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The chainset
for a three-chainwheel Derailleur gearbox is shown in the photograph.
The forged metal crank (A) has a 'spider' that carries the set of chainwheels
(B) that will expand the overall range of the Derailleur gearing. The spacers,
screws, and washers (D) hold this gearset together.
The length
of the pedal crank is important as it determines the torque that the rider
can generate about the crank spindle and governs the amplitude of the leg movement.
A longer crank will cause the riders foot to move a larger distance
in one revolution. For a 165 mm crank the foot travel per crank rotation
is 1.04 m and for a 170 mm crank, 1.07 m. The longest cranks that are consistent
with the leg length and comfort of the rider will provide the largest torque
capability.
In mountain bike applications, the ground clearance
of the pedals and chain wheels will also be an important consideration in
the selection of the crank length and gearset. |
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