Compared to V-twins and flat-twins, straight-twins are more compact and usually cheaper to make, but may generate more vibration during operation. Straight-twin engines have been used in motorcycles, but are used in automobiles. Automobiles with straight-twin engines are very small and include city cars. Recent examples of cars with straight-twin engines include the Tata Nano, powersports applications include use in outboard motors, personal water craft, all-terrain vehicles and ultralight aircraft. Different crankshaft angles are used in four-stroke straight-twins to achieve different characteristics of firing intervals and engine balance, affecting vibrations, the traditional British parallel twin had 360° crankshafts, while some larger Japanese twins of the 1960s adopted the 180° crankshaft. In the 1990s, new engines appeared with a 270° crankshaft, straight-twins have the advantage of being more compact, relatively simple, and cheaper to make in comparison to V- or flat-twins. They may be prone to vibration, either because of the irregular firing interval present in 180° crank engines or the large uncountered reciprocating mass in 360° crank engines, inline-twins suffer further from torsional torque reactions and vibration.
Unlike V-twins, straight-twin engines do not use a crank pin for both connecting rods, each cylinder has its own crank pin. Honda straight-twin engines, which began appearing in the late 1950s, had four main bearings, subsequent engines had four or occasionally three main bearings, ball bearings being better than shell bearings for this engine configuration. In motorcycles, as cars and other vehicles, the terms parallel-twin, vertical-twin and inline-twin are used. The term parallel twin has used to refer specifically to a four-stroke straight-two engine with 360° crankshaft causing the pistons to travel parallel to each other. Other times, parallel-twin, inline-twin and the variants have been used interchangeably. The first production motorcycle using a motor was the Hildebrand & Wolfmuller of 1894. Its cylinders lay flat and forward-facing, its pistons connected directly to the wheel with a locomotive-style connecting rod. Approximately 2000 were produced through 1897, the second production motorcycle to use a straight twin design, this time a parallel twin with vertical cylinders akin to the British type, was the Werner of 1903.
It used cast-iron cylinders with integral heads, and side valves, the most famous example of the straight-twin engine was produced by Triumph from 1937 onwards, the 5T Speed Twin. Experiments with this type began as designer Edward Turner and his supervisor. From the experiments, it was shown that a 360° crank angle was better suited to the use of a single carburettor than a 180° crank angle
Bicycle and motorcycle geometry
Bicycle and motorcycle geometry is the collection of key measurements that define a particular bike configuration. Primary among these are wheelbase, steering angle, fork offset. These parameters have an influence on how a bike handles. Wheelbase is the distance between the centers of the front and rear wheels. Wheelbase is a function of rear frame length, steering axis angle and it is similar to the term wheelbase used for automobiles and trains. Wheelbase has an influence on the longitudinal stability of a bike, along with the height of the center of mass of the combined bike. Short bikes are more suitable for performing wheelies and stoppies. The steering axis angle, called caster angle or head angle, is the angle that the steering axis makes with the horizontal or vertical, the steering axis is the axis about which the steering mechanism pivots. The steering axis angle usually matches the angle of the head tube, in bicycles, the steering axis angle is called the head angle and is measured from the horizontal, a 90° head angle would be vertical.
Due to front fork suspension, modern Mountain Bikes as opposed to Road Bikes, tend to have slacker head tube angles, at least one manufacturer, Cane Creek, offers an after-market threadless headset that enables changing the steering axis angle. When all else remains the same, this alters the trail of the bicycle, in motorcycles, the steering axis angle is called the rake angle or just rake and is measured from the vertical. A 0° rake would be vertical, in bicycles, fork offset is called fork rake. Road racing bicycle forks have an offset of 40–50 mm, the development of forks with curves is attributed to George Singer. Other, less-common motorcycle forks, such as trailing link or leading link forks, the length of a fork is measured parallel to the steer tube from the lower fork crown bearing to the axle center. Trail, or caster, is the distance from where the front wheel touches the ground to where the steering axis intersects the ground. The measurement is considered if the front wheel ground contact point is behind the steering axis intersection with the ground.
