The Daimler L15 , sometimes later known as the Daimler-Klemm L15 or the Klemm-Daimler L15 was an early two-seat low-powered light aircraft intended to popularise flying. In mid-career it flew as a glider .
123-743: By the end of the First World War , Hanns Klemm had moved from Dornier to the aircraft branch of Daimler Motors and had designed two prototype fighters, the Daimler L11 and L14 . With military aviation ended by the terms of the Versailles Treaty , he turned to developing a low-power light aircraft. The 1919 Daimler L15 was a high cantilever wing aircraft with a 6 kW (7.5 hp) Indian motorcycle engine. Rather little detailed information on it seems to have survived; it had unusual rotating wingtips for roll control instead of ailerons and
246-547: A Roots blower , had been designed specifically for light aircraft and produced 15 kW (20 hp), but could not be developed to produce higher powers and was soon abandoned in favour of the Harley-Davidson. The last new engine to power the L15 was a much more powerful (30 kW (40 hp)) Salmson . With it in place, the L15 was considerably refined with flaps , slats and pneumatic, rubber-tyred wheels. The flights with
369-630: A blue-water navy was vital for global power projection; Tirpitz had his books translated into German, while Wilhelm made them required reading for his advisors and senior military personnel. However, it was also an emotional decision, driven by Wilhelm's simultaneous admiration for the Royal Navy and desire to surpass it. Bismarck thought that the British would not interfere in Europe, as long as its maritime supremacy remained secure, but his dismissal in 1890 led to
492-583: A grenade at the Archduke's car and injured two of his aides. The other assassins were also unsuccessful. An hour later, as Ferdinand was returning from visiting the injured officers in hospital, his car took a wrong turn into a street where Gavrilo Princip was standing. He fired two pistol shots, fatally wounding Ferdinand and his wife Sophie . According to historian Zbyněk Zeman , in Vienna "the event almost failed to make any impression whatsoever. On 28 and 29 June,
615-536: A guerrilla warfare campaign and only surrendered two weeks after the armistice took effect in Europe. Before the war, Germany had attempted to use Indian nationalism and pan-Islamism to its advantage, a policy continued post-1914 by instigating uprisings in India , while the Niedermayer–Hentig Expedition urged Afghanistan to join the war on the side of Central Powers. However, contrary to British fears of
738-415: A power-valve system . The valves are normally in or around the exhaust ports. They work in one of two ways; either they alter the exhaust port by closing off the top part of the port, which alters port timing, such as Rotax R.A.V.E, Yamaha YPVS, Honda RC-Valve, Kawasaki K.I.P.S., Cagiva C.T.S., or Suzuki AETC systems, or by altering the volume of the exhaust, which changes the resonant frequency of
861-421: A rotary valve is that it enables the two-stroke engine's intake timing to be asymmetrical, which is not possible with piston-port type engines. The piston-port type engine's intake timing opens and closes before and after top dead center at the same crank angle, making it symmetrical, whereas the rotary valve allows the opening to begin and close earlier. Rotary valve engines can be tailored to deliver power over
984-421: A DKW design that proved reasonably successful employing loop charging. The original SAAB 92 had a two-cylinder engine of comparatively low efficiency. At cruising speed, reflected-wave, exhaust-port blocking occurred at too low a frequency. Using the asymmetrical three-port exhaust manifold employed in the identical DKW engine improved fuel economy. The 750-cc standard engine produced 36 to 42 hp, depending on
1107-408: A change in policy and an Anglo-German naval arms race began. Despite the vast sums spent by Tirpitz, the launch of HMS Dreadnought in 1906 gave the British a technological advantage. Ultimately, the race diverted huge resources into creating a German navy large enough to antagonise Britain, but not defeat it; in 1911, Chancellor Theobald von Bethmann Hollweg acknowledged defeat, leading to
1230-448: A crossflow engine) is always best and support is good. In some engines, the small end is offset to reduce thrust in the intended rotational direction and the forward face of the piston has been made thinner and lighter to compensate, but when running backward, this weaker forward face suffers increased mechanical stress it was not designed to resist. This can be avoided by the use of crossheads and also using thrust bearings to isolate
1353-592: A direct threat. The 1908–1909 Bosnian Crisis began when Austria annexed the former Ottoman territory of Bosnia and Herzegovina , which it had occupied since 1878. Timed to coincide with the Bulgarian Declaration of Independence from the Ottoman Empire, this unilateral action was denounced by the European powers, but accepted as there was no consensus on how to resolve the situation. Some historians see this as
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#17330851112781476-467: A gap between the German armies as they closed on Paris. The French army, reinforced by the British expeditionary corps, seized this opportunity to counter-attack and pushed the German army 40 to 80 km back. Both armies were then so exhausted that no decisive move could be implemented, so they settled in trenches, with the vain hope of breaking through as soon as they could build local superiority. In 1911,
1599-421: A passenger. In the autumn of 1924 the L15 was fitted with floats and took off from water successfully, at first carrying only the pilot and then with a passenger. Takeoff took 12 seconds in both cases, even with 12.5 hp. Early in these tests a new engine, an uncowled Daimler-Versuchmotor F7506 was flown for the first time. This unusual small, two-stroke , six-cylinder, air-cooled radial engine , fitted with
1722-465: A patent in 1880 in Germany. The first truly practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott , who started producing twin-cylinder water-cooled motorcycles in 1908. Two-stroke gasoline engines with electrical spark ignition are particularly useful in lightweight or portable applications such as chainsaws and motorcycles. However, when weight and size are not an issue,
1845-540: A possibility. This was accentuated by British and Russian support for France against Germany during the 1911 Agadir Crisis . German economic and industrial strength continued to expand rapidly post-1871. Backed by Wilhelm II, Admiral Alfred von Tirpitz sought to use this growth to build an Imperial German Navy , that could compete with the British Royal Navy . This policy was based on the work of US naval author Alfred Thayer Mahan , who argued that possession of
