Stairs - Wikipedia. A straight stairway with tiled treads, a double railing and two landings in the "Porta Garibaldi" station, Milan. A stairway, staircase, stairwell, flight of stairs, or simply stairs is a construction designed to bridge a large vertical distance by dividing it into smaller vertical distances, called steps.

Stairs may be straight, round, or may consist of two or more straight pieces connected at angles. Special types of stairs include escalators and ladders. Some alternatives to stairs are elevators (lifts in British English), stairlifts and inclined moving walkways as well as stationary inclined sidewalks (pavements in British English). Components and terms[edit]A stair, or a stairstep is one step in a flight of stairs.[1] In buildings, stairs is a term applied to a complete flight of steps between two floors. A stair flight is a run of stairs or steps between landings. A staircase or stairway is one or more flights of stairs leading from one floor to another, and includes landings, newel posts, handrails, balustrades and additional parts.

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A stairwell is a compartment extending vertically through a building in which stairs are placed. A stair hall is the stairs, landings, hallways, or other portions of the public hall through which it is necessary to pass when going from the entrance floor to the other floors of a building. Box stairs are stairs built between walls, usually with no support except the wall strings.[1]Stairs may be in a straight run, leading from one floor to another without a turn or change in direction. Stairs may change direction, commonly by two straight flights connected at a 9. Stairs may also return onto themselves with 1.

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Many variations of geometrical stairs may be formed of circular, elliptical and irregular constructions.[1]Stairs may be a required component of egress from structures and buildings. Stairs are also provided for convenience to access floors, roofs, levels and walking surfaces not accessible by other means. Watch Dead Sea Online (2017).

Stairs may also be a fanciful physical construct such as the stairs that go nowhere located at the Winchester Mystery House. Stairs are also a subject used in art to represent real or imaginary places built around impossible objects using geometric distortion, as in the work of artist M. C. Escher."Stairway" is also a common metaphor for achievement or loss of a position in the society; or as a metaphor of hierarchy (e. Jacob's Ladder, The Battleship Potemkin). Each step is composed of tread and riser.

Tread. The part of the stairway that is stepped on. It is constructed to the same specifications (thickness) as any other flooring. The tread "depth" is measured from the outer edge of the step to the vertical "riser" between steps.

The "width" is measured from one side to the other. Riser. The vertical portion between each tread on the stair. This may be missing for an "open" stair effect.

Nosing. An edge part of the tread that protrudes over the riser beneath. If it is present, this means that, measured horizontally, the total "run" length of the stairs is not simply the sum of the tread lengths, as the treads overlap each other. Starting step or Bullnose. Where stairs are open on one or both sides, the first step above the lower floor or landing may be wider than the other steps and rounded. The balusters typically form a semicircle around the circumference of the rounded portion and the handrail has a horizontal spiral called a "volute" that supports the top of the balusters.

Besides the cosmetic appeal, starting steps allow the balusters to form a wider, more stable base for the end of the handrail. Handrails that simply end at a post at the foot of the stairs can be less sturdy, even with a thick post. A double bullnose can be used when both sides of the stairs are open.

Stringer, Stringer board or sometimes just String. The structural member that supports the treads and risers in standard staircases. There are typically three stringers, one on either side and one in the center, with more added as necessary for wider spans. Side stringers are sometimes dadoed to receive risers and treads for increased support. Stringers on open- sided stairs are called "cut stringers". Winders. Winders are steps that are narrower on one side than the other.

They are used to change the direction of the stairs without landings. A series of winders form a circular or spiral stairway.

When three steps are used to turn a 9. Trim. Various moldings are used to decorate and in some instances support stairway elements. Scotia or quarter- round are typically placed beneath the nosing to support its overhang. The railing system[edit]. A multi- flight stairway with handrails. Two flights of stairs joined by a landing.

Example of winder stairs with a simple handrail supported by three newel posts. The balustrade is the system of railings and balusters that prevents people from falling over the edge. Banister, Railing or Handrail The angled member for handholding, as distinguished from the vertical balusters which hold it up for stairs that are open on one side; there is often a railing on both sides, sometimes only on one side or not at all, on wide staircases there is sometimes also one in the middle, or even more. The term "banister" is sometimes used to mean just the handrail, or sometimes the handrail and the balusters or sometimes just the balusters.[2]Volute A handrail end element for the bullnose step that curves inward like a spiral. A volute is said to be right or left- handed depending on which side of the stairs the handrail is as one faces up the stairs. Turnout Instead of a complete spiral volute, a turnout is a quarter- turn rounded end to the handrail.

