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I need to learn about *real* gears

  1. Feb 28, 2016 #1
    I am interested in the design of real gears. I know much of the theory as covered in "physics 101."

    Here is an example of the things I want to learn to compute: Given a gear made of some specific material and a given face width with say Module 1.0 tooth size how much tangential force can be applied before the gear fails? What is an industry accepted load (or safety) factor?

    Or re-worded I ask it this way: how big must I make a gear so that it will not "strip out".

    Yes I know it is a complicated subject and a single formula is not going to cover everything. What i need is a pointer to some educational material. Is there a beginner mechanical engineering text e-book on-line? My goal is to make the smallest and lightest gears that will do a given job with reasonable service life. I need to learn to make the required engineering trade offs.

  2. jcsd
  3. Feb 28, 2016 #2

    Randy Beikmann

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    The first place I'd go is "Mechanical Engineering Design" by Shigley. There are about 10 editions, with various coauthors. Of course there's a lot of other good stuff in there too.
  4. Feb 29, 2016 #3
    You might also check the Standard Handbook for Mechanical Engineers. Gears are discussed in chapter 8.

    Alternatively, there is the Tool & Manufacturing Engineers Handbook. Gears are discussed in chapter 11.
  5. Feb 29, 2016 #4


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    Think of a gear tooth as a cantilever. The thickness of the tooth and the presence of undercutting determine the cross section of the tooth (cantilever structure). Both tooth contact angle and the number of teeth on a gearwheel control the degree of undercutting.

    When a sudden force is applied to a tooth face, there will be a deflection. That may bring an adjacent tooth pair into contact and share the load, or it may be sufficient to break the tooth. It comes down to cantilever analysis.
  6. Feb 29, 2016 #5


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    Go to the KHK gear site. http://khkgears.net/gear-knowledge/
    Gear Technical Reference. 13.8 MB. http://khkgears.net/wp-content/uploads/2015/10/gear_guide.pdf
    The ABCs of Gears – A. 4.7 MB. http://khkgears.net/wp-content/uploads/2015/10/gearabc_a1.pdf
    The ABCs of Gears – B. 7.2 MB. http://khkgears.net/wp-content/uploads/2015/10/gearabc_b.pdf
    See also the Q & A about Gears. Plastic gears etc.

    NASA Reference Publication 1152. Stress analysis starts on page 26.

    Take a look at; http://www.meshingwithgears.us/
    The FAQ section has many useful links.
    Last edited: Feb 29, 2016
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