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Discussion in 'Space & Aeronautics' started by lizzienewell, Nov 8, 2017.
Tell them to "Mush them dogs".
Yeah. That's what I experimented with--rice paper and acrylic medium. I love the tissue paper and balsa look. I should also try Econokot. I've got a role of it.
Try Ultracote, works better than "Monocote", or "Econocote" when you re-supply. I have used both on 6 foot R/C aircraft I used to fly. The "Ultracote" has better adhesive qualities. I preferred "Monocote" over "Econocote' as it adhered better, was stronger. "Ultracoate" beat them both though. Seems like there was a lot better color selection too.
I'll start with econocote because I've got an unused roll of it. I've had it for awhile I hope it doesn't go bad. If it looks good then I might try the other products. I'm getting impatient for the arrival of my cutter. The case I ordered for it arrived yesterday, but still no cutter. I spent the day sewing a replacement zipper into my winter coat. Mending doesn't seem to be something people do anymore, but handsewing a zipper isn't all that different from cutting and assembling little pieces of paper.
I've got the Cameo Silhouette set up and it's back to work on the models.
Here's the skin I was using. It's taken from a icosahedral map ornament and it's not quite right because I end up cutting off the edges of each facet when placing it on a sphere. That's part of why the map skin wasn't lining up right.
So I did a trace in Coreldraw to convert to vector and then joined shapes to get a line map. I might come back to the colored map later. I'm going to go for water color painting on the surface of the globe.
Here is the line map laid out with a grid of triangles. This took way more work that it looks like. Maybe I spent to long on it and could have gone with a easier way to get the map.
I copied each triangle with the map parts inside and the used envelop in Corel to match the triangle with the desired shape. It's the perfect way to do this because Coral only has rectangular envelopes so it's a matter of eyeballing and slow adjustment. Then remove the triangles.
Here is the file ready to go to Silhouette with the cut marks in red and blue.
And the cutting set up in Silhouette.
Here's the sheet ready for cutting.
Looks good! a bit small but that can be changed easy enough...does your planar mapping need a relief cut on the sides? to allow it to lay smooth on the buckyball? hmm ...you might want to take a look at this if you have not done so already..
waiting to see it in 3d
I may have to dust of my Cameo!!
I'm looking forward to seeing the results!
My brain hurts from all that geometry....
That said, looking forward to the results!
I remain mostly interested in the internal structure. I have three different sized models. all three scaled to each other as the Moon is to Earth. This is the 2 inch model. It seems to go the quickest if I work things out in this scale because I can fit the parts on four sheets of paper. The 8" requires over 32 sheets. That's a big difference in time. So I'm working it out in the 2 inch size before scaling up. With the 2 inch I put three darts on each facet, each dart in the middle of the side of the triangle. With 8" inch I put in two darts on each side.
But I keep getting caught up in designing the interior structure. I come up with ways which may help with making it faster or more accurately. Once I get the structure nailed, I can do a variety of skins. I've been thinking of setting these up as kits. Yesterday I had another idea for a kit/market. I might do one for educators to use as projects to teach mathematics. Building these is a hands on way to understand geometry. I realized I started thinking in this direction during a university chemistry class. It was a honors class and I felt like a faker in over my head. The professor had been a Rhodes scholar and he wanted us to memorize the periodic table, his idea of useful information. that way if we ever found ourselves on a deserted island we could do chemistry??
He was trying to show a carbon molecule and was struggling to draw a tetrahedron. That's when I realized he'd memorized a bunch of data but didn't really know what he was talking about. I resolved to be able to imagine tetrahedrons from any angle. These models are built off tetrahedrons. That is geodesic sphere is an icosahedron projected on a sphere. And an icosahedron can be thought of as 20 tetrahedrons. I'd like to set this up in a way that would be understandable and appealing to a middle school student. I might do a model which shows the relationship between tetrahedrons and geodesic spheres. I could do a kit with maybe 3 or 4 related models. If I do this I want to cut the parts in a way which leaves them still attached to the page so that it's easy to see the 12 vertices and the 20 tetrahedrons. Understanding this kind of geometry is useful if you want to design fullerines to be used in nano-tech machines. Also useful for understanding the crystal structure of quartz. Anyway if I were stranded on a deserted island I think knowing how to build a geodesic dome would be more useful that having memorized the periodic table. Maybe. The best thing to have when on a deserted island is some way to communicate.
I just saw the joke about binary. 1! ;-)
I think you will find paper thickness crucial. Since you are putting on a sphere, as Gandalf said, you have to measure that paper. A plastic set of vernier calipers would be fine for that. You would be surprised how the thickness is all over the place. Paper is sold by the lb., not thickness. I tend to use 110 lb. and 67 lb. paper for most things, and regular printer paper, maybe a little "doped" up, for extremely thing objects, to keep scale. The ones below are $6.56, have the depth gauge and read Millemeter and in Thousands of an inch. I wouldn't use them for rebuilding an engine, but for paper, they more and adequate.
