All silent chains are made up of stacked rows of flat, tooth shaped driving links that mesh with sprockets having compatible tooth spaces, much the way a rack and pinion mesh. Typically, chains will also contain guide links, whose purpose is to maintain proper tracking of the chain on sprockets. Washers or spacers may be present in some chain constructions. All of these components are held together by riveted pins located in each chain joint. Although all silent chains have these basic features there are still many many different styles, designs, and configurations.
Given the many possible variations in silent chain design it is important to understand some of the options that are available.
Note: Chains must always be accompanied by compatible sprockets. When considering different silent chain designs, it is essential that sprocket compatibility also be considered.
Chains intended for power transmission(PT) will contain components that are designed to transmit an axial tensile load and resist wear, often while running at high speeds. Chains built specifically for conveying will contain components that are designed to provide a stable, wear resistant conveying surface, while loaded perpendicular to the direction of travel and running at a relatively low speed. In some instances a PT chain will also serve as a satisfactory conveying chain but it is unlikely that a conveying chain will provide adequate service in a PT application.
The guide links which maintain chain tracking on sprockets may be located within the chain(center guide) or along the outer edges of the chain(side guide). A chain with two rows of guide links within the chain is referred to as Two Center Guide. In many applications, any of these guide types will be satisfactory but it is essential that sprockets be selected with same guide type as the chain. In rare instances a chain may contain no guides and special flanged sprockets are required to maintain chain tracking.
Two pin joints have pins that roll or rock on one another when the chain flexes. This type of joint minimizes friction, vibration, and wear while maximizing efficiency. Single pin chains contain a single round or oval pin in each joint. These are very simple to connect, resist fouling, and can be more economical for conveying or less rigorous PT applications.
Silent chains are available in pitches ranging from 3/16” to over 2” pitch. Smaller pitches provide smoother action and less vibration than larger pitches. Larger pitches are more robust with higher tensile load capacity. Pitch is most commonly expressed in inches, even when other chain dimensions may be in metric units. The most reliable method for determining chain pitch is to measure the distance between the centers of three consecutive pin heads and divide that number by 2.
Silent chain widths can range from less than 1 inch to over 20 inches. As width increases, so does cost, so it is most economical to choose the smallest width suitable for the application at hand. Whenever possible it is also advisable to choose from stock or standard widths rather than specifying a width that must be specially ordered.
Overall width is often referred to as the “width over heads” or “width over rivets”. “Width between guides” is an important dimension for side guide chains:
Most silent chains have teeth that engage sprockets on only one side of the chain. Duplex silent chains have teeth on both sides and are designed for use in serpentine drives, where sprockets are driven from both sides of the chain
Often the pattern of links with a chain can be varied during manufacture to suit a particular application. Also, other components, such as spacers, can be added to provide a more open chain buildup. Such options are quite common, particularly with conveying chains.