Did you know that Leonardo da Vinci drew pictures of a roller chain nearly 300 years before the roller chain was (again) invented by Hans Renold in 1880?
The roller chain is used nowadays for many types of machinery including bicycles, cars, motorcycles, conveyers and printing presses, as it is an efficient, reliable way to transmit mechanical power.
There are two different kinds of roller chains. Though they are constructed slightly differently, they work in the same way.
In both types, there are two sets of links (inner and outer), joined together with pins. In the more traditional type, the inner plates (see 2 in the diagram below) are joined together by a hollow bushing (or sleeve) (4), which rotates on two hollow rollers (4), allowing for a rolling movement. Alternating the inner plates are the outer plates (1), which are held together with a pin (3), which passes through the middle of the bushing. The other (bushingless) type of roller chain is simpler – the plate is constructed with a tube protruding from it, so there is no need for a bushing. Having these two sets of links is what allows the roller chain to roll along the sprocket (the toothed wheel that you see, for example, in the middle of a bicycle wheel).
The unique feature of the roller chain is the roller itself. Previously, in chains used for power transmission, the pins that held together the plates lay directly on the sprocket. While this design allowed for the movement that allowed power to be transmitted, it created a considerable amount of friction, which led to significant wear on both the sprocket teeth and the pins. The addition of rollers significantly reduced friction, thereby increasing efficiency and reducing wear.
To get the most out of a roller chain, however, lubrication needs to be optimal. Roller chains that are used in dirty environments (for example, on farms) need to be well maintained: if they are not lubricated well enough then the moisture and dirt in the environment will increase friction between the various parts, leading to reduced efficiency and more rapid wear. This, in turn, will affect the lifespan of the chain.
The roller chain is a simple, and yet strong and efficient, way of transmitting power, and is relied on in many types of machinery.