)" title="Douglas (motorcycles)">Douglas N3</a> engine</figcaption></figure> <p>The benefits of using a flat-twin engine mounted with the crankshaft running perpendicular to the frame (therefore the cylinders being in line with the frame) are a low centre of gravity<sup id="cite_ref-Willoughby_13-0" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> and that a belt-drive or chain-drive system can be used to transmit drive to the rear wheel.<sup id="cite_ref-Willoughby_13-1" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Norbye_14-0" class="reference"><a href="#cite_note-Norbye-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> However, the downsides are uneven heat distribution (the front cylinder is more heavily cooled than the rear cylinder)<sup id="cite_ref-Willoughby_13-2" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Norbye_14-1" class="reference"><a href="#cite_note-Norbye-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> and a longer wheelbase is often required due to the length of the engine.<sup id="cite_ref-Willoughby_13-3" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>The first flat-twin <a href="/wiki/Motorcycle_engine" title="Motorcycle engine">motorcycle engine</a> was built in 1905 by the Light Motors Company in the United Kingdom. Originally named the Fée (renamed "Fairy" soon after its introduction),<sup id="cite_ref-TMCfuture_15-0" class="reference"><a href="#cite_note-TMCfuture-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> it was designed as a "bicycle engine system" which transmitted power to a pulley on the rear wheel via a chain.<sup id="cite_ref-Partridge_16-0" class="reference"><a href="#cite_note-Partridge-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Manufacture of the Fairy was taken over by the <a href="/wiki/Douglas_(motorcycles)" title="Douglas (motorcycles)">Douglas Engineering Company</a>, one of Light Motors' suppliers, when the Light Motors Company folded in 1907.<sup id="cite_ref-Wilson_1-1" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Pages: 218–219">: 218–219 </span></sup> Later in 1907, Douglas changed the drivetrain from the chain and pulley design to a belt-drive system driven directly from the engine.<sup id="cite_ref-FOOTNOTEPartridge197642_17-0" class="reference"><a href="#cite_note-FOOTNOTEPartridge197642-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> Later developments of the Douglas motorcycle were made with the cylinders in line with the frame until the Second World War.<sup id="cite_ref-Wilson_1-2" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 51">: 51 </span></sup> </p><p>Other early flat-twin motorcycles used a similar layout, with their cylinders aligned along the frame and therefore with the crankshaft running transverse to the frame.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (February 2024)">citation needed</span></a></i>]</sup> </p><p>In 1914 the main supplier of rear-hub gearboxes, <a href="/wiki/Sturmey-Archer" title="Sturmey-Archer">Sturmey-Archer</a>, introduced a 3-speed countershaft gearbox with integral kick-starter,<sup id="cite_ref-MC1914_18-0" class="reference"><a href="#cite_note-MC1914-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> which posed a design problem for motorcycles with transversely-mounted flat-twin engines. This gearbox could be relatively easily located behind a single-cylinder or V-twin engine, however this arrangement would result in an excessively long wheelbase for flat-twin engines. Solutions to this problem included using a countershaft below the engine (as used by the Douglas Fairy),<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> or a gearbox located above the engine,<sup id="cite_ref-Willoughby_13-4" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> although in some cases the cylinders were short enough to use the gearbox in the traditional location behind the engine.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>In 1916, most flat-twin motorcycles still used a transversely-mounted engine. The European models at this time included the <a href="/wiki/Bradbury_Motor_Cycles" title="Bradbury Motor Cycles">Bradbury</a> 3.5 hp (2.6 kW), the <a href="/wiki/Brough_Motorcycles" title="Brough Motorcycles">Brough HB</a>, the <a href="/wiki/Douglas_(motorcycles)" title="Douglas (motorcycles)">Douglas</a> 2.75 hp (2.05 kW) and 4 hp (3.0 kW) models, the <a href="/wiki/Humber_motorcycles" title="Humber motorcycles">Humber</a> 3.5 hp and 6 hp (4.5 kW) models, the <a href="/wiki/Matchless" title="Matchless">Matchless</a> 6 hp, the <a href="/wiki/Montgomery_Motorcycles" title="Montgomery Motorcycles">Montgomery</a> 6 hp, <a href="/wiki/Williamson_Flat_Twin" title="Williamson Flat Twin">Williamson Flat Twin</a> 8 hp (6.0 kW), and the Bayerische Flugzeugwerke Helios (the predecessor to BMW's first motorcycle). Models produced in the United States included the <a href="/wiki/Indian_Model_O" title="Indian Model O">Indian Model O</a> and the <a href="/wiki/Harley-Davidson_Model_W" title="Harley-Davidson Model W">Harley-Davidson Model W</a>.<sup id="cite_ref-MC1916_22-0" class="reference"><a href="#cite_note-MC1916-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Norbye_14-2" class="reference"><a href="#cite_note-Norbye-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Wilson_1-3" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 26">: 26 </span></sup><sup id="cite_ref-Indian_and_Harley_23-0" class="reference"><a href="#cite_note-Indian_and_Harley-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Longitudinal_mounting">Longitudinal mounting</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=7" title="Edit section: Longitudinal mounting"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:204px;max-width:204px"><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Xa-engine.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Xa-engine.jpg/200px-Xa-engine.jpg" decoding="async" width="200" height="154" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Xa-engine.jpg/300px-Xa-engine.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/c/cb/Xa-engine.jpg 2x" data-file-width="400" data-file-height="308" /></a></span></div><div class="thumbcaption">1942 <a href="/wiki/Harley-Davidson_XA" title="Harley-Davidson XA">Harley-Davidson XA</a> engine</div></div></div><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/0/0a/Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg/200px-Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg" decoding="async" width="200" height="195" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/0/0a/Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg/300px-Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/0/0a/Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg/400px-Opposed_cylinders_on_a_1967_BMW_motorcycle.jpg 2x" data-file-width="800" data-file-height="778" /></a></span></div><div class="thumbcaption">1967 <a href="/wiki/BMW_R60/2" title="BMW R60/2">BMW R 60/2</a> engine</div></div></div></div></div> <p>The main benefit of mounting a flat-twin engine with the crankshaft in line with the frame (therefore the cylinders sitting sideways in the frame) is that an air-cooled engine receives the same amount of cooling for each cylinder.<sup id="cite_ref-Wilson_1-4" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Pages: 26–27">: 26–27 </span></sup><sup id="cite_ref-Willoughby_13-5" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Harley-Davidson_XA" title="Harley-Davidson XA">Harley-Davidson XA</a>, which used a flat-twin engine with the cylinders across the frame, maintained an oil temperature 100 °F (56 °C) cooler than a <a href="/wiki/Harley-Davidson_WLA" title="Harley-Davidson WLA">Harley-Davidson WLA</a> with a V-twin with the cylinders in line with the frame.<sup id="cite_ref-Wood_24-0" class="reference"><a href="#cite_note-Wood-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> A side benefit is that the cylinders provide protection to the rider in the event of a collision or fall, and keeps their feet warm in cold weather.