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98-608: The maneuverability of the motorcycle on crowded streets offer advantages not provided by larger, more traditional police vehicles. The motorcycle's relatively small size allows it to get to accident scenes more quickly when incidents such as traffic collisions slow down access by four-wheel vehicles, and to access routes unavailable to other motor vehicles, such as narrow streets and footpaths . Police motorcycles are also used in police escorts for parades , funeral processions , motorcades , Olympic torch relays , and other events. Police officers have used motorcycles—primarily for

196-619: A pilgrimage . Examples of the latter are the Pilgrim's Way in England and Pilgrim's Route (St. Olav's Way or the Old Kings' Road) in Norway. Some landowners allow access over their land without dedicating a right of way. These permissive paths are often indistinguishable from normal paths, but they are usually subject to restrictions. Such paths are often closed at least once a year, so that

294-576: A Wankel engine are thus mainly limited by tooth load on the synchronizing gears. Hardened steel gears are used for extended operation above 7,000 or 8,000   rpm. In practice, automotive Wankel engines are not operated at much higher output shaft speeds than reciprocating piston engines of similar output power. Wankel engines in auto racing are operated at speeds up to 10,000   rpm, but so are four-stroke reciprocating piston engines with relatively small displacement per cylinder. In aircraft, they are used conservatively, up to 6500 or 7500   rpm. In

392-405: A Wankel rotary engine, the chamber volume V k {\displaystyle V_{k}} is equivalent to the product of the rotor surface A k {\displaystyle A_{k}} and the rotor path s {\displaystyle s} . The rotor surface A k {\displaystyle A_{k}} is given by the rotor tips' path across

490-400: A Wankel rotary engine, the eccentric shaft must make three full rotations (1080°) per combustion chamber to complete all four phases of a four-stroke engine. Since a Wankel rotary engine has three combustion chambers, all four phases of a four-stroke engine are completed within one full rotation of the eccentric shaft (360°), and one power pulse is produced at each revolution of the shaft. This

588-399: A boundary layer from overheating working parts. The University of Florida proposed the use of heat pipes in an air-cooled Wankel to overcome this uneven heating of the block housing. Pre-heating of certain housing sections with exhaust gas improved performance and fuel economy, also reducing wear and emissions. The boundary layer shields and the oil film act as thermal insulation, leading to

686-492: A figure-eight-like epitrochoidal housing around a fixed-toothed gearing. The midpoint of the rotor moves in a circle around the output shaft, rotating the shaft via a cam. In its basic gasoline fuelled form, the Wankel engine has lower thermal efficiency and higher exhaust emissions relative to the four-stroke reciprocating piston engine. The thermal inefficiency has restricted the engine to limited use since its introduction in

784-406: A fresh air supply to the exhaust port. It also proved that a Reed-valve in the intake port or ducts improved the low rpm and partial load performance of Wankel engines, by preventing blow-back of exhaust gas into the intake port and ducts, and reducing the misfire-inducing high EGR, at the cost of a slight loss of power at top rpm. Elasticity is improved with a greater rotor eccentricity, analogous to

882-439: A glow-plug for the leading site spark plug improved low rpm, part load, specific fuel consumption by 7%, and emissions and idle. A later alternative solution to spark plug boss cooling was provided with a variable coolant velocity scheme for water-cooled rotaries, which has had widespread use, being patented by Curtiss-Wright, with the last-listed for better air-cooled engine spark plug boss cooling. These approaches did not require

980-431: A high incidence of sealing loss, both between the rotor and the housing and also between the various pieces making up the housing. Also, in earlier model Wankel engines, carbon particles could become trapped between the seal and the casing, jamming the engine and requiring a partial rebuild. It was common for very early Mazda engines to require rebuilding after 50,000 miles (80,000 km). Further sealing problems arose from

1078-441: A high-conductivity copper insert, but did not preclude its use. Ford tested a Wankel engine with the plugs placed in the side plates, instead of the usual placement in the housing working surface ( CA 1036073   , 1978). Wankel engines are capable of high-speed operation, meaning they do not necessarily need to produce high torque to produce high power. The positioning of the intake port and intake port closing greatly affect

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1176-423: A legally protected right to travel. Other public rights of way in England and Wales, such as bridleways , byways , towpaths , and green lanes are also used by pedestrians. In Scotland there is no legal distinction between a footpath and a bridleway and it is generally accepted that cyclists and horse riders may follow any right of way with a suitable surface. The law is different in both Northern Ireland and

1274-423: A longer stroke in a reciprocating engine. Wankel engines operate better with a low-pressure exhaust system. Higher exhaust back pressure reduces mean effective pressure, more severely in peripheral intake port engines. The Mazda RX-8 Renesis engine improved performance by doubling the exhaust port area relative to earlier designs, and there have been studies of the effect of intake and exhaust piping configuration on

