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Thread: Segmented using multiple size wedges

  1. #1
    Join Date
    Jan 2011
    Location
    Norristown, Pa
    Posts
    227

    Segmented using multiple size wedges

    I have been making segmented bowls and vases using wedges cut at 4 different angles and different number of wedges of each size (), 30(3), 221/2(4), 18(5), and 15(6) degrees(number of each). Per math friend there is over 7 million arrangements for each ring. I have found that you can get interesting patterns by mixing the wedges. Each group makes up ¼ of the ring. You can group them in any arrangements to form the rings. They make nice “Ikea” type packages to give to friends or “sa” and let them form the rings, return them when glued to their liking and then give rings back to assemble and turn the rings. Neighbor 85 years old love the doing one. I use Excel or LibreOffice Calc to calculate the wedge sizes. Here are two samples.BowlVase.jpg

    Here is how they are calculated.
    This sheet can be used in excel or LibreOffice Cal to find the wedge length to cut. Row1 is the number of wedges for a normal ring of degrees in row 2.
    Ie 12 for 30 degrees. Row 3 shows the degrees and how many [ number ] of that degree is used in a ring for this project.
    Column 1 is the diameter of the ring you wish to make. And the result in columns 2 - 5 is the estimated wedge size. It is the actual arc length, but is a good estimate for wedge size.
    The math is circumference ( Pie * diameter)/ number of wedges.
    To use, paste the four rows below into either spreadsheet. Select one cell from row 3 and copy it to row 4 and remove the " both front and back. Repeat for other columns. With the 4 in column 1 you should see the same numbers. You can also format the cells to 2 decimals or fractions.
    Place your desired diameters in successive rows of column 1 and then use the copy feature in both. (Hint: Highlight the columns 2 -5 for row 4 and the rows that you entered data and then press ctrl and d key). This should have copied all the formulas and used your diameters from your numbers entered in column 1.


    12 16 20 24
    30 [3] 22.5 [4] 18 [5] 15 [6]
    "=PI()*RC[-1]/R1C2” "=PI()*RC[-2]/R1C3" "=PI()*RC[-3]/R1C4' "=PI()*RC[-4]/R1C5"
    4 1.0471975511966 0.785398163397448 0.628318530717959 0.523598775598299

  2. #2
    Join Date
    Mar 2013
    Location
    Trenton SC, in the CSRA
    Posts
    295
    Thanks Bob.
    I found this a little hard to follow. So here's my MSEXCEL reproduction.

    # of Segments 12 16 20 24
    Degrees 30 22.5 18 15
    Equation Template "=PI()*RC[-1]/R1C2” "=PI()*RC[-2]/R1C3" "=PI()*RC[-3]/R1C4' "=PI()*RC[-4]/R1C5"
    Dia. (mm or ins)
    4 =PI()*$A4/B$1 =PI()*$A4/C$1 =PI()*$A4/D$1 =PI()*$A4/E$1
    5 =PI()*$A5/B$1 =PI()*$A5/C$1 =PI()*$A5/D$1 0.654498469
    6 =PI()*$A6/B$1 =PI()*$A6/C$1 =PI()*$A6/D$1 0.785398163
    7 =PI()*$A7/B$1 =PI()*$A7/C$1 1.099557429 0.916297857
    8 =PI()*$A8/B$1 1.570796327 1.256637061 1.047197551
    9 2.35619449 1.767145868 =PI()*$A9/D$1 1.178097245
    10 2.617993878 1.963495408 1.570796327 =PI()*$A10/E$1


    You should be able to drag any calc cell across all other cells. Formulas shown for illustration purposes. The "$" will make 'static' the column or row.

  3. #3
    Join Date
    Jan 2011
    Location
    Norristown, Pa
    Posts
    227
    Yea, I was worried on the best way to describe it, I will try yours again, but first attempt failed. Everyone has there own way to work excel

  4. #4
    Join Date
    Jan 2011
    Location
    Norristown, Pa
    Posts
    227
    Eugene,
    Found how to change RC cell reference to Letter Number reference like you use in excel,it was much easier to do in LibreOffice Calc as you do. I will stick with RC reference.

    Here is a quick explanation of my excel reference.
    R specifies a row and the number with [] is a relative reference either back or forward that many cells from current.

    C likewise is column and the number in [] is relative reference either left or right of current cell.

    R and/or C without [] and a number is absolute cell reference.
    Example R1C1 refers to top left cell.
    RC[-1] refers to cell to left of current cell.

    R[-1] C refers to cell above the current cell.

    Bob

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