<sup id="cite_ref-Willoughby_13-6" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Wilson_1-5" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 27">: 27 </span></sup> The downsides are that the engine cannot be mounted as close to the ground (otherwise the cylinders can scrape the ground during cornering)<sup id="cite_ref-Cocco_25-0" class="reference"><a href="#cite_note-Cocco-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> and that it exposes the cylinders and valve covers to the danger of collision damage.<sup id="cite_ref-Willoughby_13-7" class="reference"><a href="#cite_note-Willoughby-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Wilson_1-6" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 27">: 27 </span></sup> </p><p>Longitudinal mounting also means that the torque reaction will twist the motorcycle to one side (such as on sharp acceleration/deceleration or when opening the throttle in neutral) instead of shifting the weight balance between the front and rear wheels. However, many modern motorcycles reduce this effect by rotating flywheels or alternators in the opposite direction to that of the crankshaft.<sup id="cite_ref-motorcyclecruiser.com_26-0" class="reference"><a href="#cite_note-motorcyclecruiser.com-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Battisson_27-0" class="reference"><a href="#cite_note-Battisson-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p><p>One of the first motorcycles with a longitudinally-mounted flat-twin engine was the 1916 <a href="/wiki/ABC_motorcycles" title="ABC motorcycles">ABC</a>, which was built in the United Kingdom.<sup id="cite_ref-MC1916_22-1" class="reference"><a href="#cite_note-MC1916-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> To accommodate chain drive, the ABC used a <a href="/wiki/Bevel_gear" title="Bevel gear">bevel drive</a> at the gearbox to change the direction of the drive through ninety degrees.<sup id="cite_ref-Wilson_1-7" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 10">: 10 </span></sup> BMW's first motorcycle, the 1923 <a href="/wiki/BMW_R32" title="BMW R32">BMW R 32</a> was another early example of a longitudinally-mounted flat-twin engine, although it this case the power was transmitted to the rear wheel via a shaft drive.<sup id="cite_ref-Wilson_1-8" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 26">: 26 </span></sup> </p><p>Over time, longitudinal mounting became more common for flat-twin engines. <a href="/wiki/BMW_Motorrad" title="BMW Motorrad">BMW</a> has a long history of flat-twin engine motorcycles,<sup id="cite_ref-Wilson_1-9" class="reference"><a href="#cite_note-Wilson-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Pages: 26–32">: 26–32 </span></sup><sup id="cite_ref-BMWMotorcycles_28-0" class="reference"><a href="#cite_note-BMWMotorcycles-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> as do <a href="/wiki/IMZ-Ural" title="IMZ-Ural">Ural</a> (Russia) and <a href="/wiki/Dnepr_(motorcycle)" title="Dnepr (motorcycle)">Dnepr</a> (Ukraine). </p> <div style="clear:right;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Aviation">Aviation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=8" title="Edit section: Aviation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Bristol_Cherub_II.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Bristol_Cherub_II.jpg/170px-Bristol_Cherub_II.jpg" decoding="async" width="170" height="248" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Bristol_Cherub_II.jpg/255px-Bristol_Cherub_II.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Bristol_Cherub_II.jpg/340px-Bristol_Cherub_II.jpg 2x" data-file-width="537" data-file-height="783" /></a><figcaption><a href="/wiki/Bristol_Cherub" title="Bristol Cherub">Bristol Cherub</a> II installed in aircraft</figcaption></figure> <p>In 1902, the <a href="/wiki/Pearse_monoplane" class="mw-redirect" title="Pearse monoplane">Pearse monoplane</a> (which would later become one of the first aircraft to achieve flight) was powered by a flat-twin engine built on a farm by a hobbyist inventor.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-SciMedia_30-0" class="reference"><a href="#cite_note-SciMedia-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> This engine used the unusual design of a single shared <a href="/wiki/Crank_pin" class="mw-redirect" title="Crank pin">crank pin</a> and double acting pistons.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> In 1908, the French company Dutheil-Chalmers began production of flat-twin aircraft engines, which used two counter-rotating crankshafts.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> The Dutheil-Chlamers engine was used by the 1907 <a href="/wiki/Santos-Dumont_Demoiselle" title="Santos-Dumont Demoiselle">Santos-Dumont Demoiselle</a> <i>No. 20</i> experimental airplane, with later versions of this airplane being produced with flat-twin engines from <a href="/wiki/Darracq" class="mw-redirect" title="Darracq">Darracq</a> and <a href="/wiki/Cl%C3%A9ment-Bayard" title="Clément-Bayard">Clément-Bayard</a>. </p><p>Most piston-engined aircraft used more than two cylinders, however other flat-twin aircraft engines from the 1920s and 1930s include the American <a href="/wiki/Aeronca_E-107" title="Aeronca E-107">Aeronca E-107</a> and <a href="/wiki/Aeronca_E-113" title="Aeronca E-113">Aeronca E-113</a>, the British <a href="/wiki/Bristol_Cherub" title="Bristol Cherub">Bristol Cherub</a>, and the Czechoslovakian <a href="/wiki/Praga_B2" title="Praga B2">Praga B2</a>. The <a href="/wiki/HKS_700E" title="HKS 700E">HKS 700E</a> is an oil-cooled flat twin for ultralight aircraft that is currently<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items" title="Wikipedia:Manual of Style/Dates and numbers"><span title="The time period mentioned near this tag is ambiguous. (February 2024)">when?</span></a></i>]</sup> in production.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p><p>In larger aircraft, flat-twin engines have been used in <a href="/wiki/Auxiliary_power_unit" title="Auxiliary power unit">auxiliary power units</a> (APUs). A notable example was made by <a href="/wiki/ABC_Motors" title="ABC Motors">ABC Motors</a> in the 1920s and 1930s.<sup id="cite_ref-Chaplin_37-0" class="reference"><a href="#cite_note-Chaplin-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> During World War II, the <a href="/wiki/Norbert_Riedel" title="Norbert Riedel">Riedel</a> firm in Germany designed and manufactured a two-stroke flat-twin engine as <a href="/wiki/Aircraft_engine_starting#Gas_turbine_engines" title="Aircraft engine starting">jet engine starter motors</a> for the Junkers Jumo 004, BMW 003 and Heinkel HeS 011 jet engines<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gunston_39-0" class="reference"><a href="#cite_note-Gunston-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Other_uses">Other uses</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=9" title="Edit section: Other uses"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Maytag" title="Maytag">Maytag</a> 'Model 72' flat-twin engines— produced from 1937 until some time between 1952 and 1960— were used in various applications including clothes washing machines.<sup id="cite_ref-Shelton_40-0" class="reference"><a href="#cite_note-Shelton-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Kinney_41-0" class="reference"><a href="#cite_note-Kinney-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hunn_43-0" class="reference"><a href="#cite_note-Hunn-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-MaytagClub37_44-0" class="reference"><a href="#cite_note-MaytagClub37-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> </p><p>Electrical generators using flat-twin engines were built by Norman Engineering Company from 1932 to 1968 and by Douglas during World War II.