1968-799: A revolt in India, the outbreak of the war saw a reduction in nationalist activity. Leaders from the Indian National Congress and other groups believed support for the British war effort would hasten Indian Home Rule , a promise allegedly made explicit in 1917 by Edwin Montagu , the Secretary of State for India . In 1914, the British Indian Army was larger than the British Army itself, and between 1914 and 1918 an estimated 1.3 million Indian soldiers and labourers served in Europe, Africa, and
2091-449: A scavenging function. The units run in pairs, with the lower half of one piston charging an adjacent combustion chamber. The upper section of the piston still relies on total-loss lubrication, but the other engine parts are sump lubricated with cleanliness and reliability benefits. The mass of the piston is only about 20% more than a loop-scavenged engine's piston because skirt thicknesses can be less. Many modern two-stroke engines employ
2214-567: A series of competitions on the Wasserkuppe that became known as the Rhön contests. Perhaps stimulated by these events, Klemm proposed in 1922 that the L15 should be rebuilt as a glider and obtained approval from the Daimler management. The engine was demounted and replaced with a long, smooth nose, deliberately designed to be easily removable so that the engine could be reinstalled if desired. The pilot sat at
2337-504: A significant escalation, ending any chance of Austria cooperating with Russia in the Balkans, while also damaging diplomatic relations between Serbia and Italy. Tensions increased after the 1911–1912 Italo-Turkish War demonstrated Ottoman weakness and led to the formation of the Balkan League , an alliance of Serbia, Bulgaria, Montenegro , and Greece . The League quickly overran most of
2460-658: A similar system. Traditional flywheel magnetos (using contact-breaker points, but no external coil) worked equally well in reverse because the cam controlling the points is symmetrical, breaking contact before top dead center equally well whether running forward or backward. Reed-valve engines run backward just as well as piston-controlled porting, though rotary valve engines have asymmetrical inlet timing and do not run very well. Serious disadvantages exist for running many engines backward under load for any length of time, and some of these reasons are general, applying equally to both two-stroke and four-stroke engines. This disadvantage
2583-436: A single axle undercarriage . It suffered serious propeller damage in 1919, early in the testing programme. From then on Daimler and Klemm abandoned aviation; Klemm remained with Daimler, concentrating on streamlined racing cars and locomotives. During 1920 some German aviation enthusiasts realised that, though Germany was forbidden by the allies to build aeroplanes, gliders were not included in that category, resulting in
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#17330851112782706-443: A single piece wing but gliders need to be easily transportable and so the wings were rebuilt in three pieces. The rudder and elevators were removable and the outer parts of the tailplane could be hinged upwards, again for ease of transport. At some point during the reconstruction the fixed axle undercarriage was replaced with a more refined arrangement where the wheels were separately mounted on hinged and faired V- struts from
2829-518: A turbocharger. Crankcase-compression two-stroke engines, such as common small gasoline-powered engines, are lubricated by a petroil mixture in a total-loss system . Oil is mixed in with their petrol fuel beforehand, in a fuel-to-oil ratio of around 32:1. This oil then forms emissions, either by being burned in the engine or as droplets in the exhaust, historically resulting in more exhaust emissions, particularly hydrocarbons, than four-stroke engines of comparable power output. The combined opening time of
2952-867: A two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust (or scavenging ) functions occurring at the same time. Two-stroke engines often have a higher power-to-weight ratio than a four-stroke engine, since their power stroke occurs twice as often. Two-stroke engines can also have fewer moving parts , and thus be cheaper to manufacture and weigh less. In countries and regions with stringent emissions regulation, two-stroke engines have been phased out in automotive and motorcycle uses. In regions where regulations are less stringent, small displacement two-stroke engines remain popular in mopeds and motorcycles. They are also used in power tools such as chainsaws and leaf blowers . The first commercial two-stroke engine involving cylinder compression
3075-471: A war on two fronts; the Schlieffen Plan envisaged using 80% of the army to defeat France, then switching to Russia. Since this required them to move quickly, mobilisation orders were issued that afternoon. Once the German ultimatum to Russia expired on the morning of 1 August, the two countries were at war. At a meeting on 29 July, the British cabinet had narrowly decided its obligations to Belgium under
3198-402: A weak Ottoman government, rather than an ambitious Slav power like Bulgaria . Russia had ambitions in northeastern Anatolia while its clients had overlapping claims in the Balkans. These competing interests divided Russian policy-makers and added to regional instability. Austrian statesmen viewed the Balkans as essential for the continued existence of their Empire and saw Serbian expansion as
3321-451: A whole, the Somme offensive led to an estimated 420,000 British casualties, along with 200,000 French and 500,000 Germans. The diseases that emerged in the trenches were a major killer on both sides. The living conditions led to disease and infection, such as trench foot , lice , typhus , trench fever , and the ' Spanish flu '. At the start of the war, German cruisers were scattered across
3444-400: A wider speed range or higher power over a narrower speed range than either a piston-port or reed-valve engine. Where a portion of the rotary valve is a portion of the crankcase itself, of particular importance, no wear should be allowed to take place. In a cross-flow engine, the transfer and exhaust ports are on opposite sides of the cylinder, and a deflector on the top of the piston directs
3567-413: Is accepted in most cases where cost, weight, and size are major considerations. The problem comes about because in "forward" running, the major thrust face of the piston is on the back face of the cylinder, which in a two-stroke particularly, is the coolest and best-lubricated part. The forward face of the piston in a trunk engine is less well-suited to be the major thrust face, since it covers and uncovers
3690-422: Is attributed to Scottish engineer Dugald Clerk , who patented his design in 1881. However, unlike most later two-stroke engines, his had a separate charging cylinder. The crankcase -scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day . On 31 December 1879, German inventor Karl Benz produced a two-stroke gas engine, for which he received
3813-590: Is being phased out. Honda , for instance, ceased selling two-stroke off-road motorcycles in the United States in 2007, after abandoning road-going models considerably earlier. Due to their high power-to-weight ratio and ability to be used in any orientation, two-stroke engines are common in handheld outdoor power tools including leaf blowers , chainsaws , and string trimmers . Two-stroke diesel engines are found mostly in large industrial and marine applications, as well as some trucks and heavy machinery. Although
