A former is an object, such as a template, gauge or cutting die, used to form something such as a boat's hull. A former gives shape to a structure that may have complex curvature. A former may become an integral part of the finished structure, as in an aircraft fuselage, or it may be disposable, being using in the construction process and discarded. Here, a former is a structural member of an aircraft fuselage, of which a typical fuselage has a series from the nose to the empennage perpendicular to the longitudinal axis of the aircraft; the primary purpose of formers is to establish the shape of the fuselage and reduce the column length of stringers to prevent instability. Formers are attached to longerons, which support the skin of the aircraft; the "former-and-longeron" technique was adopted from boat construction, was typical of light aircraft built until the advent of structural skins, such as fiberglass and other composite materials. Many of today's light aircraft, homebuilt aircraft in particular, are still designed in this way.
A former may instead be a temporary shape over which a structure is built, the former subsequently being discarded in whole or part, as follows: Strip-built boat construction uses formers over which thin plank strips are applied and glued. in some cases, some of the formers may be incorporated as structural ribs. In civil engineering, bridge building, architecture, arches may be built upon a wooden former, removed once the keystone is securely in place
In a fixed-wing aircraft, the spar is the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction sharing the loads where it is used. There may be more than one spar in a none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar. Spars are used in other aircraft aerofoil surfaces such as the tailplane and fin and serve a similar function, although the loads transmitted may be different from those of a wing spar; the wing spar provides the majority of the weight support and dynamic load integrity of cantilever monoplanes coupled with the strength of the wing'D' box itself. Together, these two structural components collectively provide the wing rigidity needed to enable the aircraft to fly safely. Biplanes employing flying wires have much of the flight loads transmitted through the wires and interplane struts enabling smaller section and thus lighter spars to be used at the cost of increasing drag.
Some of the forces acting on a wing spar are: Upward bending loads resulting from the wing lift force that supports the fuselage in flight. These forces are offset by carrying fuel in the wings or employing wing-tip-mounted fuel tanks. Downward bending loads while stationary on the ground due to the weight of the structure, fuel carried in the wings, wing-mounted engines if used. Drag loads dependent on airspeed and inertia. Rolling inertia loads. Chordwise twisting loads due to aerodynamic effects at high airspeeds associated with washout, the use of ailerons resulting in control reversal. Further twisting loads are induced by changes of thrust settings to underwing-mounted engines; the "D" box construction is beneficial to reduce wing twisting. Many of these loads are reversed abruptly in flight with an aircraft such as the Extra 300 when performing extreme aerobatic manoeuvers. Early aircraft used spars carved from solid spruce or ash. Several different wooden spar types have been used and experimented with such as spars that are box-section in form.
Wooden spars are still being used in light aircraft such as its relatives. A disadvantage of the wooden spar is the deteriorating effect that atmospheric conditions, both dry and wet, biological threats such as wood-boring insect infestation and fungal attack can have on the component. Wood wing spars of multipiece construction consist of upper and lower members, called spar caps, vertical sheet wood members, known as shear webs or more webs, that span the distance between the spar caps. In modern times, "homebuilt replica aircraft" such as the replica Spitfires use laminated wooden spars; these spars are laminated from spruce or douglas fir. A number of enthusiasts build "replica" Spitfires that will fly using a variety of engines relative to the size of the aircraft. A typical metal spar in a general aviation aircraft consists of a sheet aluminium spar web, with "L" or "T" -shaped spar caps being welded or riveted to the top and bottom of the sheet to prevent buckling under applied loads. Larger aircraft using this method of spar construction may have the spar caps sealed to provide integral fuel tanks.
Fatigue of metal wing spars has been an identified causal factor in aviation accidents in older aircraft as was the case with Chalk's Ocean Airways Flight 101. The German Junkers J. I armoured fuselage ground-attack sesquiplane of 1917 used a Hugo Junkers-designed multi-tube network of several tubular wing spars, placed just under the corrugated duralumin wing covering and with each tubular spar connected to the adjacent one with a space frame of triangulated duralumin strips — in the manner of a Warren truss layout — riveted onto the spars, resulting in a substantial increase in structural strength at a time when most other aircraft designs were built completely with wood-structure wings; the Junkers all-metal corrugated-covered wing / multiple tubular wing spar design format was emulated after World War I by American aviation designer William Stout for his 1920s-era Ford Trimotor airliner series, by Russian aerospace designer Andrei Tupolev for such aircraft as his Tupolev ANT-2 of 1922, upwards in size to the then-gigantic Maksim Gorki of 1934.