1372-412: A low temperature of the lubricating film (approximate maximum 200 °C or 390 °F on a water-cooled Wankel engine). This gives a more constant surface temperature. The temperature around the spark plug is about the same as in the combustion chamber of a reciprocating engine. With circumferential or axial flow cooling, the temperature difference remains tolerable. Problems arose during research in

1470-406: A more steady idle, because it helps to prevent blow-back of burned gases into the intake ducts, which cause "misfirings" caused by alternating cycles where the mixture ignites and fails to ignite. Peripheral porting (PP) gives the best mean effective pressure throughout the rpm range, but PP was also linked to worse idle stability and part-load performance. Early work by Toyota led to the addition of

1568-1248: A number of countries. These can be rural in nature, such as the Essex Way , in southern England, which crosses farmland, or urban as with various routes in London, England , or along a coastline like the South West Coast Path in the West of England , or in the high mountains, like the Pacific Crest Trail in the US, which reaches 13,153 feet (4,009 m) at Forester Pass in the Sierra Nevada . Many footpaths require some maintenance. Most rural paths have an earth or grass surface with stiles , and or gates, including kissing gates . A few will have stepping stones , fords, or bridges. Urban footpaths may be constructed of masonry , brick , concrete , asphalt, cut stone or wood boardwalk . Crushed rock , decomposed granite , fine wood chips are also used. The construction materials can vary over

1666-537: A one-tier system) has a statutory duty to maintain a definitive map, though in national parks the national park authority usually maintains the map. The Inner London boroughs are exempt from the statutory duty though they have the powers to maintain a map: currently none does so. Currently, the number of footpaths in the UK totals 427,301 (around 81% of all rights of way) with a net combined route length of 105,125 miles. In Scotland different legislation applies and there

1764-482: A park is found along the seawall in Stanley Park , Vancouver, British Columbia , Canada. This is a segregated path, with one lane for skaters and cyclists and the other for pedestrians. In the US and Canada, where urban sprawl has begun to strike even the most rural communities, developers and local leaders are currently striving to make their communities more conducive to non-motorized transportation through

1862-443: A pavement/ sidewalk in some English-speaking countries (such as Australia, New Zealand, and Ireland). A footpath can also take the form of a footbridge , linking two places across a river. Public footpaths are rights of way originally created by people walking across the land to work, market, the next village, church, and school. This includes mass paths and corpse roads . Some footpaths were also created by those undertaking

1960-854: A permanent right of way cannot be established in law. A mass path is a pedestrian track or road connecting destinations frequently used by rural communities, most usually the destination of Sunday Mass . They were most common during the centuries that preceded motorised transportation in Western Europe, and in particular the British Isles and the Netherlands (where such a path is called "kerkenpad" (lit. Church path). Mass paths typically included stretches crossing fields of neighboring farmers and were likely to contain stiles , when crossing fences or other boundaries, or plank footbridges to cross ditches. Some mass paths are still used today in

2058-478: A result of the poor efficiency, a Wankel engine with peripheral exhaust porting has a larger amount of unburnt hydrocarbons (HC) released into the exhaust. The exhaust is, however, relatively low in nitrogen oxide (NOx) emissions, because the combustion is slow, and temperatures are lower than in other engines, and also because of the Wankel engine's good exhaust gas recirculation (EGR) behavior. Carbon monoxide (CO) emissions of Wankel and Otto engines are about

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2156-513: A rotary internal combustion engine with Felix Wankel, based upon Wankel's supercharger design for their motorcycle engines. Since Wankel was known as a "difficult colleague", the development work for the DKM was carried out at Wankel's private Lindau design bureau. According to John B. Hege, Wankel received help from his friend Ernst Höppner, who was a "brilliant engineer". The first working prototype, DKM 54 (see figure 2.), first ran on 1 February 1957, at

2254-422: A route along a country path can be impeded by ploughing, crops, overgrown vegetation, illegal barriers (including barbed wire ), damaged stiles , etc. There have been numerous problems over the years in England and Wales with landowners. One notable example was with the millionaire property tycoon Nicholas Van Hoogstraten who had a long-standing dislike of and dispute with ramblers, describing them as "scum of

2352-498: A single-rotor Wankel engine produces the same average power as a V h {\displaystyle V_{h}} single-cylinder two-stroke engine , with the same average torque, with the shaft running at the same speed, operating the Otto cycles at triple the frequency. Richard Franz Ansdale, Wolf-Dieter Bensinger and Felix Wankel based their analogy on the number of cumulative expansion strokes per shaft revolution. In

2450-403: A stationary center shaft, the DKM engine was impractical. Wolf-Dieter Bensinger explicitly mentions that proper engine cooling cannot be achieved in a DKM engine, and argues that this is the reason why the DKM design had to be abandoned. NSU development chief engineer Walter Froede solved this problem by using Hanns-Dieter Paschke's design and converting the DKM into what would later be known as

