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Excel Sheet to calculate Deflection V3

deflection, v-slot, excel

  1. maleuffy

    maleuffy New
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  2. maleuffy

    maleuffy New
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  3. Mark Carew

    Mark Carew OpenBuilds Team
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    Very nice thank you for putting this together @maleuffy
     
  4. maleuffy

    maleuffy New
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  5. David Klug

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    This is amazingly useful. Helped me decide what size v-slot to get. Thanks
     
  6. maleuffy

    maleuffy New
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    Glad it helped!
     
  7. rwensley

    rwensley New
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    @maleuffy I am looking at a build that would either stack two c-beams or place them back to back, or both, and I am looking at your spreadsheet for aid in calculating the sag. Your spreadsheet is very nicely done and extremely useful by the way.

    So I am wondering how you calculated the moments for the complex shape of the beams? I see that the X axis I for the C-Beam is 1.1774E-07. How is this derived?
    Electrical engineers know little about this gear head stuff;)

    Thanks for your work on this.
    Ron
     
  8. maleuffy

    maleuffy New
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    Hello,

    I wish I could help you more on this but the Excel sheet is actually an interpretation of this guide.
     
  9. Art melanson

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    Hello. I am not sure but I think there is a mistake in your conversions for I in your deflection spreadsheet. You use powerE -9 in the spread sheet. It shoud be power E-8
    Hello.
    I have tried your deflection calculation and cannot get the same results as I get in other calculators.

    It seems your deflections are 10 times too high.

    you do not put your units in so it is hard for me to confirm which calculator is right.

    I believe the issue is with your conversion of I.

    For instance: simple beam deflection calculation.
    for the 40x40 beam I= 81.407 cm^4 (i assume units)

    Your speadsheet converts this to

    Inertia on X : 8.141E-08 m^4 (i assume units again)

    my conversion would be to 8.14E-07 m^4 or 81.4E-08


    Am I missing something??
     
  10. Rob Stehlik

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    Art,

    I did not create this spreadsheet, but it is based on a guide I wrote a while back:
    How to calculate V-Slot® deflection

    The units for the area moment of inertia in the table are m^4. This is shown at the top of the table, but perhaps it would be best to show units next to the values as well.

    I took a quick look and it appears that the spreadsheet matches the results I got. It's quite possible I made a mistake in my document, please take a look and let me know if you find anything.

    Rob
     
  11. Art melanson

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    OK Rob
    I see your calculations now from the guide. The spead sheet is right in its calculations, but is giving the wrong number for inertia in the table (then corrects it with the calculations). The numbers shown for the inertia should be corrected adding the power and showing the units.
    Great help though. thanks.
    Art.
     
  12. Quas7

    Quas7 New
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    Hi there,

    sorry for pulling this out of the grave but here is another EE trying to get some simple mechanic first principle calcuations done with only two lectures on structural mechanics over 15 years ago. :blackeye:
    The spread sheet link: Excel Sheet to calculate Deflection

    First a general question: Do I correctly understand "Deflection X" in the spread sheet as "deflection resulting from a force applied in X-direction"? (spoiler alert: it does not)

    In the guide, there is a coordinate system for every beam shape and the Ix, Iy values are in the spread sheet accordingly and the formulars are also right (and reviewed here, as I see it):

    upload_2020-6-22_17-1-45.png

    But, if I look at the X,Y deflection results in the spread sheet, they look just interchanged to me
    Also, my mechanic simulations give me the opposite general directions.

    I mean, if I apply 100N in Y-direction to a 20x80 "X"x"Y" I would get much less deflection compared to a force in X direction, right?

    But the spreadsheed gives me:
    Cantilever beam with a concentrated load
    Deflection X 1,4398 mm
    Deflection Y 21,1044 mm
     
    #12 Quas7, Jun 22, 2020
    Last edited: Jun 22, 2020
  13. Rob Stehlik

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    I don't have the spreadsheet in front of me, but I believe the X and Y directions refer to the axis around which the bending occurs. So your instinct is correct that a force applied in the Y direction would result in much less deflection than a force applied in the X direction.
     
  14. Quas7

    Quas7 New
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    Thanks Rob for confirmation. And after re-reading and watching one youtube video, I got it.
    So, I have to us Ix for a bending force coming Fy.
     
    #14 Quas7, Jun 22, 2020
    Last edited: Jun 22, 2020
  15. Quas7

    Quas7 New
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    Alright. The mystery is solved by a little youtube education:


    As Rob explained, the moment of inertia is referencing to the bending axis and therefore to calculate deflection for a force in Fx includes Iy and vice versa.

    In the spread sheet "Deflection X" therefore means "Deflection on X bending axis (by Fy)"
     
    #15 Quas7, Jun 22, 2020
    Last edited: Jun 22, 2020

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