A design aspect of the Supermarine Spitfire wing that contributed to its success was an innovative spar boom design, made up of five square concentric tubes that fitted into each other. Two of these booms were linked together by an alloy web, creating a lightweight and strong main spar. A version of this spar construction method is used in the BD-5, designed and constructed by Jim Bede in the early 1970s; the spar used in the BD-5 and subsequent BD projects was aluminium tube of 2 inches in diameter, joined at the wing root with a much larger internal diameter aluminium tube to provide the wing structural integrity. In aircraft such as the Vickers Wellington, a geodesic wing spar structure was employed, which had the advantages of being lightweight and able to withstand heavy battle damage with only partial loss of strength. Many modern aircraft use carbon fibre and Kevlar in their construction, ranging in size from large airliners to small h
GM New Look bus
The GM New Look bus commonly known by the nickname "Fishbowl", is a transit bus introduced in 1959 by the Truck and Coach Division of General Motors and produced until 1986. More than 44,000 New Look buses were built, its high production figures and long service career made it an iconic North American transit bus. The design is listed as U. S. Patent D182,998 by William P. Strong. 44,484 New Look buses were built over the production lifespan, of which 33,413 were built in the U. S. and 11,071 were built in Canada. Separated by general type, the production figures comprised 510 29-foot city buses; the total production of New Looks was 3,271 suburban coaches. Other than demonstrators, Washington, D. C. was the first city to take delivery of any GM New Look buses TDH-5301s built in 1959 for O. Roy Chalk's D. C. Transit System, which operated in Washington, D. C. and the suburbs of Maryland and Virginia. Several different models were introduced over the following years, modifications made to the design. See the section below, headed "Description".
Production of the New Look in the U. S. ceased in 1977. Production continued after this, however, at General Motors Diesel Division in Canada, due to the RTS design being rejected by Canadian transit agencies, with the name plate changing from "GM" to "GMC". Few were produced after 1983 due to the GMDD's introduction of the Classic in that year; the last New Looks to be built were an order for Santa Monica Municipal Bus Lines of Santa Monica, California in 1986. The completion of that order brought a final end to New Look production in April 1986. A few transit systems are still operating them to this day, nearly 60 years after introduction and more than 30 years after mass production ended; the last American-built New Look GM buses were ordered by the city of Wausau, which placed an order for twelve 35-foot transit buses, model T6H-4523N, the last of, delivered in March 1977. The GM Buffalo bus, a group of intercity bus models built between 1966 and 1980, shared many mechanical and body parts with the fishbowl models, were discontinued by the Pontiac, Michigan plant shortly after the RTS replaced fishbowl model production there.
GM sold the rights to produce both Classic and RTS models to other manufacturers, exited the heavy-duty transit and intercity markets for full-sized buses, although production of some medium-duty and light-duty chassis products sold in these markets continued. Like GM's over-the-road buses, including the Greyhound Scenicruiser, the air-sprung New Look did not have a traditional ladder frame. Instead it used an airplane-like stressed-skin construction in which an aluminum riveted skin supported the weight of the bus; the wooden floor kept the bus's shape. The engine cradle was hung off the back of the roof; as a result, the GM New Look weighed less than competitors' city buses. All New Look buses were powered by Detroit Diesel 71-series two-cycle Diesel engines; the original engine was the 6V71. GM buses used; the transmission angled off at a 45-or-so degree angle to connect to the rear axle. The engines were canted backwards for maintenance access; the entire engine-transmission-radiator assembly was mounted on a cradle that could be removed and replaced, allowing the bus to return to service with minimal delay when the powertrain required major maintenance.