2548-456: A thermal reactor or catalyst converter may be used to reduce hydrocarbon and carbon monoxide from the exhaust. Mazda uses a dual ignition system with two spark plugs per chamber. This increases the power output and at the same time reduces HC emissions. At the same time, HC emissions can be lowered by reducing the pre-ignition of the T leading plug relative to the L trailing plug. This leads to internal afterburning and reduces HC emissions. On

2646-425: A thin dimensional galvanized chrome layer. This allowed Mazda to return to the 3mm and later even 2mm thick metal apex seals. Another early problem was the build-up of cracks in the stator surface near the plug hole, which was eliminated by installing the spark plugs in a separate metal insert/ copper sleeve in the housing instead of a plug being screwed directly into the block housing. Toyota found that substituting

2744-614: A trial basis 40-octane gasoline was produced by BV Aral, which was used in the Wankel DKM54 test engine with a compression ratio of 8:1; it ran without complaint. This upset the petrochemical industry in Europe, which had invested considerable sums of money in new plants for the production of higher quality gasoline. Direct injection stratified charge engines can be operated with fuels with particularly low octane numbers. Such as diesel fuel, which only has an octane number of ~25. As

2842-663: Is Britain's oldest national conservation body. The society was founded as the Commons Preservation Society and merged with the National Footpaths Society in 1899, and adopted their present name. Much of the Open Spaces Society's work is concerned with the preservation and creation of public paths. Before the introduction of definitive maps of public paths in the early 1950s, the public did not know where paths were, and

2940-538: Is a narrow, usually paved, pedestrian path, often between the walls of buildings in towns and cities. This type is usually short and straight, and on steep ground can consist partially or entirely of steps. In older cities and towns in Europe, alleys are often what is left of a medieval street network, or a right of way or ancient footpath. Similar paths also exist in some older North American towns and cities. In some older urban development in North America lanes at

3038-440: Is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel , followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle , with the sides having less curvature. The rotor spins inside

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3136-568: Is a type of thoroughfare that is intended for use only by pedestrians and not other forms of traffic such as motorized vehicles , bicycles and horses . They can be found in a wide variety of places, from the centre of cities, to farmland, to mountain ridges. Urban footpaths are usually paved, may have steps, and can be called alleys , lanes, steps, etc. National parks , nature preserves , conservation areas and other protected wilderness areas may have footpaths ( trails ) that are restricted to pedestrians. The term footpath can also describe

3234-585: Is an integrated walkway system that has over 160 kilometers (99 mi) of footpaths which link every major park, river, pond, and green space in six municipalities. In London , England, there are several long-distance walking routes which combine footpaths and roads to link green spaces. These include the Capital Ring , London Outer Orbital Path and the Jubilee Walkway , the use of which have been endorsed by Transport for London . An alley

3332-558: Is depicted in figure 7. Seals at the rotor's apices seal against the housing's periphery. The rotor moves in its rotating motion guided by gears and the eccentric output shaft, not being guided by the external chamber. The rotor does not make contact with the external engine housing. The force of expanded gas pressure on the rotor exerts pressure on the center of the eccentric part of the output shaft. All practical Wankel engines are four-cycle (i.e., four-stroke) engines. In theory, two-cycle engines are possible, but they are impractical because

3430-428: Is described in the thermodynamic disadvantages section , the early Wankel engines had poor fuel economy. This is caused by the Wankel engine's design of combustion chamber shape and huge surface area. The Wankel engine's design is, on the other hand, much less prone to engine knocking, which allows using low- octane fuels without reducing compression. NSU tested low octane gasoline at the suggestion of Felix Wankel. On

3528-440: Is different from a four-stroke piston engine, which needs to make two full rotations per combustion chamber to complete all four phases of a four-stroke engine. Thus, in a Wankel rotary engine, according to Bensinger, displacement ( V h {\displaystyle V_{h}} ) is: If power is to be derived from BMEP, the four-stroke engine formula applies: Eugen Wilhelm Huber, and Karl-Heinz Küttner counted all

3626-589: Is no legally recognised record of rights of way. However, there is a National Catalogue of Rights of Way (CROW), compiled by the Scottish Rights of Way and Access Society (Scotways), in partnership with Scottish Natural Heritage, and the help of local authorities. The Open Spaces Society is a charitable British organisation that works to protect public rights of way and open spaces in the United Kingdom, such as common land and village greens . It

3724-397: Is the number of chambers considered for each rotor and i {\displaystyle i} the number of rotors, then the total displacement is: If p m e {\displaystyle p_{me}} is the mean effective pressure , N {\displaystyle N} the shaft rotational speed and n c {\displaystyle n_{c}}