<sup id="cite_ref-Brown_45-0" class="reference"><a href="#cite_note-Brown-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> <i>Enfield Industrial Engines</i> (part of <a href="/wiki/Royal_Enfield" title="Royal Enfield">Royal Enfield</a>) produced flat-twin two-stroke petrol engines during World War II which were used for generators and other military uses. After 1945, Enfield produced flat-twin diesel engines, with applications including farm and marine use. <a href="/wiki/Coventry_Victor" title="Coventry Victor">Coventry Victor</a> introduced a diesel version of its existing 688 cc petrol flat-twin in 1932, and went on to produce flat-twin diesel and petrol engines for a variety of industrial and marine uses into the 1950s.<sup id="cite_ref-Baldwin_46-0" class="reference"><a href="#cite_note-Baldwin-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 111">: 111 </span></sup> </p><p>Two-stroke flat-twins were often used as <a href="/wiki/Outboard_motor" title="Outboard motor">outboard motors</a> for boats,<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items" title="Wikipedia:Manual of Style/Dates and numbers"><span title="The time period mentioned near this tag is ambiguous. (August 2019)">when?</span></a></i>]</sup> as they were smoother than single-cylinder engines. In the 1940s, they were largely replaced by straight-twin two-stroke engines, which were easier to start and no longer had excessive amounts of vibration.<sup id="cite_ref-Holcolmb_47-0" class="reference"><a href="#cite_note-Holcolmb-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Flat-twin_engine&action=edit&section=10" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-Wilson-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Wilson_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Wilson_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Wilson_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Wilson_1-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Wilson_1-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Wilson_1-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Wilson_1-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Wilson_1-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Wilson_1-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-Wilson_1-9"><sup><i><b>j</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFWilson1995" class="citation book cs1">Wilson, Hugo (1995). "The A-Z of Motorcycles". <i>The Encyclopedia of the Motorcycle</i>. London, UK: Dorling Kindersley. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7513-0206-6" title="Special:BookSources/0-7513-0206-6"><bdi>0-7513-0206-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+A-Z+of+Motorcycles&rft.btitle=The+Encyclopedia+of+the+Motorcycle&rft.place=London%2C+UK&rft.pub=Dorling+Kindersley&rft.date=1995&rft.isbn=0-7513-0206-6&rft.aulast=Wilson&rft.aufirst=Hugo&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1 cs1-prop-unfit"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20170627021204/http://www.animatedpiston.com/BMW.htm">"BMW Motorcycle Engine Animation"</a>. <i>www.animatedpiston.com</i>. Archived from the original on 27 June 2017.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.animatedpiston.com&rft.atitle=BMW+Motorcycle+Engine+Animation&rft_id=http%3A%2F%2Fwww.animatedpiston.com%2FBMW.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-2CVStuff-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-2CVStuff_3-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120316122922/http://www.2cvstuff.com/Files/ignition.pdf">"2CV Stuff: A Series Ignition System - Specifications"</a> <span class="cs1-format">(PDF)</span>. <i>2CV Stuff</i>. Grantham, Lincolnshire, UK: Oui2. Archived from <a rel="nofollow" class="external text" href="http://www.2cvstuff.com/Files/ignition.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2012-03-16<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-05-18</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=2CV+Stuff&rft.atitle=2CV+Stuff%3A+A+Series+Ignition+System+-+Specifications&rft_id=http%3A%2F%2Fwww.2cvstuff.com%2FFiles%2Fignition.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Cameron-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Cameron_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCameron1992" class="citation journal cs1"><a href="/wiki/Kevin_Cameron_(journalist)" title="Kevin Cameron (journalist)">Cameron, Kevin</a> (January 1992). 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Retrieved <span class="nowrap">17 April</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Cycle+World&rft.atitle=TDC%3A+Pumped&rft.volume=31&rft.issue=1&rft.pages=14&rft.date=1992-01&rft.issn=0011-4286&rft.aulast=Cameron&rft.aufirst=Kevin&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DeToxUA1LZbsC%26pg%3DPA14&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20190119174443/https://discourse-cdn-sjc1.com/cartalk/uploads/default/optimized/2X/0/0e996467337b68f98a6b64844e16ba92610daec2_2_1035x567.gif">"Citroen 2CV engine operation animation"</a>. <i>www.discourse.com</i>. Archived from <a rel="nofollow" class="external text" href="https://discourse-cdn-sjc1.com/cartalk/uploads/default/optimized/2X/0/0e996467337b68f98a6b64844e16ba92610daec2_2_1035x567.gif">the original</a> on 19 January 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.discourse.com&rft.atitle=Citroen+2CV+engine+operation+animation&rft_id=https%3A%2F%2Fdiscourse-cdn-sjc1.com%2Fcartalk%2Fuploads%2Fdefault%2Foptimized%2F2X%2F0%2F0e996467337b68f98a6b64844e16ba92610daec2_2_1035x567.gif&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-English-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-English_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFEnglish2010" class="citation news cs1">English, Bob (2010-04-29). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20131220085552/http://www.theglobeandmail.com/globe-drive/car-life/classic-cars/the-engine-that-benz-built-still-survives/article4317376/">"The engine that Benz built still survives"</a>. <i>The Globe and Mail</i>. Toronto, Canada. Archived from <a rel="nofollow" class="external text" href="https://www.theglobeandmail.com/globe-drive/car-life/classic-cars/the-engine-that-benz-built-still-survives/article4317376/">the original</a> on 2013-12-20<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-12-19</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Globe+and+Mail&rft.atitle=The+engine+that+Benz+built+still+survives&rft.date=2010-04-29&rft.aulast=English&rft.aufirst=Bob&rft_id=https%3A%2F%2Fwww.theglobeandmail.com%2Fglobe-drive%2Fcar-life%2Fclassic-cars%2Fthe-engine-that-benz-built-still-survives%2Farticle4317376%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Rogliatti-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-Rogliatti_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Rogliatti_7-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Rogliatti_7-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Rogliatti_7-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRogliatti1973" class="citation book cs1">Rogliatti, Gianni (1973). <i>Period Cars</i>. Feltham, Middlesex, UK: Hamlyn. p. 140. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-600-33401-5" title="Special:BookSources/0-600-33401-5"><bdi>0-600-33401-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Period+Cars&rft.place=Feltham%2C+Middlesex%2C+UK&rft.pages=140&rft.pub=Hamlyn&rft.date=1973&rft.isbn=0-600-33401-5&rft.aulast=Rogliatti&rft.aufirst=Gianni&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Smith-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-Smith_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Smith_8-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Smith_8-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSmith2010" class="citation web cs1">Smith, Sam (October 2010). <a rel="nofollow" class="external text" href="http://www.caranddriver.com/features/the-10-most-unusual-engines-of-all-time-feature">"The 10 Most Unusual Engines of All Time"</a>. <i><a href="/wiki/Car_and_Driver" title="Car and Driver">Car and Driver</a></i>. Hearst. Lanchester Twin-Crank Twin. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120703192824/http://www.caranddriver.com/features/the-10-most-unusual-engines-of-all-time-feature">Archived</a> from the original on 2012-07-03<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-05-17</span></span>. <q>One crank lived above the other, and each piston had three connecting rods—two light outer ones and a heavier one in the centre. The light rods went to one crank, the heavy rods to the other, and the two shafts counterrotated.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Car+and+Driver&rft.atitle=The+10+Most+Unusual+Engines+of+All+Time&rft.pages=Lanchester+Twin-Crank+Twin&rft.date=2010-10&rft.aulast=Smith&rft.aufirst=Sam&rft_id=http%3A%2F%2Fwww.caranddriver.com%2Ffeatures%2Fthe-10-most-unusual-engines-of-all-time-feature&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Kimes-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-Kimes_9-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKimes1996" class="citation book cs1">Kimes, Beverly (1996). <i>Standard Catalog of American Cars 1805-1942</i>. Krause Publications. p. 572. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-87341-428-4" title="Special:BookSources/0-87341-428-4"><bdi>0-87341-428-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Standard+Catalog+of+American+Cars+1805-1942&rft.pages=572&rft.pub=Krause+Publications&rft.date=1996&rft.isbn=0-87341-428-4&rft.aulast=Kimes&rft.aufirst=Beverly&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Brooke-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-Brooke_10-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrooke2008" class="citation book cs1">Brooke, Lindsay (2008). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=dvZjf-4qbeAC&pg=PA29">"Chapter 1 Before the Model T"</a>. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=dvZjf-4qbeAC&pg=PA38"><i>Ford Model T: The Car that Put the World on Wheels</i></a>. Minneapolis, MN USA: Motorbooks. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-76032-728-9" title="Special:BookSources/978-0-76032-728-9"><bdi>978-0-76032-728-9</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-05-18</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+1+Before+the+Model+T&rft.btitle=Ford+Model+T%3A+The+Car+that+Put+the+World+on+Wheels&rft.place=Minneapolis%2C+MN+USA&rft.pub=Motorbooks&rft.date=2008&rft.isbn=978-0-76032-728-9&rft.aulast=Brooke&rft.aufirst=Lindsay&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DdvZjf-4qbeAC%26pg%3DPA29&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=hVZWnZbUJOYC&pg=PA189">Specification tables</a></span> </li> <li id="cite_note-Culshaw&Horrobin-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-Culshaw&Horrobin_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Culshaw&Horrobin_12-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCulshawHorrobin2013" class="citation book cs1">Culshaw, David; Horrobin, Peter (2013) [1974]. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=hVZWnZbUJOYC"><i>The Complete Catalogue of British Cars 1895 - 1975</i></a> (e-book ed.). Poundbury, Dorchester, UK: Veloce Publishing. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-845845-83-4" title="Special:BookSources/978-1-845845-83-4"><bdi>978-1-845845-83-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Complete+Catalogue+of+British+Cars+1895+-+1975&rft.place=Poundbury%2C+Dorchester%2C+UK&rft.edition=e-book&rft.pub=Veloce+Publishing&rft.date=2013&rft.isbn=978-1-845845-83-4&rft.aulast=Culshaw&rft.aufirst=David&rft.au=Horrobin%2C+Peter&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DhVZWnZbUJOYC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Willoughby-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Willoughby_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Willoughby_13-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Willoughby_13-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Willoughby_13-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Willoughby_13-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Willoughby_13-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Willoughby_13-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Willoughby_13-7"><sup><i><b>h</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWilloughby1977" class="citation book cs1">Willoughby, Vic (1977) [1975]. "Douglas". <i>Classic Motorcycles</i> (Third impression ed.). The Hamlyn Publishing Group. p. 23. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-600-31870-2" title="Special:BookSources/0-600-31870-2"><bdi>0-600-31870-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Douglas&rft.btitle=Classic+Motorcycles&rft.pages=23&rft.edition=Third+impression&rft.pub=The+Hamlyn+Publishing+Group&rft.date=1977&rft.isbn=0-600-31870-2&rft.aulast=Willoughby&rft.aufirst=Vic&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Norbye-14"><span class="mw-cite-backlink">^ <a href="#cite_ref-Norbye_14-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Norbye_14-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Norbye_14-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNorbye1984" class="citation book cs1">Norbye, Jan P. (1984). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/bmwbavariasdrivi00norb/page/15">"The Origins of BMW: From Flying Machines to Driving Machines"</a></span>. <i>BMW - Bavaria's Driving Machines</i>. New York, NY, USA: Beekman House. p. <a rel="nofollow" class="external text" href="https://archive.org/details/bmwbavariasdrivi00norb/page/15">15</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-517-42464-9" title="Special:BookSources/0-517-42464-9"><bdi>0-517-42464-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Origins+of+BMW%3A+From+Flying+Machines+to+Driving+Machines&rft.btitle=BMW+-+Bavaria%27s+Driving+Machines&rft.place=New+York%2C+NY%2C+USA&rft.pages=15&rft.pub=Beekman+House&rft.date=1984&rft.isbn=0-517-42464-9&rft.aulast=Norbye&rft.aufirst=Jan+P.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fbmwbavariasdrivi00norb%2Fpage%2F15&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-TMCfuture-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-TMCfuture_15-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1">"The engine of the future". <i><a href="/wiki/The_Motor_Cycle_(magazine)" class="mw-redirect" title="The Motor Cycle (magazine)">The Motor Cycle</a></i>. Iliffe & Sons Ltd.: 283 October 5, 1916.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Motor+Cycle&rft.atitle=The+engine+of+the+future&rft.pages=283&rft.date=1916-10-05&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Partridge-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-Partridge_16-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPartridge1976" class="citation cs2">Partridge, Michael (1976), "1905 2 1⁄2hp Joseph Barter motorcycle", <i>Motorcycle Pioneers: The Men, the Machines, the Events 1860-1930</i>, David & Charles (Publishers), p. 42, <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7153-7-209-2" title="Special:BookSources/0-7153-7-209-2"><bdi>0-7153-7-209-2</bdi></a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=1905+2+1%E2%81%842hp+Joseph+Barter+motorcycle&rft.btitle=Motorcycle+Pioneers%3A+The+Men%2C+the+Machines%2C+the+Events+1860-1930&rft.pages=42&rft.pub=David+%26+Charles+%28Publishers%29&rft.date=1976&rft.isbn=0-7153-7-209-2&rft.aulast=Partridge&rft.aufirst=Michael&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-FOOTNOTEPartridge197642-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEPartridge197642_17-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFPartridge1976">Partridge 1976</a>, p. 42.</span> </li> <li id="cite_note-MC1914-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-MC1914_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1">"A Sturmey-Archer Countershaft Gear". <i><a href="/wiki/The_Motor_Cycle_(magazine)" class="mw-redirect" title="The Motor Cycle (magazine)">The Motor Cycle</a></i>. Iliffe & Sons Ltd.: 274 27 August 1914.