The crankset (in the US) or chainset (in the UK), is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings[1][2][3] or chainwheels[3] attached to the cranks, arms,[4] or crankarms[5] to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain. Reciprocating motion, also called reciprocation, is a repetitive up-and-down or back-and-forth motion. It is found in a wide range of mechanisms, including reciprocating engines and pumps. The two opposite motions that comprise a single reciprocation cycle are called strokes.[citation needed] A crank can be used to convert circular motion into reciprocating motion, or conversely turn reciprocating motion into circular motion. For example, inside an internal combustion engine (a type of reciprocating engine), the expansion of burning fuel in the cylinders periodically pushes the piston down, which, through the connecting rod, turns the crankshaft. The continuing rotation of the crankshaft drives the piston back up, ready for the next cycle. The piston moves in a reciprocating motion, which is converted into circular motion of the crankshaft, which ultimately propels the vehicle or does other useful work. The vibrations felt when the engine is running are a side effect of the reciprocatin

motion of the pistons. Reciprocating motion is clearly visible in early steam engines, particularly horizontal stationary engines and outside-cylindered steam locomotives, as the crank and connecting-rod usually are not enclosed. Reciprocating motion is close to, but different from, sinusoidal simple harmonic motion. The point on the camshaft which connects the connecting rod, rotates smoothly at a constant velocity in a circle. Thus, the horizontal displacement, of that point, is indeed exactly sinusoidal by definition. However, during the cycle, the angle of the connecting rod changes continuously. So, the horizontal displacement of the "far" end of the connecting rod (ie, connected to the piston) differs from sinusoidal. Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios. On a bicycle, the cogset or cluster[1] is the set of multiple rear sprockets that attaches to the hub on the rear wheel. A cogset works with a rear derailleur as part of the drivetrain to provide multiple gear ratios to the rider. Cogsets come in two varieties, cassettes or freewheels, of which cassettes are a newer development. Although cassettes and freewheels perform the same function and look almost the same when installed, they have important mechanical differences and are not interchangeable. The terms are sometimes incorrectly used interchangeably.[2]