All New Looks were powered by the 6V-71. GM resisted V8 power but gave in to pressure from customers. Original transmission choices were a four-speed non-synchronized manual transmission with solenoid reverse and the Allison Automatic VH hydraulic transmission; the latter was a one-speed automatic transmission which drove the wheels through a torque converter. At sufficient speed a clutch bypassed the torque converter and the engine drove the rear wheels directly. A option was the VS-2, similar to the VH but with a two-speed planetary gearset with three modes: Hydraulic and direct-overdrive; the last batch of American-built New Looks and most Canadian-built New Looks from 1977 through 1987 use the Allison V730 transmission, a traditional three-speed automatic with a lockup torque converter. These four transmissions were the only V-drive transmissions made. New Looks were available in both Suburban versions. Transits were traditional city buses with two doors; the floor beneath the seats was higher than the center aisle to accommodate the luggage bays.
There were "Suburban-style" transits which had forward-facing seats on raised platforms that gave the appearance of a dropped center aisle. GM refused to install lavatories on its buses; the New Look was built in 35 ft and 40 ft lengths and 96 and 102 in widths. 35 and 40
An aileron is a hinged flight control surface forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll, which results in a change in flight path due to the tilting of the lift vector. Movement around this axis is called'rolling' or'banking'; the modern aileron was invented and patented by the British scientist Matthew Piers Watt Boulton in 1868, based on his 1864 paper On Aërial Locomotion. Though there was extensive prior art in the 19th century for the aileron and its functional analog, wing warping, in 1906 the United States granted an expansive patent to the Wright Brothers of Dayton, for the invention of a system of aerodynamic control that manipulated an airplane's control surfaces. Considerable litigation ensued within the United States over the legal issues of lateral roll control, until the First World War compelled the U. S. Government to legislate a legal resolution; the name "aileron", from French, meaning "little wing" refers to the extremities of a bird's wings used to control their flight.
It first appeared in print in the 7th edition of Cassell's French-English Dictionary of 1877, with its lead meaning of "small wing". In the context of powered airplanes it appears in print about 1908. Prior to that, ailerons were referred to as rudders, their older technical sibling, with no distinction between their orientations and functions, or more descriptively as horizontal rudders. Among the earliest printed aeronautical use of'aileron' was that in the French aviation journal L'Aérophile of 1908. Ailerons had more or less supplanted other forms of lateral control, such as wing warping, by about 1915, well after the function of the rudder and elevator flight controls had been standardised. Although there were many conflicting claims over who first invented the aileron and its function, i.e. lateral or roll control, the flight control device was invented and described by the British scientist and metaphysicist Matthew Piers Watt Boulton in his 1864 paper On Aërial Locomotion. He was the first to patent an aileron control system in 1868.
Boulton's description of his lateral flight control system was both complete. It was "the first record we have of appreciation of the necessity for active lateral control as distinguished from.... With this invention of Boulton's we have the birth of the present-day three torque method of airborne control" as was praised by Charles Manly; this was endorsed by C. H. Gibbs-Smith. Boulton's British patent, No. 392 of 1868, issued about 35 years before ailerons were "reinvented" in France, became forgotten and lost from sight until after the flight control device was in general use. Gibbs-Smith stated on several occasions that if the Boulton patent had been revealed at the time of the Wright brothers' legal filings, they might not have been able to claim priority of invention for the lateral control of flying machines; the fact that the Wright brothers were able to gain a patent in 1906 did not invalidate Boulton's lost and forgotten invention. Boulton had described and patented ailerons in 1868 and they were not used on manned aircraft until they were employed on Robert Esnault-Pelterie’s glider in 1904, although in 1871 a French military engineer, Charles Renard and flew an unmanned glider incorporating ailerons on each side, activated by a Boulton-style pendulum controlled single-axis autopilot device.
