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The theory was that while the cranks are horizontal you can pedal more efficiently, and thus can push a higher gear. When the cranks are vertical, you get a lower gear due to the smaller effective radius of the chainwheel. The lower gear is easier to push, and you get through the dead spot sooner. This looks great on paper, but doesn't work out so well in practice. | The theory was that while the cranks are horizontal you can pedal more efficiently, and thus can push a higher gear. When the cranks are vertical, you get a lower gear due to the smaller effective radius of the chainwheel. The lower gear is easier to push, and you get through the dead spot sooner. This looks great on paper, but doesn't work out so well in practice. | ||
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Durham Camel -- | ''Beispiel für ein klassisches elliptisches Kettenblatt - Durham Camel'' | ||
[[Datei:Chainwheel-durham-640.jpg|center|Durham elliptisches Kettenblatt]] | |||
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The major problem is that this design tends to hurt people's knees. The high gear when the cranks are horizontal encourages the rider to push too hard, and we all know that pushing too high a gear is a common cause of knee problems. In addition, the low gear when the cranks are vertical means that the knees are moving extra fast when they are changing direction from going up to down and vice versa. This "whiplash" effect caused most users to abandon elliptical chainwheels. Ever since the chain driven bicycle was invented, elliptical chainwheels have been re-invented and re-abandoned for the same reason every ten or fifteen years. | |||
==Biopace== | ==Biopace== | ||