3822-1061: The Harley-Davidson FLHTP Electra Glide, the FLHP Road King , the XL883 Sportster and the new XB12XP Buell Ulysses Police motorcycle. The FLHTP Electra Glide and the FLHP Road King are also offered as Fire/Rescue motorcycles. In 2014, the Los Angeles Police Department added the Zero Motorcycles MMX electric motorcycle to its fleet. The motorcycle was praised over the traditional bulky Harley-Davidson and BMW bikes for its stealth, low operational costs, immediate tactical advantage, and low environmental footprint. Footpaths A footpath (also pedestrian way, walking trail , nature trail )

3920-478: The Isle of Man . He became frustrated at the lack of privacy at his home when ramblers deviated from a pathway to take photographs of his dwelling. Clarkson's property bordered a small 250-metre strip of land that had no definitive status as a public right of way but was used by walkers regardless. Clarkson aimed to close access to this small strip of his land, thereby forcing ramblers to take a small diversion to stick to

4018-633: The Kawasaki Concours 14 is being modified and marketed for police use in some markets. In Germany, BMW Motorrad is the largest provider of motorcycles for authority use. In the United Kingdom, the most common police motorcycles are the BMW R1200RT and the Yamaha FJR1300 . Some police forces also use scooters within towns for parking enforcement, or special-purpose machines such as unmarked (covert), or off-road motorcycles. Of

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4116-548: The Republic of Ireland and there are far fewer rights of way in Ireland as a whole (see Keep Ireland Open ). Footpaths and other rights of way in England and Wales are shown on definitive maps . A definitive map is a record of public rights of way in England and Wales. In law it is the definitive record of where a right of way is located. The highway authority (normally the county council , or unitary authority in areas with

4214-728: The Republic of Ireland , but are usually subject to Ireland's complicated rights of way law. Corpse roads provided a practical means for transporting corpses, often from remote communities, to cemeteries that had burial rights, such as parish churches and chapels of ease . In Great Britain , such routes can also be known by a number of other names: bier road, burial road, coffin road, coffin line, lyke or lych way, funeral road, procession way, corpse way, etc. Nowadays footpaths are mainly used for recreation and have been frequently linked together, along with bridle paths and newly created footpaths, to create long-distance trails . Also, organizations have been formed in various countries to protect

4312-594: The 1950s and 1960s. For a while, engineers were faced with what they called "chatter marks" and "devil's scratch" in the inner epitrochoid surface, resulting in chipping of the chrome coating of the trochoidal surfaces. They discovered that the cause was the apex seals reaching a resonating vibration, and the problem was solved by reducing the thickness and weight of the apex seals as well as using more suitable materials. Scratches disappeared after introducing more compatible materials for seals and housing coatings. Yamamoto experimentally lightened apex seals with holes. Now, weight

4410-492: The 1960s. However, many disadvantages have mainly been overcome over the succeeding decades as the production of road-going vehicles progressed. The advantages of compact design, smoothness, lower weight, and fewer parts over the reciprocating piston internal combustion engines make the Wankel engine suited for applications such as chainsaws , auxiliary power units (APUs), loitering munitions , aircraft , jet skis , snowmobiles , and range extenders in cars . The Wankel engine

4508-604: The British manufacturers themselves, Triumph motorcycles, built at Meriden , were used by many British (including the Metropolitan Police ) and Commonwealth police forces until 1983 when the factory closed. From the late 1940s, Triumph was also, for a time, the choice of the Parisian police, a fact promoted in a factory-produced movie, It's A Triumph ! . The police version of the 650cc 6T Triumph Thunderbird

4606-550: The DKM engine were built; the design is described to have a displacement V h of 250 cm (equivalent to a working chamber volume V k of 125 cm ). The fourth unit built is said to have received several design changes, and eventually produced 29 PS (21 kW) at 17,000 rpm; it could reach speeds up to 22,000 rpm. One of the four engines built has been on static display at the Deutsches Museum Bonn (see figure. 2). Due to its complicated design with

4704-508: The KKM (see figure 5.). The KKM proved to be a much more practical engine, as it has easily accessible spark plugs, a simpler cooling design, and a conventional power take-off shaft. Wankel disliked Froede's KKM engine because of its inner rotor's eccentric motion, which was not a pure circular motion, as Wankel had intended. He remarked that his "race horse" was turned into a "plough horse". Wankel also complained that more stresses would be placed on

4802-460: The KKM type. Felix Wankel designed a rotary compressor in the 1920s, and received his first patent for a rotary type of engine in 1934. He realized that the triangular rotor of the rotary compressor could have intake and exhaust ports added producing an internal combustion engine. Eventually, in 1951, Wankel began working at German firm NSU Motorenwerke to design a rotary compressor as a supercharger for NSU's motorcycle engines. Wankel conceived

