Tiny, toothed wheels that help propel a chain, sprockets are part of a mechanical cog and lock system that dates back to the 19th century. While sprockets are readily available for purchase online and in specialty stores -- particularly those that cater to specific brands of bikes, motorcycles, film projectors or industrial machinery -- you can also create your own out of steel or aluminum.
According to Gizmology, the four types of sprockets -- plain plate, one-sided hub, two-sided hub and detachable hub -- accommodate the various types of chains to which they're applied. The larger the sprocket, the more evenly it will distribute the working load for the application. You can pair larger sprockets with smaller chains to gain efficiency, but Gizmology recommends keeping the chain speed under 1,200 feet per minute.
Sprocket elements include the shoulder, which carries the chain’s thread, and the plate, which is the flat piece that has the sprocket’s teeth around its periphery. To make your own chain sprocket for a bicycle, you must first determine the chain’s pitch, roller diameter and the roller width. From there, you need to determine the number of teeth in the sprocket, according to the chain speed; then you’ll calculate the angle of the teeth by creating a schematic that measures the distance of the rollers and the pitch circle and incorporates the diameter of the roller centers.
Sprockets are most commonly made of steel or an alloy, such as aluminum. Though aluminum is a lighter metal that can become soft or easily deformed, improvements in treatment technologies have produced an alloy that is hardier and flexible. Steel, on the other hand, is a proven sprocket material that withstands shocks and pressure.
Will Meister, editor of the website 63xc, notes that the sprocket maker has two options: the right way and the wrong way. The right way, he says, is to machine the sprocket directly out of a piece of solid metal. The wrong way is to laser-cut or press-form the sheet metal, which Meister says can result in a soft sprocket.
The forces that act upon a chain in motion can cause wear and damage to your sprocket. After making your own, watch for signs of stress, such as teeth that wear out, a chain that slips out of the sprocket or bent rear chain guards. Replace the chain and sprockets, as a unit, to prevent the uneven wear of one component over the other.
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