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Thread: Engaging gears

  1. #1
    Associate Engineer
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    Question Engaging gears

    I am attempting to Engage a set of gears. The first and larger gear is stationary, it can rotate, however the center of rotation is fixed. The second gear is mounted on an assembly that will cause the second gear to rotate into and out of contact with the first gear. The assembly will rotate in such a manner that the second gear will rotate into contact with the first gear in the same plane. More simply stated the secondary gear engages the primary gear radially (not Axialy). I am having a difficult time getting these gears to mesh successfully. I have chosen to use spur gears, and I am attempting to rotate the primary gear when the secondary gear comes into contact. The Issue seems to be that the Addendum circles interfere on occasion, and I am affraid that the gears will eventually damage each other, or they will damage the drive or other components of the assembly. I have done some reading and I suspect that helical gears may improve performance in this application. I would appreciate it if anyone could help me in this application.

    Thanks for your help.

  2. #2
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by Chile dog View Post
    The Issue seems to be that the Addendum circles interfere on occasion, and I am affraid that the gears will eventually damage each other, or they will damage the drive or other components of the assembly.
    This seems to be more of a manufacturing or specification and/or design problem from description.

    What AGMA tolerance structure has been specified for the gear train?

  3. #3
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    Could you not try something along the lines of the lead-in for the "Drive dogs" teeth here? Probably not exactly the orientation you are looking for but the best pic I could find to illustrate the concept.

    http://www.motorera.com/dictionary/p...ynchromesh.jpg

  4. #4
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    It is impossible to "rotate" one gear into another of your description.
    If you look at the profiles they accommodate one, and only one motion that just makes contact, and that is the motion of 2 fixed center gears, not one that is variable.

    I think you may need a sloppier fit between the 2 gears, like a pinwheel, if you don't need the precision of mated gearing.
    If you know the path of the pinion gear, you may want to layout the motion of a pin to get an idea .

    I suggest you can give us that motion of the pinion and the required precision of the subsequent meshing requirement, so we may be of further assistance

  5. #5
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    Engaging gears

    Quote Originally Posted by Kelly Bramble View Post
    This seems to be more of a manufacturing or specification and/or design problem from description.

    What AGMA tolerance structure has been specified for the gear train?
    There are no tight tolerences or timing issues to deal with. Let me paint a little more of the picture and it may become more clear. The primary gear is direct drive on a motor. and the motor spindle is stationary. At some distance away I have another spindle that acts as the center of rotation for four (4) shafts, located at 90 apart, centered around the secondary spindle. The whole idea is to engage the secondary gears on the four (4) shafts (One at a time) with the stationary gear (On the motor drive). This will produce momentary rotary motion on one (1) of the shafts while the other three (3) shafts are stationary. Then the whole assembly containing the four (4) shafts will rotate to a position that will engage the next shaft in the assembly. All I really need is to produce rotary motion of a single shaft at a time in a given position, while the other three (3) shafts are stationary. No timing of the shafts relative to one another is required, therefore the backlash in the gears could be relatively large.

  6. #6
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by Chile dog View Post
    There are no tight tolerences or timing issues to deal with. Let me paint a little more of the picture and it may become more clear. The primary gear is direct drive on a motor. and the motor spindle is stationary. At some distance away I have another spindle that acts as the center of rotation for four (4) shafts, located at 90 apart, centered around the secondary spindle. The whole idea is to engage the secondary gears on the four (4) shafts (One at a time) with the stationary gear (On the motor drive). This will produce momentary rotary motion on one (1) of the shafts while the other three (3) shafts are stationary. Then the whole assembly containing the four (4) shafts will rotate to a position that will engage the next shaft in the assembly. All I really need is to produce rotary motion of a single shaft at a time in a given position, while the other three (3) shafts are stationary. No timing of the shafts relative to one another is required, therefore the backlash in the gears could be relatively large.

    Can you post a sketch?

  7. #7
    Lead Engineer RWOLFEJR's Avatar
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    Again a sketch would help... but if I'm understanding this correctly it doesn't sound like any type of gear is going to hold up. But maybe I'm not seeing what you're doing?

    Are you talking about two gears starting out like this... O O then coming together like this... OO with the full face or full length of the gear teeth engaging all at once while one is spinning?

    Maybe you could consider a belt drive with a tensioning pulley of some sort???

  8. #8
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    Quote Originally Posted by RWOLFEJR View Post
    Are you talking about two gears starting out like this... O O
    I think he has something like this in rotating stages. Of the four stations only one gets to mesh with the motor at a time.
    Attached Images Attached Images

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