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How to work out a closed loop GT2 belt length?

Discussion in '3D printers' started by cmwwebfx, Jan 11, 2018.

  1. cmwwebfx

    cmwwebfx New
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    Hi there,

    I am designing at the moment a new printer. Rather than ordering a few closed loop belts to see which one fits, is there a way in fusion 360 to work out the belt size based on the distance apart of a 20 tooth and 40 tooth pulley for the GT2 belt?

    If so I would love some hints please as I do not have the pulleys just yet.

    Thank you.

    gt2 area - loop.png gt2 distance.png
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Using pitch diameter on the gears should work but it's far easier (and definitely more reliable) to use - SDP/SI eStore.
     
    Joe Santarsiero likes this.
  3. Prometheus

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    That is very useful for the use of 2 gears BUT, what if there are 3 gears being used?? Kinda like a V shape of gears where the main is 20t and is driving 2- 40t gears??
    [​IMG]
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Same story, lay it out using pitch diameter and then let the program calculate the continuous length. Not sure what program you're using but I know it's fairly simple in AutoCad. (I use the 2008 version)
     
  5. Prometheus

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    I am using Fusion 360. Sorry, not sure I understand what you mean for procedure :(
     

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  6. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    First determine pitch diameter for the pulleys. Pitch diameter = (number of teeth x tooth spacing) / pi.

    So in this case pitch diameter = (40 x 2) / pi = 25.46mm.

    Draw the diagram based on the pitch diameters located at the proper center-to-center spacing. Connect the circles with tangential lines.

    Belt Length 1.jpg
    Total belt length equals the 3 tangential lengths plus the 3 radial lengths. Radial length = (the included angle divided by 360) x (number of teeth x tooth spacing).

    In Autocad rather than doing all the math you just trim away anything unnecessary, join all the line segments together, and then take a properties on the combined line form and it'll give you the total length.

    Belt Length 2.jpg
    Sorry, not sure how to do that in Fusion360.
     
    Rob Taylor likes this.
  7. Prometheus

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    Thank you Rick! I have it figured out. Seems like an ~80t belt will work out fine for this job ;)
     

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