Posted by: Ron Walker Jan 18 2007, 02:42 PM
More Q&A from elsewhere.
Thanks Karrie,
I did look at that 10 foot portable dome that GOTO makes (they still do as of six months ago) but I really wanted something bigger. Also its cost was about $2K with another $500 added for packaging and shipping. This seems a bit steep for the size, but everything having to do with planetariums seems steep.
I have an area that I can set this up in, but size limits me to about 18 feet in diameter. Still much bigger then the 10 foot one and I think will make for a better presentation.
Anyway, this experiment is just that, an experiment. I wanted to make it as cheap as possible while still having something useful. Further experiments will most certainly include more gores, probably twice as many. As Gare says, your never really ever finished anyway.
The water pipe was a cheap out, but I must admit that I didn't even think of the fiber pole idea which is very intriguing. Do they make standard sections and can you put as many as you want together? Will the joints hold up a large dome without collapsing? Do you have any web sites, off the top of your head, that show what's available? Perhaps the place you purchased your spines from.
The more and more I think of it, the more I like the idea.
Ron
bergieberglund <bergieberglund@ yahoo.com> wrote:
Hey Ron,
Nice work! I have a couple of thoughts for you and others
contemplating this route:
1) Goto, Inc. used to make an umbrella dome. I'm not sure if they
still make it or if it's been discontinued, but apparently it could be
set up in 20 minutes or so. They marketed it for use with their
portable NEX projector. Here's a link to a Goto webpage from 2003 with
an image of that dome:
www.goto. co.jp/products/ nex/nexoption- e.html
I thought you might find the images helpful.
2) Have you considered fiberglass tent poles for the ribs? They can be
purchased in different lengths, or you can get pole kits and build to
your own specs. They'd be easier to move around than 10' long pipes,
and they're designed for extreme flexion.
We have a tiny inflatable dome (8.5' in diameter) that we take to
conferences, and we use tent poles to keep the dome from collapsing on
people's heads while the door is open. Our poles are 19.5' long,
collapse into sections about 25" long, and I pack them in a box I take
on a plane as luggage. We considered the plastic pipe route for that
dome, but the tent poles are WORLDS easier.
If you're not planning to move your dome often, portability is not as
great a concern. I take our little dome to 10+ conferences and
demonstrations per year, usually via airplane, so portability was one
of the primary factors for me.
Again, congratulation, and thanks for sharing the pictures!
Cheers,
Karrie
--- In small_planetarium@ yahoogroups. com, Ron Walker <walkprod16@ ...>
wrote:
>
> Actually Perter, the rods are under tension. If you took them out
they would pretty much straighten out. The upper and lower support
hold them in place and the cloth itself holds them at the proper
curvature. I actually wanted them to provide some back tension to
hold the dome in place. As you can see, I was planning on using 1/4
inch wooded rod as they bent fine in the store. However, as I started
to put then into the cloth, well....
>
> As for the larger dome, I didn't stick with steel for a couple of
reasons. Weight for one. I would have to go up to about a 3/8
diameter rod to hold the weight of that much material (will probably
be up around 50 or so lbs of fabric). I'm not at all sure if that
thickness would "bend" the required 90*. Since I might support this
entire dome from above, I wanted it as light as possible. Also if I
ever want to move it from place to place, the lighter the better.
>
> Cost comes next. Plastic water pipe is very cheap and easy to
find. I'll admit that I didn't do a lot of looking but my initial
search only came up with four foot sections. Thus a lot of joints
which would probably cause havoc with my 90* bends. The plastic pipe
comes standard in ten foot lengths so there will only be one joint per
rib. Hopefully this larger dome will work as well as the smaller one
did, but I am approaching this as an experiment and made a few
compromises to keep the cost as low as possible. If things don't work
out as planned then not a lot of money lost and it can always become
the outer structure for a negative pressure dome within. I don't
think this will be the case however, I think the large dome will work
out all right. The big problem will be working with such large
sections of material, both in sewing and in mounting. Time will tell.
>
> Ron
>
> Peter Hartmann <ascensiontech@ ...> wrote:
> Wow Ron! That's fantastic! I'm curious how you bent your
steel rods so perfectly. How come you decided to depart from them
with your larger dome?
>
> Thanks,
> Peter
>
> On 1/13/07, Ron Walker <walkprod16@ ...> wrote:
> They are coming very soon. Just keep a look out.
>
> Ron
>
> Peter Hartmann <ascensiontech@ gmail.com> wrote:
> Hey Ron,
> Do you have pictures of your test dome with support stucture? I
only see a picture of a gore template.
>
> Thanks,
> Peter
>
> On 1/12/07, Ron Walker < walkprod16@. ..> wrote:
> Greg, et. all:
>
> I've got the formula I used for my test dome and am going to use
for my large dome over at AstroSkies.com forum. The small 4 ft.
diameter test dome came out great and now I'm working on an 18 foot
one. All my "trials and tribulations" are laid out there. Even some
pictures of projections under the HomeStar review.
>
> Ron