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  1. #1

    Down FP measurement

    Hi,

    I harvested some down from old quilts, and I would like to measure the fill power.
    I could not measure like the original method, but I figured out something, please check if Iam wrong (or any other measuring methods are welcome).

    As I know the method is:

    "taken of one-ounce sample of down in a plexiglas cylinder with a weighted piston compressing the down"

    "US 2000 norm: cylinder diameter: 241 mm
    compression cylinder: 68,3 grams
    Mass of the sample: 1 oz = 28,4 grams"

    This is clear I guess, I saw two videos about this.
    My problem, I can not get this size of measurement cylinder.

    I think about it and I can get cheap PVC tube from the local store with inner diameter of 105mm.

    May I get same result If I downscale the method based on the section area?

    I guess the base is the same pressure of the down at each method.
    P=F/A
    F_original/A_original=F_my/A_my
    A_original=241^2*pi/[email protected]=45593,5mm2
    A_my=8654,6mm2

    So the weight of compression cylinder is:
    F_my=F_original*A_my/A_original
    F_my=68,3g*8654,6mm2/45593,5mm2=12,96=13g

    And the sample weight of down also must be scale down.
    I guess if the density of down is constant and the height is still cinstant, the modified weight of sample is the ratio of cross section areas:
    m_original/A_original=m_my/A_my
    m_my=m_original*A_my/A_original
    m_my=28,4g*8654,6mm2/45593,5mm2= 5,4g

    When I put the sample weight of down in the tube and the compression weight to the top of the down, the down will compressed.
    The FP will be the height of the compressed down.

    CUIN is cubic inch= Area*Height
    1in^3=25,4mm^3=16 387,1mm3
    In the original measurement cylinder, 1 CUIN FP is equal of the height of 1in of compressed down:
    H=16387,1/A_original=0,359416671mm
    .. so 100CUIN FP=35,9mm
    200CUIN FP=71,9mm
    ..and so on

    If I am right, In my downscaled measurement this height is still the same as the original, because I scale down the diameter and the amount of the down also.

    Am I right or wrong?

    Thank you

  2. #2
    Senior Member Cruiser51's Avatar
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    Since you are using non standard abbreviations in your equations, it makes it more work to figure it all out .... but I think you are "off track".

    I was going to setup to testing as well ... I read the "official" method and my interpretation of the method was that it was centered around the idea of applying a specific wght/inch^2 to a batch of down in a volumetrically marked column.

    So if you want to change the column, I think the process is:
    1) adjust the flat compression plate to achieve the same wght/inch^2 loading on the down column
    2) stay with 1 ounce of down
    3) mark up the new column by volume
    4) adjust the weight of the new compression top plate to apply the same wght/inch^2


    Brian

  3. #3
    GilligansWorld's Avatar
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    Quote Originally Posted by Cruiser51 View Post
    Since you are using non standard abbreviations in your equations, it makes it more work to figure it all out .... but I think you are "off track".

    I was going to setup to testing as well ... I read the "official" method and my interpretation of the method was that it was centered around the idea of applying a specific wght/inch^2 to a batch of down in a volumetrically marked column.

    So if you want to change the column, I think the process is:
    1) adjust the flat compression plate to achieve the same wght/inch^2 loading on the down column
    2) stay with 1 ounce of down
    3) mark up the new column by volume
    4) adjust the weight of the new compression top plate to apply the same wght/inch^2


    Brian
    Brilliant

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  4. #4
    Quote Originally Posted by Cruiser51 View Post
    Since you are using non standard abbreviations in your equations, it makes it more work to figure it all out .... but I think you are "off track".

    I was going to setup to testing as well ... I read the "official" method and my interpretation of the method was that it was centered around the idea of applying a specific wght/inch^2 to a batch of down in a volumetrically marked column.

    So if you want to change the column, I think the process is:
    1) adjust the flat compression plate to achieve the same wght/inch^2 loading on the down column
    2) stay with 1 ounce of down
    3) mark up the new column by volume
    4) adjust the weight of the new compression top plate to apply the same wght/inch^2


    Brian
    Hmm.. your interpretation seems right.
    A question: in the process step 1 and 4 means the same?

    Thank you

  5. #5
    One more thing.. my thaugt was that, if I "cut half" the original cylinder vertically, then
    - the weight of sample down will be half of the original,
    - the compression weight will be half of the original,
    - the cylinders cross section will be the half of the original
    - the volumetric height scale still the same as the original
    .. but I have to get the same result.
    So the weight of down, the compression cylinders weight can scaleble by the ratio of cross sections area.
    Am I wrong?

  6. #6
    Senior Member Cruiser51's Avatar
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    LightofNord .... Correct... step 1 and four are the same thing .... it was early.

    Also I think you could scale the whole thing as well .... so I don't think you are wrong. The "BUT" is that if you reduce the volume that way, (i.e. 1 cubic inch actually counts for 2) then the measurement uncertainty increases proportionately ... so scaling at some point will start to give results that are less reliable.

    If I was going to the bother of setting it up, i would keep my sample size up and adjust that plate, it should give more reliable final results IMO.


    Brian

  7. #7
    Quote Originally Posted by Cruiser51 View Post
    LightofNord .... Correct... step 1 and four are the same thing .... it was early.

    Also I think you could scale the whole thing as well .... so I don't think you are wrong. The "BUT" is that if you reduce the volume that way, (i.e. 1 cubic inch actually counts for 2) then the measurement uncertainty increases proportionately ... so scaling at some point will start to give results that are less reliable.

    If I was going to the bother of setting it up, i would keep my sample size up and adjust that plate, it should give more reliable final results IMO.


    Brian
    I git it now, thank you.
    I check it on the week and write a feedback

  8. #8
    Senior Member Strung out's Avatar
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    you can build your own cylinder with a piece of flat cardboard (not corrugated) and some tape.
    it is easy to match the original testing specifications this way.
    good luck

  9. #9
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    Quote Originally Posted by Strung out View Post
    you can build your own cylinder with a piece of flat cardboard
    Great idea. MacGyver plans are the best!

    Sent from my BLA-A09 using Tapatalk

  10. #10
    Quote Originally Posted by Strung out View Post
    you can build your own cylinder with a piece of flat cardboard (not corrugated) and some tape.
    it is easy to match the original testing specifications this way.
    good luck
    yes, this is what I thought after some calculations.. with smaller diameter I have to use much higher cylinder.. in my company we have lots of cardboard, I'll try it

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