Information about Bearing (mechanical)
A bearing is a device to permit constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation.
There are at least six common principles of operation:
Forces can be radial, axial (thrust bearings) or moments perpendicular to the main axis.
The maximum speeds that rotational bearings can support also vary, generally performance is defined in terms of the product 'DN' where D is the diameter (often in mm) of the bearing and N is the rotation rate in revolutions per minute.
The first plain and rolling-element bearings were wood, but ceramic, sapphire or glass can be used, and steel, bronze, other metals, and plastic (e.g., nylon, polyoxymethylene, teflon, and UHMWPE) are all common today. Indeed, stone was even used in various forms. Think of the "jeweled pocket watch", which incorporated stones to reduce frictional loads, and allow a smoother running watch. Of course, with older, mechanical timepieces, the smoother the operating properties, then the higher the accuracy and value. Wooden bearings can still be seen today in old water mills where the water has implications for cooling and lubrication.
Rotary bearings are required for many applications, from heavy-duty use in vehicle axles and machine shafts, to precision clock parts. The simplest rotary bearing is the sleeve bearing, which is just a cylinder inserted between the wheel and its axle. This was followed by the roller bearing, in which the sleeve was replaced by a number of cylindrical rollers. Each roller behaves as an individual wheel. The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper. This used the bearing for a very limited oscillating motion but Harrison also used a similar bearing in a truly rotary application in a contemporaneous regulator clock.
An early example of a wooden ball bearing (see rolling-element bearing), supporting a rotating table, was retrieved from the remains of the Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated to 40 AD. Leonardo da Vinci is said to have described a type of ball bearing around the year 1500. One of the issues with ball bearings is that they can rub against each other, causing additional friction, but this can be prevented by enclosing the balls in a cage. The captured, or caged, ball bearing was originally described by Galileo in the 1600s. The mounting of bearings into a set was not accomplished for many years after that. The first patent for a ball race was by Philip Vaughan of Carmarthen in 1794.
Friedrich Fischer's idea from the year 1883 for milling and grinding balls of equal size and exact roundness by means of a suitable production machine formed the foundation for creation of an independent bearing industry. The modern, self-aligning design of ball bearing is attributed to Sven Wingquist of the SKF ball-bearing manufacturer in 1907.
Henry Timken, a 19th century visionary and innovator in carriage manufacturing, patented the tapered roller bearing, in 1898. The following year, he formed a company to produce his innovation. Through a century, the company grew to make bearings of all types, specialty steel and an array of related products and services.
The Timken Company(Sale $4,973.4M, 2006), The SKF company($6,195.1M, 2005), the Schaeffler Group (Private), the NSK company($5,344.5M, 2006), and the NTN Bearing company($3,697.8M, 2006) are now the largest bearing manufacturers in the world.
Major types
Common motions include linear/axial and rotary/radial. A linear bearing allows motion along a straight line, for example a drawer being pulled out and pushed in. A rotary bearing or thrust bearing allows motion about a center, such as a wheel on a shaft or a shaft through a housing. Common kinds of rotary motion include both one-direction rotation and oscillation where the motion only goes through part of a revolution, such as with a hinge. Other kinds of bearings include spherical bearings such as ball joints which are used in car suspensions and some computer mice.Bearing friction
Low friction bearings are often quite important for efficiency and wear and facilitate high speeds. Essentially, bearings can reduce friction by shape, by its material, or by introducing a fluid between surfaces.- By shape, gains advantage usually by using spheres or rollers.
- By material, exploits the nature of the bearing material used. (An example would be using plastics that have low surface friction.)
- By fluid, exploits the low viscosity of a layer of fluid, such as a lubricant or as a pressurised medium to keep the two solid parts from touching.
- By fields, exploits electromagnetic fields, such as magnetic fields, to keep solid parts from touching.
Principles of operation
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Animation of ball bearing
- sliding bearings, usually called "bushes", "bushings", "journal bearings", "sleeve bearings", "rifle bearings", or "plain bearings"
- rolling-element bearings such as ball bearings and roller bearings
- jewel bearings, in which the load is carried by rolling the axle slightly off-center
- fluid bearings, in which the load is carried by a gas or liquid
- magnetic bearings, in which the load is carried by a magnetic field
- flexure bearings, in which the motion is supported by a load element which bends.
