A chain is a series of connected links. This article is about the literal, physical chain. A chain may consist of two or more links.
A chain is usually made of metal.
Chains are usually made in one of two styles, according to their intended use:
* Those designed for lifting, such as when used with a hoist; for pulling; or for securing, such as with a bicycle lock, have links that are torus shaped, which makes the chain flexible in two dimensions.
* Those designed for transferring power in machines have links designed to mesh with the teeth of the sprockets of the machine, and are flexible in only one dimension. They are known as Roller chains.
Chains can also be decorative as jewellery.
July 10th, 2008
A key is a device which is used to open a lock. A typical key consist of two parts: the blade, which slides into the keyway of the lock and distinguishes between different keys, and the bow, which is left protruding so that torque can be applied by the user. The blade is usually designed to open one specific lock, although master keys are designed to open sets of similar locks.
Keys provide an inexpensive, though imperfect, method of authentication for access to properties like buildings and vehicles. As such, keys are an essential feature of modern living in the developed world, and are common around the globe. It is common for people to carry the set of keys they need for their daily activities around with them, often linked by a keyring adorned by key fobs and known as a keychain.
July 10th, 2008
Reduction gears on Pratt & Whitney Canada PT6 gas turbine engine.]] A gear is a component within a transmission device that transmits rotational force to another gear or device. A gear is different from a pulley in that a gear is a round wheel which has linkages (”teeth” or “cogs”) that mesh with other gear teeth, allowing force to be fully transferred without slippage. Depending on their construction and arrangement, geared devices can transmit forces at different speeds, torques, or in a different direction, from the power source. Gears are a very useful simple machine. The most common situation is for a gear to mesh with another gear, but a gear can mesh with any device having compatible teeth, such as linear moving racks. A gear’s most important feature is that gears of unequal sizes (diameters) can be combined to produce a mechanical advantage, so that the rotational speed and torque of the second gear are different from that of the first. In the context of a particular machine, the term “gear” also refers to one particular arrangement of gears among other arrangements (such as “first gear”). Such arrangements are often given as a ratio, using the number of teeth or gear diameter as units. The term “gear” is also used in non-geared devices which perform equivalent tasks:
“…broadly speaking, a gear refers to a ratio of engine shaft speed to driveshaft speed. Although CVTs change this ratio without using a set of planetary gears, they are still described as having low and high “gears” for the sake of convention
July 10th, 2008
A fastener is a hardware device that mechanically joins or affixes two or more objects together.
Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container, etc. There are also special purpose closing devices, e.g. a bread clip. Fasteners used in these manners are often temporary, in that they may be fastened and unfastened repeatedly.
Some types of woodworking joints make use of separate internal reinforcements, such as dowels or biscuits, which in a sense can be considered fasteners within the scope of the joint system, although on their own they are not general purpose fasteners.
Furniture supplied in flat-pack form often uses cam dowels locked by cam locks, also known as conformat fasteners.
Items like a rope, string, wire (e.g. metal wire, possibly coated with plastic, or multiple parallel wires kept together by a plastic strip coating), cable, chain, or plastic wrap may be used to mechanically join objects; but are not generally categorized as fasteners because they have additional common uses. Likewise hinges and springs may join objects together, but are ordinarily not considered a fasteners because their primary purpose is to allow articulation rather than rigid affixment.
Other alternative methods of joining materials include crimping, welding, soldering, brazing, taping, gluing, cementing, or the use of other adhesives. The use of force may also be used, such as with magnets, vacuum (like suction cups), or even friction.
July 10th, 2008
A bucket (also called a scoop to qualify shallower designs of tools) is a specialized container attached to a machine, to the difference of a domesic bucket adapted to the physionomy of a human being. It is a bulk material handling component.
The bucket has an inner volume to the difference of other types of machine attachments like blades or shovels.
The bucket could be attached to the lifting hook of a crane, at the end of the arm of an excavating machine, to a the wires of a dragline excavator, to the arms of a power shovel or a tractor equipped with a backhoe loader or to a loader, or to a dredge.
The name bucket can have been coined from buckets used in water wheels, then in used in water turbines or in similar-looking devices.
July 10th, 2008
A Belt is a looped strip of flexible material, used to mechanically link two or more rotating shafts. They may be used as a source of motion, to efficiently transmit power, or to track relative movement.
Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the same direction, or the belt may be crossed, so that the direction of the shafts is opposite.
As a source of motion, a conveyor belt is one application where the belt is adapted to continually carry a load between two points.
July 10th, 2008
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 as well as by the directions of applied loads they can handle.
Low friction bearings are often important for efficiency, to reduce wear and to facilitate high speeds. Essentially, a bearing can reduce friction by virtue of its shape, by its material, or by introducing and containing 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 pressurized medium to keep the two solid parts from touching.
* By fields, exploits electromagnetic fields, such as magnetic fields, to keep solid parts from touching.
Combinations of these can even be employed with the same bearing. An example of this is where the cage is made of plastic, and it separates the rollers/balls, which reduce friction by their shape and finish.
July 10th, 2008
An axle is a central shaft for a rotating wheel or gear. In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle. In other cases the wheel or gear may be fixed to the axle, with bearings or bushings provided at the mounting points where the axle is supported. Sometimes, especially on bicycles, the latter type is referred to as a spindle.
July 10th, 2008
In physics and mechanics a simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. A simple machine uses a single applied force to do work against a single load force. Ignoring friction losses, the work done on the load is equal to the work done by the applied force. They can be used to increase the amount of the output force, at the cost of a proportional decrease in the distance moved by the load. The ratio of the output to the input force is called the mechanical advantage.
Usually the term refers to the six classical simple machines which were defined by Renaissance scientists:.
* Lever
* Wheel and axle
* Pulley
* Inclined plane
* Wedge
* Screw
They are the elementary ‘building blocks’ of which all complicated machines are composed. For example, wheels, levers, and pulleys are all used in the mechanism of a bicycle. In the 20th century, a realization that at least one simple machine, the hydraulic press, had been left out, and arguments that some of the six classical devices can be considered as modifications of others (see below), has led some modern sources to avoid specifying any list of simple machines as ‘basic’. Nevertheless, the above six are what is usually meant by ’simple machine’ and are still regarded as the foundation of mechanical technology, although the only reason for preferring this list to others is tradition.
Simple machines fall into two classes; those dependent on the vector resolution of forces (inclined plane, wedge, screw) and those in which there is an equilibrium of torques (lever, pulley, wheel).
July 10th, 2008
A machine is anything that makes work easier.
People have used mechanisms to, or transform one form of motion or energy into another.
The mechanical advantage of a simple machine is the ratio between the force it exerts on the load and the input force applied. This does not entirely describe the machine’s performance, as force is required to overcome friction as well. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). Functioning physical machines are always less than 100% efficient.
Modern power tools, automated machine tools, and human-operated power machinery are tools that are also machines. Machines used to transform heat or other energy into mechanical energy are known as engines.
Compound machines are composed of more elementary machines called simple machines, such as the wedge and the pulley. Machines are considered simple machines if they perform their action in one movement. These devices may also be used to support industrial applications, although devices entirely lacking rigid moving parts are not commonly considered machines. Hydraulics are widely used in heavy equipment industries, automobile industries, marine industries, aeronautical industries, construction equipment industries, and earthmoving equipment industries.
July 10th, 2008
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