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3936-565: Is common in on-road, off-road, and stationary two-stroke engines ( Detroit Diesel ), certain small marine two-stroke engines ( Gray Marine Motor Company , which adapted the Detroit Diesel Series 71 for marine use ), certain railroad two-stroke diesel locomotives ( Electro-Motive Diesel ) and large marine two-stroke main propulsion engines ( Wärtsilä ). Ported types are represented by the opposed piston design in which two pistons are in each cylinder, working in opposite directions such as
4059-503: Is known, however, that from 1908 to 1913, military spending by the six major European powers increased by over 50% in real terms. The years before 1914 were marked by a series of crises in the Balkans, as other powers sought to benefit from the Ottoman decline. While Pan-Slavic and Orthodox Russia considered itself the protector of Serbia and other Slav states, they preferred the strategically vital Bosporus straits to be controlled by
4182-432: Is that the two-stroke's crankcase is sealed and forms part of the induction process in gasoline and hot-bulb engines . Diesel two-strokes often add a Roots blower or piston pump for scavenging . The reed valve is a simple but highly effective form of check valve commonly fitted in the intake tract of the piston-controlled port. It allows asymmetric intake of the fuel charge, improving power and economy, while widening
4305-409: Is under every circumstance more efficient than cross-flow scavenging. In a uniflow engine, the mixture, or "charge air" in the case of a diesel, enters at one end of the cylinder controlled by the piston and the exhaust exits at the other end controlled by an exhaust valve or piston. The scavenging gas-flow is, therefore, in one direction only, hence the name uniflow. The design using exhaust valve(s)
4428-558: The Schutzkorps was established, and carried out the persecution of Serbs. The assassination initiated the July Crisis, a month of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France and Britain. Believing that Serbian intelligence helped organise Franz Ferdinand's murder, Austrian officials wanted to use the opportunity to end their interference in Bosnia and saw war as
4551-626: The World War . In August 1914, the magazine The Independent wrote "This is the Great War. It names itself". In October 1914, the Canadian magazine Maclean's similarly wrote, "Some wars name themselves. This is the Great War". Contemporary Europeans also referred to it as " the war to end war " and it was also described as "the war to end all wars" due to their perception of its unparalleled scale, devastation, and loss of life. The first recorded use of
4674-665: The Australian Naval and Military Expeditionary Force landed on the island of New Britain , then part of German New Guinea . On 28 October, the German cruiser SMS Emden sank the Russian cruiser Zhemchug in the Battle of Penang . Japan declared war on Germany before seizing territories in the Pacific, which later became the South Seas Mandate , as well as German Treaty ports on
4797-808: The First World War (28 July 1914 – 11 November 1918), also known as the Great War , was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers . Fighting took place mainly in Europe and the Middle East , as well as in parts of Africa and the Asia-Pacific , and in Europe was characterised by trench warfare ; the widespread use of artillery , machine guns, and chemical weapons (gas); and
4920-458: The Junkers Jumo 205 and Napier Deltic . The once-popular split-single design falls into this class, being effectively a folded uniflow. With advanced-angle exhaust timing, uniflow engines can be supercharged with a crankshaft-driven blower, either piston or Roots-type. The piston of this engine is "top-hat"-shaped; the upper section forms the regular cylinder, and the lower section performs
5043-706: The Rüstungswende or 'armaments turning point', when he switched expenditure from the navy to the army. This decision was not driven by a reduction in political tensions but by German concern over Russia's quick recovery from its defeat in the Russo-Japanese War and subsequent 1905 Russian Revolution . Economic reforms led to a significant post-1908 expansion of railways and transportation infrastructure, particularly in its western border regions. Since Germany and Austria-Hungary relied on faster mobilisation to compensate for their numerical inferiority compared to Russia,
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5166-784: The United States entered the war on the Allied side following Germany's resumption of unrestricted submarine warfare against Atlantic shipping. Later that year, the Bolsheviks seized power in the Russian October Revolution , and Soviet Russia signed an armistice with the Central Powers in December, followed by a separate peace in March 1918. That month, Germany launched an offensive in
5289-506: The expansion chamber , such as the Suzuki SAEC and Honda V-TACS system. The result is an engine with better low-speed power without sacrificing high-speed power. However, as power valves are in the hot gas flow, they need regular maintenance to perform well. Direct injection has considerable advantages in two-stroke engines. In carburetted two-strokes, a major problem is a portion of the fuel/air mixture going directly out, unburned, through
5412-419: The fuselage underside and with vertical shock absorber struts to the wing underside, allowing much larger wheel deflections on landing than with the less than half wheel-diameter allowed by end-sprung rigid axle mountings. Unusually, the wheels, which had three-ply centres, were ash-tyred because rubber was expensive in postwar Germany. Given the limitations of its relatively low aspect ratio (about 7.5),
5535-480: The hydrophone and depth charges were introduced, destroyers could potentially successfully attack a submerged submarine. Convoys slowed the flow of supplies since ships had to wait as convoys were assembled; the solution was an extensive program of building new freighters. Troopships were too fast for the submarines and did not travel the North Atlantic in convoys. The U-boats sunk more than 5,000 Allied ships, at
5658-473: The oil reservoir does not depend on gravity. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab , German manufacturers DKW , Auto-Union , VEB Sachsenring Automobilwerke Zwickau , VEB Automobilwerk Eisenach , and VEB Fahrzeug- und Jagdwaffenwerk , and Polish manufacturers FSO and FSM . The Japanese manufacturers Suzuki and Subaru did
5781-789: The tank . After the First Battle of the Marne in September 1914, Allied and German forces unsuccessfully tried to outflank each other, a series of manoeuvres later known as the " Race to the Sea ". By the end of 1914, the opposing forces confronted each other along an uninterrupted line of entrenched positions from the Channel to the Swiss border. Since the Germans were normally able to choose where to stand, they generally held
