Adjustable Screen , torus to flat - AVS Forum
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post #1 of 8 Old 06-24-2007, 09:20 PM - Thread Starter
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Hi Folks!

I've been active in the "Pearl Silver Laminate" thread, and thought this would be the appropriate forum to post some information about the rather unusual construction of our screen. For a variety of reasons, we opted for a 4:3 screen, made out of WilsonArt "Pearl Silver Crystal" laminate. We also wanted to make the screen adjustable from a torus (required for our current stone-age projector), to flat (if the old dinosaur dies, or if someone donates a better PJ! ).

I've stolen a lot of great ideas from this group, and I really appreciate the depth of knowlege available in the AVS forum.

The first interesting fact is that the "four-foot by eight-foot" sheet of laminate actually measured closer to 49 1/4 x 97 1/4 inches! I'm guessing that's so in case the edges get chipped in shipping, the customer can still get a 48"x96" sheet out of it. We cut ours to 48 3/4" x 64 3/4", which we planned to leave a 1/8" clearance all the way around, inside our frame. We first 'rough cut' the sheet with laminate snips, then cut it to final size with a router. Here's a photo of the cut sheet -


We made a frame out of nominal 1"x4" poplar (actually 3/4" x 3 1/2"). We used half-lap joints made on the tablesaw for the corners, and reinforced them with triangles cut from the poplar- raised 1/4" above, and set into the back of the frame- which will also support the back of the screen when in 'flat' configuration. (photos below). The frame is 50 1/2" x 66 1/2" outside measure, and 49" x 65" inside dimensions. We used "Titebond III" wood glue for all wood joints. Here's a shot of one of the corners-


We then made a vertical 'crossbar assembly' out of nominal 1"x2" red oak (actually 3/4" x 1 1/2"), again with half-lap joints, and glued and screwed it to the back of the frame. This will be the attachment point for the mounting plate described and pictured below. Here's a shot of the assembled frame-


After running the numbers for a torus, we decided to fudge just a little. We cut four corner blocks 2 1/4" high, at an 83 degree slope to support the corners of the screen above the rear of the frame- for the 'torus' configuration. These blocks are screwed-in, but not glued, so they can be removed. Again, a photo of the blocks is below-


We attached 'cleats' at each corner, and at the center of each board, to rear-mount a velvet-covered 'picture frame'.

Lastly, we made a 'mounting plate' for the center of the finished screen. This was a piece of 24" x 32" (very nice, silver-coated) pegboard, with the corners cut off at 6" in (to allow the outside corners of the screen to flex smoothly). We made a cross-shaped brace (1"x2" poplar and half-laps, again...), and glued and screwed it to the 'rough side' of the pegboard mounting plate. This makes for a flatter center than a perfect torus, but not by much- the ideal screen torus for our setup curves very little at the center-- and we needed enough surface area for a good bond with the contact cement. Here is a photo of the rear of the completed 'mounting plate', showing the crossbrace-



Then we ground down the screw heads and any 'stress-swollen' masonite around the screwheads. After grinding, they were filled with "JB Kwik" epoxy, and sanded flat again (I've worked with laminate in the past, and it 'telegraphs' things like screwheads somethin' awful....). Here's the 'face' of the mounting plate, with the epoxy covering the screwheads-



After thoroughly cleaning and drying both the pegboard and the back of screen, we masked-off the area on the back of the screen where the mounting-plate was to be affixed. Using a roller, we applied two coats of contact cement (solvent-based) onto both the masked-off area of the screen, and on the entire 'smooth-side' of the pegboard, according to the directions on the can.

We peeled off the masking tape, and affixed the pegboard to the screen (with contact cement, you get exactly ONE chance at this!). We used a "J-roller", and then for good measure, a wood block and hammer (it wants 75 pounds per square inch for proper adhesion). This stuff adheres instantly, but doesn't achieve full strength for 7 days, so we then left it alone for a week- it'll be under some stress, so we let it rest. Here is the rear of the screen, with the pegboard mounting plate attached-


We've made a "picture frame", mitered at the corners, with an inside diameter of 48" x 64" (od= 55" x 71"), also made of the nominal 1x4 poplar. One of the guys is covering it with the black velvet we got. We'll also be using the black velvet on the inside of the frame. In both cases we'll be using 3M 77 multipurpose spray adhesive to hold the stuff on. Finally, everything will get a coat of 'Rust-O-Leum satin black applied with a foam brush.

I just 'dropped-in' the screen assembly to take these next photos--
Screen in 'flat' configuration-


Screen in 'torus' configuration-


We haven't "pinned-down" the corners yet, so these photos were all taken with the laminate just 'laying' on the frame. The curves are exactly what we were hoping. I'll get some more photos as we continue to assemble and test this thing!

