|
Screw Jack
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 rem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
House Jack 2
A house is a single-unit residential building. It may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, electrical, and heating, ventilation, and air conditioning systems.Schoenauer, Norbert (2000). ''6,000 Years of Housing'' (rev. ed.) (New York: W.W. Norton & Company). Houses use a range of different roofing systems to keep precipitation such as rain from getting into the dwelling space. Houses generally have doors or locks to secure the dwelling space and protect its inhabitants and contents from burglars or other trespassers. Most conventional modern houses in Western cultures will contain one or more bedrooms and bathrooms, a kitchen or cooking area, and a living room. A house may have a separate dining room, or the eating area may be integrated into the kitchen or another room. Some large houses in North America have a recreation room. In traditional agriculture-oriented societies, domes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isambard Kingdom Brunel
Isambard Kingdom Brunel ( ; 9 April 1806 – 15 September 1859) was an English civil engineer and mechanical engineer who is considered "one of the most ingenious and prolific figures in engineering history", "one of the 19th-century engineering giants", and "one of the greatest figures of the Industrial Revolution, hochanged the face of the English landscape with his groundbreaking designs and ingenious constructions". Brunel built dockyards, the Great Western Railway (GWR), a series of steamships including the first purpose-built transatlantic steamship, and numerous important bridges and tunnels. His designs revolutionised public transport and modern engineering. Though Brunel's projects were not always successful, they often contained innovative solutions to long-standing engineering problems. During his career, Brunel achieved many engineering firsts, including assisting his father in the building of the first tunnel under a navigable river (the River Thames) and ... [...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] |
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] |
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] |
Actuator
An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an actuating system). The effect is usually produced in a controlled way. An actuator translates such an input signal into the required form of mechanical energy. It is a type of transducer. In simple terms, it is a "mover". An actuator requires a control device (which provides control signal) and a source of energy. The control signal is relatively low in energy and may be voltage, electric current, Compressed air, pneumatic, or hydraulic fluid pressure, or even human power. In the electric, hydraulic, and pneumatic sense, it is a form of automation, automation or automatic control. The displacement achieved is commonly linear or rotational, as exemplified by linear motors and rotary motors, respectively. Rotary motion is more natural for s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buttress Thread
Buttress thread forms, also known as sawtooth thread forms or breech-lock thread forms. are screw thread profiles with an asymmetric shape, having one square face and the other slanted. They are most commonly used for leadscrews where the load is principally applied in one direction. The asymmetric thread form allows the thread to have low friction and withstand greater loads than other forms in one direction, but at the cost of higher friction and inferior load bearing in the opposite direction. They are typically easier to manufacture than square thread forms but offer higher load capacity than equivalently sized trapezoidal thread forms. Buttress thread characteristics The buttress thread form is designed to handle axial thrust applied principally in one direction. The load-bearing thread face is perpendicular or at a slight slant (usually no greater than 7°) to the screw axis. The trailing face is slanted, often at 45°. The resulting thread form has the same low frictio ... [...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] |