Most bikes have positive trail, though a few, such as the two-mass-skate bicycle, trail is a function of steering axis angle, fork offset, and wheel size. Trail can be increased by increasing the size, decreasing or slackening the head angle
A motorcycle is a two- or three-wheeled motor vehicle. Motorcycle design varies greatly to suit a range of different purposes, long travel, cruising, sport including racing. Motorcycling is riding a motorcycle and related social activity such as joining a motorcycle club, in 1894, Hildebrand & Wolfmüller became the first series production motorcycle, and the first to be called a motorcycle. In 2014, the three top motorcycle producers globally by volume were Honda and Hero MotoCorp, in developing countries, motorcycles are overwhelmingly utilitarian due to lower prices and greater fuel economy. Of all the motorcycles in the world, 58% are in the Asia-Pacific and Southern and Eastern Asia regions, according to the United States Department of Transportation the number of fatalities per vehicle mile traveled was 37 times higher for motorcycles than for cars. The term motorcycle has different legal definitions depending on jurisdiction, there are three major types of motorcycle, off-road, and dual purpose.
Within these types, there are many sub-types of motorcycles for different purposes, there is often a racing counterpart to each type, such as road racing and street bikes, or motocross and dirt bikes. Street bikes include cruisers, sportbikes and mopeds, off-road motorcycles include many types designed for dirt-oriented racing classes such as motocross and are not street legal in most areas. Dual purpose machines like the style are made to go off-road but include features to make them legal. Each configuration offers either specialised advantage or broad capability, and each design creates a different riding posture, the first internal combustion, petroleum fueled motorcycle was the Daimler Reitwagen. It was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt, instead, it relied on two outrigger wheels to remain upright while turning. The inventors called their invention the Reitwagen and it was designed as an expedient testbed for their new engine, rather than a true prototype vehicle.
The first commercial design for a cycle was a three-wheel design called the Butler Petrol Cycle. He exhibited his plans for the vehicle at the Stanley Cycle Show in London in 1884, the vehicle was built by the Merryweather Fire Engine company in Greenwich, in 1888. The engine was liquid-cooled, with a radiator over the driving wheel. Speed was controlled by means of a valve lever. No braking system was fitted, the vehicle was stopped by raising and lowering the rear driving wheel using a foot-operated lever, the driver was seated between the front wheels. It wasnt, however, a success, as Butler failed to find sufficient financial backing, many authorities have excluded steam powered, electric motorcycles or diesel-powered two-wheelers from the definition of a motorcycle, and credit the Daimler Reitwagen as the worlds first motorcycle
In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels. For road vehicles with more than two axles, the wheelbase is defined as the distance between the axle and the centerpoint of the driving axle group. In the case of a truck, the wheelbase would be the distance between the steering axle and a point midway between the two rear axles. The wheelbase of a vehicle equals the distance between its front and rear wheels, at equilibrium, the total torque of the forces acting on a vehicle is zero. So, for example, when a truck is loaded, its center of gravity shifts rearward, the amount the vehicle sinks will depend on counter acting forces like the size of the tires, tire pressure, and the stiffness of the suspension. If the vehicle is accelerating or decelerating, extra torque is placed on the rear or front tire respectively, so, as is common experience, when the vehicle accelerates, the rear usually sinks and the front rises depending on the suspension.
Likewise, when braking the front noses down and the rear rises, because of the effect the wheelbase has on the weight distribution of the vehicle, wheelbase dimensions are crucial to the balance and steering. For example, a car with a greater weight load on the rear tends to understeer due to the lack of the load on the front tires. This is why it is crucial, when towing a single-axle caravan, likewise, a car may oversteer or even spin out if there is too much force on the front tires and not enough on the rear tires. Also, when turning there is lateral torque placed upon the tires which imparts a turning force that depends upon the length of the distances from the CM. Wheelbases provide the basis for one of the most common vehicle size class systems, some luxury vehicles are offered with long-wheelbase variants to increase the spaciousness and therefore the luxury of the vehicle. Prime Minister of the United Kingdom Tony Blair was given a version of the Rover 75 for official use. In contrast, coupé varieties of vehicles such as the Honda Accord are usually built on shorter wheelbases than the sedans they are derived from.
The wheelbase on many commercially available bicycles and motorcycles is so short, relative to the height of their centers of mass, in skateboarding the word wheelbase is used for the distance between the two inner pairs of mounting holes on the deck. This is different from the distance between the centers of the two wheel pairs. A reason for this use is that decks are sold with prefabricated holes. It is therefore easier to use the holes for measuring and describing this characteristic of the deck. A common misconception is that the choice of wheelbase is influenced by the height of the skateboarder, the length of the deck would be a better candidate, because the wheelbase affects characteristics useful in different speeds or terrains regardless of the height of the skateboarder
In physics, power is the rate of doing work. It is the amount of energy consumed per unit time, having no direction, it is a scalar quantity. In the SI system, the unit of power is the joule per second, known as the watt in honour of James Watt, another common and traditional measure is horsepower. Being the rate of work, the equation for power can be written, because this integral depends on the trajectory of the point of application of the force and torque, this calculation of work is said to be path dependent. As a physical concept, power requires both a change in the universe and a specified time in which the change occurs. This is distinct from the concept of work, which is measured in terms of a net change in the state of the physical universe. The output power of a motor is the product of the torque that the motor generates. The power involved in moving a vehicle is the product of the force of the wheels. The dimension of power is divided by time. The SI unit of power is the watt, which is equal to one joule per second, other units of power include ergs per second, metric horsepower, and foot-pounds per minute.