4900-488: The KKM ;502 was a powerful engine with decent potential, smooth operation, and low noise emissions at high engine speeds. It was a single-rotor PP engine with a displacement of 996 cm (61 in ), a rated power of 40 kW (54 hp) at 6,000   rpm and a BMEP of 1 MPa (145 lbf/in ). The Wankel engine has a spinning eccentric power take-off shaft, with a rotary piston riding on eccentrics on

4998-462: The KKM's apex seals due to the eccentric hula-hoop motion of the rotor. NSU could not afford to finance developing both the DKM and the KKM, and eventually decided to drop the DKM in favor of the KKM, because the latter seemed to be the more practical design. Wankel obtained the US patent 2,988,065 on the KKM engine on 13 June 1961. Throughout the design phase of the KKM, Froede's engineering team had to solve problems such as repeated bearing seizures,

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5096-547: The NSU research and development department Versuchsabteilung TX . It produced 21 PS (15 kW). Soon after that, a second prototype of the DKM was built. It had a working chamber volume V k of 125 cm and also produced 21 kW (29 PS) at 17,000   rpm. It could even reach speeds of up to 25,000   rpm. However, these engine speeds distorted the outer rotor's shape, thus proving impractical. According to Mazda Motors engineers and historians, four units of

5194-505: The Open Spaces Society helped the successful campaign for paths to be shown on Ordnance Survey maps. It advises the Department for Environment, Food and Rural Affairs and National Assembly for Wales on applications for works on common land. Local authorities are legally required to consult the society whenever there is a proposal to alter the route of a public right of way. The Ramblers are another British organisation concerned with

5292-554: The R1200RT-P and R900RT-P. More than 225 U.S. law enforcement agencies, including the California Highway Patrol , have BMW authority motorcycles in their fleets of patrol vehicles. The new BMW bikes outperformed the aging Harley-Davidson fleet. Harley-Davidson has maintained a long relationship with police departments and law-enforcement agencies in some countries. For the 2009 model year, Harley-Davidson offers

5390-567: The UK newspaper, Motor Cycle News reported Derbyshire's Chief Constable comparing these Triumphs very unfavorably to BMW, in particular, its anti-vibration engine mounts. Supported by an article in rival publication, Motor Cycle Weekly , this criticism was strongly refuted by the factory and Derbyshire eventually accepted evaluation of police versions of the new Triumph T140W TSS in anti-vibration mounts. Norton 's Commando Interpol and later Wankel rotary engine Interpol 2 motorcycle were used by some British forces until that firm's collapse in

5488-443: The Wankel engine run much smoother. This is because the Wankel engine has a lower moment of inertia and less excess torque area due to its more uniform torque delivery. For example, a two-rotor Wankel engine runs more than twice as smoothly as a four-cylinder piston engine. The eccentric output shaft of a Wankel engine also does not have the stress-related contours of a reciprocating piston engine's crankshaft. The maximum revolutions of

5586-615: The armed forces also grew, providing a stable production market for the more utilitarian machines, especially as Europe rearmed after World War I . As of 2004 police departments in the United States typically use purpose-built motorcycles marketed by Harley-Davidson, Kawasaki , or BMW Motorrad . Kawasaki police motorcycles , which were built for the US market in Lincoln, Nebraska , ceased production in September 2005. However,

5684-613: The average torque, with the shaft running at 2/3 the speed, operating the Otto cycles at the same frequency: Applying a 2/3 gear set to the output shaft of the three-cylinder (or a 3/2 one to the Wankel), the two are analogous from the thermodynamic and mechanical output point of view, as pointed out by Huber. NSU licensed the Wankel engine design to companies worldwide, in various forms, with many companies implementing continual improvements. In his 1973 book Rotationskolben-Verbrennungsmotoren , German engineer Wolf-Dieter Bensinger describes

5782-422: The axially closer side housings in the cooler intake lobe areas was dealt with by using an axial rotor pilot radially inboard of the oils seals, plus improved inertia oil cooling of the rotor interior (C-W US 3261542   , C. Jones, 5/8/63, US 3176915   , M. Bentele, C. Jones. A.H. Raye. 7/2/62), and slightly "crowned" apex seals (different height in the center and in the extremes of seal). As

5880-407: The chambers, since each one operates its own thermodynamic cycle. So y = 3 {\displaystyle y=3} and n c = 3 {\displaystyle n_{c}=3} : With these values, a single-rotor Wankel engine produces the same average power as a V h {\displaystyle V_{h}} three-cylinder four-stroke engine, with 3/2 of

5978-426: The design of a triangular rotor in the compressor. With the assistance of Prof. Othmar Baier  [ de ] from Stuttgart University of Applied Sciences, the concept was defined mathematically. The supercharger he designed was used for one of NSU's 50 cm one-cylinder two-stroke engines. The engine produced a power output of 13.5 PS (10 kW) at 12,000   rpm. In 1954, NSU agreed to develop