Gooseneck The vertical handrail that joins a sloped handrail to a higher handrail on the balcony or landing is a gooseneck. Rosette Where the handrail ends in the wall and a half- newel is not used, it may be trimmed by a rosette. Easings Wall handrails are mounted directly onto the wall with wall brackets. At the bottom of the stairs such railings flare to a horizontal railing and this horizontal portion is called a "starting easing". At the top of the stairs, the horizontal portion of the railing is called a "over easing".

Core rail Wood handrails often have a metal core to provide extra strength and stiffness, especially when the rail has to curve against the grain of the wood. The archaic term for the metal core is "core rail".

Baluster A term for the vertical posts that hold up the handrail. Sometimes simply called guards or spindles. Treads often require two balusters.

The second baluster is closer to the riser and is taller than the first. The extra height in the second baluster is typically in the middle between decorative elements on the baluster. That way the bottom decorative elements are aligned with the tread and the top elements are aligned with the railing angle. Newel A large baluster or post used to anchor the handrail.

Since it is a structural element, it extends below the floor and subfloor to the bottom of the floor joists and is bolted right to the floor joist. A half- newel may be used where a railing ends in the wall. Visually, it looks like half the newel is embedded in the wall. For open landings, a newel may extend below the landing for a decorative newel drop. Finial A decorative cap to the top of a newel post, particularly at the end of the balustrade.

Baserail or Shoerail For systems where the baluster does not start at the treads, they go to a baserail. This allows for identical balusters, avoiding the second baluster problem. Fillet A decorative filler piece on the floor between balusters on a balcony railing. Handrails may be continuous (sometimes called over- the- post) or post- to- post (or more accurately "newel- to- newel"). For continuous handrails on long balconies, there may be multiple newels and tandem caps to cover the newels. At corners, there are quarter- turn caps.

For post- to- post systems, the newels project above the handrails.

Escapement - Wikipedia. An escapement is a device in mechanical watches and clocks that transfers energy to the timekeeping element (the "impulse action") and allows the number of its oscillations to be counted (the "locking action"). The impulse action transfers energy to the clock's timekeeping element (usually a pendulum or balance wheel) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The escapement is driven by force from a coiled spring or a suspended weight, transmitted through the timepiece's gear train. Each swing of the pendulum or balance wheel releases a tooth of the escapement's escape wheel gear, allowing the clock's gear train to advance or "escape" by a fixed amount. This regular periodic advancement moves the clock's hands forward at a steady rate.

At the same time the tooth gives the timekeeping element a push, before another tooth catches on the escapement's pallet, returning the escapement to its "locked" state. The sudden stopping of the escapement's tooth is what generates the characteristic "ticking" sound heard in operating mechanical clocks and watches. Escapements are used elsewhere as well. Manual typewriters used escapements to step the carriage as each letter (or space) was typed. History[edit]The importance of the escapement in the history of technology is that it was the key invention that made the all- mechanical clock possible.[1][2] The invention of the first all- mechanical escapement, the verge escapement, in 1. Europe initiated a change in timekeeping methods from continuous processes, such as the flow of water in water clocks, to repetitive oscillatory processes, such as the swing of pendulums, which could yield more accuracy.[2] Oscillating timekeepers are used in every modern clock.

Liquid- driven escapements[edit]The earliest liquid- driven escapement was described by the Greek engineer Philo of Byzantium (3rd century BC) in his technical treatise Pneumatics (chapter 3. A counterweighted spoon, supplied by a water tank, tips over in a basin when full, releasing a spherical piece of pumice in the process. Once the spoon has emptied, it is pulled up again by the counterweight, closing the door on the pumice by the tightening string. Remarkably, Philo's comment that "its construction is similar to that of clocks" indicates that such escapement mechanisms were already integrated in ancient water clocks.[3]In China, the Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 7. Song dynasty (9. 60–1. Zhang Sixun (fl. late 1.

