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21-413: It is undesirable for an airplane to bounce on landing as it could lead to a loss of control, and the landing gear should not add to this tendency. A steel coil spring stores impact energy from landing and then releases it, while an oleo strut instead absorbs this energy, reducing bounce. As the strut compresses, the spring rate increases dramatically because the air is being compressed. The viscosity of

42-457: A damper. A tapered rod is used on some designs to change the size of the orifice as the piston moves, providing greater resistance as compression of the strut increases. Additionally, a check valve is sometimes used to uncover additional orifices so that damping during compression is less than during rebound. Oleo struts absorb and dissipate forces by converting a portion of the accumulated kinetic energy into thermal energy. Pneumatic systems like

63-515: A lighter arrangement but enabling the whole strut to be inverted and to work while at an angle, eliminating the weakness of using an oil and air mixture. Oleo-pneumatic technology was subsequently reused by the manufacturer to produce several other products, including hydraulic railway buffers and industrial shock absorbers. During 1926, the Cleveland Pneumatic Tool Company designed and introduced an oleo strut, one of

84-441: A wide range of different shock-absorbing struts were in use, but typically employ common principles, despite considerable variations in size, weight, and other characteristics. Refinements continued to be made to the technology behind the oleo strut. During 1954, hydropneumatic suspension was introduced, which uses the same principle of a gas that compresses ( nitrogen ) and a fluid that does not; in this use, an engine-driven pump

105-443: A wire around a shaped former – a cylinder is used to form cylindrical coil springs. Coil springs for vehicles are typically made of hardened steel . A machine called an auto-coiler takes spring wire that has been heated so it can easily be shaped. It is then fed onto a lathe that has a metal rod with the desired coil spring size. The machine takes the wire and guides it onto the spinning rod as well as pushing it across

126-418: Is a mechanical device that is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix that returns to its natural length when unloaded. Under tension or compression, the material (wire) of a coil spring undergoes torsion. The spring characteristics therefore depend on

147-451: Is an aircraft that has a maximum gross takeoff weight of 12,500 lb (5,670 kg) or less. Light aircraft are used as utility aircraft commercially for small-scale passenger and freight transport ; for sightseeing, photography, cropdusting , and other so-called aerial work roles of civil aviation ; for the personal-use aspect of general aviation ; and in certain aspects of military aviation . Examples of aircraft that are at

168-403: Is divided into two chambers that are connected by a small orifice of a precise, calculated size. When the aircraft is stationary on the ground, its weight is supported by the compressed gas in the cylinder. During landing, or when the aircraft taxis over bumps, the piston slides up and down. This movement compresses the gas, which acts as a spring, and forces oil through the orifice, which acts as

189-618: Is used to pressurize the hydraulic fluid . Another such example was a US patent filed by Jarry Hydraulics during 1958. During the 1960s, the British Ministry of Technology sponsored research into theoretical studies into improved oleo-damping technology. In 2012, it was proposed that the vibration-damping qualities of the oleo strut could be enhanced by using semi-active control to adjust fluid viscosity. The use of oleo struts for electric-powered automatic guided vehicles has also been evaluated. According to Engineering360, by 2019,

210-452: The shear modulus . A coil spring may also be used as a torsion spring : in this case the spring as a whole is subjected to torsion about its helical axis. The material of the spring is thereby subjected to a bending moment , either reducing or increasing the helical radius. In this mode, it is the Young's Modulus of the material that determines the spring characteristics. Spring rate is

231-551: The Quadro range of motor scooters use the oleo strut, which is claimed to give favourable low speed lean characteristics. An oleo strut consists of an inner metal tube or piston , which is attached to the wheel axle, and which moves up and down in an outer (or upper) metal tube, or cylinder, that is attached to the airframe . The cavity within the strut and piston is filled with gas (usually nitrogen, sometimes air—especially on light aircraft ) and oil (usually hydraulic fluid), and

