Chain drive

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Roller chain and sprocket Chain.gif
Roller chain and sprocket

Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in a wide variety of machines besides vehicles.

Contents

Most often, the power is conveyed by a roller chain, known as the drive chain or transmission chain, [1] passing over a sprocket gear, with the teeth of the gear meshing with the holes in the links of the chain. The gear is turned, and this pulls the chain putting mechanical force into the system. Another type of drive chain is the Morse chain, invented by the Morse Chain Company of Ithaca, New York, United States. This has inverted teeth. [2]

Sometimes the power is output by simply rotating the chain, which can be used to lift or drag objects. In other situations, a second gear is placed and the power is recovered by attaching shafts or hubs to this gear. Though drive chains are often simple oval loops, they can also go around corners by placing more than two gears along the chain; gears that do not put power into the system or transmit it out are generally known as idler-wheels. By varying the diameter of the input and output gears with respect to each other, the gear ratio can be altered. For example, when the bicycle pedals' gear rotate once, it causes the gear that drives the wheels to rotate more than one revolution. Duplex chains are another type of chain which are essentially two chains joined side by side which allow for more power and torque to be transmitted.

History

The oldest known illustration of an endless power-transmitting chain drive, from Su Song's book of 1092 AD, describing his clock tower of Kaifeng Chain drive, Su Song's book of 1092.jpg
The oldest known illustration of an endless power-transmitting chain drive, from Su Song's book of 1092 AD, describing his clock tower of Kaifeng
Sketch of pin-jointed chain by Leonardo da Vinci The sketch (drawing) of roller chain, Leonardo da Vinci.jpg
Sketch of pin-jointed chain by Leonardo da Vinci

The oldest known application of a chain drive appears in the Polybolos, described by the Greek engineer Philon of Byzantium (3rd century BC). Two flat-linked chains were connected to a windlass, which by winding back and forth would automatically fire the machine's arrows until its magazine was empty. [3] Although the device did not transmit power continuously since the chains "did not transmit power from shaft to shaft, and hence they were not in the direct line of ancestry of the chain-drive proper", [4] the Greek design marks the beginning of the history of the chain drive since "no earlier instance of such a cam is known, and none as complex is known until the 16th century." [3] It is here that the flat-link chain, often attributed to Leonardo da Vinci, [5] actually made its first appearance." [3]

The first continuous as well as the first endless chain drive was originally depicted in the written horological treatise of the Song Dynasty by the medieval Chinese polymath mathematician and astronomer Su Song (1020-1101 AD), who used it to operate the armillary sphere of his astronomical clock tower, which is the first astronomical clock, [6] as well as the clock jack figurines presenting the time of day by mechanically banging gongs and drums. [7] The chain drive itself converted rotary to reclinear motion and was given power via the hydraulic works of Su's water clock tank and waterwheel, the latter which acted as a large gear. [8]

Alternatives

Belt drive

Most chain drive systems use teeth to transfer motion between the chain and the rollers. This results in lower frictional losses than belt drive systems, which often rely on friction to transfer motion.

Although chains can be made stronger than belts, their greater mass increases drive train inertia.

Drive chains are most often made of metal, while belts are often rubber, plastic, urethane, or other substances. If the drive chain is heavier than an equivalent drive belt, the system will have a higher inertia. Theoretically, this can lead to a greater flywheel effect, however in practice the belt or chain inertia often makes up a small proportion of the overall drivetrain inertia.

One problem with roller chains is the variation in speed, or surging, caused by the acceleration and deceleration of the chain as it goes around the sprocket link by link. It starts as soon as the pitch line of the chain contacts the first tooth of the sprocket. This contact occurs at a point below the pitch circle of the sprocket. As the sprocket rotates, the chain is raised up to the pitch circle and is then dropped down again as sprocket rotation continues. Because of the fixed pitch length, the pitch line of the link cuts across the chord between two pitch points on the sprocket, remaining in this position relative to the sprocket until the link exits the sprocket. This rising and falling of the pitch line is what causes chordal effect or speed variation. [9]

In other words, conventional roller chain drives suffer the potential for vibration, as the effective radius of action in a chain and sprocket combination constantly changes during revolution ("Chordal action" [10] ). If the chain moves at constant speed, then the shafts must accelerate and decelerate constantly. If one sprocket rotates at a constant speed, then the chain (and probably all other sprockets that it drives) must accelerate and decelerate constantly. This is usually not an issue with many drive systems; however, most motorcycles are fitted with a rubber bushed rear wheel hub to virtually eliminate this vibration issue. Toothed belt drives are designed to limit this issue by operating at a constant pitch radius [11] ).

Chains are often narrower than belts, and this can make it easier to shift them to larger or smaller gears in order to vary the gear ratio. Multi-speed bicycles with derailleurs make use of this. Also, the more positive meshing of a chain can make it easier to build gears that can increase or shrink in diameter, again altering the gear ratio. However, some newer synchronous belts claim to have "equivalent capacity to roller chain drives in the same width". [12]

Both can be used to move objects by attaching pockets, buckets, or frames to them; chains are often used to move things vertically by holding them in frames, as in industrial toasters, while belts are good at moving things horizontally in the form of conveyor belts. It is not unusual for the systems to be used in combination; for example the rollers that drive conveyor belts are themselves often driven by drive chains.

Drive shafts

Drive shafts are another common method used to move mechanical power around that is sometimes evaluated in comparison to chain drive; in particular belt drive vs chain drive vs shaft drive is a key design decision for most motorcycles. Drive shafts tend to be tougher and more reliable than chain drive, but the bevel gears have far more friction than a chain. For this reason virtually all high-performance motorcycles use chain drive, with shaft-driven arrangements generally used for non-sporting machines. Toothed-belt drives are used for some (non-sporting) models.

Use in vehicles

Bicycles

Chain drive was the main feature which differentiated the safety bicycle introduced in 1885, with its two equal-sized wheels, from the direct-drive penny-farthing or "high wheeler" type of bicycle. The popularity of the chain-driven safety bicycle brought about the demise of the penny-farthing, and is still a basic feature of bicycle design today.

Automobiles

Austin 25-30 chassis top view.jpg
1906 Austin- plan view
Austin 25-30 chassis side view.jpg
1906 Austin- top view
1920s Mack AC truck.jpg
1920s Mack truck

Many early cars used a chain drive system, which was a popular alternative to the Système Panhard (which used a rigid Hotchkiss drive system with universal joints). A common design was using a differential located near the centre of the car, which then transferred drive to the rear axle via roller chains. This system allowed for a relatively simple design which could accommodate the vertical axle movement associated with the rear suspension system. Chain drive also resulted in less unsprung mass at the rear wheels than the Hotchkiss drive (where the differential and half of the driveshaft contributes to the unsprung mass), resulting in greater effectiveness of the rear suspension and therefore a smoother ride.

Frazer Nash were strong proponents of this system using one chain per gear selected by dog clutches. The Frazer Nash chain drive system, (designed for the GN Cyclecar Company by Archibald Frazer-Nash and Henry Ronald Godfrey) was very effective, allowing extremely fast gear selections. The Frazer Nash (or GN) transmission system provided the basis for many "special" racing cars of the 1920s and 1930s. The last popular chain drive automobile was the Honda S600 of the 1960s. [13]

Many modern piston engines use a roller chain (called a "timing chain") to drive the camshaft(s), replacing the previous designs of pushrods or toothed timing belts. For this application, chains last longer, but are often harder to replace, as they must be enclosed in a space into which lubricating oil can be introduced.

The transfer case in a car or light truck is another application where chain drives are used.

Motorcycles

Chain drive versus belt drive or use of a driveshaft is a fundamental design decision in motorcycle design; nearly all motorcycles use one of these three designs.

See also

Related Research Articles

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for this is the law of the lever. Machine components designed to manage forces and movement in this way are called mechanisms. An ideal mechanism transmits power without adding to or subtracting from it. This means the ideal mechanism does not include a power source, is frictionless, and is constructed from rigid bodies that do not deflect or wear. The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal.

Pulley Wheel to support movement and change of direction of a taut cable

A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that does not transfer power to a shaft, but is used to guide the cable or exert a force, the supporting shell is called a block, and the pulley may be called a sheave.

Bicycle chain Roller chain that transfers power from the pedals to the drive-wheel of a bicycle

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.

Roller chain Type of chain drive

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.

Transmission (mechanics) Machine which provides controlled application of power

A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque block conversions from a rotating power source to another device.

Continuously variable transmission Automatic transmission that can change seamlessly through a continuous range of effective gear ratios

A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds.

Freewheel

In mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. An overdrive is sometimes mistakenly called a freewheel, but is otherwise unrelated.

Sprocket Toothed wheel or cog

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.