Su Song (1. 02. 0–1. According to historian Derek J. Solla Price, the medieval Chinese escapement spread west and was the source for Western escapement technology.[7] According to Ahmad Y. Hassan, a mercury escapement in a Spanish work for Alfonso X in 1. Arabic sources.[8][unreliable source?] Knowledge of these mercury escapements may have spread through Europe with translations of Arabic and Spanish texts.[8][9]However, none of these were true mechanical escapements, since they still depended on the flow of liquid through an orifice to measure time. For example, in Su Song's clock, water flowed into a container on a pivot. The escapement's role was to tip the container over each time it filled up, thus advancing the clock's wheels each time an equal quantity of water was measured out.

The time between releases depended on the rate of flow, which decreased with water pressure as the level of water in the source container dropped. The development of mechanical clocks depended on the invention of an escapement which would allow a clock's movement to be controlled by an oscillating weight. Unlike the continuous flow of water in the Chinese device, the medieval escapement was characterized by a regular, repeating sequence of discrete actions and the capability of self- reversing action: Both techniques used escapements, but these have only the name in common. The Chinese one worked intermittently; the European, in discrete but continuous beats. Both systems used gravity as the prime mover, but the action was very different. In the mechanical clock, the falling weight exerted a continuous and even force on the train, which the escapement alternately held back and released at a rhythm constrained by the controller. Ingeniously, the very force that turned the scape wheel then slowed it and pushed it part of the way back..

In other words, a unidirectional force produced a self- reversing action—about one step back for three steps forward. In the Chinese timekeeper, however, the force exerted varied, the weight in each successive bucket building until sufficient to tip the release and lift the stop that held the wheel in place. This allowed the wheel to turn some ten degrees and bring the next bucket under the stream of water while the stop fell back.. In the Chinese clock, then unidirectional force produced unidirectional motion.[1. Mechanical escapements[edit]Although some sources claim that French architect Villard de Honnecourt invented the first escapement around 1. The first mechanical escapement, the verge escapement, was used in a bell ringing apparatus called an alarum for several centuries before it was adapted to clocks.[1.

In 1. 4th- century Europe it appeared as the timekeeper in the first mechanical clocks, which were large tower clocks.[1. Its origin and first use is unknown because it is difficult to distinguish which of these early tower clocks were mechanical, and which were water clocks.[2. However, indirect evidence, such as a sudden increase in cost and construction of clocks, points to the late 1. Astronomer Robertus Anglicus wrote in 1. On the other hand, most sources agree that mechanical escapement clocks existed by 1.

Actually, the earliest description of an escapement, in Richard of Wallingford's 1. Tractatus Horologii Astronomici on the clock he built at the Abbey of St. Watch Not Cool Download Full.

Albans, was not a verge, but a variation called a strob escapement.[2. It consisted of a pair of escape wheels on the same axle, with alternating radial teeth. The verge rod was suspended between them, with a short crosspiece that rotated first in one direction and then the other as the staggered teeth pushed past. Although no other example is known, it is possible that this was the first clock escapement design.[2. However the verge was the standard escapement used in every other early clock and watch, and remained the only escapement for 4. Its friction and recoil limited its performance, but the accuracy of these verge and foliot clocks was more limited by their early foliot type balance wheels, which because they lacked a balance spring had no natural "beat", so there was not much incentive to improve the escapement. The great leap in accuracy resulting from the invention of the pendulum and balance spring around 1.

The next two centuries, the "golden age" of mechanical horology, saw the invention of perhaps 3. These are described individually below. The invention of the crystal oscillator and the quartz clock in the 1. Reliability[edit]The reliability of an escapement depends on the quality of workmanship and the level of maintenance given. A poorly constructed or poorly maintained escapement will cause problems. The escapement must accurately convert the oscillations of the pendulum or balance wheel into rotation of the clock or watch gear train, and it must deliver enough energy to the pendulum or balance wheel to maintain its oscillation. In many escapements, the unlocking of the escapement involves sliding motion; for example, in the animation shown above, the pallets of the anchor slide against the escapement wheel teeth as the pendulum swings.

The pallets are often made of very hard materials such as polished stone (for example, artificial ruby), but even so they normally require lubrication. Since lubricating oil degrades over time due to evaporation, dust, oxidation, etc., periodic re- lubrication is needed.