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Geometical Problem https://forums.clankiller.com/viewtopic.php?f=8&t=2640 |
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Author: | derf [ Mon Oct 29, 2007 12:28 pm ] |
Post subject: | Geometical Problem |
Alas a problem that my brain is incapable of even putting into context... The G-meister might be able to get his head around it, even Satis might try but i fear he will eventually turn to his beer bottle sitting on his desk and think...."nah, fuck it". I need to be able to make cones from a flat piece of flexible plastic. The tips of these cones will be snipped off to let a paintball easily through. The purpose of these cones is that theyll be glued inside a cylinder which will act as a silencer for a paintball marker. Does anyone know how to go about drawing the right dimensions on the flat plastic so i can start cutting them out? The approx diameter of my silencer cylinder is 47mm. Obviously, the diameter of a paintball is about 17mm so I need a 25mm hole on the top of the cone for any ballistic mishaps. |
Author: | RB [ Mon Oct 29, 2007 1:56 pm ] |
Post subject: | |
I found you a nice image: http://de.wikipedia.org/wiki/Bild:Kegelstumpf.PNG So, you need to make a ring sector. As for dimensions, let see. I will provide the calculations too, so that you can correct it, if I'm doing something wrong. To construct it, you'll firstly need s and S. (see the attached images) Let first determine y: y/12,5 = (y+30)/23,5 => y = 34,(09) Now: s = sqrt( (23,5 - 12,5)² + 30² ) = sqrt(1021) ≈ 31,95 S = sqrt((23,5)² + (30+34,(09))²) ≈ 68,26 Now, the length of the bigger arc is 2rπ = 2(23,5)π, while the whole perimeter is 2Sπ = 2(68,26)π. The angle α is thereby α = 2rπ / (2Sπ) · 360° = r/S · 360° ≈ 123,93° That's enough to construct the thing. Thou, try it with paper first. Now tips: 1. You may like to try with a bigger angle (say 130°) and then overlap two ends in order to attach them with superglue. 2. If you need it to have bottom, just make a circle of radius bigger than 23,5. Say 23,7. 3. And again: try it with paper first. (you can scale it by 1/10 or 1/5 in order to use just an A4 piece) |
Author: | derf [ Mon Oct 29, 2007 2:18 pm ] |
Post subject: | |
Tried it with paper to scale and checked dimensions & angles. Result = perfection. Thanks G. Would never have found this out. |
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