One horsepower is equivalent to 33,000 foot-pounds per minute, or the required to lift 550 pounds by one foot in one second. Other units include dBm, a logarithmic measure with 1 milliwatt as reference, food calories per hour, Btu per hour. This shows how power is an amount of energy consumed per unit time. If ΔW is the amount of work performed during a period of time of duration Δt and it is the average amount of work done or energy converted per unit of time. The average power is simply called power when the context makes it clear. The instantaneous power is the value of the average power as the time interval Δt approaches zero. P = lim Δ t →0 P a v g = lim Δ t →0 Δ W Δ t = d W d t. In the case of constant power P, the amount of work performed during a period of duration T is given by, W = P t
A four-stroke engine is an internal combustion engine in which the piston completes four separate strokes while turning a crankshaft. A stroke refers to the travel of the piston along the cylinder. The four separate strokes are termed, known as induction or suction This stroke of the piston begins at top dead center and ends at bottom dead center. In this stroke the valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing vacuum pressure into the cylinder through its downward motion. Compression, This stroke begins at B. D. C, or just at the end of the suction stroke, in this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke. Both the intake and exhaust valves are closed during this stage, known as power or ignition This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution, while the piston is at T. D. C. The compressed air-fuel mixture is ignited by a plug or by heat generated by high compression.
This stroke produces mechanical work from the engine to turn the crankshaft, during the exhaust stroke, the piston once again returns from B. D. C. to T. D. C. While the exhaust valve is open and this action expels the spent air-fuel mixture through the exhaust valve. Nikolaus August Otto as a man was a traveling salesman for a grocery concern. In his travels he encountered the internal combustion engine built in Paris by Belgian expatriate Jean Joseph Etienne Lenoir, in 1860, Lenoir successfully created a double-acting engine that ran on illuminating gas at 4% efficiency. The 18 litre Lenoir Engine produced only 2 horsepower, the Lenoir engine ran on illuminating gas made from coal, which had been developed in Paris by Philip Lebon. In testing a replica of the Lenoir engine in 1861 Otto became aware of the effects of compression on the fuel charge, in 1862, Otto attempted to produce an engine to improve on the poor efficiency and reliability of the Lenoir engine. He tried to create an engine that would compress the fuel prior to ignition.
Many other engineers were trying to solve the problem, with no success, in 1864, Otto and Eugen Langen founded the first internal combustion engine production company, NA Otto and Cie. Otto and Cie succeeded in creating an atmospheric engine that same year. The factory ran out of space and was moved to the town of Deutz, in 1872, Gottlieb Daimler was technical director and Wilhelm Maybach was the head of engine design
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. All diesel engines use fuel injection by design, petrol engines can use gasoline direct injection, where the fuel is directly delivered into the combustion chamber, or indirect injection where the fuel is mixed with air before the intake stroke. On petrol engines, fuel injection replaced carburetors from the 1980s onward, the functional objectives for fuel injection systems can vary. All share the task of supplying fuel to the combustion process. Carburetors have the potential to atomize fuel better, Fuel injection dispenses with the need for a separate mechanical choke, which on carburetor-equipped vehicles must be adjusted as the engine warms up to normal temperature. Furthermore, on spark ignition engines, fuel injection has the advantage of being able to facilitate stratified combustion which have not been possible with carburetors, Fuel injection generally increases engine fuel efficiency.
With the improved cylinder-to-cylinder fuel distribution of multi-point fuel injection, less fuel is needed for the power output. Exhaust emissions are cleaner because the precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine. The more consistent and predictable composition of the exhaust makes emissions control devices such as catalytic converters more effective, herbert Akroyd Stuart developed the first device with a design similar to modern fuel injection, using a jerk pump to meter out fuel oil at high pressure to an injector. This system was used on the engine and was adapted and improved by Bosch. Fuel injection was in commercial use in diesel engines by the mid-1920s. Another early use of direct injection was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925. Hesselman engines use the ultra lean-burn principle, fuel is injected toward the end of the compression stroke and they are often started on gasoline and switched to diesel or kerosene.