The pioneering U. S. aeronautical engineer Octave Chanute published descriptions and drawings of the Wright brothers' 1902 glider in the leading aviation periodical of the day, L'Aérophile, in 1903. This prompted Esnault-Pelterie, a French military engineer, to build a Wright-style glider in 1904 that used ailerons in lieu of wing warping; the French journal L’Aérophile published photos of the ailerons on Esnault-Pelterie’s glider which were included in his June 1905 article, its ailerons were copied afterward. The Wright brothers used wing warping instead of ailerons for roll control on their glider in 1902, about 1904 their Flyer II was the only aircraft of its time able to do a coordinated banked turn. During the early years of powered flight the Wrights had better roll control on their designs than airplanes that used movable surfaces. From 1908, as aileron designs were refined it became clear that ailerons were much more effective and practical than wing warping. Ailerons had the advantage of not weakening the airplane's wing structure as did the wing warping technique, one reason for Esnault-Pelterie's decision to switch to ailerons.
By 1911 most biplanes used ailerons rather than wing warping—by 1915 ailerons had become universal on monoplanes as well. The U. S. Government, frustrated by the lack of its country's aeronautical advances in the years leading up to World War I, enforced a patent pool putting an end to the Wright brothers patent war; the Wright company changed its aircraft flight controls from wing warping to the use of ailerons at that time as well. Others who were thought to have been the first to introduce ailerons included: American John J. Montgomery included spring-loaded trailing edge flaps on his second glider: these were operable by the pilot as ailerons. In 1886 his third glider design used rotation of the entire wing rather than just a trailing edge portion for roll control. By his own accounts all of these changes in addition to his use of an elevator for pitch control provided "entire control of the machine in the wind, preventing it from upsetting." New Zealander Richard Pearse reputedly made a power
In mechanics, compression is the application of balanced inward forces to different points on a material or structure, that is, forces with no net sum or torque directed so as to reduce its size in one or more directions. It is contrasted with the application of balanced outward forces; the compressive strength of materials and structures is an important engineering consideration. In uniaxial compression, the forces are directed along one direction only, so that they act towards decreasing the object's length along that direction; the compressive forces may be applied in multiple directions. Technically, a material is under a state of compression, at some specific point and along a specific direction x, if the normal component of the stress vector across a surface with normal direction x is directed opposite to x. If the stress vector itself is opposite to x, the material is said to be under normal compression or pure compressive stress along x. In a solid, the amount of compression depends on the direction x, the material may be under compression along some directions but under traction along others.
If the stress vector is purely compressive and has the same magnitude for all directions, the material is said to be under isotropic or hydrostatic compression at that point. This is the only type of static compression that liquids and gases can bear In a mechanical longitudinal wave, or compression wave, the medium is displaced in the wave's direction, resulting in areas of compression and rarefaction; when put under compression, every material will suffer some deformation if imperceptible, that causes the average relative positions of its atoms and molecules to change. The deformation may be reversed when the compression forces disappear. In the latter case, the deformation gives rise to reaction forces that oppose the compression forces, may balance them. Liquids and gases cannot bear steady uniaxial or biaxial compression, they will deform promptly and permanently and will not offer any permanent reaction force; however they can bear isotropic compression, may be compressed in other ways momentarily, for instance in a sound wave.
Every ordinary material will contract in volume when put under isotropic compression, contract in cross-section area when put under uniform biaxial compression, contract in length when put into uniaxial compression. The deformation may not be aligned with the compression forces. What happens in the directions where there is no compression depends on the material. Most materials will expand in those directions, but some special materials will remain unchanged or contract. In general, the relation between the stress applied to a material and the resulting deformation is a central topic of continuum mechanics. Compression of solids has many implications in materials science and structural engineering, for compression yields noticeable amounts of stress and tension. By inducing compression, mechanical properties such as compressive strength or modulus of elasticity, can be measured. Compression machines range from small table top systems to ones with over 53 MN capacity. Gases are stored and shipped in compressed form, to save space.
