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Gear Angular Velocity & Tooth Count

  1. Jun 3, 2014 #1
    Hi,

    If I put an 8 tooth on axle A and meshed a 12 tooth on axle B then I put a 16 tooth on axle A and meshed a 20 tooth on axle B but the 16 and 20 have the equivalent angular velocity/tooth profile will it rotate properly or will it jam due to the two gear sets going at different speeds.

    The gear size and tooth spacing/profile is what determines the speed of it, with one being the 'driver gear' of course. This is what angular velocity is right?
     
  2. jcsd
  3. Jun 3, 2014 #2

    Baluncore

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    The system will lock if the gear ratios are not absolutely identical.

    Where the two gear sets have very similar, but different ratios, the extreme forces that can be wound up in the system will break gear teeth or twist the shafts.
     
  4. Jun 4, 2014 #3
    How about if there's 2 of the same gear both connected to the same driven gear, however one of the driver gears has a tooth missing per every 2 teeth so there - missing - there -missing etc
    the teeth should align still with the gear that has all the teeth present right?
    this is sort of what im talking about however you could remove say 1 tooth per 3 teeth or something else.
     
  5. Jun 4, 2014 #4

    Baluncore

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    The thing that is important is the gear ratio. If some teeth are missing then that does not matter so long as other teeth can carry the load and not skip a tooth.
    You need to find a few small plastic gears and experiment with them.
     
  6. Jun 4, 2014 #5
    I have many plastic gears but doesn't the number of teeth determine the ratio but the space between them too/the diameter of the gear

    you can have a 1 cm diameter gear and a 3 cm diameter gear but they can still have the same amount of teeth
     
  7. Jun 4, 2014 #6

    Baluncore

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    The shape of gear teeth is such that they roll against each other when they are mesh correctly.
    You will notice that some of your plastic gears mesh and some do not.
    In any meshed gear set the contacting gears must have the same tooth “size”.
    Tooth size is specified as DP=“dimetral pitch” or as MM=”metric module”.

    Take a look at: http://en.wikipedia.org/wiki/Gear and; http://en.wikipedia.org/wiki/Gear#Pitch_nomenclature
     
  8. Jun 4, 2014 #7
    All my gears have the same tooth size but if they didn't they could still mesh, just increase the gap between them
     
  9. Jun 5, 2014 #8

    Baluncore

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    Measure the diameter of a gear in millimetres, between points half way up the tooth faces.
    Count the number of teeth around the same gear.
    Divide the diameter by the number of teeth and you have the tooth size as a metric module, MM.
    Divide 25.4 by the MM and you will get the diametral pitch, DP.

    Gears will only mesh correctly if they have the same tooth size, measured in MM or DP.
    Measure some of your gears and identify their size.

    To mesh correctly they must also have the same tooth profile, usually an involute, but sometimes a cycloidal curve.
     
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