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Thread: Planetary gear speed reducer design

  1. #1
    Associate Engineer
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    May 2011
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    Bang Head Planetary gear speed reducer design

    Hello,

    I have to design a series planetary gear speed reducer.
    I have to ask first that what is SERIES planetary gear? Can anyone give some detail about this.

    I have to design a gearbox with three stages with a motor power of 45 KW. Input speed of Motor is 2800 rpm, Max outer dia of gearbox is 100 mm. the gear ratio is 4:1 which is same in all three stages. I am doing this for the first time so please anyone can tell me in detail about how I can proceed....
    Thanks in advance.
    Regards,
    Zain

  2. #2
    Administrator Kelly Bramble's Avatar
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    Welcome to Engineers Edeg Zain.

    First, see: http://www.engineeringmotion.com/vid...rive-animation

    I think you need to seek out an organizational engineer or designer whom is experienced in Planetary Gear design and ask for guidance. Designing a gear system is not trivial and it is easy to spend lots of time and money learning on your own.

  3. #3
    Technical Fellow
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    Hi Zain,

    Is this homework or a real project?

    First off, I would question the possibility of this project with the constraints you have defined. You say 45KW (60HP) and 100mm (3.9") outside diameter of the gearbox. At a guess, the input shaft for 60HP would be about 1.5" diameter and that alone is 38mm. At 450lbs-ft torque, the output shaft is probably going to be 50-percent larger than that. It does not leave you much for the outer casing, outer-gear, inner-gear and planetary gears per set. I do not see this happening for you in 100mm.

    A "series" gear set is where you have multiple planetary sets on the same shaft center-line. The overall ratio would be 4:1 but each gear set would be a ratio of 4 / 3 stages = 1.33-recurring, per set. Given the "recurring," the output will not be exactly 4:1.

    You appear to be working this project from the wrong end. I agree with Kelly, seeks some very experienced and competent advice on this. It will be money saved in the long run.

    Dave
    Generally, I will not give you the answer to your question, but I *will* guide you into discovering how to solve this yourself.

  4. #4
    Lead Engineer RWOLFEJR's Avatar
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    Some places to look for design basics...
    SADI
    BREVINI
    GRAHAM GEAR SYSTEMS
    REXNORD

  5. #5
    Associate Engineer
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    May 2011
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    Hello,
    Thanks for the replies,
    This gearbox is basically for an oil rig. which have limitations of size. the gearbox is of 3 stages because of this small size.
    the gear ratio is 4:1 for all three stages that means I have to keep the gears of same size in all three stages......... This is because of the small size to divide the forces and torques

  6. #6
    Technical Fellow
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    Quote Originally Posted by zain View Post
    ...to divide the forces and torques
    45KW at 2800rpm = 113-lb-ft of torque
    45KW at 700rpm (4:1) = 452-lb-ft of torque

    Good luck with that project.

    Dave
    Generally, I will not give you the answer to your question, but I *will* guide you into discovering how to solve this yourself.

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