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6076-583: The early 1990s. Other marques such as BSA were used by some forces, although only the Velocette LE "noddy-bike" model proved as popular with the police as the Triumphs. In 2008, BMW claimed to be the largest seller of motorcycles for authority use, as more than 100,000 BMW motorcycles were in official use in over 150 countries on five continents. In 2007, BMW sold 4,284 police motorcycles worldwide. BMW produces factory built police-specific models such as

6174-448: The early days, unique, dedicated production machines had to be built for different housing dimensional arrangements. However, patented designs such as U.S. patent 3,824,746 , G. J. Watt, 1974, for a "Wankel Engine Cylinder Generating Machine", U.S. patent 3,916,738 , "Apparatus for machining and/or treatment of trochoidal surfaces" and U.S. patent 3,964,367 , "Device for machining trochoidal inner walls", and others, solved

6272-494: The earth". In 1999 Hoogstraten erected a large fence across a footpath on his country estate in East Sussex. Local ramblers staged a protest against the erection of the fence outside the boundary of Van Hoogstraten's estate. On 10 February 2003 and after a 13-year battle and numerous legal proceedings, the path was finally re-opened. Another conflict involved Jeremy Clarkson , a TV presenter and Top Gear host who lives on

6370-490: The enforcement of traffic laws and as escort vehicles—since the early 20th century. Chief August Vollmer of the Berkeley Police Department is credited with organizing the first official police motorcycle patrol in the United States in 1911. However, several police forces around the country reported using motorcycles as patrol vehicles earlier. Harley-Davidson credits Detroit, Michigan as being

6468-416: The engine's torque production. Early closing of the intake port increases low-end torque, but reduces high-end torque (and thus power). In contrast, late closing of the intake port reduces low-end torque while increasing torque at high engine speeds, thus resulting in more power at higher engine speeds. A peripheral intake port gives the highest mean effective pressure ; however, side intake porting produces

6566-431: The engine. While this puts great demands on the materials used, the simplicity of the Wankel makes it easier to use alternative materials, such as exotic alloys and ceramics . A commonplace method is, for engine housings made of aluminum, to use a spurted molybdenum layer on the engine housing for the combustion chamber area, and a spurted steel layer elsewhere. Engine housings cast from iron can be induction-brazed to make

6664-421: The experience gained, from carbon alloys, to steel, ferritic stainless , Ferro-TiC, and other materials. The combination of housing plating and the apex and side seal materials was determined experimentally, to obtain the best duration of both seals and housing cover. For the shaft, steel alloys with little deformation on load are preferred, the use of Maraging steel has been proposed for this. Leaded petrol fuel

6762-463: The factor that controls the amount of unburnt hydrocarbons in the exhaust is the rotor surface temperature, with higher temperatures resulting in fewer hydrocarbons in the exhaust. Curtiss-Wright widened the rotor, keeping the rest of engine's architecture unchanged, thus reducing friction losses and increasing displacement and power output. The limiting factor for this widening was mechanical, especially shaft deflection at high rotative speeds. Quenching

6860-404: The farthest, and a {\displaystyle a} as the shortest parallel transfer of the rotor and the inner housing and assuming that R 1 = R + a {\displaystyle R_{1}=R+a} and R 2 = R + a ′ {\displaystyle R_{2}=R+a'} . Then, Including the parallel transfers of the rotor and

6958-555: The first purchaser of police motorcycles in 1908. The police department in Evanston , Illinois also purchased a belt-driven motorcycle for its first motorcycle police officer in 1908, and the Portland Police Bureau had a police officer who used his personal motorcycle to patrol the city as early as 1909. The role of the motorcycle as inexpensive public transportation evolved in the 1930s, and their use by police and

7056-529: The following licensees, in chronological order, which is confirmed by John B. Hege: In 1961, the Soviet research organizations of NATI, NAMI, and VNIImotoprom began developing a Wankel engine. Eventually, in 1974, development was transferred to a special design bureau at the AvtoVAZ plant. John B. Hege argues that no license was issued to any Soviet car manufacturer. Felix Wankel managed to overcome most of

7154-449: The inner housing provides sufficient accuracy for determining chamber volume. Different approaches have been used over time to evaluate the total displacement of a Wankel engine in relation to a reciprocating engine: considering only one, two, or all three chambers. Part of this dispute was because of Europe vehicle taxation being dependent on engine displacement, as reported by Karl Ludvigsen . If y {\displaystyle y}

7252-536: The intake gas and the exhaust gas cannot be properly separated. The operating principle is similar to the Otto operating principle; the Diesel operating principle with its compression ignition cannot be used in a practical Wankel engine. Therefore, Wankel engines typically have a high-voltage spark ignition system. In a Wankel engine, one side of the triangular rotor completes the four-stage Otto cycle of intake, compression, expansion, and exhaust each revolution of