Load bearing and performance capacities
Bearings vary greatly over the forces and speeds that they can support.Forces can be radial, axial (thrust bearings) or moments perpendicular to the main axis.
The maximum speeds that rotational bearings can support also vary, generally performance is defined in terms of the product 'DN' where D is the diameter (often in mm) of the bearing and N is the rotation rate in revolutions per minute.
History and development
An early type of linear bearing was an arrangement of tree trunks laid down under sleds. This technology may date as far back as the construction of the Pyramids of Giza, though there is no definitive evidence. Modern linear bearings use a similar principle, sometimes with balls in place of rollers.The first plain and rolling-element bearings were wood, but ceramic, sapphire or glass can be used, and steel, bronze, other metals, and plastic (e.g., nylon, polyoxymethylene, teflon, and UHMWPE) are all common today. Indeed, stone was even used in various forms. Think of the "jeweled pocket watch", which incorporated stones to reduce frictional loads, and allow a smoother running watch. Of course, with older, mechanical timepieces, the smoother the operating properties, then the higher the accuracy and value. Wooden bearings can still be seen today in old water mills where the water has implications for cooling and lubrication.
Rotary bearings are required for many applications, from heavy-duty use in vehicle axles and machine shafts, to precision clock parts. The simplest rotary bearing is the sleeve bearing, which is just a cylinder inserted between the wheel and its axle. This was followed by the roller bearing, in which the sleeve was replaced by a number of cylindrical rollers. Each roller behaves as an individual wheel. The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper. This used the bearing for a very limited oscillating motion but Harrison also used a similar bearing in a truly rotary application in a contemporaneous regulator clock.
An early example of a wooden ball bearing (see rolling-element bearing), supporting a rotating table, was retrieved from the remains of the Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated to 40 AD. Leonardo da Vinci is said to have described a type of ball bearing around the year 1500. One of the issues with ball bearings is that they can rub against each other, causing additional friction, but this can be prevented by enclosing the balls in a cage. The captured, or caged, ball bearing was originally described by Galileo in the 1600s. The mounting of bearings into a set was not accomplished for many years after that. The first patent for a ball race was by Philip Vaughan of Carmarthen in 1794.
Friedrich Fischer's idea from the year 1883 for milling and grinding balls of equal size and exact roundness by means of a suitable production machine formed the foundation for creation of an independent bearing industry. The modern, self-aligning design of ball bearing is attributed to Sven Wingquist of the SKF ball-bearing manufacturer in 1907.
Henry Timken, a 19th century visionary and innovator in carriage manufacturing, patented the tapered roller bearing, in 1898. The following year, he formed a company to produce his innovation. Through a century, the company grew to make bearings of all types, specialty steel and an array of related products and services.
The Timken Company(Sale $4,973.4M, 2006), The SKF company($6,195.1M, 2005), the Schaeffler Group (Private), the NSK company($5,344.5M, 2006), and the NTN Bearing company($3,697.8M, 2006) are now the largest bearing manufacturers in the world.
See also
- Hertz contact stress
- Main bearing
- Ball bearing
- Ball spline
- Combined bearing
- Journal bearing
- Fluid bearing
- Rolamite
External links
- How Bearings Work - Animations and functioning
- How Bearings Work - - Animations on www.mechanismen.be
- Early Bearing Failure Detection - Case study
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Axial has different meanings: meaning
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- In geometry it means: along the same line as an axis (coaxial) or centerline: parallel (geometry), contrary to radial or perpendicular
- In anatomy it relates to an anatomical direction of animals and humans.
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Rotary can refer to:
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- Rotary engine, a type of internal combustion engine from the early 20th century
- Rotary Woofer, a type of loudspeaker capable of very low frequency sound
- Rotary International, a service organization
- Rotary milking shed
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Radial can refer to:
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- Vector (spatial), a line
- radius, adjective form of
- A radial pattern is one that appears to radiate from a point, like the spokes from the hub of a wheel
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line can be described as an ideal zero-width, infinitely long, perfectly straight curve (the term curve in mathematics includes "straight curves") containing an infinite number of points. In Euclidean geometry, exactly one line can be found that passes through any two points.
