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Discussion Starter · #1 ·
Nothing special with the construction. About the same as have been posted before. I used materials that I had layin around. Size is about 220x125cm (87x49"). Horizontal radius is about 4.6m, and vertical radius is about 6.4m. I didn`t bother much with the finish, as the screen will be moved to a future HT-room in the basement. I didn`t cut the corners, as I may use the fabric for something else later. The white tubes on the frame is plastic tubes for electrical wiring, They have slightly larger diameter than the frame thichness. The fabric is attached to the frame with nails thru eyelets. I attached eyelets for every 4" .


The screen fabric is Draper M2500, which I have used on different frames. It has some marks and streaks, and I would like to try a different fabric later if I deceide to still use a "Torus" screen. Picture is bright, and the viewing angle is larger than I thought it would be. I attach a few construction pictures, and a screenshot from a HD-demo from www.dvico.com.


Projector is BG-808s CRT-projector.


Gunnar

http://home.broadpark.no/~gku/images/1.jpg
http://home.broadpark.no/~gku/images/2.jpg
http://home.broadpark.no/~gku/images/3.jpg
http://home.broadpark.no/~gku/images/hd1.jpg
 

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Nice project. Enjoy it.
 

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Very nice looking. The curves probably are beyond my meager carpentry means.


What did you use to attach the eyelets to the fabric? Attaching the fabric to the frame is something I'm mentally struggling with - stapling just doesn't seem like a good idea to me.


Thanks,

Mike
 

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Discussion Starter · #5 ·
I don`t have a dictionary at the moment, but eyelet pliers is a word that comes to mind? The pliers can both cut holes, and press in the eyelets. I folded the fabric to get about 1/2" of overlap where I mounted the eyelets.


Attaching the fabric to the frame was easier than I thought. Not harder than on a flat frame. I started at the middle of the long side, attached a few nails, then over to the other long side. worked from side to side until close to the short sides. Not much stretching, just enough to make the fabric lay flat. Then a few nails at the middle of the short sides, and finally the corners. The fabric is nice and flat, even without the vacuum. Ofcourse, no vertical curve around the middle withouy the vacuum.


Gunnar
 

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Great screen- Im curious as to how one would determine the amount of curve, or was it just a guess?



While others have probably thought of this, I have not seen it suggested:


Why not start with a different material which restricts air flow similar to the screen material. After installation, turn on vacuum- and while the vacuum is running brush the material with fiberglass resin. After the resin hardens turn off the vacuum. Then you could remove the resin coated cloth and fiberglass-reinforce the back. Assuming it is done smooth enough, you could then attach your "real" screen fabric to the front using spray glue, or one could simply paint the resin coated front. 'voila - no more noisy vacuum fans, and you could eliminate the wood frame afterward -- or use it as a mold to produce more screens.


Thoughts??


Kieth
 

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kieth:

Great idea. It seems that you're handy at stuff like that. I would definitely be interested to see the results of that idea.

My visualization of a light point source (ideally) falling onto the screen is this:

Basically the projector emits rays that are the radii of an imaginable sphere. Therefore, the screen curvature would be a piece of the sphere (I forget the mathematical term).

Since we know the distance from projector to screen, that would determine the radius both vertically and horizontally. What do you think of this?

Would the dimensions (curvature) be impractical to implement?


Gunnar:

Fantastic screen, well done! :)
 

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Discussion Starter · #8 ·
Kieth,

I have thought of making a mold that way, but after finishing this screen I don`t think it`s worth the hassle. Also, I`d have to build it in the HT-room, since it is too bulky to get down the stairs to the basement. Attaching the fabric to the frame was easy, but I`m not so sure that it would be easy to get it flat and even inside that curved screen. I thought of painting it, and some here at AVS have used aluminum paint.


The curves were based on earlier threads here at the screen forum. It could probably be optimized, but it workes well as it is also. I think it was Guy Kuo who posted a method using a double string to "trace" the screen surface. If I remember correctly, you attach a string at the front of your green tube, then run the string to the middle of the screen and back to the viewing position where your eyes would be. Then the folded end at the screen center can be moved around, and would describe your screen curves. These curves would probably have too small radius for my projector, but I didn`t try it.


Gunnar
 

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Gunner:

Can you describe your fan size and configuation to obtain the correct curve?

I thought of either a variable speed control for the fan, or a vent to control air flow.

What did you do?
 
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