7350-740: The length of the footpath and may start with a well constructed hard surface in an urban area, and end with an inexpensive soft or loose surface in the countryside. Stairs or steps are sometimes found in urban alleys , or cliff paths to beaches. The main issues in urban areas include maintenance, litter, crime, and lighting after dark. In the countryside there are issues relating to conflicts between walkers and livestock, and these occasionally result in people being injured or even killed. Dogs often contribute to such conflicts – see in England and Wales The Dogs (Protection of Livestock) Act 1953 . Also footpaths in remote locations can be difficult to maintain and

7448-414: The material suited for withstanding combustion heat stress. Among the alloys cited for Wankel housing use are A-132, Inconel 625, and 356 treated to T6 hardness. Several materials have been used for plating the housing working surface, Nikasil being one. Citroën, Daimler-Benz, Ford, A P Grazen, and others applied for patents in this field. For the apex seals, the choice of materials has evolved along with

7546-430: The number of shaft revolutions needed to complete a cycle ( N / n c {\displaystyle N/n_{c}} is the frequency of the thermodynamic cycle), then the total power output is: Kenichi Yamamoto and Walter G. Froede placed y = 1 {\displaystyle y=1} and n c = 1 {\displaystyle n_{c}=1} : With these values,

7644-546: The official public right of way and therefore protecting his claimed right to privacy on his own property. In May 2010 the former transport minister, Hon. David Anderson MHK, accepted the conclusions of a public inquiry that all except five of the paths claimed at the inquiry as public rights of way have been dedicated as public rights of way and should be added to the definitive map. [REDACTED] Media related to Public footpaths at Wikimedia Commons Wankel engine The Wankel engine ( /ˈvaŋkəl̩/ , VUN -kell )

7742-546: The oil flow inside the engine, and the engine cooling. The first fully functioning KKM engine, the KKM 125, weighing in at only 17 kg (37.5 lb) displaced 125 cm and produced 26 PS (19 kW) at 11,000   rpm. Its first run was on 1 July 1958. In 1963, NSU produced the first series-production Wankel engine for a car, the KKM 502 (see Figure 6.). It was used in the NSU Spider sports car, of which about 2,000 were made. Despite its "teething troubles",

7840-506: The other hand, the same ignition timing of L and T leads to a higher energy conversion. Hydrocarbons adhering to the combustion chamber wall are expelled into the exhaust at the peripheral outlet. Mazda used 3 spark plugs in their R26B engine per chamber. The third spark plug ignites the mixture in the trailing side before the squish is generated, causing the mixture to burn completely and, also speeding up flame propagation, which improves fuel consumption. According to Curtiss-Wright research,

7938-482: The performance of Wankel engines. Side intake ports (as used in Mazda's Renesis engine) were first proposed by Hanns-Dieter Paschke in the late 1950s. Paschke predicted that precisely calculated intake ports and intake manifolds could make a side port engine as powerful as a PP engine. As formerly described, the Wankel engine is affected by unequal thermal expansion due to the four cycles taking place in fixed places of

8036-463: The problem. Wankel engines have a problem not found in reciprocating piston four-stroke engines in that the block housing has intake, compression, combustion, and exhaust occurring at fixed locations around the housing. This causes a very uneven thermal load on the rotor housing. In contrast, four-stroke reciprocating engines perform these four strokes in one chamber, so that extremes of "freezing" intake and "flaming" exhaust are averaged and shielded by

8134-421: The problems that made prior attempts to perfect the rotary engines fail, by developing a configuration with vane seals having a tip radius equal to the amount of "oversize" of the rotor housing form, relative to the theoretical epitrochoid, to minimize radial apex seal motion plus introducing a cylindrical gas-loaded apex pin which abutted all sealing elements to seal around the three planes at each rotor apex. In

8232-414: The protection of footpaths. There are a variety of footpaths in urban settings, including paths along streams and rivers, through parks and across commons . Another type is the alley , normally providing access to the rear of properties or connecting built-up roads not easily reached by vehicles. Towpaths are another kind of urban footpath, but they are often shared with cyclists. A typical footpath in

8330-460: The rear of houses, to allow for deliveries and garbage collection, are called alleys. Alleys may be paved, or unpaved, and a blind alley is a cul-de-sac . Some alleys are roofed because they are within buildings, such as the traboules of Lyon , or when they are a pedestrian passage through railway embankments in Britain. The latter follow the line of rights-of way that existed before the railway

8428-598: The right to use public footpaths, including the Ramblers Association and the Open Spaces Society in England. Footpaths are now also found in botanic gardens , arboretums , regional parks , conservation areas , wildlife gardens , and open-air museums . There are also educational trails , themed walks , sculpture trails and historic interpretive trails. In England and Wales , public footpaths are rights of way on which pedestrians have

