There are actually two types of links alternating in the bush roller chain. The initial type is inner links, having two inner plates held jointly by two sleeves or bushings upon which rotate two rollers. Inner links alternate with the next type, the Leaf Chain external links, consisting of two external plates held with each other by pins passing through the bushings of the internal links. The “bushingless” roller chain is similar in operation though not in building; instead of separate bushings or sleeves keeping the inner plates with each other, the plate has a tube stamped involved with it protruding from the hole which serves the same purpose. This has the benefit of removing one step in assembly of the chain.
The roller chain design reduces friction in comparison to simpler designs, leading to higher efficiency and less wear. The original power transmission chain types lacked rollers and bushings, with both the inner and external plates kept by pins which directly contacted the sprocket tooth; nevertheless this configuration exhibited extremely rapid use of both the sprocket tooth, and the plates where they pivoted on the pins. This problem was partially solved by the advancement of bushed chains, with the pins holding the outer plates moving through bushings or sleeves connecting the inner plates. This distributed the wear over a greater area; however the the teeth of the sprockets still wore quicker than is attractive, from the sliding friction against the bushings. The addition of rollers around the bushing sleeves of the chain and supplied rolling contact with the teeth of the sprockets leading to excellent resistance to put on of both sprockets and chain as well. There is even very low friction, so long as the chain can be sufficiently lubricated. Constant, clean, lubrication of roller chains is certainly of major importance for efficient operation along with correct tensioning.