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Motor+Cycle&rft.atitle=A+Sturmey-Archer+Countershaft+Gear&rft.pages=274&rft.date=1914-08-27&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.motorcycles20thcentury.com/motors/drawing/Douglas-1911.jpg">Drawing of 1911 Douglas</a></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.motorcycles20thcentury.com/motors/normal/Douglas-K32-1932.jpg">Drawing of 1932 Douglas K32</a></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.motorcycles20thcentury.com/motors/normal/Douglas-1926.jpg">Drawing of 1926 Douglas</a></span> </li> <li id="cite_note-MC1916-22"><span class="mw-cite-backlink">^ <a href="#cite_ref-MC1916_22-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-MC1916_22-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1">"Flat Twins". <i><a href="/wiki/The_Motor_Cycle_(magazine)" class="mw-redirect" title="The Motor Cycle (magazine)">The Motor Cycle</a></i>. Iliffe & Sons Ltd.: <span class="nowrap">400–</span>403 November 9, 1916.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Motor+Cycle&rft.atitle=Flat+Twins&rft.pages=%3Cspan+class%3D%22nowrap%22%3E400-%3C%2Fspan%3E403&rft.date=1916-11-09&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Indian_and_Harley-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-Indian_and_Harley_23-0">^</a></b></span> <span class="reference-text"> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWood2001b" class="citation journal cs1">Wood, Bill, ed. (October 2001b). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=DfsDAAAAMBAJ&pg=PA71">"Classics: 1917 Indian Model O"</a>. <i>American Motorcyclist</i>. <b>55</b> (10). Pickerington, OH US: <a href="/wiki/American_Motorcyclist_Association" title="American Motorcyclist Association">American Motorcyclist Association</a>: 71. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0277-9358">0277-9358</a><span class="reference-accessdate">. Retrieved <span class="nowrap">19 April</span> 2015</span>. <q>Like the early Douglases, the Model O had its engine placed in the frame with the cylinders facing fore and aft, rather than sticking out to each side...</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=American+Motorcyclist&rft.atitle=Classics%3A+1917+Indian+Model+O&rft.volume=55&rft.issue=10&rft.pages=71&rft.date=2001-10&rft.issn=0277-9358&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DDfsDAAAAMBAJ%26pg%3DPA71&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMitchel1997" class="citation book cs1">Mitchel, Doug (1997). <a rel="nofollow" class="external text" href="https://archive.org/details/harleydavidsonch0000mitc_u3q3/page/44">"The Early Years (1903–1928)"</a>. <i>Harley-Davidson Chronicle</i>. Lincolnwood, Illinois, USA: Publications International. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/harleydavidsonch0000mitc_u3q3/page/44">44–45</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7853-2514-X" title="Special:BookSources/0-7853-2514-X"><bdi>0-7853-2514-X</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Early+Years+%281903%E2%80%931928%29&rft.btitle=Harley-Davidson+Chronicle&rft.place=Lincolnwood%2C+Illinois%2C+USA&rft.pages=44-45&rft.pub=Publications+International&rft.date=1997&rft.isbn=0-7853-2514-X&rft.aulast=Mitchel&rft.aufirst=Doug&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fharleydavidsonch0000mitc_u3q3%2Fpage%2F44&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWood2001a" class="citation journal cs1">Wood, Bill, ed. (March 2001a). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=HPsDAAAAMBAJ&pg=PA127">"Classics: 1922 Harley-Davidson Sport Twin"</a>. <i>American Motorcyclist</i>. <b>55</b> (3). Pickerington, OH US: <a href="/wiki/American_Motorcyclist_Association" title="American Motorcyclist Association">American Motorcyclist Association</a>: 127. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0277-9358">0277-9358</a><span class="reference-accessdate">. Retrieved <span class="nowrap">19 April</span> 2015</span>. <q>In building the Sport Twin, Harley took Douglas' lead in orienting the cylinders in line with the frame.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=American+Motorcyclist&rft.atitle=Classics%3A+1922+Harley-Davidson+Sport+Twin&rft.volume=55&rft.issue=3&rft.pages=127&rft.date=2001-03&rft.issn=0277-9358&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DHPsDAAAAMBAJ%26pg%3DPA127&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></li></ul> </span></li> <li id="cite_note-Wood-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-Wood_24-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWood1999" class="citation journal cs1">Wood, Bill, ed. (March 1999). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=A_cDAAAAMBAJ&pg=PA127">"Classics: 1942 Harley-Davidson XA"</a>. <i>American Motorcyclist</i>. <b>53</b> (3). Pickerington, OH US: <a href="/wiki/American_Motorcyclist_Association" title="American Motorcyclist Association">American Motorcyclist Association</a>: 127. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0277-9358">0277-9358</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2015-04-19</span></span>. <q>Mechanically, the large cooling fins stuck straight out in the breeze, reportedly keeping the XA's oil temperature 100 degrees cooler than a standard Harley 45.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=American+Motorcyclist&rft.atitle=Classics%3A+1942+Harley-Davidson+XA&rft.volume=53&rft.issue=3&rft.pages=127&rft.date=1999-03&rft.issn=0277-9358&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DA_cDAAAAMBAJ%26pg%3DPA127&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Cocco-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-Cocco_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCocco2004" class="citation book cs1">Cocco, Gaetano (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Ydk0bgq2_3YC&pg=PA113">"Chapter 11: The Engine"</a>. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Ydk0bgq2_3YC"><i>Motorcycle Design and Technology</i></a> (English ed.). St. Paul, MN USA: Motorbooks International. p. 118. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7603-1990-1" title="Special:BookSources/0-7603-1990-1"><bdi>0-7603-1990-1</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-09-09</span></span>. <q>However, it does create some problems for longitudinal development of the bike because the boxer cylinders have to be positioned high up from the ground in order to protect them from scraping the ground when leant over in turns.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+11%3A+The+Engine&rft.btitle=Motorcycle+Design+and+Technology&rft.place=St.+Paul%2C+MN+USA&rft.pages=118&rft.edition=English&rft.pub=Motorbooks+International&rft.date=2004&rft.isbn=0-7603-1990-1&rft.aulast=Cocco&rft.aufirst=Gaetano&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DYdk0bgq2_3YC%26pg%3DPA113&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged April 2024">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup></span> </li> <li id="cite_note-motorcyclecruiser.com-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-motorcyclecruiser.com_26-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFriedmanTrevittCherneyElvidge2000" class="citation web cs1">Friedman, Art; Trevitt, Andrew; Cherney, Andrew; Elvidge, Jamie; Brasfield, Evans (April 2000). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100502180324/http://www.motorcyclecruiser.com/roadtests/sport_cruisers_comparison/index.html">"Sport Cruisers Comparison - Seven Sport-Cruiser Motorcycles"</a>. <i>Motorcycle Cruiser</i>. Source Interlink Media. "Take a Spin" section, paragraph 4. Archived from <a rel="nofollow" class="external text" href="http://www.motorcyclecruiser.com/roadtests/sport_cruisers_comparison/index.html">the original</a> on 2010-05-02<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-09-10</span></span>. <q>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.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Motorcycle+Cruiser&rft.atitle=Sport+Cruisers+Comparison+-+Seven+Sport-Cruiser+Motorcycles&rft.pages=%22Take+a+Spin%22+section%2C+paragraph+4&rft.date=2000-04&rft.aulast=Friedman&rft.aufirst=Art&rft.au=Trevitt%2C+Andrew&rft.au=Cherney%2C+Andrew&rft.au=Elvidge%2C+Jamie&rft.au=Brasfield%2C+Evans&rft_id=http%3A%2F%2Fwww.motorcyclecruiser.com%2Froadtests%2Fsport_cruisers_comparison%2Findex.