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Post by Ron Walker on Apr 21, 2023 10:33:25 GMT -7
Posted by: Ron Walker Oct 24 2007, 11:16 AM We have had a bit of talk about building up a 10 foot dome for home and portable use. Ten feet was picked because it can be set up in a spare bedroom in virtually any house and have a spring line that would still be three feet off of the floor. Charles mentioned building a dome of this size out of 1/8 inch masonite which should be self supporting. It is basically designed to get the most out of the material used by allowing three gores to be cut from each 4X8 sheet of material. These gores are designed to "butt" up against one another and be connected by two or three inch strips of material on the back side. The dimensions are in inches (even though I love the ease of metric measurements I'm so old to be comfortable with the English system. The following is a grid of two inch squares with the width dimension given for every five inches of length. I would suggest making one as a template and then just outlining the others. Twenty-four total gores would require eight sheets of material with one extra for the support pieces.  The entire length of each gore from spring line to zenith is 94 1/4 inches. Since alignment and cuts are most critical at the top, you might want to cut a separate "circle" to cover the zenith point. More on the construction to come but you can get started on cutting the gores if you like. |
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Post by Ron Walker on Apr 21, 2023 10:35:00 GMT -7
Posted by: charles jones Oct 24 2007, 07:02 PM
Hi Ron:
The one that I built cut some corners. I saved work by merely overlapping the 1/8" panel where they were bolted together. The bolt holes were the exact dimensions to form the dome, then I cut the sections oversize.
Also, I did not bring each section to a point at the top. Each wedge was flat at the top. As a result, the dome, when assembled, had a circular hole at the top. I think it was about 10" or so in diameter. This I covered over with one circular, flat piece of masonite.
The overlapping joints were really no problem for the projection, but I suppose an absolutely flat surface would be better.
I remember finding it difficult to get everything to line up when I made the wedges pointed, especially since they are overlapped instead of bolting to a separate piece of material.
If you do overlap the sections, while one bolt hole is a perfectly round drilled opening, the matching one on the other section needs to be enlongated to get the holes to line up as the sections are stretched in a circle.
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Post by Ron Walker on Apr 21, 2023 10:35:34 GMT -7
Posted by: Ron Walker Oct 25 2007, 08:37 AM
I really like the idea of having the gores butt against one another. The use of flat head screws would make for a very smooth transition. If the dome is set up semi-permanent, any spaces in the seams could be filled with caulk before the dome is painted. Otherwise a strip of white tape could be used to cover any imperfections.
If each gore is made two inches wider, the center one would have to be laid out in reverse of the outside two on each 4X8 sheet, as three bases would then be to wide to fit.
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Post by Ron Walker on Apr 21, 2023 10:36:05 GMT -7
Posted by: Ken Miller Oct 25 2007, 02:11 PM
If you have the gores butt against each other rather than overlap, what do they attach to? Strips of masonite on the back side? Metal strips, perhaps?
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Post by Ron Walker on Apr 21, 2023 10:36:34 GMT -7
Posted by: Ken Miller Oct 25 2007, 02:15 PM
OK I see that you covered that Ron. I guess some experimentation would lead to the best way to actually do it. I wish I had more space for playing around with this stuff!
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Post by Ron Walker on Apr 21, 2023 10:36:56 GMT -7
Posted by: charles jones Nov 1 2007, 01:36 AM
Hi Ron -
I just picked up on this.
If you plan to disassemble and reassemble the dome, countersunk holes in the masonite and flat screws may not work. The countersink hole will probably weaken the masonite if assembled several times.
You might try washers under the flat head screw and no countersunk hole in the material.
Experiment a bit with several small pieces. What I found, in the dark when projecting the stars, it made no difference that the sections over lapped and was a lot less work.
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Post by Ron Walker on Apr 21, 2023 10:37:40 GMT -7
Posted by: Ron Walker Nov 1 2007, 12:30 PM
QUOTE(charles jones @ Nov 1 2007, 01:36 AM) *
Hi Ron -
I just picked up on this.
If you plan to disassemble and reassemble the dome, countersunk holes in the masonite and flat screws may not work. The countersink hole will probably weaken the masonite if assembled several times.
You might try washers under the flat head screw and no countersunk hole in the material.
Experiment a bit with several small pieces. What I found, in the dark when projecting the stars, it made no difference that the sections over lapped and was a lot less work.
I guess it's just the "perfectionist" blink.gif in me. tongue.gif
How did you overlap, the right edge always overlapping the left edge of the next gore or were the odd numbered gores always overlapped on both sides by the even numbered ones?
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Post by Ron Walker on Apr 21, 2023 10:38:05 GMT -7
Posted by: charles jones Nov 4 2007, 04:21 AM
It doesn't matter which side is overlapped as long you keep it the same for each panel. However, the overlapping side is the one with elongated holes. The reason: When the side is overlapped outside the one with round holes, the actual hole position is shifted because of the overlapping. Does this make sense? Not sure how else to explain it.
Once you choose which side will be in front, the other side will overlap behind the next panel. I guess it's kind of like a paper fan. If you fold a paper fan, open it and flatten it, every left (or right) panel will overlap the next.
I used flat washers and round headed bolts and wing nuts to assemble. None of this showed up in the dark with the projections.
I remember at UCLA and their A-2 Spitz: Their dome back then was fabric with metal struts every few feet to support it. For the night sky projection in the dark, you could not perceive the metal struts at all even as stars passed over them. As the dome lights came on, the struts were clearly visable.
