Excel tool to calculate paper rolls - ricleite's method

[HamsterX]

Hello, friends

This Excel tool can be used to calculate the dimensions of the trapezoidal paper strip segments necessary to obtain geometric solids with radial symmetry, according to Ricardo’s method.

For now, two types of paper-roll-built solids can be obtained:

Domes (hemisphere, ellipsoid, deformed ellipsoid, paraboloid, cone…) – To be used e.g. as inner supports for petal constructions in missiles, fuel tanks, bombs, torpedos, radial engine crankcases;

Wheels (flat rim + tire with circular section) – Good for most WWI/WWII aircraft, and probably also for other uses (Vespa scooters maybe);

Variants/enhancements will follow soon. Ricardo uses some other shapes which are a little more complex.

I did my best to make the tool easy to use. It contains some notes and schemes drawn inside., for guidance. There is also some error checking to call your attention to mistakes and make sure that feasible measurements and options are being input. The generated data is also plotted to help visualize the final rolled shape and the set of paper strip segments.

As most of us use standard A4/letter home printers, the size of the paper limits the width of the paper strip segments. The two worksheets marked with (C) will calculate dimensions for sets of paper strips with a fixed, constant segment width (your choice). Example: for A4 (297 mm x 210 mm) I usually set this to 280 mm. All segments will be 280 mm in width.

If you have access to large-format printers/plotters, you may want to use the worksheets marked with (P). These calculate the data for a fixed number of paper segments (your choice), but with variable size. Example: I want exactly 15 segments for my shape. Segment width varies from segment to segment and some of these may be 500 mm in width.

Confused? Just have a look at the plots each worksheet generates.

Once the data is generated, you can use any CAD software you like to draw the trapezoids according to the calculated dimensions and send the drawings to a printer.

Any question? We can discuss in this thread, or just drop me a PM.

Regards

João

PS: The Excel file is totally harmless for your PC/Mac.

[Kevin WS]

That sounds interesting! Thank you!

Though I personally have no use for this not being into designing, I am curious at the approach used, and have downloaded the file so I can play at the weekend......

[papermate]

Thanks, Joao, for the Excel file. On the attachment below, I have noticed that there are four Excel pages, two pre-fixed "C" and two "P". Excuse me for the silly question as to how to apply them. The data in the red rectangle can be changed according to the radius and height we want, is that right? So we can work out, according to your Excel table, the length and no. of segments needed.

Since many of us don't have plotters and Autocad software, how can we print them out on our home printers? Is it possible to print out a shape on Excel spreadsheet and use the printscreen function to capture the shape and then enlarge it with Photoshop to the correct size? Please also see a tyre page extracted from Bobscardmodel using a roll-up techniques to do the wheel. How can we make similar images for print out?

Papermate

[papermate]

Thought it over again, "C" for constant width and "P" for plotter - variable width.
But the example of A4... with a width of 280mm still baffles me. It's almost the length of an A4 page!

Papermate

[papermate]

Oops, I meant height not length.

Papermate

[ricleite]

Looks straightforward to use, João. Being used to the method, I am suspect, of course Thanks for your work!

[HamsterX]

Originally Posted by papermate

Oops, I meant height not length.

Papermate

Originally Posted by papermate

Thought it over again, "C" for constant width and "P" for plotter - variable width.
But the example of A4... with a width of 280mm still baffles me. It's almost the length of an A4 page!

Papermate

Dear Papermate

That is exactly as you write. The red rectangle you marked (area with light-green fill) is where all dimensions should be entered. Please refer to the diagrams in the top-left of each worksheet, where these dimensions are described. Parameter s is the size of the segments, and d is the thickness of paper. It is not necessary to edit any cell outside the green area.

I may have created some confusion with when writing and mixing length/width/height... sorry. What I meant was that the maximum size of a paper segment inside an A4 sheet is 297 mm. Let's give some clearance for the margins, say 10-15 mm, and you get 280-270 mm remaining. In that screenshoot you see I used s = 270 mm, but that can be changed as you wish. If you use smaller segments, you also get more segments... The worksheet and the charts adapt accordingly.

Regards

João

[HamsterX]

Originally Posted by papermate

Since many of us don't have plotters and Autocad software, how can we print them out on our home printers? Is it possible to print out a shape on Excel spreadsheet and use the printscreen function to capture the shape and then enlarge it with Photoshop to the correct size? Please also see a tyre page extracted from Bobscardmodel using a roll-up techniques to do the wheel. How can we make similar images for print out?

That's the biggest problem now... My tool only calculates the dimensions, it doesn't produce any decent drawing. Unfortunately, Excel charts and shapes do not have an absolute orthogonal scale usable for 1:1 printing. But drawing trapezoids using Inkscape (free), CorelDraw or any vector drawing software should be straightforward. The length of the trapezoid was set at 270 mm in that example, and the last column in the grey-shaded table shows the dimensions for the sides.

Tomorrow I will post an example of the use of the tool, with the corresponding drawings that we should obtain for a small wheel.

J.

[papermate]

Thank you very much, Joao, that was very educational and may be useful to those who want to get an experience in doing rolled up wheels, tyre or cones. Look forward anxiously to your coming example.

Papermate

[jleslie48]

wow, I'm very interested, like papermate, I need an example/workflow walk-through to show how to take the inputs (thanks papermate for hilighting what is user input) and the output (????) and how to take those output numbers to make a part.