5904-588: The 1839 Treaty of London did not require it to oppose a German invasion with military force; however, Prime Minister Asquith and his senior Cabinet ministers were already committed to supporting France, the Royal Navy had been mobilised, and public opinion was strongly in favour of intervention. On 31 July, Britain sent notes to Germany and France, asking them to respect Belgian neutrality; France pledged to do so, but Germany did not reply. Aware of German plans to attack through Belgium, French Commander-in-Chief Joseph Joffre asked his government for permission to cross
6027-548: The 1879 Dual Alliance , which became the Triple Alliance when Italy joined in 1882. For Bismarck, the purpose of these agreements was to isolate France by ensuring the three Empires resolve any disputes between themselves. In 1887, Bismarck set up the Reinsurance Treaty , a secret agreement between Germany and Russia to remain neutral if either were attacked by France or Austria-Hungary. For Bismarck, peace with Russia
6150-441: The 1913 Treaty of London , which had created an independent Albania while enlarging the territories of Bulgaria, Serbia, Montenegro and Greece. However, disputes between the victors sparked the 33-day Second Balkan War , when Bulgaria attacked Serbia and Greece on 16 June 1913; it was defeated, losing most of Macedonia to Serbia and Greece, and Southern Dobruja to Romania. The result was that even countries which benefited from
6273-528: The 1960s due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was the piston could be made nearly flat or slightly domed, which allowed the piston to be appreciably lighter and stronger, and consequently to tolerate higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes, and compression losses. SAAB built 750- and 850-cc three-cylinder engines based on
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#17330851112786396-407: The 1960s, especially for motorcycles, but for smaller or slower engines using direct injection, the deflector piston can still be an acceptable approach. This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel/air mixture strikes the cylinder head , then follows the curvature of
6519-556: The Austrians and Serbs clashed at the battles of the Cer and Kolubara ; over the next two weeks, Austrian attacks were repulsed with heavy losses. As a result, Austria had to keep sizeable forces on the Serbian front, weakening their efforts against Russia. Serbia's victory against Austria-Hungary in the 1914 invasion has been called one of the major upset victories of the twentieth century. In 1915,
6642-642: The Austrians briefly occupied the Serbian capital, Belgrade . A Serbian counter-attack in the Battle of Kolubara succeeded in driving them from the country by the end of 1914. For the first 10 months of 1915, Austria-Hungary used most of its military reserves to fight Italy. German and Austro-Hungarian diplomats scored a coup by persuading Bulgaria to join the attack on Serbia. The Austro-Hungarian provinces of Slovenia , Croatia and Bosnia provided troops for Austria-Hungary. Montenegro allied itself with Serbia. Bulgaria declared war on Serbia on 14 October 1915 and joined in
6765-545: The Balkan Wars, such as Serbia and Greece, felt cheated of their "rightful gains", while for Austria it demonstrated the apparent indifference with which other powers viewed their concerns, including Germany. This complex mix of resentment, nationalism and insecurity helps explain why the pre-1914 Balkans became known as the " powder keg of Europe ". On 28 June 1914, Archduke Franz Ferdinand of Austria , heir presumptive to Emperor Franz Joseph I of Austria , visited Sarajevo ,
6888-404: The Central Powers. However, the pro-German King Constantine I dismissed the pro-Allied government of Eleftherios Venizelos before the Allied expeditionary force arrived. The Macedonian front was at first mostly static. French and Serbian forces retook limited areas of Macedonia by recapturing Bitola on 19 November 1916 following the costly Monastir offensive , which brought stabilisation of
7011-625: The Chinese Shandong peninsula at Tsingtao . After Vienna refused to withdraw its cruiser SMS Kaiserin Elisabeth from Tsingtao, Japan declared war on Austria-Hungary, and the ship was sunk in November 1914. Within a few months, Allied forces had seized all German territories in the Pacific, leaving only isolated commerce raiders and a few holdouts in New Guinea. Some of the first clashes of
7134-613: The German High Seas Fleet was confined to port. German U-boats attempted to cut the supply lines between North America and Britain. The nature of submarine warfare meant that attacks often came without warning, giving the crews of the merchant ships little hope of survival. The United States launched a protest, and Germany changed its rules of engagement. After the sinking of the passenger ship RMS Lusitania in 1915, Germany promised not to target passenger liners, while Britain armed its merchant ships, placing them beyond
7257-623: The German Army increased in size from 1908 to 1914, he changed the allocation of forces between the two wings to 70:30. He also considered Dutch neutrality essential for German trade and cancelled the incursion into the Netherlands, which meant any delays in Belgium threatened the viability of the plan. Historian Richard Holmes argues that these changes meant the right wing was not strong enough to achieve decisive success. The initial German advance in
7380-399: The German inventor of an early form in the mid-1920s, it became widely adopted in Germany country during the 1930s and spread further afield after World War II . Loop scavenging is the most common type of fuel/air mixture transfer used on modern two-stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop-scavenged, two-stroke engines. This operational feature
7503-724: The German right wing would sweep through the Netherlands and Belgium , then swing south, encircling Paris and trapping the French army against the Swiss border. The plan's creator, Alfred von Schlieffen , head of the German General Staff from 1891 to 1906, estimated that this would take six weeks, after which the German army would transfer to the East and defeat the Russians. The plan was substantially modified by his successor, Helmuth von Moltke
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#17330851112787626-480: The Germans bled heavily as well, with anywhere from 700,000 to 975,000 casualties between the two combatants. Verdun became a symbol of French determination and self-sacrifice. The Battle of the Somme was an Anglo-French offensive from July to November 1916. The opening day on 1 July 1916 was the bloodiest single day in the history of the British Army , which suffered 57,500 casualties, including 19,200 dead. As