Drive shaft Mechanical component for transmitting torque and rotation

A drive shaft, driveshaft, driving shaft, tailshaft, propeller shaft, or Cardan shaft is a component for transmitting mechanical power and torque and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them.

Belt (mechanical) Method of connecting two rotating shafts or pulleys

A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel. Belts may be used as a source of motion, to transmit power efficiently or to track relative movement. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel.

Shaft-driven bicycle

A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the wheel. Shaft drives were introduced over a century ago, but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleurs. Recently, due to advancements in internal gear technology, a small number of modern shaft-driven bicycles have been introduced.

Gear train Mechanical transmission using multiple gears.

A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage.

Toothed belt

A toothed belt; timing belt; cogged belt; cog belt; or synchronous belt is a flexible belt with teeth moulded onto its inner surface. It is sometimes designed to run over matching toothed pulleys or sprockets. Toothed belts are used in a wide array of mechanical devices, where high-power transmission is desired.

Bicycle gearing

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.

Belt-driven bicycle

A belt-driven bicycle is a chainless bicycle that uses a toothed synchronous belt to transmit power from the pedals to the wheel.

Chain Series of connected links which are typically made of metal

A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A chain may consist of two or more links. Chains can be classified by their design, which can be dictated by their use:

An idler-wheel is a wheel which serves only to transmit rotation from one shaft to another, in applications where it is undesirable to connect them directly. For example, connecting a motor to the platter of a phonograph, or the crankshaft-to-camshaft gear train of an automobile.

Motorcycle components and systems for a motorcycle are engineered, manufactured, and assembled in order to produce motorcycle models with the desired performance, aesthetics, and cost. The key components of modern motorcycles are presented below.

Motorcycle transmission Transmission for motorcycle applications

A motorcycle transmission is a transmission created specifically for motorcycle applications. They may also be found in use on other light vehicles such as motor tricycles and quadbikes, go-karts, offroad buggies, auto rickshaws, mowers, and other utility vehicles, microcars, and even some superlight racing cars.

References

  1. Machinery's Handbook (1996), pp. 2337–2361.
  2. First Directory Ltd. "First Directory Ltd - 1st for business information". 1stdirectory.com. Archived from the original on 2007-11-27. Retrieved 2008-02-01.{{cite web}}: |author= has generic name (help)
  3. 1 2 3 Werner Soedel, Vernard Foley: Ancient Catapults, Scientific American, Vol. 240, No. 3 (March 1979), p.124-125
  4. Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2, Mechanical Engineering. Cave Books, Ltd. Page 109.
  5. In the 16th century, Leonardo da Vinci made sketches of what appears to be the first iron pin-jointed chain. These chains were probably designed to transmit pulling, not wrapping, power because they consist only of plates and pins and have metal fittings. However, da Vinci's sketch does show a roller bearing. Tsubakimoto Chain Co., ed. (1997). The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240. ISBN   0-9658932-0-0. p. 211. Retrieved 17 May 2006.
  6. "Su Song's Clock".
  7. Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2, Mechanical Engineering. Cave Books, Ltd. Page 111, 165, 456–457.
  8. Needham, Joseph (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering. Taipei: Caves Books Ltd, pp. 445 & 448, 469471.
  9. This is because there is a pitch length in chains, and they can only bend at the pitch point. Tsubakimoto Chain Co., ed. (1997). The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240. ISBN   0-9658932-0-0 . Retrieved 24 March 2020.
  10. 2.2.1 Chordal Action: You will find that the position in which the chain and the sprockets engage fluctuates, and the chain vibrates along with this fluctuation. Tsubakimoto Chain Co., ed. (1997). The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240. ISBN   0-9658932-0-0 . Retrieved 24 March 2020.
  11. But in toothed-belt systems, chordal action occurs by circle and chord, the same as chains. Generally this effect is less than 0.6 percent, but when combined with the deflection of the pulley center and errors of belt pitch or pulley pitch, it can amount to 2 to 3 percent. Tsubakimoto Chain Co., ed. (1997). The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240. ISBN   0-9658932-0-0 . Retrieved 24 March 2020.
  12. "Poly Chain GT Carbon Belts - Gates Corporation". gates.com.
  13. "Honda Packs Big Ideas Into the Small S600". Petrolicious. Retrieved 16 November 2019.
  14. M, Saif (August 17, 2021). "CHAIN DRIVES AND TYPES OF CHAINS". The Engineers post. Archived from the original on 2021-04-21.

Bibliography