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thrust bearing is a particular type of rotary bearing. Like other rotary bearings they permit rotation between parts, but they are designed to support a high axial load while doing this.
Thrust bearings come in several varieties.
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Thrust bearings come in several varieties.
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wheel is a circular device capable of rotating on its axis, facilitating movement or transportation or performing labour in machines. A wheel together with an axle overcomes friction by facilitating motion by rolling. Common examples are found in transport applications.
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Shaft can refer to:
In fiction:
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In fiction:
- A 1971 novel by Ernest Tidyman about an African-American private detective
- Shaft (1971 film), a film based on the novel
- Shaft
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A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Hinges may be made of flexible material or of moving components. In biology, many joints function as hinges.
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spherical bearing is a bearing that permits angular rotation about a central point in two orthogonal directions within a specified angular limit based on the bearing geometry.
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In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles.
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Purpose
Ball joints are the pivot between the wheels and the suspension of an automobile...... Click the link for more information.
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bushing is a cylindrical lining designed to reduce friction and wear, or constrict and restrain motion of mechanical parts.
In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
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In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
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bushing is a cylindrical lining designed to reduce friction and wear, or constrict and restrain motion of mechanical parts.
In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
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In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
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In mechanical engineering, a journal is the section of a rotating shaft (such as an axle, driveshaft, or spindle) that contacts and turns in a bearing. In automotive engineering, the term journal
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bushing is a cylindrical lining designed to reduce friction and wear, or constrict and restrain motion of mechanical parts.
In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
..... Click the link for more information.
In the electrical field bushings are circular plastic ring fittings that slide or screw onto conduit or connectors to provide protection to the
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rolling-element bearing is a bearing which carries a load by placing round elements between the two pieces. The relative motion of the pieces causes the round elements to roll (tumble) with little sliding.
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jewel bearing is a bearing which an unlubricated metal shaft spins in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter.
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Fluid bearings are bearings which solely support the bearing's loads on a thin layer of liquid or gas.
They can be broadly classified as fluid dynamic bearings, hydrostatic or gas bearings.
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They can be broadly classified as fluid dynamic bearings, hydrostatic or gas bearings.
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A magnetic bearing is a bearing which supports a load using magnetic levitation. Magnetic bearings support moving machinery without physical contact, for example, they can levitate a rotating shaft and permit relative motion without friction or wear.
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magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields.
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A flexure bearing is a bearing which allows motion by bending a load element.
A typical flexure bearing is just one part, joining two other parts. For example, a hinge may be made by attaching a long strip of a flexible element to a door and to the door frame.
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A typical flexure bearing is just one part, joining two other parts. For example, a hinge may be made by attaching a long strip of a flexible element to a door and to the door frame.
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thrust bearing is a particular type of rotary bearing. Like other rotary bearings they permit rotation between parts, but they are designed to support a high axial load while doing this.
Thrust bearings come in several varieties.
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Thrust bearings come in several varieties.
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State Party Egypt
Type Cultural
Criteria i, iii, vi
Reference 86
Region Egypt
Inscription History
Inscription 1979 (3rd Session)
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Type Cultural
Criteria i, iii, vi
Reference 86
Region Egypt
Inscription History
Inscription 1979 (3rd Session)
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The WOOD callsign may refer to:
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- WOOD-TV – an NBC-affiliated television station in Grand Rapids, Michigan
- WOOD (AM) – an AM radio station in Grand Rapids, Michigan
- WOOD-FM - an FM radio station in Grand Rapids, Michigan
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ceramic is derived from the Greek word κεραμικός (keramikos). The term covers inorganic non-metallic materials which are formed by the action of heat.
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Sapphire is the blue variety of the mineral corundum, an aluminium oxide (Al2O3). It can be found naturally or manufactured in large crystal boules for varied applications, including infrared optical components, watch faces, high-durability windows, and wafers
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Glass is a noncrystalline material that can maintain indefinitely, if left undisturbed, its overall form and amorphous microstructure at a temperature below its glass transition temperature.
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Steel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight (C:1000–10,8.67Fe), depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese and
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Bronze is any of a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, or silicon. (See table below.) It was particularly significant in antiquity, giving its name to the Bronze Age.
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