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252-545: The first to be purpose-designed for use on airplanes. The company subsequently marketed the product as an Aerol strut, which had entered widespread use within the United States within the space of a decade. By 1931, innovations in the field were being made in the United Kingdom , France , and North America. The oleo strut became commonly used for aviation purposes around the world. By the twenty-first century,

273-508: The maximum gross takeoff weight for this category include the de Havilland Canada DHC-6 Twin Otter and Beechcraft B200 Super King Air . Uses include aerial surveying, such as monitoring pipelines, light cargo operations, such as "feeding" cargo hubs, and passenger operations. Light aircraft are used for marketing purposes, such as banner towing and skywriting , and flight instruction . The majority of personal aircraft are light aircraft,

294-580: The measurement of how much a coil spring can hold until it compresses 1 inch (2.54 cm). The spring rate is normally specified by the manufacture. If a spring has a rate of 100 then the spring would compress 1 inch with 100 pounds (45 kg) of load. Types of coil spring are: Coil springs have many applications; notable ones include: Coil springs are commonly used in vehicle suspension . These springs are compression springs and can differ greatly in strength and in size depending on application. A coil spring suspension can be stiff to soft depending on

315-583: The oil damps the rebound movement. The original design for the oleo-pneumatic shock-absorbing strut was patented by British manufacturing conglomerate Vickers Armstrong during 1915. It had been derived from the recuperative gear design of the Vickers gun , controlling recoil by forcing oil through precisely sized orifices. Vickers' oleo strut was first applied to an aeroplane by the French aircraft company Breguet Aviation . The design proved to be viable and

336-444: The oleo strut generally have long operating lives, and the construction is not unusually complex for maintenance purposes. Nitrogen is usually used as the gas instead of air, since it is less likely to cause corrosion . The various parts of the strut are sealed with O-rings or similar elastomeric seals, and a scraper ring is used to keep dust and grit adhering to the piston from entering the strut. Coil spring A coil spring

357-548: The oleo-pneumatic strut had become the most common type of shock absorber in use on modern aircraft. The oleo strut has seen much use on the largest cargo airplanes in the world, such as the Antonov An-124 Ruslan ; it reportedly provides for a rough-field landing capacity while carrying payloads of up to 150 tons. This design also cushions the airframe from the impacts of taxiing , resulting in greater levels of comfort for passengers and crew. In non-aircraft use,

378-446: The rod to form multiple coils. The spring is then ejected from the machine and an operator will put it in oil to cool off. The spring is then tempered to lose the brittleness from being cooled. The coil size and strength can be controlled by the lathe rod size and material used. Different alloys are used to get certain characteristics out of the spring, such as stiffness, dampening and strength Light aircraft A light aircraft

399-479: The vehicle it is used on. Coil spring can be either mounted with a shock absorber or mounted separately. Coil springs in trucks allow them to ride smoothly when unloaded and once loaded the spring compresses and becomes stiff. This allows the vehicle to bounce less when loaded. Coil spring suspension is also used in high performance cars so that the car can absorb bumps and have low body roll. In off-road vehicles they are used because of their range of travel they allow at

420-521: The wheel. Coil springs used in the engine are compression springs and play an important role in closing the valves that feed air and let exhaust gasses out of the combustion chamber. The spring is attached to a rocker that is connected to the valve. Tension and extension coil springs of a given material, wire diameter and coil diameter exert the same force when fully loaded; increased number of coils merely (linearly) increases free length and compressed/extended length. Metal coil springs are made by winding

441-436: Was extensively adopted across the aviation industry for fixed undercarriages, becoming simply referred to as an "Oleo unit" or undercarriage leg. Vickers' initial design had placed air above the oil, an arrangement that did not pose any problem until the introduction of retractable landing gear during the mid-1930s. The engineer, Peter Thornhill, devised a novel undercarriage strut that used a free-floating piston, not only being

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