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What Is a Sprocket?

Stacked sprockets of varying size.
The sprockets on bicycles sprocket pull a linked chain which transforms the movement of the rider's feet into rotation of the wheels.
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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 16 March 2014
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A sprocket is a toothed wheel that is designed to engage with something that will be pulled over the wheel as the wheel rotates. These wheels look a great deal like gears, but unlike gears, they are not designed to be meshed with other gears. The basic design of this simple mechanical device has been use around the world for quite a long time, and it has a number of applications, from advancing the film in throwaway disposable cameras to powering professional-class bicycles.

One of the most familiar settings for a sprocket is in the bicycle, where the device pulls a linked chain to transform the movement of the rider's feet into rotation of the wheels. The size can be adjusted to change the gearing of the bicycle for different cycling situations, allowing bicyclists to make their movements as powerful and efficient as possible. This design is also used on motorcycles and some other types of motorized vehicles.

Tracked vehicles like tanks and certain types of farm equipment also use them. In this case, the sprocket interfaces with the links of a track, pulling them as it rotates, and causing the vehicle to move. This design distributes the weight of the vehicle across the entire track, rather than focusing it on individual wheels, and as a result, tracked vehicles can traverse unstable ground more safely.

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Another use for these devices can be found in film cameras, where they are used to hold the film in place and move it as photographs are taken. Sprockets are also used to thread movies on film. Certain types of printers may also use the design, with paper being equipped with small perforations that are threaded onto sprockets that move the paper through the printer as the print head applies ink.

One of the problems with the sprocket is that, if the material being threaded through the teeth runs off track, it can cause serious problems. These systems are often more difficult to repair than the alternatives, which is one reason that they have fallen out of favor in applications such as printers. Damage to the sprockets or the track of a tracked vehicle can render the machine useless until the damage can be repaired or addressed, and high speed failures on bicycles can turn the chain into a cracking whip that can cause serious damage or injuries to equipment and people.

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Discuss this Article

BigManCar
Post 3

I just changed the sprocket on my KLR dirt bike. It was a bit of a pain, but not so bad. On a motorcycle, the sprocket is a wear item that has to be inspected frequently. When it starts to wear out, it should be changed, and at some point it really needs changing or it can make your chain come off at freeway speed and possibly cause an ugly crash.

When embarking on a long trip on the bike, I usually give it a new chain and two new sprockets all at the same time (front and rear).

MaPa
Post 2

@winslo2004 - I highly prefer the sprocket on my mountain bike for repair purposes. Your story makes me glad I joined the Air Force.

Bike sprockets, easy to replace that they may be, have still gotten a lot more complicated over the years. When I was a kid, the sprocket was permanently mounted to your bike, and you had to replace the whole assembly to change anything (pedals and sprocket).

Now, most cranks have multiple pieces, which means you can change the cranks, pedals, or sprocket individually. Some people order everything separately and build the setup that they want. This makes it better suited for different types of riding conditions, speeds, and terrains. It also makes it a lot more expensive, and requires you to be somewhat of a mechanic to get your bike running right, and keep it running right.

winslo2004
Post 1

I was a tanker in the Army, and the word "sprocket" still makes me break out in a cold sweat.

You see, when the chain on a bicycle or other small vehicle slips off the sprocket, it's no big deal. Often you can just put it back on. Worst case, you take a few minutes and replace the chain. No big deal.

On a take, if it throws a track you now have a filthy, really long length of steel track that weighs hundreds of pounds. And it needs to go back on right now, now matter where you are. Day, night, rain, snow, mud, nobody cares. Out you go and you don't come back in until the tank has its track back on it.

I suppose it makes sense. The tank is a sitting duck without the ability to move, and you have to train like you fight. But you'd think just once the think would break in the garage, where it's clean and there are tools, and maybe on a nice day with no mud. Oh, no. Never happens. Always out in the field on a day that somehow manages to be both freezing cold and wet, right around sundown, with the tank on some kind of crazy odd angle. Story of my life.

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