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Crazy Rear Projection Screen

Discussion in 'Special Effects' started by DarSax, Mar 16, 2007.

  1. DarSax

    DarSax Active Member

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    So it seems I'm in quite a pickle; I need to move the projection screen I was talking about in the "high school projection thread" more towards the audience so I can get a longer throw from the projector.


    The set is basically like an open-topped box with one of the sides removed. It has three walls |__| and either a roof or no roof, depending on what I choose. It's on a 4' tall platform.

    I need a way to have a projection screen either drop from the ceiling or come up from the floor, and then be able to retract it, then put it up again, then retract, etc. The closest thing I can think of is something like a garage door....or something.

    Could I do it with a pulley system? This might work out to be quite the problem :eek:
     
  2. Van

    Van CBMod CB Mods Premium Member

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    I'm assuming you can't just fly it ?
    If that's the case what about build a roll drop out of RP material ? you can order the material easily enough and check out the thread on here, I think it was something about drop boxes, anyway i posted a really easy to build roll drop setup.
     
  3. Footer

    Footer Senior Team Senior Team Premium Member

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    Roll drop would be the way to go, doing a "garage door" setup I don't thing would work the way you want it to. Its safe to assume you don't have a fly system?
     
  4. SHARYNF

    SHARYNF Well-Known Member

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    Not sure how you can make this work, must rear projection skins need to be stretched out in on a frame to work, there is some material that you can hang, but it takes over a day for the wrinkles to drop out, and it is no where near as good a rear projection surface.

    SO maybe one of the old solid one piece garage door type of systems might work, have the skin/surface for the rear projection stretched out on the frame, then have like on the solid garage door, have a combination of a swivel on the side so that it can tilt and then get raised up in a track so that it swings up and out of the way. Not sure if I have ever seen this type of garage door work eith an auto open system
    Sharyn
     
  5. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    It's Olio/Oleo time!! (There seems to be a disagreement in spelling from my quick internet search... and you won't find much either) That's what they called a Roll Drop back in the good old days. I built one of these about 5 years ago. It was really fun to work with because this is like 1000 year old theater technology... but it works perfectly. For my purpose I had a 16 foot scrim I needed to roll up and down with no fly space. You hang the top from a batten. The bottom needs a THICK pipe to roll around. I used two 10 foot sections of heavy cardboard carpet tube with an 8 foot plywood spline (a very long "+" shaped piece of wood) screwed in the middle to make it one very solid 20 foot tube. You need at least 2 feet of extra tube on both ends. I've also heard of using PVC drain pipe or even aluminum. Use what you can find and afford as long as it's rigid and about 4-6 inches in diameter. It uses a lot more rope than you think it will so buy two large lengths and you won't have to worry about it. The bottom of the drop must be attached and fixed to the bottom pipe, if the bottom pipe is just in a pocket it will just spin in place. Other than that you just need a couple of pulleys. The trick to the whole thing is that the drop is rolled one way around the bottom of the pipe while the rope rolls the other way. This way, as one is rolled up the other one releases and your drop goes up and down.

    Below is my quick Microsoft Paint drawing of how it works. See the backstage handbook for a little better drawing.

    EDIT... and the weight of the bottom pipe will stretch that fabric tight like Sharyn is worried about.
     

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  6. SHARYNF

    SHARYNF Well-Known Member

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    IMO this works fine with scrim type material but will NOT work for a rear projection surface, these are basically stretchable material that needs to be Under tension on all sides, not just top and bottom, if you just roll and un roll the sides are going to not stretch out the surface and you will get lots of distortion.
    If distance is the only problem they there are a few other options, on is to use a mirror surface to double up the distance, Mylar film works quite well.

    Here is a link to some mylar,
    http://www.jonsplantfactory.com/qs/category/63/4187/0/0

    An other option if you are into some dumpster diving is to find a rear projection tv like the big toshibas that are out of date and not very good image quality BUT have a top quality mirror in them that is used to double back the image from the the three crts to the screen.

    Sharyn
     
  7. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Have only used rear projection material once long ago under ideal situation so I've got to give Sharyn the nod of expertise on if the Olio won't stretch it properly.

    The mirror out of a rear projection TV is a great idea. I bet you can easily find one for free just call around to the small independent TV repair places.
     
  8. 6ftstudios

    6ftstudios Member

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    Whenever I've used a rear projection screen we've always traveled with a mirror that minimized the nessesary throw distance to 4'. It was fun to try to adjust it everyday (being in a new venue everyday) but it worked. Also, many screen/projector suppliers offer a pre-made mirror solution.

    Best of luck.

    - D
     
  9. DarSax

    DarSax Active Member

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    Waitwait...mirror? I mean, using a mirror to redirect the beam seems simple enough, but any caveats about using one? Is it really as simple as
    /----->
    ^
    |
    |
    [xx]
     
  10. Van

    Van CBMod CB Mods Premium Member

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    Yes it has to be a really,really, good mirror. It's size is going to vary a lot and get quite big quite quick .
     
  11. BillESC

    BillESC Well-Known Member Premium Member

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    How about having your RP screen be the roof of your set. When needed it pivots down into projection position. When done, it simply swings back up into the roof position.
     
  12. DarSax

    DarSax Active Member

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    The opposite (of sorts) is more likely--it'll be hanging off of the back, and then will fall down/be pulled back up. I'lll probably have to work a way to drop some pulleys off of a batten to get it pulled up/down.

    Thanks for all the tips btw, I hopefully will not need to use a mirror because we modified the set a little bit.
     
  13. 6ftstudios

    6ftstudios Member

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    Typically we set up the projector right behind the screen projecting to the mirror up stage and the mirror then reflected the picture onto the screen.
     

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