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Jackscrew
A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderate and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable supports for heavy loads, such as the foundations of houses. Description A screw jack consists of a heavy-duty vertical screw with a load table mounted on its top, which screws into a threaded hole in a stationary support frame with a wide base resting on the ground. A rotating collar on the head of the screw has holes into which the handle, a metal bar, fits. When the handle is turned clockwise, the screw moves further out of the base, lifting the load resting on the load table. In order to support large load forces, the screw is usually formed with Acme threads. Advantages An advantage of jackscrews over some other types of jack is that they are ''self-locking'', which means when the rotational force on the screw is removed, it will remain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaska Airlines Flight 261
Alaska Airlines Flight 261 was a scheduled international passenger flight from Licenciado Gustavo Díaz Ordaz International Airport in Puerto Vallarta, Puerto Vallarta, Jalisco, Mexico, to Seattle–Tacoma International Airport in Seattle, Washington, United States, with an intermediate stop at San Francisco International Airport in San Francisco, California. On January 31, 2000, the aircraft operating the route, a McDonnell Douglas MD-80, McDonnell Douglas MD-83, crashed into the Pacific Ocean roughly north of Anacapa Island, California, following a catastrophic loss of Pitch (flight), pitch control. The accident killed all 88 on board: two pilots, three cabin crew members, and 83 passengers. The subsequent investigation by the National Transportation Safety Board (NTSB) determined that inadequate maintenance led to excessive wear and eventual failure of a critical Aircraft flight control system, flight control system during flight. The probable cause was stated to be "a loss o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jackscrew
A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderate and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable supports for heavy loads, such as the foundations of houses. Description A screw jack consists of a heavy-duty vertical screw with a load table mounted on its top, which screws into a threaded hole in a stationary support frame with a wide base resting on the ground. A rotating collar on the head of the screw has holes into which the handle, a metal bar, fits. When the handle is turned clockwise, the screw moves further out of the base, lifting the load resting on the load table. In order to support large load forces, the screw is usually formed with Acme threads. Advantages An advantage of jackscrews over some other types of jack is that they are ''self-locking'', which means when the rotational force on the screw is removed, it will remain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
McDonnell Douglas MD-80
The McDonnell Douglas MD-80 is a series of five-abreast single-aisle airliners developed by McDonnell Douglas. It was produced by the developer company until August 1997 and then by Boeing Commercial Airplanes. The MD-80 was the second generation of the DC-9 family, originally designated as the DC-9-80 (DC-9 Series 80) and later stylized as the DC-9 Super 80 (short ''Super 80''). Stretched, enlarged wing and powered by higher bypass Pratt & Whitney JT8D-200 engines, the aircraft program was launched in October 1977. The MD-80 made its first flight on October 18, 1979, and was certified on August 25, 1980. The first airliner was delivered to launch customer Swissair on September 13, 1980, which introduced it into service on October 10, 1980. Keeping the fuselage cross-section, longer variants are stretched by 14 ft (4.3 m) from the DC-9-50 and have a 28% larger wing. The larger variants (MD-81/82/83/88) are 148 ft (45.1 m) long to seat 155 passengers in coach an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aeroflot Flight 8641
Aeroflot Flight 8641 was a Yakovlev Yak-42 airliner on a domestic scheduled passenger flight from Leningrad (now Saint Petersburg) to Kiev (now Kyiv). On 28 June 1982, the flight crashed south of Mazyr, Byelorussian SSR, killing all 132 people on board. The accident was both the first and deadliest crash of a Yakovlev Yak-42, and remains the deadliest aviation accident in Belarus. The cause was a failure of the jackscrew controlling the horizontal stabilizer due to a design flaw. Aircraft and crew The Yakovlev Yak-42 involved in the accident was registered to Aeroflot as СССР-42529. The aircraft made its maiden flight on 21 April 1981 and was delivered to the Ministry of Civil Aviation on 1 June 1981. At the time of the accident, it had 795 flight hours and 496 takeoff and landing cycles. All 124 passenger seats were filled, 11 were children. The flight crew consisted of: * Captain Vyacheslav Nikolaevich Musinskiy * Co-pilot Alexander Sergeevich Stigariev * Flight engine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Screw (simple Machine)
The screw is a mechanism that converts rotational motion to linear motion, and a torque (rotational force) to a linear force. It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called '' threads'' around the outside. The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it; for example rotating a wood screw forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a nut can rotate around a stationary screw shaft. Geometrically, a screw can be viewed as a narrow inclined plane wrapped around a cylinder. Like the other simple machines a screw can amplify force; a small rotational forc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yakovlev Yak-42