Direct fuel injection was used in notable World War II aero-engines such as the Junkers Jumo 210, the Daimler-Benz DB601, the BMW801, German direct injection petrol engines used injection systems developed by Bosch from their diesel injection systems. Later versions of the Rolls-Royce Merlin and Wright R-3350 used single point fuel injection, due to the wartime relationship between Germany and Japan, Mitsubishi had two radial aircraft engines utilizing fuel injection, the Mitsubishi Kinsei and the Mitsubishi Kasei. Alfa Romeo tested one of the first electronic systems in Alfa Romeo 6C2500 with Ala spessa body in 1940 Mille Miglia. The engine had six electrically operated injectors and were fed by a semi-high-pressure circulating fuel pump system, all diesel engines have fuel injected into the combustion chamber. The invention of mechanical injection for gasoline-fueled aviation engines was by the French inventor of the V8 engine configuration, Leon Levavasseur in 1902, the first post-World War I example of direct gasoline injection was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925
Kawasaki W series
The Kawasaki W series is a line of motorcycles made by Kawasaki since 1965 that shares some characteristics of classic British vertical-twin standard motorcycles. Sold as a 1966 model in the North American market, the first Kawasaki W1 had the largest engine displacement of any model manufactured in Japan at the time, Kawasaki continues to build models of the W brand similar to the W1. In 1960 the Akashi-based Kawasaki Aircraft Company acquired an interest in the Meguro motorcycle company, Meguro had been Japans largest motorcycle manufacturer but in the late 1950s its models had become less competitive and it was short of money. Kawasakis investment enabled Meguro to launch its A7 copy as the Meguro K, the BSA A7, Meguro K and their respective derivatives have an overhead valve straight-twin engine with a pre-unit construction architecture. All have a 360° crankshaft angle, which provides an even firing interval between the two cylinders but high vibration caused by the two pistons rising and falling together, since the introduction of the K2, the Meguro K model has tended to become known retrospectively as the K1.
The K2 has a larger timing cover which distinguishes it from the model K, the K2 chassis has a different rear subframe, fuel tank and side panels. These changes gave the K2 a typically conservative Meguro image, dissimilar to the original BSA A7, in 1965 the K2 was enlarged to 624 cc to become the Meguro X-650 prototype, which was displayed at the 1965 Tokyo Motor Show. The X-650 became in turn the prototype for the Kawasaki W1, the Society of Automotive Engineers of Japan, includes the 1966 Kawasaki 650-W1 as one of their 240 Landmarks of Japanese Automotive Technology. The Kawasaki W1 is based heavily on the post-war, pre-unit construction, 650cc vertical-twin BSA A7 design inherited from Meguro, but as time passed and this slightly oversquare design favors higher engine speeds, while reducing stresses on the crankshaft. Even though the BSA and Kawasaki 650cc engines were different from each other. From 1966 to 1968 W1 engines were built with a single 31 mm Mikuni carburetor, starting in 1968, the W1SS with two 28 mm Mikuni carbs took the place of the original W1.
Also in 1968, the W2 emerged, the W2SS was a restyled W1SS with slightly more horsepower, and the W2TT was a high-pipe version with twin mufflers on the left side. Due to flat sales in North America the W2TT was discontinued in 1969, the W2SS ended in 1970, the 650 remained popular in Japan, and although some were exported to Europe in the 70s, subsequent models were produced primarily for the domestic market. The final version was the 1973 W3 model with upgraded suspension as well as disc brakes in front. W series production ceased in 1974, the W1 had to compete with other Japanese twin-cylinder street bikes, such as the Suzuki T500 and the Honda CB450. If the W1 was seen as being behind the times, Kawasaki came back with an engine that was clearly ahead of its time. The following year the W series faced a new competitor in a state-of-the-art twin from Yamaha, in 1968 the domination of the inline-twin engine for high-performance street bikes came to an end when Triumph Engineering developed an inline-triple engine for the BSA Rocket 3/Triumph Trident.