7749-442: The L.15 performed satisfactorily as a glider. In the summer of 1922 it made flights of up to 13 minutes, with an estimated L/D of about 16. Towards the end of 1923 the L15 received a second-hand, 9 kW (12.5 hp) Harley-Davidson motorcycle engine, mounted with its cylinders exposed for cooling and driving a two-bladed propeller though 3:1 epicyclic reduction gearing . There were again two open cockpits in tandem , but since
7872-675: The Middle East. In all, 140,000 soldiers served on the Western Front and nearly 700,000 in the Middle East, with 47,746 killed and 65,126 wounded. The suffering engendered by the war, as well as the failure of the British government to grant self-government to India afterward, bred disillusionment, resulting in the campaign for full independence led by Mahatma Gandhi . Pre-war military tactics that had emphasised open warfare and individual riflemen proved obsolete when confronted with conditions prevailing in 1914. Technological advances allowed
7995-859: The Ottoman Empire , which disturbed the long-standing balance of power in Europe, as well as economic competition between nations triggered by industrialisation and imperialism . Growing tensions between the great powers and in the Balkans reached a breaking point on 28 June 1914, when a Bosnian Serb named Gavrilo Princip assassinated Archduke Franz Ferdinand , heir to the Austro-Hungarian throne. Austria-Hungary held Serbia responsible, and declared war on 28 July. After Russia mobilised in Serbia's defence, Germany declared war on Russia and France , who had an alliance . The United Kingdom entered after Germany invaded Belgium , whose neutrality it guaranteed, and
8118-709: The Ottomans joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France, then to transfer its forces to the east, but its advance was halted in September , and by the end of the year the Western Front consisted of a continuous line of trenches stretching from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. Italy , Bulgaria , Romania , Greece and others joined in from 1915 onward. In April 1917,
8241-449: The Ottomans' territory in the Balkans during the 1912–1913 First Balkan War , much to the surprise of outside observers. The Serbian capture of ports on the Adriatic resulted in partial Austrian mobilisation, starting on 21 November 1912, including units along the Russian border in Galicia . The Russian government decided not to mobilise in response, unprepared to precipitate a war. The Great Powers sought to re-assert control through
8364-549: The Russian Stavka agreed with the French to attack Germany within fifteen days of mobilisation, ten days before the Germans had anticipated, although it meant the two Russian armies that entered East Prussia on 17 August did so without many of their support elements. By the end of 1914, German troops held strong defensive positions inside France, controlled the bulk of France's domestic coalfields, and inflicted 230,000 more casualties than it lost itself. However, communications problems and questionable command decisions cost Germany
8487-429: The Serbian retreat toward the Adriatic coast in the Battle of Mojkovac on 6–7 January 1916, but ultimately the Austrians also conquered Montenegro. The surviving Serbian soldiers were evacuated to Greece. After the conquest, Serbia was divided between Austro-Hungary and Bulgaria. In late 1915, a Franco-British force landed at Salonica in Greece to offer assistance and to pressure its government to declare war against
8610-455: The West was very successful. By the end of August, the Allied left, which included the British Expeditionary Force (BEF), was in full retreat , and the French offensive in Alsace-Lorraine was a disastrous failure, with casualties exceeding 260,000. German planning provided broad strategic instructions while allowing army commanders considerable freedom in carrying them out at the front, but von Kluck used this freedom to disobey orders, opening
8733-430: The Younger . Under Schlieffen, 85% of German forces in the west were assigned to the right wing, with the remainder holding along the frontier. By keeping his left-wing deliberately weak, he hoped to lure the French into an offensive into the "lost provinces" of Alsace-Lorraine , which was the strategy envisaged by their Plan XVII . However, Moltke grew concerned that the French might push too hard on his left flank and as
8856-496: The aggressor, German Chancellor Bethmann Hollweg delayed the commencement of war preparations until 31 July. That afternoon, the Russian government were handed a note requiring them to "cease all war measures against Germany and Austria-Hungary" within 12 hours. A further German demand for neutrality was refused by the French who ordered general mobilisation but delayed declaring war. The German General Staff had long assumed they faced
8979-466: The attack by the Austro-Hungarian army under Mackensen's army of 250,000 that was already underway. Serbia was conquered in a little more than a month, as the Central Powers, now including Bulgaria, sent in 600,000 troops in total. The Serbian army, fighting on two fronts and facing certain defeat, retreated into northern Albania . The Serbs suffered defeat in the Battle of Kosovo . Montenegro covered
9102-535: The best way of achieving this. However, the Foreign Ministry had no solid proof of Serbian involvement. On 23 July, Austria delivered an ultimatum to Serbia, listing ten demands made intentionally unacceptable to provide an excuse for starting hostilities. Serbia ordered general mobilisation on 25 July, but accepted all the terms, except for those empowering Austrian representatives to suppress "subversive elements" inside Serbia, and take part in
9225-483: The border and pre-empt such a move. To avoid violating Belgian neutrality, he was told any advance could come only after a German invasion. Instead, the French cabinet ordered its Army to withdraw 10 km behind the German frontier, to avoid provoking war. On 2 August, Germany occupied Luxembourg and exchanged fire with French units when German patrols entered French territory; on 3 August, they declared war on France and demanded free passage across Belgium, which
9348-423: The bore diameter for reasonable piston ring life. Beyond this, the piston rings bulge into the exhaust port and wear quickly. A maximum 70% of bore width is possible in racing engines, where rings are changed every few races. Intake duration is between 120 and 160°. Transfer port time is set at a minimum of 26°. The strong, low-pressure pulse of a racing two-stroke expansion chamber can drop the pressure to -7 psi when
9471-480: The campaign saw the first use of anti-aircraft warfare after an Austrian plane was shot down with ground-to-air fire, as well as the first medical evacuation by the Serbian army. Upon mobilisation, in accordance with the Schlieffen Plan , 80% of the German Army was located on the Western Front, with the remainder acting as a screening force in the East. Rather than a direct attack across their shared frontier,
