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    Discussion in 'The main mechanical design forum' started by theripley, Jan 31, 2011.

    1. theripley

      theripley New Member

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      Hi,

      I'm a newbie so I hope you'll pardon my question since I'm an Electronics engr. by profession. Although I'm not so familiar with machine designing, my job requires me to be familiar.

      I am scanning thru a catalogue & wondered what is the significant of the term "MODuLE"? I read thru wiki about its definition but I'm kinda not getting it. Example, if I have two gears (1 having 20 teeth ,other 40 teeth <1:2>) with the same pressure angle but different module, am I able to couple this two gears?

      Pls help..Thanks
       
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    3. xmechanic

      xmechanic Active Member

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      I'm not an engineer but it appears to me that module refers to gear tooth size and number of teeth per distance on circumference, therefore both gears would need same module.

      I think I'm right on this
       
    4. knwd

      knwd New Member

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      xmechanic is correct. Module is a way of specifying a sort of "size" for gear teeth, basically how they are spaced.

      m = d / N, where d = diameter (SI units) and N = number of teeth.

      Essentially, the modulus determines the size of the gear, depending on the gear ratio you intend to use.

      Hope this helps!
       
    5. theripley

      theripley New Member

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      I've been reading thru the net about module, truly it is the distance between each tooth on the gear therefore the pinion gear & the idler gear must have the same module. Both pinion & idler can be coupled even if they have different pressure angle, as long as they have the same module. (Please correct this if its wrong).

      Question:
      Does module affects the load capacity of my gear? What is its other significance aside from ensuring both gears would fit in perfectly?

      What affects the load capacity of the gear?

      Thanks in advance.
       
    6. maniacal_engineer

      maniacal_engineer Well-Known Member

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      gears need to be the same pressure angle to mate. They must also be the same module, or the same diametral pitch.
      There are good articles by a guy named Kapelevich that give a very detailed theory of gear tooth geometry. gear teeth are involutes, the surface of the tooth being the curve swept by a point on a string as it unwinds. So a gear mesh can be though of as the curve swept by a point on a string that unwinds from one cylinder onto another cylinder. A series of evenly spaced points on the string gives evenly spaced teeth, and this spacing is the same on both cylinders. The spacing is basically the module, and so the gears must be the same module. The angle that the string makes with a line connecting the centers is the pressure angle, and it must be the same on both gears. The cylinders winding and unwinding the string would be the base circles. this gives a good overview:

      http://www.qtcgears.com/Q410/PDF/Q410P335.pdf

      It is also possible to have assymetric teeth, but that is pretty advanced/ esoteric
      http://www.akgears.com/pdf/direct_desig ... _gears.pdf
       

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