An example of two ‘ghost’ sprockets tensioning a triplex roller chain system
Roller chains are used in low- to mid-speed drives at around 600 to 800 feet per minute; however, at higher speeds, around 2,000 to 3,000 feet per minute, V-belts are normally used due to wear and noise issues.
A bicycle chain is a form of roller chain. Bicycle chains may have a master link, or may require a chain tool for removal and installation. A similar but larger and thus stronger chain is used on most motorcycles although it is sometimes replaced by either a toothed belt or a shaft drive, which offer lower noise level and fewer maintenance requirements.
The great majority of automobile engines use roller chains to drive the camshaft(s). Very high performance engines often use gear drive, and starting in the early 1960s toothed belts were used by some manufacturers.
Chains are also used in forklifts using hydraulic rams as a pulley to raise and lower the carriage; however, these chains are not considered roller chains, but are classified as lift or leaf chains.
Chainsaw cutting chains superficially resemble roller chains but are more closely related to leaf chains. They are driven by projecting drive links which also serve to locate the chain onto the bar.
Sea Harrier FA.2 ZA195 front (cold) vector thrust nozzle – the nozzle is rotated by a chain drive from an air motor
A perhaps unusual use of a pair of motorcycle chains is in the Harrier Jump Jet, where a chain drive from an air motor is used to rotate the movable engine nozzles, allowing them to be pointed downwards for hovering flight, or to the rear for normal forward flight, a system known as Thrust vectoring.
The effect of wear on a roller chain is to increase the pitch (spacing of the links), causing the chain to grow longer. Note that this is due to wear at the pivoting pins and bushes, not from actual stretching of the metal (as does happen to some flexible steel components such as the hand-brake cable of a motor vehicle).
With modern chains it is unusual for a chain (other than that of a bicycle) to wear until it breaks, since a worn chain leads to the rapid onset of wear on the teeth of the sprockets, with ultimate failure being the loss of all the teeth on the sprocket. The sprockets (in particular the smaller of the two) suffer a grinding motion that puts a characteristic hook shape into the driven face of the teeth. (This effect is made worse by a chain improperly tensioned, but is unavoidable no matter what care is taken). The worn teeth (and chain) no longer provides smooth transmission of power and this may become evident from the noise, the vibration or (in car engines using a timing chain) the variation in ignition timing seen with a timing light. Both sprockets and chain should be replaced in these cases, since a new chain on worn sprockets will not last long. However, in less severe cases it may be possible to save the larger of the two sprockets, since it is always the smaller one that suffers the most wear. Only in very light-weight applications such as a bicycle, or in extreme cases of improper tension, will the chain normally jump off the sprockets.
The lengthening due to wear of a chain is calculated by the following formula:
In industry, it is usual to monitor the movement of the chain tensioner (whether manual or automatic) or the exact length of a drive chain (one rule of thumb is to replace a roller chain which has elongated 3% on an adjustable drive or 1.5% on a fixed-center drive). A simpler method, particularly suitable for the cycle or motorcycle user, is to attempt to pull the chain away from the larger of the two sprockets, whilst ensuring the chain is taut. Any significant movement (e.g. making it possible to see through a gap) probably indicates a chain worn up to and beyond the limit. Sprocket damage will result if the problem is ignored. Sprocket wear cancels this effect, and may mask chain wear.
Bicycle chain wear
The lightweight chain of a bicycle with derailleur gears can snap (or rather, come apart at the side-plates, since it is normal for the “riveting” to fail first) because the pins inside are not cylindrical, they are barrel-shaped. Contact between the pin and the bushing is not the regular line, but a point which allows the chain’s pins to work its way through the bushing, and finally the roller, ultimately causing the chain to snap. This form of construction is necessary because the gear-changing action of this form of transmission requires the chain to both bend sideways and to twist, but this can occur with the flexibility of such a narrow chain and relatively large free lengths on a bicycle.
Chain failure is much less of a problem on hub-geared systems (e.g. Bendix 2-speed, Sturmey-Archer AW) since the parallel pins have a much bigger wearing surface in contact with the bush. The hub-gear system also allows complete enclosure, a great aid to lubrication and protection from grit.
The most common measure of roller chain’s strength is tensile strength. Tensile strength represents how much load a chain can withstand under a one-time load before breaking. Just as important as tensile strength is a chain’s fatigue strength. The critical factors in a chain’s fatigue strength is the quality of steel used to manufacture the chain, the heat treatment of the chain components, the quality of the pitch hole fabrication of the linkplates, and the type of shot plus the intensity of shot peen coverage on the linkplates. Other factors can include the thickness of the linkplates and the design (contour) of the linkplates. The rule of thumb for roller chain operating on a continuous drive is for the chain load to not exceed a mere 1/6 or 1/9 of the chain’s tensile strength, depending on the type of master links used (press-fit vs. slip-fit). Roller chains operating on a continuous drive beyond these thresholds can and typically do fail prematurely via linkplate fatigue failure.
The standard minimum ultimate strength of the ANSI 29.1 steel chain is 12,500 x (pitch, in inches)2. X-ring and O-Ring chains greatly decrease wear by means of internal lubricants, increasing chain life. The internal lubrication is inserted by means of a vacuum when riveting the chain together.
Standards organizations (such as ANSI and ISO) maintain standards for design, dimensions, and interchangeability of transmission chains. For example, the following Table shows data from ANSI standard B29.1-2011 (Precision Power Transmission Roller Chains, Attachments, and Sprockets) developed by the American Society of Mechanical Engineers (ASME). See the references for additional information.
For mnemonic purposes, below is another presentation of key dimensions from the same standard, expressed in fractions of an inch (which was part of the thinking behind the choice of preferred numbers in the ANSI standard):
1. The pitch is the distance between roller centers. The width is the distance between the link plates (i.e. slightly more than the roller width to allow for clearance).
2. The right-hand digit of the standard denotes 0 = normal chain, 1 = lightweight chain, 5 = rollerless bushing chain.
3. The left-hand digit denotes the number of eighths of an inch that make up the pitch.
4. An “H” following the standard number denotes heavyweight chain. A hyphenated number following the standard number denotes double-strand (2), triple-strand (3), and so on. Thus 60H-3 denotes number 60 heavyweight triple-strand chain.
A typical bicycle chain (for derailleur gears) uses narrow 1⁄2-inch-pitch chain. The width of the chain is variable, and does not affect the load capacity. The more sprockets at the rear wheel (historically 3-6, nowadays 7-12 sprockets), the narrower the chain. Chains are sold according to the number of speeds they are designed to work with, for example, “10 speed chain”. Hub gear or single speed bicycles use 1/2″ x 1/8″ chains, where 1/8″ refers to the maximum thickness of a sprocket that can be used with the chain.
Typically chains with parallel shaped links have an even number of links, with each narrow link followed by a broad one. Chains built up with a uniform type of link, narrow at one and broad at the other end, can be made with an odd number of links, which can be an advantage to adapt to a special chainwheel-distance; on the other side such a chain tends to be not so strong.
Roller chains made using ISO standard are sometimes called as isochains.
As much as 98% efficient under ideal conditions, according to Kidd, Matt D.; N. E. Loch; R. L. Reuben (1998). “Bicycle Chain Efficiency”. The Engineering of Sport conference. Heriot-Watt University. Archived from the original on 6 February 2006. Retrieved 16 May 2006.
In the 16th century, Leonardo da Vinci made sketches of what appears to be the first steel 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.
“What is MicPol?”. Lubrication. Retrieved 3 October 2018.
Chains operating at high speeds comparable to those on motorcycles should be used in conjunction with an oil bath, according to: Lubrecht, A. and Dalmaz, G., (eds.) Transients Processes in Tribology, Proc 30th Leeds-Lyon Symposium on Tribology. 30th Leeds-Lyon Symposium on Tribology, 2-5 September 2003, Lyon. Tribology and Interface Engineering Series (43). Elsevier, Amsterdam, pp. 291-298.
Oil drip feed provided the greatest wear protection between chain roller and pin, Oil drip feed provided the greatest power saving over unlubricated chains and sprockets, according to Lee, P.M. and Priest, M. (2004) An innovation integrated approach to testing motorcycle drive chain lubricants. In: Lubrecht, A. and Dalmaz, G., (eds.) Transients Processes in Tribology, Proc 30th Leeds-Lyon Symposium on Tribology. 30th Leeds-Lyon Symposium on Tribology, 2-5 September 2003, Lyon. Tribology and Interface Engineering Series (43). Elsevier, Amsterdam, pp. 291-298.
ASME B29.1-2011 – Precision Power Transmission Roller Chains, Attachments, and Sprockets.
Tsubakimoto Chain Co., ed. (1997). “Transmission Chains”. The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240. ISBN 0-9658932-0-0. p. 86. Retrieved 30 January 2015.
Green 1996, pp. 2337-2361
“ANSI G7 Standard Roller Chain – Tsubaki Europe”. Tsubaki Europe. Tsubakimoto Europe B.V. Retrieved 18 June 2009.
Oberg, Erik; Jones, Franklin D.; Horton, Holbrook L.; Ryffel, Henry H. (1996), Green, Robert E.; McCauley, Christopher J. (eds.), Machinery’s Handbook (25th ed.), New York: Industrial Press, ISBN 978-0-8311-2575-2, OCLC 473691581.
Wikimedia Commons has media related to Roller chains.
The Complete Guide to Chain
Categories: Chain drivesMechanical power transmissionMechanical power control