All of this means, I think, that if you are projecting a normal planetarium sky, the overlapping will not be objectionable. If you are planning to project a 35mm slide image or the like, then it will show up and not be as good as a flat surface. But with any dome that is made to take apart, the seams between sections will still be visible for this kind of projected image.
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Post by Ron Walker on Apr 21, 2023 10:38:39 GMT -7
Posted by: mrgare5050 Jan 7 2010, 05:01 AM
QUOTE(Ron Walker @ Oct 24 2007, 06:16 PM) *
We have had a bit of talk about building up a 10 foot dome for home and portable use. Ten feet was picked because it can be set up in a spare bedroom in virtually any house and have a spring line that would still be three feet off of the floor.
Charles mentioned building a dome of this size out of 1/8 inch masonite which should be self supporting. It is basically designed to get the most out of the material used by allowing three gores to be cut from each 4X8 sheet of material. These gores are designed to "butt" up against one another and be connected by two or three inch strips of material on the back side.
The dimensions are in inches (even though I love the ease of metric measurements I'm so old to be comfortable with the English system.
The following is a grid of two inch squares with the width dimension given for every five inches of length. I would suggest making one as a template and then just outlining the others. Twenty-four total gores would require eight sheets of material with one extra for the support pieces.
The entire length of each gore from spring line to zenith is 94 1/4 inches. Since alignment and cuts are most critical at the top, you might want to cut a separate "circle" to cover the zenith point.
More on the construction to come but you can get started on cutting the gores if you like.
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Ive been looking for some 'bible' type specs for building domes to include on HPA website, and this looks biblical .. is this what Ken used in his recent BedRoom-o-Rama? Im just data-mining our own posting board! g
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Post by Ron Walker on Apr 21, 2023 10:39:02 GMT -7
Posted by: Ken Miller Jan 7 2010, 08:31 AM
QUOTE(mrgare5050 @ Jan 7 2010, 04:01 AM) *
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Ive been looking for some 'bible' type specs for building domes to include on HPA website, and this looks biblical .. is this what Ken used in his recent BedRoom-o-Rama? Im just data-mining our own posting board! g
My dome is 9ft diameter. That was the largest that I could fit into the space available. Charles Jones originally made an 11ft dome using the overlapping gore technique. That dimension was based on the largest size gores that could be cut from 4ft by 8ft sheets of wood. That size is possible because the gores are truncated at the top, and covered with a circular plate when assembled. I can furnish the gore dimensions for a 9ft dome, and I can fairly quickly calculate the dimensions for an 11ft dome.
Ken
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Post by Ron Walker on Apr 21, 2023 10:39:23 GMT -7
Posted by: mrgare5050 Jan 7 2010, 05:58 PM
QUOTE(Ken Miller @ Jan 7 2010, 03:31 PM) *
My dome is 9ft diameter. That was the largest that I could fit into the space available. Charles Jones originally made an 11ft dome using the overlapping gore technique. That dimension was based on the largest size gores that could be cut from 4ft by 8ft sheets of wood. That size is possible because the gores are truncated at the top, and covered with a circular plate when assembled. I can furnish the gore dimensions for a 9ft dome, and I can fairly quickly calculate the dimensions for an 11ft dome.
Ken
great ken! would they simply be proportional to those ron provided above? gare
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Post by Ron Walker on Apr 21, 2023 10:39:47 GMT -7
Posted by: Ken Miller Jan 8 2010, 09:07 AM
QUOTE(mrgare5050 @ Jan 7 2010, 04:58 PM) *
great ken! would they simply be proportional to those ron provided above? gare
The quick answer is yes.....but...
I wanted to use smaller increments for laying out the template, and I wanted to precisely locate the connecting bolt positions, so I made up an Excel spreadsheet to customize the measurements. Maybe it would be worthwhile to make up sketches for each dome size.
Ken
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Post by Ron Walker on Apr 21, 2023 10:40:20 GMT -7
Posted by: mrgare5050 Jan 8 2010, 11:00 AM
QUOTE(Ken Miller @ Jan 8 2010, 04:07 PM) *
The quick answer is yes.....but...
I wanted to use smaller increments for laying out the template, and I wanted to precisely locate the connecting bolt positions, so I made up an Excel spreadsheet to customize the measurements. Maybe it would be worthwhile to make up sketches for each dome size.
Ken
A table perhaps? Its even got me wanting to build a perfectly symetrical (mine havent been) dome! g
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Post by Ron Walker on Apr 21, 2023 10:40:39 GMT -7
Posted by: mrgare5050 Jun 6 2010, 12:30 PM
any new dome action?
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Post by Ron Walker on Apr 21, 2023 10:41:13 GMT -7
Posted by: Ken Miller Jun 10 2010, 08:49 AM
QUOTE(mrgare5050 @ Jun 6 2010, 12:30 PM) *
any new dome action?
I've been getting a lot of use out of my 9 ft home dome based on the Charles Jones design, and I really like it. I could smooth the edges, but they don't cause that much distraction, even with the video projection. The edges are practically invisible with star projection. Everybody that sees the dome in action wants to go home and build one of their own. It takes a few days of work to fabricate, paint, and assemble it, but the results are worth it. The design works up to about an 11 ft size. There are mechanical problems with the structure when it gets bigger.
I've been thinking about ways to do an inflatable dome after seeing the one that Higekita brought over from Japan. I could use an inflatable dome occasionally, but not often enough to justify the $4000 to $6000 that a nice commercial dome would cost.
Ken
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