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Battisson-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-Battisson_27-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBattisson1997" class="citation web cs1">Battisson, Stephen (1997). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110708092245/http://www.breganzane.com/vm/history/v6/page3.html">"Developing the V6 - Taming The Beast"</a>. <i>The Laverda V6</i>. Stephen Battisson. p. 3. Archived from <a rel="nofollow" class="external text" href="http://www.breganzane.com/vm/history/v6/page3.html">the original</a> on July 8, 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-09-10</span></span>. <q>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.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Laverda+V6&rft.atitle=Developing+the+V6+-+Taming+The+Beast&rft.pages=3&rft.date=1997&rft.aulast=Battisson&rft.aufirst=Stephen&rft_id=http%3A%2F%2Fwww.breganzane.com%2Fvm%2Fhistory%2Fv6%2Fpage3.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-BMWMotorcycles-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-BMWMotorcycles_28-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080822022309/http://www.bmwmotorcycles.com/bikes/index.jsp?bikeSection=">"BMW Motorrad USA - Bikes"</a>. <i>bmwmotorcycles.com/</i>. Archived from <a rel="nofollow" class="external text" href="http://www.bmwmotorcycles.com/bikes/index.jsp?bikeSection=">the original</a> on 2008-08-22<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-12-22</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=bmwmotorcycles.com%2F&rft.atitle=BMW+Motorrad+USA+-+Bikes&rft_id=http%3A%2F%2Fwww.bmwmotorcycles.com%2Fbikes%2Findex.jsp%3FbikeSection%3D&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://nzhistory.govt.nz/culture/richard-pearse">"Richard Pearse"</a>. <i>www.nzhistory.govt.nz</i><span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.nzhistory.govt.nz&rft.atitle=Richard+Pearse&rft_id=https%3A%2F%2Fnzhistory.govt.nz%2Fculture%2Frichard-pearse&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-SciMedia-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-SciMedia_30-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSciMedia2012" class="citation web cs1"><a rel="nofollow" class="external text" href="http://sciencelearn.org.nz/Contexts/Flight/Sci-Media/Images/Richard-Pearse-s-monoplane">"Richard Pearse's monoplane"</a>. University of Waikato. 2012-04-26.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Richard+Pearse%27s+monoplane&rft.pub=University+of+Waikato&rft.date=2012-04-26&rft_id=http%3A%2F%2Fsciencelearn.org.nz%2FContexts%2FFlight%2FSci-Media%2FImages%2FRichard-Pearse-s-monoplane&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://worldhistory.us/american-history/richard-pearse-designed-and-built-early-flying-machine.php">"Richard Pearse Designed and Built Early Flying Machine"</a>. <i>www.worldhistory.us</i>. 1 July 2017<span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.worldhistory.us&rft.atitle=Richard+Pearse+Designed+and+Built+Early+Flying+Machine&rft.date=2017-07-01&rft_id=https%3A%2F%2Fworldhistory.us%2Famerican-history%2Frichard-pearse-designed-and-built-early-flying-machine.php&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.billzilla.org/ffeng.gif">Drawing of replica engine</a></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.ctie.monash.edu.au/hargrave/pearse1.html">"Richard Pearse : New Zealand Pioneer Aviator (1877 - 1953)"</a>. <i>www.monash.edu.au</i><span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.monash.edu.au&rft.atitle=Richard+Pearse+%3A+New+Zealand+Pioneer+Aviator+%281877+-+1953%29&rft_id=http%3A%2F%2Fwww.ctie.monash.edu.au%2Fhargrave%2Fpearse1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://oldmachinepress.com/2017/07/20/dutheil-chalmers-eole/">"Dutheil-Chalmers Éole Opposed-Piston Aircraft Engine"</a>. <i>www.oldmachinepress.com</i>. 20 July 2017<span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.oldmachinepress.com&rft.atitle=Dutheil-Chalmers+%C3%89ole+Opposed-Piston+Aircraft+Engine&rft.date=2017-07-20&rft_id=https%3A%2F%2Foldmachinepress.com%2F2017%2F07%2F20%2Fdutheil-chalmers-eole%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20190803093713/http://www.oldengine.org/members/diesel/Duxford/1910.htm">"Principal Aero Engines of 1910: Page 141 - Horizontal Engines"</a>. <i>www.oldengine.org</i>. Archived from <a rel="nofollow" class="external text" href="http://www.oldengine.org/members/diesel/Duxford/1910.htm">the original</a> on 3 August 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.oldengine.org&rft.atitle=Principal+Aero+Engines+of+1910%3A+Page+141+-+Horizontal+Engines&rft_id=http%3A%2F%2Fwww.oldengine.org%2Fmembers%2Fdiesel%2FDuxford%2F1910.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.hksengines.com/">"HKS Aviation Engines"</a>. <i>www.hksengines.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.hksengines.com&rft.atitle=HKS+Aviation+Engines&rft_id=http%3A%2F%2Fwww.hksengines.com%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Chaplin-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-Chaplin_37-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFChaplinNixon1939" class="citation journal cs1">Chaplin, R. H.; Nixon, F. (1939-04-06). Poulsen, C. M. (ed.). <a rel="nofollow" class="external text" href="http://www.flightglobal.com/pdfarchive/view/1939/1939%20-%201031.html">"Ancillary Power Services"</a>. <i>Flight</i>. <b>35</b> (1580). London: <span class="nowrap">357–</span>359<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-12-29</span></span>. <q>Both lecturers discussed the claims of the auxiliary engine for supplying service power. This is a well-known British example, the A.B.C. flat twin.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Flight&rft.atitle=Ancillary+Power+Services&rft.volume=35&rft.issue=1580&rft.pages=%3Cspan+class%3D%22nowrap%22%3E357-%3C%2Fspan%3E359&rft.date=1939-04-06&rft.aulast=Chaplin&rft.aufirst=R.+H.&rft.au=Nixon%2C+F.&rft_id=http%3A%2F%2Fwww.flightglobal.com%2Fpdfarchive%2Fview%2F1939%2F1939%2520-%25201031.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchulte1946" class="citation web cs1">Schulte, Rudolph C. (1946). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180929074301/http://legendsintheirowntime.com/LiTOT/Content/1946/Av_4603_DA_BMW003.html">"Design Analysis of BMW 003 Turbojet - "Starting the Engine"<span class="cs1-kern-right"></span>"</a>. <i>legendsintheirowntime.com</i>. United States Army Air Force - Turbojet and Gus Turbine Developments, HQ, AAF. Archived from <a rel="nofollow" class="external text" href="http://legendsintheirowntime.com/LiTOT/Content/1946/Av_4603_DA_BMW003.html">the original</a> on September 29, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">September 3,</span> 2016</span>. <q>Starting procedure is as follows: Starting engine is primed by closing electric primer switch, then ignition of turbojet and ignition and electric starting motor of <a href="/wiki/Norbert_Riedel" title="Norbert Riedel">Riedel engine</a> are turned on (this engine can also be started manually by pulling a cable). After the Riedel unit has reached a speed of about 300 rpm, it automatically engages the compressor shaft of the turbojet. At about 800 rpm of the starting engine, the starting fuel pump is turned on, and at 1,200 rpm the main (J-2) fuel is turned on. The starter engine is kept engaged until the turbojet attains 2,000 rpm, at which time the starter engine and starting fuel are turned off, the turbojet rapidly accelerating to rated speed of 9,500 rpm on the J-2 fuel</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=legendsintheirowntime.com&rft.atitle=Design+Analysis+of+BMW+003+Turbojet+-+%22Starting+the+Engine%22&rft.date=1946&rft.aulast=Schulte&rft.aufirst=Rudolph+C.&rft_id=http%3A%2F%2Flegendsintheirowntime.com%2FLiTOT%2FContent%2F1946%2FAv_4603_DA_BMW003.