Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A follow up of the question about gears of the winder

  1. Sep 5, 2005 #1
    Hi all!
    I open a new thread since I am gonna post another picture, and this would overload the old thread.

    The first picture shows the number of teeth of the meshing gears.
    I was wrong that the pair of worm gears are glued. They are not glued as mentioned by Q_Goest. And the two gears are rotating at different rates.

    The second picture shows the label of the counter.

    What I am going to ask is the meaning of the label.

    From the number of teeth of the gears indicated in the first picture, it is known that the 102 worm gear rotate at a lower speed than the 100 one.
    I find that for every 30 turns of gear A would finally cause Gear C(102teeth) to lag behind GearC(100teeth) by 1/51 turns.

    So in the label, it can be visualised that when the 30 turns are rotated, the outer point would just finished rotating one complete circle. And the inner pointer would move one little grid. (Some error in the picture drawn, the inner circle should be divided into 51 divisons, instead of 50 divisions. I find this in the real label provided.)

    First of all, is my intepretation correct?

    If yes, I have got some questions.

    Why do the calibration of the inner circle so strange? Why don't it just writes "10, 20, 30, 40, 51" but "1000, 2000, 3000, 4000, 5100" instead?

    Second, if I am the user of the this winder, and I am going to count how many revolution of have I rotated the handle. If I am to do so, I need to multipy the readings of 30, right? Don't you think this is strange? Have I interpreted the usage wrongly?

    And it seems to me that the outer circle is of no practical use...It only returns to zero for every 30 times of rotation of the handle.

    Sorry for such a long thread....I am really such an idiot. Hope to receive your nice help~

    Attached Files:

  2. jcsd
  3. Sep 5, 2005 #2
    I just knew that I could post pictures in the 'reply'..
    sorry for starting another thread...
    Please relocate this thread if any inconvenience is caused.
  4. Sep 6, 2005 #3
    I discovered that I asked a silly question.
    The winder is not going to record how many turns the handle retotate but the 30 teeth gear...So the label should really be marked "1000, 2000, 3000, 4000.etc"
    I think I now understand the entire mechanism.

    But I still don't quite understand the orientation of the pair of worm gears. i.e. the "turbine" shape...
    Q_Geost, do you mean the pair of grears' orientation is such that the drive gear would have a greater contact area with the pair of worm gear? And this reduce the pressure?
  5. Sep 6, 2005 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Each time gear B rotates, the worm gear rotates once and the two gears it is rotating (the 100 tooth and 102 tooth worm wheels) only rotate by 1 tooth. Also, gear B will rotate 100/30 or 3.333 times for each time you rotate the handle. This assumes there is only an idler gear between the two which isn't certain given the picture.

    Regarding the "turbine" look of those two gears, I'm assuming you're refering to the slighty slanted angle on the teeth. There's a couple of pictures of typical worm gear and worm wheel assemblies here:
    http://www.qtcgears.com/e-store/Images/Worm.jpg [Broken]
    http://www.tasonic.com.tw/images/PAGE6/6-2.JPG [Broken]
    In each case you can see the teeth on the worm wheel are slightly angled so they mesh with the worm gear (screw shaped gear). Is that what you were referring to? If so, the reason for the slight angle on the teeth should be fairly obvious. It allows the worm gear and worm wheels to contact over a larger area.
    Last edited by a moderator: May 2, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook