Roller chain or bush roller chain is the type of chain most commonly used for transmission of mechanical power on bicycles, motorcycles, and in industrial and agricultural machinery. It is simple, reliable, and efficient, but requires more attention to maintain than may be desired by potential owners. There has, therefore, been of late a tendency towards the use of other modes of power transmission such as the cog, or timing belt.
The roller chain design reduces friction compared to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain varieties lacked rollers and bushings, with both the inner and outer plates held by pins which directly contacted the sprocket teeth; however this configuration exhibited extremely rapid wear of both the sprocket teeth, and the plates where they pivoted on the pins. This problem was partially solved by the development of bushed chains, with the pins holding the outer plates passing through bushings or sleeves connecting the inner plates. This distributed the wear over a greater area; however the teeth of the sprockets still wore more rapidly than is desirable, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and provided rolling contact with the teeth of the sprockets resulting in excellent resistance to wear of both sprockets and chain as well. There is even very low friction, as long as the chain is sufficiently lubricated. Continuous, clean, lubrication of roller chains is of primary importance for efficient operation.
It is no surprise, then, that some owners, from one end of the scale to the other, simply use the "do-nothing" alternative. They accept more friction, less efficiency, more noise and more frequent replacement as they only minimally maintain the lubrication of their roller chains. This is a classic "trade-off." Many major roller chain manufacturers such as Tsubaki, Diamond, Morse, Renold, and Rexnord have developed low-maintenance roller chains such as o-ring (grease sealed into the joints) and Duralube or Lambda (with an oil-impregnated sintered metal bushing).
Roller chain is made in several sizes, the most common ANSI standards being 40, 50, 60, and 80. The first digit(s) indicate the pitch of the chain in eighths of an inch, with the last digit being 0 for standard chain, 1 for lightweight chain, and 5 for bushed chain with no rollers. Thus, a bicycle chain with half inch pitch would be a #40 while a #160 sprocket would have teeth spaced 2 inches apart, etc. Metric pitches are expressed in sixteenths of an inch; thus a metric #8 chain (08B-1) would be equivalent to an ANSI #40. Most roller chain is made from plain carbon or alloy steel, but stainless steel is used in food processing machinery or other places where lubrication is a problem, and nylon or brass are occasionally seen for the same reason.
Roller chain is ordinarily hooked up using a master link (also known as a connecting link), which typically has one pin held by a C clip rather than friction fit, allowing it to be inserted or removed with simple tools. Half links (also known as offsets) are available and are used to increase the length of the chain by a single roller.
Although it is unusual for a chain to wear until it becomes so worn out that it breaks, a worn chain leads to the rapid onset of a great increase in the rate of wear of the drive sprocket and driven sprockets with which it mates. The sprockets cannot change the spacing of their teeth to match the ever-widening chain links' spacing or "pitch." The wear a worn chain causes on the sprockets is asymmetrical. It grinds a characteristic hooked shape into the rearward face of the sprocket teeth. As this pattern progresses, the sprocket teeth naturally begin to hook the rollers of the chain links, preventing them from rolling off the sprocket teeth until later in the rotation than they should. This causes a jittery transmission of power rather than smooth; in bicycles, for instance, this translates into the common problem of the chain "jumping" off its sprockets. In automotive engine timing chains this translates into a jittery timing of both the valves and the distributor, which becomes especially evident when trying to time the ignition with a timing light. The only cure in such cases of roller chain wear becoming extreme is to replace not only the chain, but also both the drive sprocket and driven sprocket.
It is advisable either to monitor the exact length of a drive chain (the generally accepted 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), or just replace it at established intervals of use to minimize wear on the sprockets. Thus, any savings in maintenance costs from skimping on lubrication result in increased costs for monitoring wear and for replacement. This need for frequent maintenance, comprising lubrication, assessing wear, and replacement of the chain and/or the sprockets, represents the major drawback of the utilization of roller chain.
Contract Notice: Department of the Army (Texas) Issues Solicitation for "Corpus Christi Army Depot Steel Shot Peen Requirement"
Mar 22, 2013; WASHINGTON, March 22 -- Department of the Army, Army Contracting Command has a requirement for "Corpus Christi Army Depot Steel...
Shot peen hardness with nanoindentation: Jorge Ramirez of Nanovea tells finishing how how shot peening can alter the mechanical properties of a surface.(COATING)
Mar 01, 2012; The intention of shot peening is ultimately to alter the mechanical properties of a given surface. By hitting the surface with...