Link = https://www.amazon.com/PRECISE-Non-...sr=1-4&keywords=plastic vernier dial calipers
Ahh ..So you are basically working from the "Greater Circles" idea, hence the 32 sheets for the 8" ball, with subdivided pentagons for the buckyballs. Thats a lot of parts! You could do something like this...
It would take 20 of these for any size ball, and by folding the flat shape on the left, and always glueing the two short sections to a solid full section, you would end up doubling the card at each joint, then perhaps a flat strip at 90 to each rib created for a gluing surface for your map? Your planar surfaces should still work, with only a little tweaking.. Just a thought...
You've got the idea
I start with 20 full circles then twist each circle back on itself to form a trefoil knot. If I design the model as a mathematical teaching set I will put in part about trefoil knots and knot theory. I probably need to make some design changes to that each loop of the knot twists the same way.
The result is that each of the twenty units which you show above is subdivided into four triangles and each lamination is two layers thick. It's only twenty parts.
I put on twelve stringer parts(pentagonal) as you describe for attaching the skin. The stingers all end up being 2 layers thick. My goal has been to make the model as simply as possible with the fewest number of steps and parts. The tiny version is more like what you describe but each part is a full circle and forms two units. The circle glues back to itself and then glues to adjacent units. It's kind of a pain to do since it's so small that it takes tweezers.
I'll have to get on my other computer to send photos.
I've been sizing the skin by trial and error I may have to do the math.
I'm considering getting adhesive backed paper. The parts would remaining on the backing(I hope so anyway) and it would require no glue to put together the model. Surprisingly most of the glue surfaces could be faced inwards. --I just had an idea which would cover more of the glue surfaces when assembled. This would work well as an educational kit because the kid could spend their time folding and assembling, not cutting or spreading glue. If I do go with sticky-backed paper, I'll have to adjust the skin size based what is available for paper thickness.
Good talking to you on this. I see that I probably can figure out the equation for the size of the skin.
Another thought from this. When the stringers go on the result is a low spot in the middle of each facet equivalent to two thicknesses of paper. I could cut the underlying parts in a way which compensates for this. It's easier than trying to piece in additional stringer material, which I've done with the 8 inch.
I love you guys. Thanks.
Here are the images the one oh the right shows how the trefoil goes together. I've since made changes. The cut in the ring now aligns so that the knot can be glued closed. Also the folds on the side of each loop is now rolled rather than a hard fold. This is because the triangle in the middle is actually bigger than the other 3 triangles. I want to change the slot arrangement so that the slots are up, down, up, down, up, down--crossing the same way for each loop.
The thumbnails sown the units going together into a sphere. And the last is the 8" globe--two versions. I was still working with stringers when I set it aside and also trying different materials for the skin. It has an LED light inside. It's a lot faster working things out at 2" which is why I'm focusing on that size.
Pack one of those full of snow (make an Ice Ball) and you could really bop somebody in the head pretty hard. An over sized slingshot comes to mind.
Here ... http://www.wolframalpha.com/input/?i=Archimedean solids&x=2&y=7
save some time!
That's an interesting program. I'm downloading it, just to check it out. I wonder if it exports. You could do the same thing with Polar to rectangular equations, but the spherical nature of the curves seems Non-Euclidean. In non -Euclidean triangles the angles can never equal 180 degrees, and this kind of math is used to do spherical objects. Such as a triple right sided triangle on a sphere.
What?! and miss the fun of figuring it out? It's either play Freecell or make models for me. They are both a type of puzzle.
The trick is how to do it using the tools available in Coreldraw.
Here's how I think I do it start with the diameter of the internal structure and add 2 times the thickness of the paper for the necessary outer diameter of the skin.
For the circumference use 10 x one side of the internal triangle. That is the one in the center of the trefoil.
10 x innerside=circumference.
In Coreldraw, set up a rectangle with the length of the desired circumference.
Group the non-euclidian triangles.
Adjust size of the group of triangles so that the middle of the second row lines up with the edges of the rectangle.
Easy as pi.
I think I'll leave the sizing rectangle in the Corelfile and place the equation right on the page. That way when I change paper I can quickly make the adjustments.
Much more fun than Freecell.
For drawing the non-euclidean triangles I used the Coreldraw polygon tool and pulled the central node of the triangle sides outward. I eyeballed it and did it in the 8" size. So it gets more precise when scaled down. I suppose the fit would be more precise if I accounted for the darts when drawing the polygons.