The 1969 Kawasaki H1 Mach III with an inline-triple two-stroke, the W series engines were oil-tight and reliable, but by comparison they had low levels of performance with high levels of vibration, and were ultimately unsuccessful on the sales floor
A motorcycle transmission is a transmission created specifically for motorcycle applications. Most manual transmission two-wheelers use a sequential gearbox, most modern motorcycles change gears by foot lever. A five-speed of this configuration would be known as one down, neutral is to be found half a click away from first and second gears, so shifting directly between the two gears can be made in a single movement. Automatic transmissions are less common on motorcycles than manual, and are found only on scooters and some custom cruisers. Types include continuously variable transmission, semi-automatic transmission and dual clutch transmission, the weight of the largest touring motorcycles is such that they cannot effectively be pushed backwards by a seated rider, and they are fitted with a reverse gear as standard. In some cases, including the Honda Gold Wing and BMW K1200LT, this is not really a reverse gear, but a feature of the starter motor which when reversed, performs the same function.
To avoid accidental operation, reverse is often engaged using a separate control switch - e. g. a pull-toggle at the head of the fuel tank - when the main gearshift is in neutral. In earlier times, hand-operated gear changes were common, with a lever provided to the side of the fuel tank and many other motorcycles after World War II used a lever on the right, but today gear-changing is standardised on a foot-operated lever to the left. Traditional scooters still have manual gear-changing by a twist grip on the hand side of the handlebar. Modern scooters were often fitted with a continuously variable transmission. Underbone and miniature motorcycles often have a three to five-speed foot change, but the clutch is automatic. Whether wet or dry, the plates are squeezed together by a spring, causing friction build up between the plates until they rotate as a unit, driving the transmission directly. A lever on the handlebar exploits mechanical advantage through a cable or hydraulic arrangement to release the spring, allowing the engine to freewheel with respect to the transmission.
Automatic and semi-automatics typically use a clutch which operates in a different fashion. At idle, the engine is disconnected from the input shaft. The effective bite point is found automatically by equilibrium where the power being transmitted through the clutch is equal to what the engine can provide. This allows relatively fast full-throttle takeoffs without the engine slowing or bogging down, as well as more relaxed starts and low-speed maneuvers at lower throttle settings and rpms. Also, when the engine is turning fast enough to lock the clutch, it will stay fully engaged until the RPMs fall below that point again
The BSA A7 was a motorcycle made by Birmingham Small Arms Company at their factory in Armoury Road, Small Heath, Birmingham in 1946. There were two versions of the A7, the original 495 cc version, and an improved 497 cc version launched in 1950, although its name was changed to the Star Twin and the Shooting Star the BSA A7 continued in production with minor modifications until 1961. The very first A7 off the line was flown to Paris for the first motorcycle show after the end of the war. There was huge demand for transport after the war and the simplicity of the A7 twin was helped along by the slogan Its time YOU had a BSA. The 495 cc twin cylinder engine produced 26 bhp and was capable of 85 mph, a single camshaft behind the cylinders operated the valves via long pushrods passing through a tunnel in the cast iron block. As with other British motorcycles of the period, this kind of set-up regularly led to oil leaks, most motorcycles of this period tensioned the primary chain by drawing or rotating the gearbox backwards on a hinge with threaded rods, this was known as pre-unit construction.
The first A7 had a gearbox, bolted to the back of the crankcase. This gave it the appearance of unit construction and pioneered the system used in unit-construction engines such as the BSA C15, BSA B40, Triumph 3TA. However, in 1954 a re-design reverted to the older system, the electrics consisted of two independent systems, the very reliable and self-contained Lucas magneto, with a dynamo generator to charge the battery and provide lights. Carburation was a single Amal remote float Type 6 until 1955 when it was upgraded to a 376 Monobloc, in October 1949 BSA launched the Bert Hopwood designed 650 cc twin cylinder BSA A10. Although resembling the A7500 cc twin, it had an engine design. Launched as the BSA Star Twin SS the new model had twin carburettors and it had the latest design of cylinder head with austenitic steel inlet and exhaust valves. The uprated engine was fitted to a frame and finished extra chrome. Both models were produced with an option of rigid or plunger frames until 1954, the new frame led to a separate gearbox to replace the bolted on version.
In 1952 three BSA A7s were entered for the Maudes Trophy and the International Six Days Trial, achieving 4,500 miles without problems and confirming the reliability of the design. All three bikes were randomly selected from the line, picked up Gold medals and earned BSA the Team award as well as the Trophy. The three bikes were ridden by Brian Martin, Fred Rist and Norman Vanhouse, from Birmingham the team rode to Vienna on through Germany, Denmark and Norway before returning safely and with a clean sheet to Birmingham. Also in 1952 American BSA dealer Hap Alzina prepared a BSA Star Twin for an attempt on the American Class C speed record for standard catalogue motorcycles.69 mph, list of motorcycles of the 1940s BSA A7 review Fully restored 1949 BSA A7 BSA Sales Brochure