9594-636: The capital of the recently annexed Bosnia and Herzegovina . Cvjetko Popović , Gavrilo Princip , Nedeljko Čabrinović , Trifko Grabež , Vaso Čubrilović ( Bosnian Serbs ) and Muhamed Mehmedbašić (from the Bosniaks community), from the movement known as Young Bosnia , took up positions along the Archduke's motorcade route, to assassinate him. Supplied with arms by extremists within the Serbian Black Hand intelligence organisation, they hoped his death would free Bosnia from Austrian rule. Čabrinović threw
9717-466: The chance of a decisive outcome, while it had failed to achieve the primary objective of avoiding a long, two-front war. As was apparent to several German leaders, this amounted to a strategic defeat; shortly after the First Battle of the Marne , Crown Prince Wilhelm told an American reporter "We have lost the war. It will go on for a long time but lost it is already". On 30 August 1914, New Zealand occupied German Samoa (now Samoa ). On 11 September,
9840-459: The combustion chamber, and then is deflected downward. This not only prevents the fuel/air mixture from traveling directly out the exhaust port, but also creates a swirling turbulence which improves combustion efficiency , power, and economy. Usually, a piston deflector is not required, so this approach has a distinct advantage over the cross-flow scheme (above). Often referred to as "Schnuerle" (or "Schnürle") loop scavenging after Adolf Schnürle,
9963-511: The cost of 199 submarines. World War I also saw the first use of aircraft carriers in combat, with HMS Furious launching Sopwith Camels in a successful raid against the Zeppelin hangars at Tondern in July 1918, as well as blimps for antisubmarine patrol. Faced with Russia in the east, Austria-Hungary could spare only one-third of its army to attack Serbia. After suffering heavy losses,
10086-453: The crankshaft commonly spins in the same axis and direction as do the wheels i.e. "forward". Some of the considerations discussed here apply to four-stroke engines (which cannot reverse their direction of rotation without considerable modification), almost all of which spin forward, too. It is also useful to note that the "front" and "back" faces of the piston are - respectively - the exhaust port and intake port sides of it, and are not to do with
10209-513: The creation of new independent states, including Poland , Finland , the Baltic states , Czechoslovakia , and Yugoslavia . The League of Nations was established to maintain world peace, but its failure to manage instability during the interwar period contributed to the outbreak of World War II in 1939. Before World War II , the events of 1914–1918 were generally known as the Great War or simply
10332-449: The creation of strong defensive systems largely impervious to massed infantry advances, such as barbed wire , machine guns and above all far more powerful artillery , which dominated the battlefield and made crossing open ground extremely difficult. Both sides struggled to develop tactics for breaching entrenched positions without heavy casualties. In time, technology enabled the production of new offensive weapons, such as gas warfare and
10455-948: The crowds listened to music and drank wine, as if nothing had happened". Nevertheless, the impact of the murder of the heir to the throne was significant, and has been described by historian Christopher Clark as a " 9/11 effect, a terrorist event charged with historic meaning, transforming the political chemistry in Vienna". Austro-Hungarian authorities encouraged subsequent anti-Serb riots in Sarajevo . Violent actions against ethnic Serbs were also organised outside Sarajevo, in other cities in Austro-Hungarian-controlled Bosnia and Herzegovina, Croatia and Slovenia. Austro-Hungarian authorities in Bosnia and Herzegovina imprisoned approximately 5,500 prominent Serbs, 700 to 2,200 of whom died in prison. A further 460 Serbs were sentenced to death. A predominantly Bosniak special militia known as
10578-415: The cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion , railway locomotives , and electricity generation . In a two-stroke engine, the exhaust gases transfer less heat to the cooling system than a four-stroke, which means more energy to drive the piston, and if present,
10701-400: The engine from end loads. Large two-stroke ship diesels are sometimes made to be reversible. Like four-stroke ship engines (some of which are also reversible), they use mechanically operated valves, so require additional camshaft mechanisms. These engines use crossheads to eliminate sidethrust on the piston and isolate the under-piston space from the crankcase. On top of other considerations,
10824-415: The exhaust port in the cylinder, the hottest part of the engine, where piston lubrication is at its most marginal. The front face of the piston is also more vulnerable since the exhaust port, the largest in the engine, is in the front wall of the cylinder. Piston skirts and rings risk being extruded into this port, so having them pressing hardest on the opposite wall (where there are only the transfer ports in
10947-409: The exhaust port, and direct injection effectively eliminates this problem. Two systems are in use: low-pressure air-assisted injection and high-pressure injection. Since the fuel does not pass through the crankcase, a separate source of lubrication is needed. For the purpose of this discussion, it is convenient to think in motorcycle terms, where the exhaust pipe faces into the cooling air stream, and
11070-622: The expansion of the French colonial empire . In 1873, Bismarck negotiated the League of the Three Emperors , which included Austria-Hungary , Russia and Germany. After the 1877–1878 Russo-Turkish War , the League was dissolved due to Austrian concerns over the expansion of Russian influence in the Balkans , an area they considered to be of vital strategic interest. Germany and Austria-Hungary then formed
11193-400: The first time on the Western Front. Several types of gas soon became widely used by both sides and though it never proved a decisive, battle-winning weapon, it became one of the most feared and best-remembered horrors of the war. In February 1916, the Germans attacked French defensive positions at the Battle of Verdun , lasting until December 1916. Casualties were greater for the French, but
11316-413: The fresh intake charge into the upper part of the cylinder, pushing the residual exhaust gas down the other side of the deflector and out the exhaust port. The deflector increases the piston's weight and exposed surface area, and the fact that it makes piston cooling and achieving an effective combustion chamber shape more difficult is why this design has been largely superseded by uniflow scavenging after
11439-586: The front. Serbian and French troops finally made a breakthrough in September 1918 in the Vardar offensive , after most German and Austro-Hungarian troops had been withdrawn. The Bulgarians were defeated at the Battle of Dobro Pole , and by 25 September British and French troops had crossed the border into Bulgaria proper as the Bulgarian army collapsed. Bulgaria capitulated four days later, on 29 September 1918. The German high command responded by despatching troops to hold
