#11
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Hi all
Here is an example of the use of the tool to calculate the segments necessary to obtain a small wheel 20 mm diameter, using a tire 8 mm thick (check screenshot). With 280 mm segments and 80 g/m2 paper (0.113 mm thick) the tool estimates we need 2 + 9 segments (rim+tire). Its dimensions are shown in the rightmost columns of each table. I must say that drawing the trapezoidal segments is easier said than done... I could not find any drawing/CAD software with ready-to-use trapezoid shapes where its dimensions could be defined precisely... I had to draw all trapezoids from a set of straight lines. I started with a main line with 280 mm (dotted line). Then I attached the sides (its dimensions are obtained from the tool) to the extremes of the dotted line, through the respective midpoints. Finally, the top and bottom were obtained by connecting these sides with additional lines. This set of lines was then grouped and copied to start drawing the next segment/trapezoid. Now you just have to adjust one side, reconnect the top/bottom, flip/mirror the shape and repeat. It took me around 30 minutes to draw everything in PowerPoint. The final PDF/PPTX(zipped) file includes some annotations to help comparing with the Excel output. If you want to build the wheel, do not forget to print the PDF at 100%. Hope this helps... I'm still working around ideas to simplify all the workload of drawing that bunch of trapezoids, but really it's not that difficult once you start and get used to the method. Regards Joćo |
#12
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Thanks for doing all this work.
Many years ago, there was a paper modeling newsletter called Cardformation edited by Jon Murray, who advocated the rolled wheel method, but so far as I know, he did not use computers to develop the pattern. He must have used manual calculation or a slide rule. Don't know what ever happened to Jon Murray or the newsletter. My back issues are buried in the impenetrable basement somewhere. Don |
#13
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AC3D has the ability to make the trapezoids really easy, here is the work-flow: |
#14
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Don, that's very interesting! Really, this method has a lot of potential once we can get something to generate the shapes. The math can be worked out using this tool, and other shapes/curves can be added. The really cumbersome task is drawing the trapezoids...
JLeslie48, thanks for the suggestion. I read something about a method for drawing trapezoids with Inkscape which is similar to yours. I have yet to try other CAD/drawing software... As for how to use the trapezoids to get a wheel: Start by rolling the large rectangle in the bottom of the page, #1 green. Do it tightly and add some glue as you progress. Once you finish rolling it, continue with #2 green. Just align the ending edge of #1 with #2 and continue rolling as if it was a continuous paper strip. Finish rolling #2 green and you get the rim. Now proceed to trapezoid #1 yellow, at the top of the page. Yellow-numbered parts make the tire. Start rolling from the left side and align it with the edge of the previous segment, then continue with #2, #3... and so on until you use all strips. Always start from the left side and keep applying glue. |
#15
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I still don't get it, is this a solid tire? I I am reading this properly, it seems you are making a solid conic section and then stacking them (as a result of the trapezoid they will progress in a circle.) kinda like this: |
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#16
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here's a 6 minute tire in ac3d:
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#17
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Check ricleite's threads, he devised this method to get wheels and other shapes with axial symmetry. Example : Vought SB2U Vindicator - 1/33 - Kartonowa |
#18
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LOL! I'm looking at that thread you showed and for the life of me I can't figure out how those amazing tires are made from the strips of paper shown in the pdf file. |
#19
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Well, this is getting a little too complex to just describe by words... I hope to be able to build that wheel soon, and show you the procedure.
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#20
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Hi all
I'm finishing a new version of the tool. It enables modelling complex wheels with paper rolls. These are adequate for modern airplanes/jets, and probably also for small-scaled cars. Some really crazy shapes can also be obtained :-P Nevertheless, it comes with some added complexity... some extra parameters will be needed to define the overall curvature, but I hope you can manage. Regards Joćo |
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