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Epicyclic gear:modules for the sun,planet and ring gear

  1. Oct 13, 2013 #1
    Is the module(M) of the sun,planet and ring gear in a 'planetary gear set' equal to each other always? Is it possible for M to be different for each of the gears in the set?[-Applications of this?]

    $$PCD_{Ring}=PCD_{Sun}+2*PCD_{Planet}\Rightarrow N_{Ring}=N_{Sun}+2*N_{Planet}$$

    is valid only when the modules of all the 3 gear types are same.

    PCD- pitch circle diameter
    N- no. of teeth
  2. jcsd
  3. Oct 13, 2013 #2


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    Science Advisor

    All gears that mesh together must be of the same module or DP.
    If that was not so the teeth would not be in rolling contact.
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