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 simple machines like 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.
Though Hans Renold is credited with inventing the roller chain in 1880, sketches by Leonardo da Vinci in the 16th century show a chain with a roller bearing.
Construction of the chain
There are actually two types of links alternating in the bush roller chain. The first type is inner links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. Inner links alternate with the second type, the outer links, consisting of two outer plates held together by pins passing through the bushings of the inner links. The "bushingless" roller chain is similar in operation though not in construction; instead of separate bushings or sleeves holding the inner plates together, the plate has a tube stamped into it protruding from the hole which serves the same purpose. This has the advantage of removing one step in assembly of the chain.
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.
Lubrication
The great majority of driving chains operate in clean environments, the wearing surfaces (ie the pins and the bushings) safe from precipitation and air-born grit, many even in a sealed environment such as an oil bath.
A few other chains run unprotected and in those cases, internally sealed roller chain manufacturers such as Tsubaki,Renold, Diamond, Morse, and Rexnord produce low-maintenance versions wherein o-rings or x-rings seal in the lubricant for life.
However, there are a few chains that have to operate in dirty conditions, and for size or operational reasons cannot be sealed. One example is the bicycle chain drive on a derailleur equipped bicycle (though cheaper hub-gear bicycles may be similarly naked to the elements). These chains will necessarily have relatively high rates of wear, particularly when the operators are prepared to accept more friction, less efficiency, more noise and more frequent replacement as they neglect lubrication and adjustment.
Motorcycle chain lubrication
Chains operating at high speeds comparable to those on motorcycles should be used in conjunction with an oil bath. For modern motorcycles this is not applicable and most motorcycle chains run unprotected. They are subject to extreme forces and have to operate in tough conditions being exposed to rain, dirt, sand and road salt.
Motorcycle chains are part of the drive train to transmit the motor power to the back wheel. While properly lubricated chains can reach an efficiency of more 98% in the transmission, unlubricated chains will significantly decrease performance and increase chain and sprockets wear.
Two distinct types of aftermarket lubricants are available for motorcycle chains, spray on lubricants and oil drip feed systems.
- Spray lubricants may contain wax or PTFE. Whilst these lubricants use tack additives to stay on the chain they can also attract dirt and sand from the road and over time produce a grinding paste that accelerates component wear.
- Oil drip feed systems continuously lubricate the chain and use light oil that does not stick to the chain. Research has shown that oil drip feed systems provide the greatest wear protection and greatest power saving.
Oil drip feed systems or automatic motorcycle chain oilers are often referred to as ‘Scottoilers’. Scottoiler Ltd. is a manufacturer of automatic oil drip feed systems for motorbikes. The original product is based on a vacuum system and works by gravity feed. The engine vacuum provides the power to open a valve. The oil then siphons from the reservoir by gravity and the flow rate can be adjusted by a dial opening/closing the valve aperture.