Torus and CRT - A Torrific Combo - Part 1 - Page 4 - AVS Forum
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post #91 of 276 Old 03-09-2005, 03:33 PM
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Quote:
Originally posted by MC Maniac
Guess it would depend if the roll up Silverstar material is bonded together with a backing material to add more rigidity as a pull down..

It's worth looking into I guess. Especially if it is comparable in price. I would bet it is bonded to a backing material as wrinkles and high gain are a bad mix!

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post #92 of 276 Old 03-09-2005, 03:55 PM
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Marshall F,
I don't think you will have any difficulties with a PG. I can't imagine why a different aspect ratio would look any different, but I am sure a Torus owner can give a better response.

James and John,
According to Tryg's shootout, the Silverstar has a higher gain than the Pearl. On the price, I can't find any mention of it on the forum. I know AVS sells it. Vutec is located in Pompano Beach. I am planning to go see the Hero in the next week or so. I will see if they will let me drop in and pick up some samples. Or maybe I should rummage around in the trash and see if they threw one out.:D

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post #93 of 276 Old 03-09-2005, 04:01 PM
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Ericglo,
The 3.5" and the 7" are the measured drop of each side. So if you were to extend a string on a horizontal side (106" side) from corner to corner, and measure the maxmum depth of the curve from the string it would be 7". Same for the vertical side, string corner to corner and the depth of the curve is 3.5". Those numbers aren't the radius, which is constant. And if you were to extend a string from the upper right corner to the lower left corner, you would measure 10.5" depth to the center of the screen. When I built the first one I achieved that depth using a constant radius, I then essentially copied the radius to the vertical sides. Now I just trace from my original screen sides as a template. Make sense??
Where is Peter??? This is his job....lol

Stepen,
I'm not sure how the fan can spin faster than normal. In fact, they are spinning slower than normal as I use 12VDC fans that are operating between 4.5 and and 6 volts. The fan is constantly outputting air from the screen's box. It doesn't get hot and mine has been on for 24/7 for two years (need to check my power consumption).
What I was saying about the quiet fan I tried is that I had to turn it faster to achieve the results (depth in the center) thereby negating it's quieter operation. In fact it was louder than a normal radio shack fan. There are probibly better ones out there.
Oh I thought about a micro switch or an IR system that constantly modulates the fan so that the fan is always pulling the screen to the exact depth. But then I thought about those fancy systems you could put in your garage to tell you exactly when to stop your car and I thought about a tennis ball attached to a string that touches the windshiels and decided that the tennis ball system was more reliable......lol

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post #94 of 276 Old 03-10-2005, 09:13 AM
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Terry,
I am trying to visualize it. I guess I should just draw it on a piece of paper. Maybe this would have been easier if I would have went to Ga Tech instead of Ga State.:)

Peter is 100% in love with Rear Pro. Check out his threads in the over 20 forum. Unto each their own.:D

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post #95 of 276 Old 03-10-2005, 11:18 AM
 
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Terry, if you operated it at 12 volts, it could have problems, but not at 6 volts...
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post #96 of 276 Old 03-10-2005, 11:29 AM
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Stepan,
The load on the fan actually decreases because it is doing less work, therefore it will actually last longer. An example is your conventional home vacuum cleaner. Put your hand over the hose and the fan will speed up. It speeds up because it is not doing any work! If you put an ammmeter on the power lead, you would see that the current draw decreases.

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post #97 of 276 Old 03-10-2005, 12:39 PM
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Ericglo,
Draw a curve on a piece of paper. Now draw a straight line beyween the ends of the curve. The "drop" or depth I talk about is the distance from the straight line to the wax part of the curve.

I also like rear projection an awful lot and am considering this in my next house. BUT, if I can get blending to work properly on a HTPC, then I will have two G90's side by side blended to create a 2.35 screen about 145" wide. In that case a rear projection system would be VERY cool.

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post #98 of 276 Old 03-10-2005, 12:52 PM
 
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Oh, i feel so stupid...
NO! That is just because i do not have ampermeter...
The only measuring equipment I have is old russian oscilloscope...
I know now to measure current with voltmeter/oscilloscope...
I am actually VERY CLEVER, you know? :)

The friction in the bearing because the higher turns will be higher? So it will not last longer because of higher mechanical stress and wear... it seems that fans suffer much more from mechanical issues...
OK?
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post #99 of 276 Old 03-10-2005, 01:17 PM
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So, any tips on how to effectively attach the material to the frame?

Terry, what would you say are the most common size and ratio that you make? If I'm able to safely maximize raster on an NEC 6100, what's the maximum screen size you'd recomend in a light controlled room. I guess the material would be Vutec pearlescent, or whatever Eric can find for us in the dumpster.

Thanks,

Marshall

Back to the vacuum cleaner and suctiuoning fan behind the screen -- doesn't the phsical load placed on the motor and the lack of airflow lead to motor's demise regardless of voltage?