8526-429: The rotor (equivalent to three shaft revolutions, see Figure 8.). The shape of the rotor between the fixed apexes is to minimize the volume of the geometric combustion chamber and maximize the compression ratio , respectively. As the rotor has three sides, this gives three power pulses per revolution of the rotor. Wankel engines have a much lower degree of irregularity relative to a reciprocating piston engine, making

8624-410: The rotor housing and determined by the generating radius R {\displaystyle R} , the rotor width B {\displaystyle B} , and the parallel transfers of the rotor and the inner housing a {\displaystyle a} . Since the rotor has a trochoid ("triangular") shape, the sine of 60 degrees describes the interval at which the rotors get closest to

8722-443: The rotor housing. Therefore, The rotor path s {\displaystyle s} may be integrated via the eccentricity e {\displaystyle e} as follows: Therefore, For convenience, a {\displaystyle a} may be omitted because it is difficult to determine and small: A different approach to this is introducing a ′ {\displaystyle a'} as

8820-407: The same. The Wankel engine has a significantly higher (Δt K >100 K) exhaust gas temperature than an Otto engine, especially under low and medium load conditions. This is because of the higher combustion frequency and slower combustion. Exhaust gas temperatures can exceed 1300 K under high load at engine speeds of 6000 rpm . To improve the exhaust gas behavior of the Wankel engine,

8918-406: The shaft in a hula-hoop fashion. The Wankel is a 2:3 type of rotary engine, i.e., its housing's inner side resembles a two lobes oval-like epitrochoid (equivalent to a peritrochoid),. In contrast, its rotary piston has a three vertices trochoid shape (similar to a Reuleaux triangle ). Thus, the Wankel engine's rotor constantly forms three moving working chambers. The Wankel engine's basic geometry

9016-512: The uneven thermal distribution within the housings causing distortion and loss of sealing and compression. This thermal distortion also caused uneven wear between the apex seal and the rotor housing, evident on higher mileage engines. The problem was exacerbated when the engine was stressed before reaching operating temperature . However, Mazda Wankel engines solved these initial problems. Current engines have nearly 100 seal-related parts. The problem of clearance for hot rotor apexes passing between

9114-579: The use of less traditional paths. The Robert Wood Johnson Foundation has established the Active Living by Design program to improve the livability of communities in part through developing trails, The Upper Valley Trails Alliance has done similar work on traditional trails, while the Somerville Community Path and related paths, are examples of urban initiatives. In St. John's , Newfoundland , Canada The Grand Concourse ,

9212-579: Was also used to power motorcycles and racing cars . The Wankel engine is a type of rotary piston engine and exists in two primary forms, the Drehkolbenmotor (DKM, "rotary piston engine"), designed by Felix Wankel (see Figure 2.) and the Kreiskolbenmotor (KKM, "circuitous piston engine"), designed by Hanns-Dieter Paschke (see Figure 3.), of which only the latter has left the prototype stage. Thus, all production Wankel engines are of

9310-459: Was built. Because of topography , steps ( stairs ) are the predominant form of alley in hilly cities and towns. This includes Pittsburgh (see Steps of Pittsburgh ), Cincinnati (see Steps of Cincinnati ), Portland, Oregon , Seattle , and San Francisco in the United States, as well as Hong Kong , and Rome . Footpaths (and other rights of way) have been combined, and new paths created, so as to produce long-distance walking routes in

9408-456: Was identified as the main cause. Mazda then used aluminum-impregnated carbon apex seals in their early production engines. NSU used carbon antimony-impregnated apex seals against chrome. NSU developed ELNISIL coating to production maturity and returned to a metal sealing strip for the RO80. Mazda continued to use chrome, but provided the aluminum housing with a steel jacket, which was then coated with

9506-629: Was nicknamed the SAINT, an acronym of "Stops Anything In No Time". By the mid-1970s, with industrial problems and closures affecting their spares supply and service, Triumphs and other British marques were increasingly replaced by the smoother BMW R80 (and to a more limited extent, Norton Interpols ) than by then-current Triumph police bikes. In an attempt to win back orders from BMW, Meriden marketed Triumph Bonneville and Tiger models of 750cc size with anti-vibration mountings as well as electric starting but these still only achieved limited sales success. In 1981,

9604-573: Was the predominant type available in the first years of the Wankel engine's development. Lead is a solid lubricant, and leaded petrol is designed to reduce the wearing of seals and housings. The first engines had the oil supply calculated with consideration of petrol's lubricating qualities. As leaded petrol was being phased out, Wankel engines needed an increased mix of oil in the petrol to provide lubrication to critical engine parts. An SAE paper by David Garside extensively described Norton's choices of materials and cooling fins. Early engine designs had

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