A master link or quick-release link is a roller chain accessory that allows convenient connection and disconnection of a chain without the need for a chain tool. [1] It acts as a set of the chain's outer plates, so joining two sets of the chain's inner plate ends. Such master links may or may not be re-usable. [2] A chain tool is nonetheless needed to adjust a chain's length, for example to shorten a new chain before connecting its ends. They are used on bicycles and motorcycles. [3]
There are at least two styles of master link used to connect bicycle chain. In both cases the master link set consists of two outer plates, each of which resembles the outer plate of a chain.
The oldest type of master link, available for decades,[ when? ] has two pins connected to the same plate. (Refer to Figure 1). It has been in use mainly in single-speed, hub-geared, or other bicycle drivetrain systems with straight chainlines or widely spaced sprockets. In this assembly, the outside plate with the two pins protruding from it are spaced at the same pitch as the chain at 12.7 mm (0.50 in), and the free ends of the pins are grooved. The other plate fits over the ends of the pins and is secured with a spring clip to make the connection, and this type of master link comes closest to being re-usable.
For bicycles with derailleur gears, a special kind of master link has been developed to fit the narrow chains used on closely spaced sprockets. In this case, each plate has one pin protruding from it, and the pin ends are grooved. (Refer to Figures 2, 3 and 4). In addition to pins, each link plate has a tapered slot, one end of which is wide enough to accommodate the end of a pin, while the other presents a tight fit.
The link plates fit together, and connect the chain by feeding their pins through the bushings of the inner plates, from opposite sides. In this way the pair form a loosely interconnected, closed set, with each master link's pin located in the slot of the other, and the two bushings held captive. The connection is then made secure by pulling the chain outwards on both sides of the link. This latter action forces the pin ends into the narrow ends of the slots where they become locked. The overall security of such a master link depends upon the chain being under tension in normal use, though it can fail in extreme conditions where this condition does not hold.
The manufacturers' instructions for the removal of a master link is to press the face of the two plates together, while pressing both ends inward. When a link is new, or when otherwise difficult to remove, master link pliers can be used (see figure 5). The special pliers have curved ends to accommodate the rollers, and make easy work of even the most difficult removal.
Some links have side plates that are raised on top (figure 4), while some are straight, (figure 3), and some have more prominent pin projections than others. Since a chain on a derailleur-fitted bicycle is reversed for part of its excursion through the drive-train, and because some cogsets have close ramp tolerances, such a link might cause a malfunction if the wrong selection were made. Bushingless chains, with smaller projections, are used on bicycles with large cogsets, since their clearances are more critical than those with only seven speeds. In these former cases a master link of comparable quality is needed. As a result, some manufacturers of derailleurs (e.g. SRAM) recommend only their own products, and these days package a master link with each new chain that is purchased. Chains for small cogsets (e.g. seven-speeds) and other than derailleur-fitted bicycles are more tolerant of these master link dimensions.
A chain tool is a small mechanical device used to "break" a bicycle chain in such a way that it can be mended with the same tool. A bicycle chain has links and plates that are pinned together; these pins can be pushed out with the chain tool. Because the pins are pushed out gradually with a screw, they can be partially removed or fully removed, depending upon the intention of the user.
A derailleur is a variable-ratio bicycle gearing system consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another.
A hub gear, internal-gear hub, internally geared hub or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the shell of the hub gear, in contrast with derailleur gears where the gears and mechanism are exposed to the elements. Changing the gear ratio was traditionally accomplished by a shift lever connected to the hub with a Bowden cable, and twist-grip style shifters have become common.
The crankset or chainset, is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings or chainwheels attached to the cranks, arms, or crankarms to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain.
A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics.
A groupset or gruppo is a bicycle component manufacturer's organized collection of mechanical parts. It generally refers to all of the components that make up a bicycle excluding the bicycle frame, fork, stem, wheels, tires, and rider contact points, such as the saddle and handlebars.
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire- and tube-drawing machines, printing presses, cars, motorcycles, and bicycles. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission.
A sprocket, sprocket-wheel or chainwheel is a profiled wheel with teeth that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which radial projections engage a chain passing over it. It is distinguished from a gear in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have teeth and pulleys are smooth except for timing pulleys used with toothed belts.
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle.
A fork end, fork-end, or forkend is a slot in a bicycle frame or bicycle fork where the axle of a bicycle wheel is attached. A dropout is a type of fork end that allows the rear wheel to be removed without first derailing the chain.
On a bicycle, the cassette or cluster is the set of multiple sprockets that attaches to the hub on the rear wheel. A cogset works with a rear derailleur to provide multiple gear ratios to the rider. Cassettes come in two varieties, freewheels or cassettes, of which cassettes are a newer development. Although cassettes and freewheels perform the same function and look almost the same when installed, they have important mechanical differences and are not interchangeable.
A freehub is a type of bicycle hub that incorporates a ratcheting mechanism.
Bicycle gearing is the aspect of a bicycle drivetrain that determines the relation between the cadence, the rate at which the rider pedals, and the rate at which the drive wheel turns.
Hyperglide is the name given by cycling component manufacturer Shimano to a sprocket design in their bicycle derailleur tooth cassette systems. It varies gear tooth profiles, and/or pins along the faces of freewheel or cassette sprockets, or between the chainrings in a crankset, to ease shifting between them.
Skip-link chain is an obsolete roller chain for bicycles in which side plates are alternately short and long, and so rollers are alternately close together and far apart.
An electronic gear-shifting system is a method of changing gears on a bicycle, which enables riders to shift with electronic switches instead of using conventional control levers and mechanical cables. The switches are connected by wire or wirelessly to a battery pack and to a small electric motor that drives the derailleur, switching the chain from cog to cog. An electronic system can switch gears faster and, because the system does not use Bowden cables and can calibrate itself, it may require less maintenance.
Lucien Charles Hippolyte Juy was a French industrialist who made derailleur gears. He is credited with making the first derailleur with a collapsible parallelogram. A hinged frame swung in and out from the frame and fed the chain to one of a number of sprockets attached to the hub. Juy's derailleurs, sold as Simplex derailleurs, were novel in having a jockey wheel to correct the tension of the chain as it moved across differently sized sprockets.
Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios.
A quick release skewer is a mechanism for attaching a wheel to a bicycle. It consists of a rod threaded on one end and with a lever operated cam assembly on the other. The rod is inserted into the hollow axle of the wheel, a special nut is threaded on, and the lever is closed to tighten the cam and secure the wheel to the fork. Wheels equipped with quick release mechanisms can be removed from the bicycle frame and replaced without using tools by opening and closing the cam lever, thus more quickly than wheels with solid axles and nuts. On the negative side, a quick-release hub renders a wheel more vulnerable to theft and care must be taken to ensure that the mechanism is properly tightened.
Eight- and nine-speed chains use a PowerLink, which can be reused. SRAM's 10 and 11-speed master links are called PowerLocks and are not to be reused.
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