11562-526: The globe, some of which were subsequently used to attack Allied merchant shipping . These were systematically hunted down by the Royal Navy, though not before causing considerable damage. One of the most successful was the SMS ; Emden , part of the German East Asia Squadron stationed at Qingdao , which seized or sank 15 merchantmen, a Russian cruiser and a French destroyer. Most of the squadron
11685-534: The high ground, while their trenches tended to be better built; those constructed by the French and English were initially considered "temporary", only needed until an offensive would destroy the German defences. Both sides tried to break the stalemate using scientific and technological advances. On 22 April 1915, at the Second Battle of Ypres , the Germans (violating the Hague Convention ) used chlorine gas for
11808-443: The intake and exhaust ports in some two-stroke designs can also allow some amount of unburned fuel vapors to exit in the exhaust stream. The high combustion temperatures of small, air-cooled engines may also produce NO x emissions. Two-stroke gasoline engines are preferred when mechanical simplicity, light weight, and high power-to-weight ratio are design priorities. By mixing oil with fuel, they can operate in any orientation as
11931-435: The introductions of tanks and aircraft . World War I was one of the deadliest conflicts in history , resulting in an estimated 10 million military dead and more than 20 million wounded , plus some 10 million civilian dead from causes including genocide . The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic. The causes of World War I included the rise of Germany and decline of
12054-467: The investigation and trial of Serbians linked to the assassination. Claiming this amounted to rejection, Austria broke off diplomatic relations and ordered partial mobilisation the next day; on 28 July, they declared war on Serbia and began shelling Belgrade . Russia ordered general mobilization in support of Serbia on 30 July. Anxious to ensure backing from the SPD political opposition by presenting Russia as
12177-439: The line, but these forces were too weak to re-establish a front. Two-stroke engine A two-stroke (or two-stroke cycle ) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston (one up and one down movement) in one revolution of the crankshaft. (A four-stroke engine requires four strokes of the piston to complete a power cycle, in two crankshaft revolutions.) In
12300-591: The low-powered Harley-Davidson engine attracted attention and launched Klemm on a path which led him, after designing at least two more Daimler light aircraft, to set up his own light aircraft company in 1926. In 1924 the L15 was finally refitted with its motorcycle engine and was eventually put on display in the Deutsches Museum with the placard "The First Light Aircraft", but was destroyed during World War II . Data from Deutsches Museum Arkiv General characteristics World War I World War I or
12423-469: The model year. The Monte Carlo Rally variant, 750-cc (with a filled crankshaft for higher base compression), generated 65 hp. An 850-cc version was available in the 1966 SAAB Sport (a standard trim model in comparison to the deluxe trim of the Monte Carlo). Base compression comprises a portion of the overall compression ratio of a two-stroke engine. Work published at SAE in 2012 points that loop scavenging
12546-524: The nose was now much shorter the pilot occupied the cockpit previously used by the passenger on the glider and the passenger sat close behind him at the wing trailing edge . During tests, the powered L15 reached an altitude of 2,150 m (7,050 ft) with only the pilot on board and 1,100 m (3,610 ft) with a passenger; a solo flight lasting 185 minutes was made and one passenger-carrying flight lasted 122 minutes. Other flights covered 190 km (118 mi) solo and 190 km (118 mi) with
12669-460: The ocean, even to neutral ships. Since there was limited response to this tactic, Germany expected a similar response to its unrestricted submarine warfare. The Battle of Jutland in May/June 1916 was the only full-scale clash of battleships during the war, and one of the largest in history. The clash was indecisive, though the Germans inflicted more damage than they received; thereafter the bulk of
12792-399: The oil pump of a modern two-stroke may not work in reverse, in which case the engine suffers oil starvation within a short time. Running a motorcycle engine backward is relatively easy to initiate, and in rare cases, can be triggered by a back-fire. It is not advisable. Model airplane engines with reed valves can be mounted in either tractor or pusher configuration without needing to change
12915-483: The other - the inlet pipe having passage to the crankcase only when the two cutouts coincide. The crankshaft itself may form one of the members, as in most glow-plug model engines. In another version, the crank disc is arranged to be a close-clearance fit in the crankcase, and is provided with a cutout that lines up with an inlet passage in the crankcase wall at the appropriate time, as in Vespa motor scooters. The advantage of
13038-434: The piston covering and uncovering the ports as it moves up and down in the cylinder. In the 1970s, Yamaha worked out some basic principles for this system. They found that, in general, widening an exhaust port increases the power by the same amount as raising the port, but the power band does not narrow as it does when the port is raised. However, a mechanical limit exists to the width of a single exhaust port, at about 62% of
13161-440: The piston is at bottom dead center, and the transfer ports nearly wide open. One of the reasons for high fuel consumption in two-strokes is that some of the incoming pressurized fuel-air mixture is forced across the top of the piston, where it has a cooling action, and straight out the exhaust pipe. An expansion chamber with a strong reverse pulse stops this outgoing flow. A fundamental difference from typical four-stroke engines
13284-550: The power band. Such valves are widely used in motorcycle, ATV, and marine outboard engines. The intake pathway is opened and closed by a rotating member. A familiar type sometimes seen on small motorcycles is a slotted disk attached to the crankshaft , which covers and uncovers an opening in the end of the crankcase, allowing charge to enter during one portion of the cycle (called a disc valve). Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members with suitable cutouts arranged to rotate one within
13407-466: The principles remain the same, the mechanical details of various two-stroke engines differ depending on the type. The design types vary according to the method of introducing the charge to the cylinder, the method of scavenging the cylinder (exchanging burnt exhaust for fresh mixture) and the method of exhausting the cylinder. Piston port is the simplest of the designs and the most common in small two-stroke engines. All functions are controlled solely by