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post #100 of 276 Old 03-10-2005, 01:40 PM
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Marshal,
I ONLY make one size....106" x 60"
I use staples to attach the screen to the edge of the 1x's. I overlap 3 times. This is the hardest part that took forever on the first one I built. Lots of removing, pulling and restapling to get the creases out along the edges. Now I can do it in about an hour. Get an electric stapler......and lots of stables.

There is enough area and leakage I guess that it doesn't put any strain on the fan turning at these slow speeds.

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post #101 of 276 Old 03-10-2005, 02:02 PM
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Stepan - There are two factors in bearing wear; speed and load. Whatever the speed is, it is necessary to maintain a proper negative static pressure with respect to the viewing side. The load is minimal as the fan is not really doing any work.
Marshall - When the fan is first turned on, it has some work to do for a few seconds. It has to remove enough air from behind the screen to create a differential pressure enough to move the screen to the proper location. After that is done (probably a matter of seconds or so) it only has to move air that leaks!
That is why most any little fan will do the job. Actually, the selection of a fan should be made on its static pressure ratings from its fan curve. It doesn't take much as Mother Nature's air pressure is pushing the screen for us.
Before the advent of large variable speed AC motors, all fresh air fan systems in commercial buildings had "Vortex" dampers on the low pressure side of the fan. The dampers were used to "starve" the motor of air until the electrical load to the motor was within its rating.
This discussion is probably off subject, but in this usage, a good little fan like the ones discussed will probably last well over 100,000 hrs. That's good enough for me!

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post #102 of 276 Old 03-10-2005, 02:05 PM
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How tight do you pull the fabric, Terry? On a flat screen you pull it as tight as you can, but on this beastie I dunno what you're supposed to do.
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post #103 of 276 Old 03-10-2005, 02:09 PM
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Thanks, Terry. Without giving away any trade secrets... Is the material taught against the highest pints of the frame when you begin? Therefore it has to stretch out to be attached to the lower portion of the curve.

"overlap 3 times" you mean over three times of the 1 X?

Anyone else is free to jump in, I hate to ask Terry too much as this is a product he makes and sells.


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post #104 of 276 Old 03-10-2005, 05:49 PM
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Marshal,
It's OK. I only do these for local customers. Wish I could figure out a way to ship en in maybe a kit form....lol
I pull the fabrick pretty tight. This Vutek material has a lot of stretch. I usually start with the top two corners pulling tight. Not super tight but tight. then I'll out a few stales in the middle, Then a few staples between the middle and each edge. Then I'll look at pulling the lower corner into shape. Then the opposite corner. Then some in the middle of the vertical sides, and so on. Like I said this is the hard part. You will get to the end and there will be some wrinkles that extend into the screen that just won't pull out. and you have to work your way around removing staples and putting more back in till you get all the wrinkles pretty much out on the edges.
"Overlap"....hmmmm, I pull the material to the edge, hold with my finger, fold back about 1.2", then hold again and fold bact to the outside of the screen and put a staple in. That way more material to grab when stretching.

Hope this helps.

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post #105 of 276 Old 03-10-2005, 06:13 PM
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I think you could do it in a kit form, actually. That is supply the curved sections, screen material, fan box, fan, and hardware. I'd have a cabinet maker make a bunch and have them pre-drilled and peraps have recessed bosses for attachment.

Maybe include everything except the large back piece which anyone could have cut to size at the homer.

Cutting the curves and constructing the fanbox would (I think) be daunting to some, so this would make it easier. I think it would ship UPS oversized. That of course would be the key.

Thanks for the tips, I think I will try one. Eric, I hope you come up with enough material for everyone!

Marshall






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post #106 of 276 Old 03-10-2005, 06:52 PM
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I've only done one torus, but a gaggle of canvases, silk screen frames, pj screens. When stretching material I typically start at the center points of the sides and staple an area on the center of each brace. Work out away from the center toward the corners, pulling tight and pulling toward the corner. If you get a wrinkle, stop and restaple that area as you didn't pull it enough toward the corner. With a torus and pearlbrite, the material has to be smoothed and stretched toward the corner to help it conform to the curves. If you go slow and coax the material into shape you should be able to do it without restapling too much, although it is tricky. As you get to the corners the material should naturally be pulled tight, not completely but it will naturally fold over the edges. You will get it pretty tight but pearlbrite is heavy and stretchy so no matter how much you pull it's going to sag or flap a little unlike canvas or blackout material.
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post #107 of 276 Old 03-10-2005, 07:08 PM
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I start at the middle as well when I staple. I would get the four middles tight then work toward the corners bit by bit on all sides at once. At least that's what works for me!

I'm not sure I believe folding and stapling would make a difference. Once you fully staple the whole thing there would be very little pull on any one staple.

Of course, I've only built one Torus so far so take my advise accordingly.

Torus number two will soon be underway...

