D
duivendyk
Guest
Chains don't "stretch" ,they can wear at the link pins so that the chain length is increased.Therefore if a chains appears to have stretched,either it has been subject to wear (high chain tensionand/or lack of lubrication or the distance between the sprockets has decreased for some reason.It turns out that the slack (measured sideways) is acutely sensitive to changes in the sprocket distance.In fact the following approximate relationship holds:
(S squared) = D*d , where "S" is sideways slack, "D" is distance between sprockets and "d" is change in sprocket distance.
To clarify what all this means,lets take a typical example:
sprockets 18" a part, or D=18 , change in sprocket spacin 1/16" ,we get S squared = 18/16 or S= 1.06 ",resulting in 16 times as much "slack" as the change in sprocket distance !!.So even a small movement of the rear wheel can produce a lot of slack.This is the worst case, if the distance had changed by another 1/16" the slack would have gone up by only 0.5" instead of having doubled, as one might have been led to expect.
These computations would appear to elucidate what's been observed.My excuses to the mathphobes.
(S squared) = D*d , where "S" is sideways slack, "D" is distance between sprockets and "d" is change in sprocket distance.
To clarify what all this means,lets take a typical example:
sprockets 18" a part, or D=18 , change in sprocket spacin 1/16" ,we get S squared = 18/16 or S= 1.06 ",resulting in 16 times as much "slack" as the change in sprocket distance !!.So even a small movement of the rear wheel can produce a lot of slack.This is the worst case, if the distance had changed by another 1/16" the slack would have gone up by only 0.5" instead of having doubled, as one might have been led to expect.
These computations would appear to elucidate what's been observed.My excuses to the mathphobes.
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