13530-733: The protection of the " cruiser rules ", which demanded warning and movement of crews to "a place of safety" (a standard that lifeboats did not meet). Finally, in early 1917, Germany adopted a policy of unrestricted submarine warfare , realising the Americans would eventually enter the war. Germany sought to strangle Allied sea lanes before the United States could transport a large army overseas, but, after initial successes, eventually failed to do so. The U-boat threat lessened in 1917, when merchant ships began travelling in convoys , escorted by destroyers . This tactic made it difficult for U-boats to find targets, which significantly lessened losses; after
13653-806: The same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, due to increasingly stringent regulation of air pollution . Eastern Bloc countries continued until around 1991, with the Trabant and Wartburg in East Germany. Two-stroke engines are still found in a variety of small propulsion applications, such as outboard motors , small on- and off-road motorcycles , mopeds , motor scooters , motorized bicycles , tuk-tuks , snowmobiles , go-karts , RC cars , ultralight and model airplanes. Particularly in developed countries, pollution regulations have meant that their use for many of these applications
13776-464: The term First World War was in September 1914 by German biologist and philosopher Ernst Haeckel who stated, "There is no doubt that the course and character of the feared 'European War' ... will become the first world war in the full sense of the word". For much of the 19th century, the major European powers maintained a tenuous balance of power , known as the Concert of Europe . After 1848, this
13899-682: The threat posed by the closing of this gap was more important than competing with the Royal Navy. After Germany expanded its standing army by 170,000 troops in 1913, France extended compulsory military service from two to three years; similar measures were taken by the Balkan powers and Italy, which led to increased expenditure by the Ottomans and Austria-Hungary. Absolute figures are difficult to calculate due to differences in categorising expenditure since they often omit civilian infrastructure projects like railways which had logistical importance and military use. It
14022-511: The top or bottom of the piston. Regular gasoline two-stroke engines can run backward for short periods and under light load with little problem, and this has been used to provide a reversing facility in microcars , such as the Messerschmitt KR200 , that lacked reverse gearing. Where the vehicle has electric starting, the motor is turned off and restarted backward by turning the key in the opposite direction. Two-stroke golf carts have used
14145-577: The war ended with the Armistice of 11 November 1918 . The Paris Peace Conference of 1919–1920 imposed settlements on the defeated powers, most notably the Treaty of Versailles , by which Germany lost significant territories, was disarmed, and was required to pay large war reparations to the Allies. The dissolution of the Russian, German, Austro-Hungarian, and Ottoman Empires redrew national boundaries and resulted in
14268-581: The war involved British, French, and German colonial forces in Africa. On 6–7 August, French and British troops invaded the German protectorates of Togoland and Kamerun . On 10 August, German forces in South-West Africa attacked South Africa; sporadic and fierce fighting continued for the rest of the war. The German colonial forces in German East Africa , led by Colonel Paul von Lettow-Vorbeck , fought
14391-418: The west , which despite initial successes left the German Army exhausted and demoralised. A successful Allied counter-offensive from August 1918 caused a collapse of the German front line. By early November, Bulgaria, the Ottoman Empire and Austria-Hungary had each signed armistices with the Allies, leaving Germany isolated. Facing a revolution at home , Kaiser Wilhelm II abdicated on 9 November, and
14514-549: The wing leading edge in a cockpit within the removable nose and there was a passenger cockpit between the two wing spars at about one third chord . The fuselage was formed from four longerons, positioned by formers and wire-braced into a rectangular section, but with rounded upper and lower fairings . Its smooth fuselage and cantilever wing, together with an empennage that had no external bracing, made it aerodynamically very clean for its time. The fabric-covered , tapered wings were built around two box spars. The 1919 machine had
14637-403: Was challenged by Britain's withdrawal into so-called splendid isolation , the decline of the Ottoman Empire , New Imperialism , and the rise of Prussia under Otto von Bismarck . Victory in the 1870–1871 Franco-Prussian War allowed Bismarck to consolidate a German Empire . Post-1871, the primary aim of French policy was to avenge this defeat, but by the early 1890s, this had switched to
14760-654: Was refused. Early on the morning of 4 August, the Germans invaded, and Albert I of Belgium called for assistance under the Treaty of London . Britain sent Germany an ultimatum demanding they withdraw from Belgium; when this expired at midnight, without a response, the two empires were at war. Germany promised to support Austria-Hungary's invasion of Serbia, but interpretations of what this meant differed. Previously tested deployment plans had been replaced early in 1914, but those had never been tested in exercises. Austro-Hungarian leaders believed Germany would cover its northern flank against Russia. Beginning on 12 August,
14883-659: Was returning to Germany when it sank two British armoured cruisers at the Battle of Coronel in November 1914, before being virtually destroyed at the Battle of the Falkland Islands in December. The SMS Dresden escaped with a few auxiliaries, but after the Battle of Más a Tierra , these too were either destroyed or interned. Soon after the outbreak of hostilities, Britain began a naval blockade of Germany . This proved effective in cutting off vital supplies, though it violated accepted international law. Britain also mined international waters which closed off entire sections of
15006-759: Was the foundation of German foreign policy but in 1890, he was forced to retire by Wilhelm II . The latter was persuaded not to renew the Reinsurance Treaty by his new Chancellor , Leo von Caprivi . This gave France an opening to agree the Franco-Russian Alliance in 1894, which was then followed by the 1904 Entente Cordiale with Britain. The Triple Entente was completed by the 1907 Anglo-Russian Convention . While not formal alliances, by settling long-standing colonial disputes in Asia and Africa, British support for France or Russia in any future conflict became
15129-530: Was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ, and Walter Kaaden. Loop scavenging, disc valves, and expansion chambers worked in a highly coordinated way to significantly increase the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha, and Kawasaki. Suzuki and Yamaha enjoyed success in Grand Prix motorcycle racing in
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