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Gunston-39"><span class="mw-cite-backlink"><b><a href="#cite_ref-Gunston_39-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGunston1997" class="citation book cs1"><a href="/wiki/Bill_Gunston" title="Bill Gunston">Gunston, Bill</a> (1997) [1995]. <i>The Development of Jet and Turbine Aero Engines</i> (Second ed.). Cambridge, England: Patrick Stephens. p. 141. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-85260-586-3" title="Special:BookSources/1-85260-586-3"><bdi>1-85260-586-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Development+of+Jet+and+Turbine+Aero+Engines&rft.place=Cambridge%2C+England&rft.pages=141&rft.edition=Second&rft.pub=Patrick+Stephens&rft.date=1997&rft.isbn=1-85260-586-3&rft.aulast=Gunston&rft.aufirst=Bill&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Shelton-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-Shelton_40-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFShelton1999" class="citation journal cs1">Shelton, Charles L. (March–April 1999). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20111006154039/http://gasengine.farmcollector.com/Equipment/Maytag-Twins-or-Look-a-Likes.aspx">"Maytag Twins or 'Look-a-Likes'?"</a>. <i>Gas Engine Magazine</i>. Topeka, Kansas, United States: Ogden Publications. Archived from <a rel="nofollow" class="external text" href="http://gasengine.farmcollector.com/Equipment/Maytag-Twins-or-Look-a-Likes.aspx">the original</a> <span class="cs1-format">(aspx)</span> on 2011-10-06<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-12-28</span></span>. <q>The twin, or 72 as it was commonly referred to, was used primarily as a source of power for the Maytag washing machines. Even as late as the early '30s, some brands of washers were hand operated; thus a ready power source such as the twin had a great deal of influence on Americans' work habits.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Gas+Engine+Magazine&rft.atitle=Maytag+Twins+or+%27Look-a-Likes%27%3F&rft.date=1999-03%2F1999-04&rft.aulast=Shelton&rft.aufirst=Charles+L.&rft_id=http%3A%2F%2Fgasengine.farmcollector.com%2FEquipment%2FMaytag-Twins-or-Look-a-Likes.aspx&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Kinney-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-Kinney_41-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKinney2007" class="citation web cs1">Kinney, Keith (2007-02-27). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100117011736/http://www.herculesengines.com/Maytag/Default.htm">"Maytag Engine-Driven Wringer Washer"</a>. <i>Old Iron and Other Americana: The collections of the Kinney family</i>. Archived from <a rel="nofollow" class="external text" href="http://www.herculesengines.com/Maytag/Default.htm">the original</a> on 2010-01-17<span class="reference-accessdate">. Retrieved <span class="nowrap">2009-01-08</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Old+Iron+and+Other+Americana%3A+The+collections+of+the+Kinney+family&rft.atitle=Maytag+Engine-Driven+Wringer+Washer&rft.date=2007-02-27&rft.aulast=Kinney&rft.aufirst=Keith&rft_id=http%3A%2F%2Fwww.herculesengines.com%2FMaytag%2FDefault.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-42">^</a></b></span> <span class="reference-text">*<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110125120854/http://www.oldengine.org/docs/Maytag_SM.pdf">"Maytag Service Instructions"</a> <span class="cs1-format">(PDF)</span>. pp. <span class="nowrap">11–</span>16. Archived from <a rel="nofollow" class="external text" href="http://www.oldengine.org/docs/Maytag_SM.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2011-01-25<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-12-27</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Maytag+Service+Instructions&rft.pages=%3Cspan+class%3D%22nowrap%22%3E11-%3C%2Fspan%3E16&rft_id=http%3A%2F%2Fwww.oldengine.org%2Fdocs%2FMaytag_SM.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Hunn-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-Hunn_43-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHunn2005" class="citation book cs1">Hunn, Peter (Jun 13, 2005). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=ZKz21Fy2_r8C&q=Maytag+two+cylinder+engine&pg=PA24">"Short Profiles of Manufacturers"</a>. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=ZKz21Fy2_r8C&q=Maytag+two+cylinder+engine"><i>The Small-Engine Handbook</i></a>. Motorbooks Workshop. MotorBooks International. p. 42. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-76032-049-5" title="Special:BookSources/978-0-76032-049-5"><bdi>978-0-76032-049-5</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">2012-07-05</span></span>. <q>Often equipped with a foot pedal kick-starter, Maytag motors were available in both single-cylinder and opposed-twin formats.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Short+Profiles+of+Manufacturers&rft.btitle=The+Small-Engine+Handbook&rft.series=Motorbooks+Workshop&rft.pages=42&rft.pub=MotorBooks+International&rft.date=2005-06-13&rft.isbn=978-0-76032-049-5&rft.aulast=Hunn&rft.aufirst=Peter&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DZKz21Fy2_r8C%26q%3DMaytag%2Btwo%2Bcylinder%2Bengine%26pg%3DPA24&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-MaytagClub37-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-MaytagClub37_44-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20090527131149/http://www.maytagclub.com/page-37.htm">"Maytag Multi-Motor Engines"</a>. Maytag Collector's club. Archived from <a rel="nofollow" class="external text" href="http://www.maytagclub.com/page-37.htm">the original</a> on 2009-05-27<span class="reference-accessdate">. Retrieved <span class="nowrap">2009-01-08</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Maytag+Multi-Motor+Engines&rft.pub=Maytag+Collector%27s+club&rft_id=http%3A%2F%2Fwww.maytagclub.com%2Fpage-37.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Brown-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-Brown_45-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrown2007" class="citation journal cs1">Brown, Roland (November–December 2007). <a rel="nofollow" class="external text" href="http://www.motorcycleclassics.com/motorcycle-reviews/1955-douglas-dragonfly.aspx">"1955 Douglas Dragonfly"</a>. <i>Motorcycle Classics</i>. Ogden Publications<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-12-28</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Motorcycle+Classics&rft.atitle=1955+Douglas+Dragonfly&rft.date=2007-11%2F2007-12&rft.aulast=Brown&rft.aufirst=Roland&rft_id=http%3A%2F%2Fwww.motorcycleclassics.com%2Fmotorcycle-reviews%2F1955-douglas-dragonfly.aspx&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Baldwin-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-Baldwin_46-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBaldwin1987" class="citation book cs1">Baldwin, Nick (1987). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=iJa1AAAAIAAJ&pg=PA111"><i>The World guide to automobile manufacturers</i></a>. Facts on File Publications. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0816018448" title="Special:BookSources/0816018448"><bdi>0816018448</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">4 March</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+World+guide+to+automobile+manufacturers&rft.pub=Facts+on+File+Publications&rft.date=1987&rft.isbn=0816018448&rft.aulast=Baldwin&rft.aufirst=Nick&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DiJa1AAAAIAAJ%26pg%3DPA111&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFlat-twin+engine" class="Z3988"></span></span> </li> <li id="cite_note-Holcolmb-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-Holcolmb_47-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHolcolmb1964" class="citation journal cs1">Holcolmb, Hank (October 1964). Juettner, Walter R. (ed.). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=QYSfHsX__vgC&pg=PA34">"Inside Today's Outboards"</a>. <i>MotorBoating</i>. <b>114</b> (4). New York, NY USA: Hearst: <span class="nowrap">34–</span>35. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1531-2623">1531-2623</a><span class="reference-accessdate">. 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href="/wiki/Special:EditPage/Template:Piston_engine_configurations" title="Special:EditPage/Template:Piston engine configurations"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Engine_configurations_for_piston_engines126" style="font-size:114%;margin:0 4em"><a href="/wiki/Engine_configuration" title="Engine configuration">Engine configurations</a> for <a href="/wiki/Piston_engine" class="mw-redirect" title="Piston engine">piston engines</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Type</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Newcomen_atmospheric_engine" title="Newcomen atmospheric engine">Atmospheric</a></li> <li><a href="/wiki/Axial_engine" title="Axial engine">Axial</a></li> <li><a href="/wiki/Beam_engine" title="Beam engine">Beam</a> <ul><li><a href="/wiki/Cornish_steam_engine" class="mw-redirect" title="Cornish steam engine">Cornish</a></li> <li><a href="/wiki/Rotative_beam_engine" class="mw-redirect" title="Rotative beam engine">Rotative</a></li></ul></li> <li><a href="/wiki/Bourke_engine" title="Bourke engine">Bourke</a></li> <li><a href="/wiki/Cam_engine" title="Cam engine">Cam engine</a></li> <li><a href="/wiki/Camless_piston_engine" title="Camless piston engine">Camless</a></li> <li><a href="/wiki/Compound_steam_engine" title="Compound steam engine">Compound</a></li> <li><a href="/wiki/Double-acting_cylinder" class="mw-redirect" title="Double-acting cylinder">Double-acting cylinder</a></li> <li><a href="/wiki/Flathead_engine" title="Flathead engine">Flathead</a></li> <li><a href="/wiki/Free-piston_engine" title="Free-piston engine">Free-piston</a> <ul><li><a href="/wiki/Stelzer_engine" title="Stelzer engine">Stelzer</a></li></ul></li> <li><a href="/wiki/Hemi_engine" class="mw-redirect" title="Hemi engine">Hemi</a></li> <li><a href="/wiki/Heron_cylinder_head" title="Heron cylinder head">Heron head</a></li> <li><a href="/wiki/IOE_engine" title="IOE engine">Intake over exhaust</a></li> <li><a href="/wiki/Oscillating_cylinder_steam_engine" title="Oscillating cylinder steam engine">Oscillating cylinder</a></li> <li><a href="/wiki/Opposed-piston_engine" title="Opposed-piston engine">Opposed-piston</a></li> <li><a href="/wiki/Overhead_camshaft_engine" title="Overhead camshaft engine">Overhead camshaft</a></li> <li><a href="/wiki/Overhead_valve_engine" title="Overhead valve engine">Overhead valve</a></li> <li><a href="/wiki/Pent-roof_combustion_chamber" title="Pent-roof combustion chamber">Pentroof</a></li> <li><a href="/wiki/Rotary_engine" title="Rotary engine">Rotary</a></li> <li><a href="/wiki/Single-acting_cylinder" class="mw-redirect" title="Single-acting cylinder">Single-acting cylinder</a></li> <li><a href="/wiki/Split_cycle_engine" class="mw-redirect" title="Split cycle engine">Split cycle</a></li> <li><a href="/wiki/Swing-piston_engine" title="Swing-piston engine">Swing-piston</a></li> <li><a href="/wiki/Uniflow_steam_engine" title="Uniflow steam engine">Uniflow</a></li> <li><a href="/wiki/Watt_steam_engine" title="Watt steam engine">Watt</a></li> <li><a href="/wiki/Chrysler_wedge_engine" class="mw-redirect" title="Chrysler wedge engine">Wedge</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stroke_(engine)" title="Stroke (engine)">Stroke cycles</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Two-stroke_engine" title="Two-stroke engine">Two-stroke</a></li> <li><a href="/wiki/Four-stroke_engine" title="Four-stroke engine">Four-stroke</a></li> <li><a href="/wiki/Five-stroke_engine" title="Five-stroke engine">Five-stroke</a></li> <li><a href="/wiki/Six-stroke_engine" title="Six-stroke engine">Six-stroke</a></li> <li><a href="/wiki/Two-_and_four-stroke_engines" title="Two- and four-stroke engines">Two-and four-stroke</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Engine_configuration" title="Engine configuration">Cylinder layouts</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:10em"><a href="/wiki/Straight_engine" title="Straight engine">Inline / straight</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Single-cylinder_engine" title="Single-cylinder engine">I1</a></li> <li><a href="/wiki/Straight-twin_engine" title="Straight-twin engine">I2</a></li> <li><a href="/wiki/Straight-three_engine" title="Straight-three engine">I3</a></li> <li><a href="/wiki/Straight-four_engine" title="Straight-four engine">I4</a></li> <li><a href="/wiki/Straight-five_engine" title="Straight-five engine">I5</a></li> <li><a href="/wiki/Straight-six_engine" title="Straight-six engine">I6</a></li> <li><a href="/wiki/Straight-seven_engine" title="Straight-seven engine">I7</a></li> <li><a href="/wiki/Straight-eight_engine" title="Straight-eight engine">I8</a></li> <li><a href="/wiki/Straight-nine_engine" title="Straight-nine engine">I9</a></li> <li><a href="/wiki/Straight-twelve_engine" title="Straight-twelve engine">I12</a></li> <li><a href="/wiki/Straight-fourteen_engine" title="Straight-fourteen engine">I14</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:10em"><a href="/wiki/Flat_engine" title="Flat engine">Flat / boxer</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a class="mw-selflink selflink">F2</a></li> <li><a href="/wiki/Flat-four_engine" title="Flat-four engine">F4</a></li> <li><a href="/wiki/Flat-six_engine" title="Flat-six engine">F6</a></li> <li><a href="/wiki/Flat-eight_engine" title="Flat-eight engine">F8</a></li> <li><a href="/wiki/Flat-ten_engine" title="Flat-ten engine">F10</a></li> <li><a href="/wiki/Flat-twelve_engine" title="Flat-twelve engine">F12</a></li> <li><a href="/wiki/Flat-sixteen_engine" title="Flat-sixteen engine">F16</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:10em"><a href="/wiki/V_engine" title="V engine">V / Vee</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/V-twin_engine" title="V-twin engine">V2</a></li> <li><a href="/wiki/V3_engine" title="V3 engine">V3</a></li> <li><a href="/wiki/V4_engine" title="V4 engine">V4</a></li> <li><a href="/wiki/V5_engine" title="V5 engine">V5</a> <ul><li><a href="/wiki/VR5_engine" title="VR5 engine">VR5</a></li></ul></li> <li><a href="/wiki/V6_engine" title="V6 engine">V6</a> <ul><li><a href="/wiki/VR6_engine" title="VR6 engine">VR6</a></li></ul></li> <li><a href="/wiki/V8_engine" title="V8 engine">V8</a></li> <li><a href="/wiki/V10_engine" title="V10 engine">V10</a></li> <li><a href="/wiki/V12_engine" title="V12 engine">V12</a></li> <li><a href="/wiki/V14_engine" title="V14 engine">V14</a></li> <li><a href="/wiki/V16_engine" title="V16 engine">V16</a></li> <li><a href="/wiki/V18_engine" title="V18 engine">V18</a></li> <li><a href="/wiki/V20_engine" title="V20 engine">V20</a></li> <li><a href="/wiki/V24_engine" title="V24 engine">V24</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:10em"><a href="/wiki/W_engine" title="W engine">W</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/W_engine#W3_engines" title="W engine">W3</a></li> <li><a href="/wiki/W_engine#W6_engines" title="W engine">W6</a></li> <li><a href="/wiki/W8_engine" title="W8 engine">W8</a></li> <li><a href="/wiki/W12_engine" title="W12 engine">W12</a></li> <li><a href="/wiki/W16_engine" title="W16 engine">W16</a></li> <li><a href="/wiki/W18_engine" title="W18 engine">W18</a></li> <li><a href="/wiki/W_engine#W24_engine" title="W engine">W24</a></li> <li><a href="/wiki/W_engine#W30_engine" title="W engine">W30</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:10em">Other</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Napier_Deltic" title="Napier Deltic">Deltic</a></li> <li><a href="/wiki/H_engine" title="H engine">H</a></li> <li><a href="/wiki/Radial_engine" title="Radial engine">Radial</a></li> <li><a href="/wiki/Split-single_engine" title="Split-single engine">Split-single</a></li> <li><a href="/wiki/U_engine" title="U engine">U</a></li> <li><a href="/wiki/X_engine" title="X engine">X</a></li></ul> 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