Compressed air or other gases are used to fill balloons, rubber boats, other inflatable structures. Compressed liquids are used in fracking. In internal combustion engines the explosive mixture gets compressed. In the Otto cycle, for instance, the second stroke of the piston effects the compression of the charge, drawn into the cylinder by the first forward stroke; the term is applied to the arrangement by which the exhaust valve of a steam engine is made to close, shutting a portion of the exhaust steam in the cylinder, before the stroke of the piston is quite complete. This steam being compressed as the stroke is completed, a cushion is formed against which the piston does work while its velocity is being reduced, thus the stresses in the mechanism due to the inertia of the reciprocating parts are lessened; this compression, obviates the shock which would otherwise be caused by the admission of the fresh steam for the return stroke. Buckling Container compression test Compression member Compressive strength Longitudinal wave P-wave Rarefaction Strength of materials Resal effect
A strut is a structural component found in engineering, aeronautics and anatomy. Struts work by resisting longitudinal compression, but they may serve in tension. Part of the functionality of the clavicle is to serve as a strut between the scapula and sternum, resisting forces that would otherwise bring the upper limb close to the thorax. Keeping the upper limb away from the thorax is vital for its range of motion. Complete lack of clavicles may be seen in cleidocranial dysostosis, the abnormal proximity of the shoulders to the median plane exemplifies the clavicle's importance as a strut. Strut is a common name in timber framing for a brace of scantlings lighter than a post. Struts are found in roof framing from either a tie beam or a king post to a principal rafter. Struts may be straight or curved. In the U. K. strut is used in a sense of a lighter duty piece: a king post carries a ridge beam but a king strut does not, a queen post carries a plate but a queen strut does not, a crown post carries a crown plate but a crown strut does not.
Strutting or blocking between floor joists adds strength to the floor system. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie. In piping, struts restrain movement of a component in one direction while allowing movement or contraction in another direction. Strut channel made from steel, aluminium, or fibre-reinforced plastic is used in the building industry and is used in the support of cable trays and other forms of cable management, pipes support systems. Bracing struts and wires of many kinds were extensively used in early aircraft to stiffen and strengthen, sometimes to form, the main functional airframe. Throughout the 1920s and 1930s they fell out of use in favour of the low-drag cantilever construction. Most aircraft bracing struts are principally loaded in compression, with wires taking the tension loads. Lift struts came into increasing use during the changeover period and remain in use on smaller aircraft today where ultimate performance is not an issue.
They are applied to a high-wing monoplane and act in tension during flight. Struts have been used for purely structural reasons to attach engines, landing gear and other loads; the oil-sprung legs of retractable landing gear are still called Oleo struts. As components of an automobile chassis, struts can be passive braces to reinforce the chassis and/or body, or active components of the suspension. An example of an active unit would be a coilover design in an automotive suspension; the coilover combines a spring in a single unit. A common form of automotive suspension strut in an automobile is the MacPherson strut. MacPherson struts are purchased by the automakers in sets of four completed sub-assemblies: These can be mounted on the car bodies as part of the manufacturers' own assembly operations. A MacPherson strut combines the primary function of a shock absorber, with the ability to support sideways loads not along its axis of compression, somewhat similar to a sliding pillar suspension, thus eliminating the need for an upper suspension arm.
This means that a strut must have a more rugged design, with mounting points near its middle for attachment of such loads. Another type common type of strut used in air suspension is an air strut which combines the shock absorber with an air spring and can be designed in the same fashion as a coilover device; these come available in most types of suspension setups including beam axle and MacPherson strut style design. Transportation-related struts are used in "load bearing" applications ranging from both highway and off-road suspensions to automobile hood and hatch window supports to aircraft wing supports; the majority of struts feature a bearing, but only for the cases, when the strut mounts operate as steering pivots. For such struts, the bearing is the wear item, as it is subject to constant impact of vibration and its condition reflects both wheel alignment and steering response. In vehicle suspension systems, struts are most an assembly of coil-over spring and shock absorber. Other variants to using a coil-over spring as the compressible load bearer include support via pressurized nitrogen gas acting as the spring, rigid support which provides neither longitudinal compression/extension nor damping.
Cabane strut Chapman strut Jury strut Lift strut Spacers and standoffs Strut bar
A fixed-wing aircraft is a flying machine, such as an airplane or aeroplane, capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinct from rotary-wing aircraft, ornithopters; the wings of a fixed-wing aircraft are not rigid. Gliding fixed-wing aircraft, including free-flying gliders of various kinds and tethered kites, can use moving air to gain altitude. Powered fixed-wing aircraft that gain forward thrust from an engine include powered paragliders, powered hang gliders and some ground effect vehicles. Most fixed-wing aircraft are flown by a pilot on board the craft, but some are designed to be unmanned and controlled either remotely or autonomously. Kites were used 2,800 years ago in China, where materials ideal for kite building were available; some authors hold that leaf kites were being flown much earlier in what is now Sulawesi, based on their interpretation of cave paintings on Muna Island off Sulawesi.
