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Planet gear efficiency. Need help

  1. Feb 11, 2009 #1
    I'm having a bit of difficulty figuring out the theoretical efficiency of a compound epicyclic gear train. The math involved is a bit over my head. This train is meant to run at very slow speed under light load. I want to find the theoretical efficiency of the design so I can determine if it is feasible to build. Here are the details.

    (A) sun gear = 17 teeth
    (B) Planet gear = 51 teeth
    (C) Ring gear = 119 teeth
    (D) Planet gear = 52 teeth
    (E) Ring gear = 120 teeth
    .25 module (metric)
    input torque = 5 to 10 [N*mm]

    Input is Ring (E) rotating counter-clockwise once every 6 hours
    Output is Sun (A) rotating clockwise once every 30 seconds
    720:1 total reduction

    Ring (E) meshes with Planet (D) which is compounded to planet (B). Planet (B) meshes with ring (C) [locked] giving a -90:1 reduction on the arm (Arm spins clockwise). Compound planets spin 2.333333:1 relative to carrier. Planet (B) meshes with Sun (A) giving an 8:1 ratio for a total ratio of 720:1.

    I'm guessing this is going to be very inefficient do to the high reduction but, I have no Idea how to find out how much energy is being lost or how to figure out how much torque is actually needed to run this. I've found several methods for calculating efficiency of an epicyclic train but I'm completely lost on this because it's a bit more complex than a simple planet set. I'd describe myself as more of an amateur inventor than a mechanical engineer. Any help would be greatly appreciated.

    Thanks in advance

    Mike B.
  2. jcsd
  3. Feb 12, 2009 #2
    Build it and test?

    Or look at similar designs if you just want a ballpark estimate.
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