Wrinkles in a rollup? - AVS Forum
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post #1 of 8 Old 12-12-2001, 06:51 AM - Thread Starter
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I've been lurking around these forums for a while. I'm in the process of designing and building some custom elements for my own theatre. One of them is a rollup/down screen. As much as I'd like a fixed screen, I have no choice due to room layout and use.

I've seen mention of wrinkles being a problem for rollup screens. I guess I don't understand why. If the material is rolled up on a smooth drum/cyclinder while tension is evenly applied across the lower edge of the screen, how can wrinkles happen?

I'm attemping to build a motorized screen, about 80x60. The design calls for a micro-controller (controlled by HTPC via serial port) to change aspect ratios of the screen by rolling it up or down. The screen will have fixed masking on the sides and lower edge. A masking panel on top will be fixed to the screen housing (not the screen) so the screen will move up and down behind it, hopefully yielding different aspect ratios depending on screen height.

Back to my concerns about wrinkling. I plan on fixing a solid steel rod across the bottom edge of the screen to tension it. I expect the rod to weigh 5-10 lbs. Is this enough to prevent wrinkles?

Is the wrinkle problem simply caused by manually retracted screens where tension exists only in the middle of the lower edge where someone is holding the screen as it retracts? Am I missing something?

I'd like this project to work. If I have a basic design defect, I'd like to know now rather than later.

BTW, these forums are great! I hardly work anymore; I sit and read all day. Thanks for the insight.
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post #2 of 8 Old 12-13-2001, 05:53 AM - Thread Starter
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No replies yet? Did I stump everyone?
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post #3 of 8 Old 12-13-2001, 01:27 PM
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I have a Dalite Theater roll up (not down). I have had no wrinkle problems yet. The edges are curled-but I still get 62" of flat surface to use.

Gain at 2.2 is a bit high.

Joel
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post #4 of 8 Old 12-16-2001, 09:40 AM
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Side tension is just as critical as downward tension. This is why
tab tensioning is utilized on the better quality electric screens. Before you embark on your do-it-yourself project, it might be useful to visit a Stewart dealer and examin how they handle this aspect.

I'm curious, however: Are you doing this because you want to save money, or for the challenge of doing it?
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post #5 of 8 Old 12-17-2001, 06:22 AM - Thread Starter
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Pete,

I'm doing it for both reasons, I guess. I enjoy designing and building these kinds of things and I'd like to save a bunch of money. I'm already in the process of building a motorized lift system to lower the PJ from my 15' ceiling to about 8'. I know, the room isn't really ideal for home theatre, but someday I plan on building new. Meanwhile this is something to do. BTW, SVS Lifts sells such a lift for about $5000. I'm building mine for about $300 which includes custom machined parts, custom electronics, custom carpentry, etc. I do all the work myself. The cost difference allows me to buy the projector! I plan on building the screen for about $200 (compared to $1500 to $2000 to buy). That price includes the integrated masking for adjustable aspect ratios. Phase 3 is the HTPC.

I'll have to find a Stewart dealer local and check out the side tensioning. This is the first I've heard of such a thing. Could you describe what it is? That will give me something to chew on while my fingers are doing the walking. Thanks for the input.

-Tab
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post #6 of 8 Old 12-18-2001, 12:03 PM
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Tab-tensioning is essentially a pair of wires that run vertically along both sides of the screen and are attached to the screen via tabs. As the screen becomes fully deployed, the wires tighten against the tabs, thereby putting horizontal tension on the screen material. The black borders are cut with a slight bow shape so that the wires pull against the tabs as the weight of the screen and lower batton pull the wires outward. It's hard to describe, but if and when you see it, you'll understand what I'm trying to say.
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post #7 of 8 Old 12-18-2001, 12:10 PM - Thread Starter
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Pete.

Thanks for the description. I can sort of visualized it. I guess I'm not sure if this would work for me since I'll be adjusting the amount of screen rolled down to adjust the aspect ratio. It sounds like the tab-tensioning is only effective when the screen is fully opened. But maybe I'm wrong. I'll have to see if I can find a local dealer. Thanks again.

-Tab (no relation to the tensioning mechanism)
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post #8 of 8 Old 12-18-2001, 08:53 PM
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I am currently using a Da-Lite 16:9, 1.3gain, 93" Tab tension screen which I have had for 2.5 years. I have not experienced any wrinkles whats so ever.
The tab tension is the main reason for wrinkle free surface.
Good luck on your project.
Bill d.

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