By at least 549 AD paper kites were being flown, as it was recorded in that year a paper kite was used as a message for a rescue mission. Ancient and medieval Chinese sources list other uses of kites for measuring distances, testing the wind, lifting men and communication for military operations. Stories of kites were brought to Europe by Marco Polo towards the end of the 13th century, kites were brought back by sailors from Japan and Malaysia in the 16th and 17th centuries. Although they were regarded as mere curiosities, by the 18th and 19th centuries kites were being used as vehicles for scientific research. Around 400 BC in Greece, Archytas was reputed to have designed and built the first artificial, self-propelled flying device, a bird-shaped model propelled by a jet of what was steam, said to have flown some 200 m; this machine may have been suspended for its flight. One of the earliest purported attempts with gliders was by the 11th-century monk Eilmer of Malmesbury, which ended in failure.
A 17th-century account states that the 9th-century poet Abbas Ibn Firnas made a similar attempt, though no earlier sources record this event. In 1799, Sir George Cayley set forth the concept of the modern aeroplane as a fixed-wing flying machine with separate systems for lift and control. Cayley was building and flying models of fixed-wing aircraft as early as 1803, he built a successful passenger-carrying glider in 1853. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, by having his glider "L'Albatros artificiel" pulled by a horse on a beach. In 1884, the American John J. Montgomery made controlled flights in a glider as a part of a series of gliders built between 1883–1886. Other aviators who made similar flights at that time were Otto Lilienthal, Percy Pilcher, protégés of Octave Chanute. In the 1890s, Lawrence Hargrave conducted research on wing structures and developed a box kite that lifted the weight of a man, his box kite designs were adopted. Although he developed a type of rotary aircraft engine, he did not create and fly a powered fixed-wing aircraft.
Sir Hiram Maxim built a craft that weighed 3.5 tons, with a 110-foot wingspan, powered by two 360-horsepower steam engines driving two propellers. In 1894, his machine was tested with overhead rails to prevent it from rising; the test showed. The craft was uncontrollable, which Maxim, it is presumed, because he subsequently abandoned work on it; the Wright brothers' flights in 1903 with their Flyer I are recognized by the Fédération Aéronautique Internationale, the standard setting and record-keeping body for aeronautics, as "the first sustained and controlled heavier-than-air powered flight". By 1905, the Wright Flyer III was capable of controllable, stable flight for substantial periods. In 1906, Brazilian inventor Alberto Santos Dumont designed and piloted an aircraft that set the first world record recognized by the Aéro-Club de France by flying the 14 bis 220 metres in less than 22 seconds; the flight was certified by the FAI. This was the first controlled flight, to be recognised, by a plane able to take off under its own power alone without any auxiliary machine such as a catapult.
The Bleriot VIII design of 1908 was an early aircraft design that had the modern monoplane tractor configuration. It had movable tail surfaces controlling both yaw and pitch, a form of roll control supplied either by wing warping or by ailerons and controlled by its pilot with a joystick and rudder bar, it was an important predecessor of his Bleriot XI Channel-crossing aircraft of the summer of 1909. World War I served as a testbed for the use of the aircraft as a weapon. Aircraft demonstrated their potential as mobile observation platforms proved themselves to be machines of war capable of causing casualties to the enemy; the earliest known aerial victory with a synchronised machine gun-armed fighter aircraft occurred in 1915, by German Luftstreitkräfte Leutnant Kurt Wintgens. Fighter aces appeared. Following WWI, aircraft technology continued to develop. Alcock and Brown crossed the Atlantic non-stop for the first time in 1919; the first commercial flights took place between the United States and Canada in 1919.
The so-called Golden Age of Aviation occurred between the two World War