-bob (UncleScurvy)
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post #2 of 8 Old 06-24-2007, 11:33 PM
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Great idea! Looking forward to seeing some pics of the finished product.

Garry
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post #3 of 8 Old 06-28-2007, 10:25 AM
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UncleScurvy

I read this thread (your thread) a couple days ago with every intent of posting to it and that somehow slipped my mind. First let me complement you on your construction so far and more importantly the nature of the screen you are building. It's always refreshing when something comes along totally different that what we normally see people do.
I think the concept and the design and build is solid and want to wish you good luck with the rest of the build when the glue sets up. Like prof55 I will also be waiting for final photos and also screen shots and how you feel it worked out.

I have thought about a few times putting a compound curve into a canvas screen and different methods to do that. Laziness and good PQ on my flat 4:3 has kept me from trying so far.

Keep it up and keep posting.


Bud

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post #4 of 8 Old 06-28-2007, 09:03 PM - Thread Starter
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Thanks for the kind words. Coming from you guys, its pretty flattering ! I'll be posting info pertinent to the laminate (WilsonArt Pearl Silver in 'crystal' finish, or in AVSspeak, "PS90"), hotspotting, and topcoating in the "New Laminate Test: Pearl Silver" thread, at http://www.avsforum.com/avs-vb/showt...&#post10872710 - in fact I'm uploading some new photos tonight.

And the completed screen and theatre, (with Before and After photos) will be shown here in this forum.

Tonight we managed to get the whole frame painted satin black, and the inside of the frame lined with the black velvet. It came out as nice as we'd hoped.

Now to figure out how to mount this monster-osity.... keeping in mind the golden rules- stable, adjustable, and inexpensive!

By the way, bud, it was you and the other folks in the 'black is beautiful' group that inspired us to get a 3' black runner carpet, and black curtains, (along with black velvet covering everything else that was exposed) in the 'viewing end' of our room.

We got cheap, semitransparent curtains, but that's OK, 'cause we covered those damned glass block walls with aluminum foil- keeps the sunlight out, and also keeps the secret world government from beaming radio waves into our heads----- whoops, that's a different forum ! With the foil keeping the light out, even the cheap curtains look, as one guy said "like Abraham Lincoln's funeral"- much thicker and luxuriant than they really are.
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post #5 of 8 Old 06-29-2007, 10:14 AM
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Thanks for the update, please keep us posted. I'm especially interested in seeing some screenshots comparing the flat/curved modes!

Garry
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post #6 of 8 Old 07-12-2007, 09:18 PM - Thread Starter
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Hi folks! just wanted to give everyone an update! Well, last week I dropped the screen, and shattered a corner . I made a patch, and its almost undectectable. Tonight, for the first time, we put the three subassemblies ('box frame', 'picture frame', and screen) together into a single finished unit. First, a shot of the patch, before filling the hairline:


Secondly, a shot of the rear of the assembled unit, I reinforced the corners with 'Gorilla' duct tape, just to help share the stress of bending. If you've had a tough time figuring out how this screen is put together, this photo should help


Lastly a shot of the screen propped up on a table, at close to its final location. You can get a feel for the curvature by looking at the shadow cast by the 'picture frame' at the top of the screen. Also, note the snappy aluminum foil covering the glass blocks, visible above the screen.


We need to do some fine-tuning on screen height, then we'll take it apart, topcoat the laminate, and reassemble the whole shebang. We'll need to reconverge the CRTs, and get everything lined up properly, but in a few weeks (we only get to work on this project thursday nites), I should have some photos of the completed installation!

-bob
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post #7 of 8 Old 08-03-2007, 04:57 AM
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Bob

We haven't heard from you in a couple weeks and I wanted to bump your thread and keep it out where people can see what you have going on. Plus nudge you to take some screen shots when you get it up and running.

This thread and your screen efforts have came to my mind quite a few times over the last few weeks. You are actually doing something that has seldom been tried in DIY and you based it around sound scientific principals. That in it self is quite an undertaking but then planning a method that anyone of limited skills could follow and reproduce your work is really great IMHO.

Even if your first attempt isn't perfect you are advancing the DIY effort a great deal here. The key to screens that will allow use in more normal rooms with higher degrees of ambient light could greatly be improved with this method. Paints and coatings will only go so far, and you are kicking this up a notch.

I hope to hear and see more of how things are going.


Bud

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post #8 of 8 Old 04-17-2008, 07:03 AM
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I thought I would bring this thread back up to the front for any newcomers to see and also see if the OP is still around and has any feedback on how things worked out.


Bud

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