The Yakovlev Yak-42 (; NATO reporting name: "Clobber") is a 100/120-seat three-engined mid-range passenger jet developed in the mid 1970s to replace the technically obsolete Tupolev Tu-134. It was the first airliner produced in the Soviet Union to be powered by modern high-bypass turbofan engines.Gunston, 1997 Development In 1972, the Yakovlev design bureau started work on a short- to medium-range airliner capable of carrying 100–120 passengers. It was intended to be a replacement for the Tupolev Tu-134 jet as well as the Ilyushin Il-18, Antonov An-24 and An-26 turboprop airliners. While the new airliner was required to operate out of relatively small airfields while maintaining good economy, as many Soviet airports had been upgraded to accommodate more advanced aircraft, it did not have to have the same ability to operate from grass strips as Yakovlev's smaller Yak-40. The requirement resulted in the largest, heaviest and most powerful aircraft designed by Yakovlev.Gor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Square Thread Form
The square thread form is a common screw thread profile, used in high load applications such as leadscrews and jackscrews. It gets its name from the square cross-section of the thread.Bhandari, p. 203. It is the lowest friction and most efficient thread form, but it is difficult to fabricate. Advantages & disadvantages The greatest advantage of square threads is that they have a much higher intrinsic efficiency than trapezoidal threads (Acme thread form, Acme or metric trapezoidal). Due to the lack of a thread angle there is no radial pressure, or bursting pressure, on the nut. This also increases the nut life. The greatest disadvantage is the difficulty in machining such a thread. The tool bit, single-point cutting tools or tap and die, taps and dies used to cut the thread cannot have efficient rake and relief angles (because of the square form), which makes the cutting slow and difficult. Square threads also cannot carry as much load as a trapezoidal thread, because the root ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydraulic Piston
Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concerns gases. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on applied engineering using the properties of fluids. In its fluid power applications, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through some parts of science and most of engineering modules, and they cover concepts such as pipe flow, dam design, fluidics, and fluid control circuitry. The principles of hydraulics are in use naturally in the human body within the vascular system and erectile tissue. ''Free surface hydraulics'' is the branch of hydraulics dealing with free surface flow, such as occurring in rivers, canals, lakes, estuaries, and seas. Its sub-fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bearing Ball
Bearing(s) may refer to: * Bearing (angle), a term for direction * Bearing (mechanical), a component that separates moving parts and takes a load * Bridge bearing, a component separating a bridge pier and deck * Bearing BTS Station in Bangkok * ''Bearings'' (album), by Ronnie Montrose in 2000 See also * Posture (other) * Bering (other) Bering may refer to: * Vitus Bering (1681–1741), Danish-born Russian explorer and navigator * Maritime features of Alaska/Siberia region: ** Bering Sea, body of water in the North Pacific Ocean ** Bering Strait, sea strait between Russia and Alas ... * Baring (other) {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball Screw
A ball screw (or ballscrew) is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with minimum internal friction. They are made to close tolerances and are therefore suitable for high-precision applications. The ball assembly acts as the nut while the threaded shaft is the screw. In contrast to conventional leadscrews, ball screws tend to be rather bulky, due to the need to have a mechanism to recirculate the balls. History The ball screw was invented independently by H.M. Stevenson and D. Glenn who were issued in 1898 patents 601,451 and 610,044 respectively. Early precise screwshafts were produced by starting with a low-precision screwshaft, and then lapping the shaft with several spring-loaded nut laps. By rearranging and inverting the nut laps, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acme Thread Form
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most common forms used for leadscrews (power screws). They offer high strength and ease of manufacture. They are typically found where large loads are required, as in a vise or the leadscrew of a lathe. Standardized variations include multiple-start threads, left-hand threads, and self-centering threads (which are less likely to bind under lateral forces). The original trapezoidal thread form, and still probably the one most commonly encountered worldwide, with a 29° thread angle, is the Acme thread form ( ). The Acme thread was developed in 1894 as a profile well suited to power screws that has various advantages over the square thread,See: * Simpson, John and Proffitt, Michael, ed.s, "acme", ''Oxford English Dictionary: Additions Series'', vol. 3 (Oxford, England: Oxford University Press, 1997)p. 10.* The Acme thread was proposed by Albert Man Powell, then president of the Powell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
