Moment of inertia of a chainwheel + pedals

Discussion in 'Cycling Equipment' started by pHUMpk1Ns, Nov 16, 2012.

  1. pHUMpk1Ns

    pHUMpk1Ns New Member

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    Hi

    I want to find information about the moment of inertia of common pedals and chainwheel. Anyone who knows where to find this?
     
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  2. alienator

    alienator Well-Known Member

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    I've not seen any published data, but this Wikipedia page has nice list of equations to calculate the moment of inertia for some common and not so common shapes. None of moments of inertia for the items about which you asked are going to be very large at all. MOI goes as the square of the object's radius. So, if you compared a 53T chainring with a 700x25 tire and wheel, and IF the tire/wheel combo and the chainring weight the same, the tire wheel combo, which is roughly 3x greater in radius, would have an MOI 9x greater. The mass of the tire/wheel combo, in reality, will be on the order of 10x greater than the chainring so in actuality, the MOI of the tire/wheel combo will be on the order of 90x (9*10) greater than the 53T chainring. The pedals will have a greater MOI than the chainring (almost always): not only do they have an MOI about their own axle, the also have an MOI about the BB, just like the chainring.....and for that matter, the crank arms.
     
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