Cyclist Time

Crankset


The crankset, or chainset, 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, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings or chainwheels attached to the cranks or arms 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.

Cranks

The two cranks, one on each side and usually mounted 180° out of phase, connect the bottom bracket axle to the pedals.

Materials

Cranks are constructed of either an aluminum alloy, titanium, carbon fiber, chromoly steel, or some less expensive steel. Tubular steel cranks (such as Tioga's Revolver) can be light and very strong, are usually found on bmx bikes, and are slowly finding their way to mountain bikes (Dirt jumping and Urban assault) . Aluminum cranks may be cast, hot forged or cold forged ("cold" in this context means the billet from which the crank is to be made is heated to a specified temperature well below the melting point, not room temperature). Cold forging gives the metal additional strength, and the cranks can therefore be made lighter without increasing the risk of breakage. Shimano "Hollowtech" aluminum cranks are made by forging the main arms around a hard steel insert which is then withdrawn, leaving an internal void to save weight. They are then welded up before final machining.

Crank (mechanism)

A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion. The arm may be a bent portion of the shaft, or a separate arm attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod. The end of the rod attached to the crank moves in a circular motion, while the other end is usually constrained to move in a linear sliding motion, in and out.

The term often refers to a human-powered crank which is used to manually turn an axle, as in a bicycle crankset or a brace and bit drill. In this case a person's arm or leg serves as the connecting rod, applying reciprocating force to the crank. Often there is a bar perpendicular to the other end of the arm, often with a freely rotatable handle on it to hold in the hand, or in the case of operation by a foot (usually with a second arm for the other foot), with a freely rotatable pedal. (From Wikipedia, the free encyclopedia)