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Determining the number of gear teeth?

  1. Jan 7, 2016 #1
    I have a system that consists of a shaft and two selected gears.

    I want the shaft to be rotating at 250 RPM and to deliver an input power to the system of 850W.
    The input torque at the shaft is 71Nm.

    How can i use this information to determine how large my driving and driven gears will be, as well as determining the number of teeth that i would use on each gear.
  2. jcsd
  3. Jan 7, 2016 #2


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    [I think you need to provide more information. A diagram or maybe a flowchart showing the inputs and outputs marking known requirements with their values and any known inputs.]

    Edit: Oops! Misread your Q.
    You want 850W at 250 RPM and have 71 Nm available.
    Your output is about 33 Nm, so your gear ratio can be up to 71:33 depending on losses. Maybe 2:1 would be enough?
    Your input shaft would therefore rotate at 125 RPM with atorque of 66 Nm + losses
    Last edited: Jan 7, 2016
  4. Jan 8, 2016 #3


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    That's not at all clear and looks inconsistent..

    You say you "want the shaft to be rotating at 250 RPM" and the torque "at the shaft is 71Nm" ? That means you need a load on the shaft of 1860W.

    250rpm = 26.2 Rads/S
    Power = 26.2 * 71 = 1860W
  5. Jan 8, 2016 #4


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    Edit: sorry my spaces have not worked. It was tabulated.
    I don't know how to delete the whole post, so I've deleted the mess! And I don't have time now to re post in another form.
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