Crank length…

CrankLengthB

Remembering that the Landseer is designed to function well at very low cadences, one of the design issues that bothered me for years was the role played by crank length in modulating power output.

Early Aventuras were fitted with 190mm cranks. The reason was, and still would be, to give enhanced leverage and control through the power phase. Unfortunately, the pedal has also to travel a long way back into the power phase again. Furthermore, your legs have to flex more at the joints.

In the case of a 190mm crank, the pedal path is about 1200mm, giving a fairly long power phase of about 300mm and your pedal has to travel about 900mm before it enters the power phase again, nearly a metre!

A 160mm crank has a pedal path of about a metre, giving a shorter power phase of only around 250mm; the return distance is reduced to about 750mm.

A shorter crank gives a significant advantage if you have both speed and momentum in your favour.

However, a climb over rough tussocky grassland, for example, will force you to slow right down and lose momentum, a shorter crank no longer has that advantage. The longer lever and power phase of a 190mm crank will give you the edge to pull yourself through the difficulty, and continue riding.

Neither a shorter crank nor a longer crank will be ideal in all situations, so mainstream bicycles use something in between, a compromise I’ve struggled with over the years.

The next page reveals the Landseer’s innovative solution to this problem.

Click here to go to the beginning of the whole story.

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About gmacleland

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One Response to Crank length…

  1. Pingback: Out of round… | Cleland > L A N D S E E R

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