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post #108 of 276 Old 03-10-2005, 09:27 PM
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I may have to try the center stapling routine.......nah, I'm pretty set in the way I do these and for me it works......lol

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post #109 of 276 Old 03-10-2005, 10:10 PM
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when i built mine, i used about 2 rolls of 1.5" painters tape. i just kept gong around till there were no wrinkles. i then stapled it.
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post #110 of 276 Old 03-10-2005, 10:24 PM
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Terry, definately have a go at starting with the centres - it has worked for centuries for getting large canvases onto frames, you never have to remove any staples that way.
Thanks to everyone so far for sharing your techniques, I'm currently trying to find a rustoleum equivalent in Australia. Any idea what type of fabric would paint up OK with rustoleum - should I use a PVC perhaps?

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post #111 of 276 Old 03-12-2005, 04:15 AM - Thread Starter
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Quote:
Originally posted by Ericglo


Has anyone thought of using Silverstar fabric in a Torus box?

I emailed Jason about the possibility..

Vutec says they won't sell it that way - it's flexible but too fragile and wouldn't hold up on a Torus..

Imagine it could work, if they bonded it to a vinyl material like the Pearlbrite is..

John
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post #112 of 276 Old 03-12-2005, 09:28 AM
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Has anyone ever had striping problems with the Vutec 3.1 material? I had heard about problems with the M2500 material, but never the 3.1. I thought perhaps I overstretched mine, although I was I was excedingly careful. It is not noticible just looking at the screen with the pj off in ambiant light...only on full white screens.
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post #113 of 276 Old 03-12-2005, 04:04 PM
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OK this may be dumb question but here goes.

Is their any benifit to making a torus with a 1.0 or 1.3 gain screen?

reason for this is I picked some screens out of the trash and they happen to be that gain. (all the torus's I've seen in movie theaters seem to be low gain or unity screens anyway.)
Will it improve light fall off with CRT?
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post #114 of 276 Old 03-12-2005, 04:44 PM
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Quote:
Originally posted by virusc
OK this may be dumb question but here goes.

Is their any benifit to making a torus with a 1.0 or 1.3 gain screen?

reason for this is I picked some screens out of the trash and they happen to be that gain. (all the torus's I've seen in movie theaters seem to be low gain or unity screens anyway.)
Will it improve light fall off with CRT?
This isn't a good idea.

A low gain screen material will have a very wide viewing cone. This is great until you have a curved screen. The light reflected from the middle will actually hit the edges (and visa-versa) and wash out the image.

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post #115 of 276 Old 03-13-2005, 10:33 PM
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James,
I understand the reasoning behind having a high gain screen, but if Virusc is correct then maybe it can work. It would be useful in certain situations.

McManiac,
Maybe we should enlighten them to the potential customer base with DIY Torus with screen material. I know this is a topic for the DIY screen forum, but I work with coatings that will stick to vinyl without microfracturing. I know some of it has been covered, but I just need to find some good high gain pigments. I have some ideas.
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post #116 of 276 Old 03-14-2005, 02:31 AM
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No real benefits to a 1.3 gain screen, it will wash out the image - you want something as retroreflective as possible.
There was a guy here selling a spray on retroreflective clear paint or something. Optibright or opticoat or some damn thing. Might also be worth a look.

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post #117 of 276 Old 03-14-2005, 03:35 AM - Thread Starter
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Quote:
Originally posted by Ericglo

McManiac,
Maybe we should enlighten them to the potential customer base with DIY Torus with screen material. I know this is a topic for the DIY screen forum, but I work with coatings that will stick to vinyl without microfracturing. I know some of it has been covered, but I just need to find some good high gain pigments. I have some ideas.
Ericglo
I put a call into Vutec and will be pushing them on the opportunity here..

I've started the redoing of my ceiling and am doing it so that I can easily move the CRT back to have a 2.35 ratio screen which I would try with a Silverstar Torus..

Good luck with your experiments - they definately are worth pursuing..

John
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post #118 of 276 Old 03-14-2005, 02:43 PM
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As I posted earlier I had issues with the bow control. I'm wondering if my curve may have been too deep. I only have room to about an 84" wide screen (when doing a curved screen) but I mad the curve depth 7.5". I also tried only doing the horizontal curve instead of a compund curved screen. Not only did I run out of bow but the screen had some serious hotspotting. Enough that even my wife noticed.

My question is did I make the horizontal curve too deep? How much does the vertical curve affect the hotspotting? I'm willing to remove the fabric and try again but from what I saw there would have to be a dramatic decrease in hotspotting for this to be an acceptable solution.

Gary
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post #119 of 276 Old 03-14-2005, 06:02 PM
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Getting the curve right has everything to do with hotspotting, too shallow and you see hotspot, too deep and you have geometry issues and less viewing cone.

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post #120 of 276 Old 03-14-2005, 07:26 PM
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I tried a retro reflective material called puck board.
It has a very high degree of finish like laminate and it's quite flexable for 1/4" material. I could not get rid of the lense face's reflecting back.
I guess tried and true veutec is next.
Gary
p.s. I just got my NeuNeo.
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