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PVC and Fog

Discussion in 'Special Effects' started by simchapup, Mar 6, 2007.

  1. simchapup

    simchapup Lighting Technician

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    I am doing beauty and the beast in a couple months i was wondering if i took pvc and drilled holes in it and placed it on the bottom of the stage if it would create a fog curtain
     
  2. TupeloTechie

    TupeloTechie Active Member

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    the pvc would have to be enleast 4"
     
  3. Footer

    Footer Senior Team Senior Team Premium Member

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    Also, you will have to force the fog through at a high rate of speed with compressed air or something of that sort. Odds are you will not get the effect you want, you might want to go with a Co2 alternative.
     
  4. Van

    Van CBMod CB Mods Premium Member

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    I've done this effect before, you can make it work. You will need a 4" Pvc pipe. Do not try to drill your own holes simply go purchase "perforated 4"PVc" this is available at any home store, and is primarily used as lateral lines on septic tanks and drain tubes for french drains.
    Ok, suspend you pipe over the area in question, Attach a chiller module, and a fogger as spec'd in previous posts on here. Viola. You are going to want some kind of fan or impeller inline with this install. If you want the fog to rise from the bottom of the stage it's not going to work quite as well. and you'll want to use a longer hang-time fog.
     
    StradivariusBone likes this.
  5. BillESC

    BillESC Well-Known Member Premium Member

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    Van is correct about purchasing the 4" PVC with the holes already in it. We built a fog curtain using the same pipe but also installed 1" PVC nipples with epoxy into the holes. The nipples directed the fog straight down and also help creat back pressure. For fog we used a Fog-it Dry ice fog machine.
     
  6. jmabray

    jmabray Active Member

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    Also - If you are using a fog machine, you will want to not put the fog machine right up against the PVC pipe. If you back it off about 2 - 3 inches - the fog will still go in the pipe, and you will get a much better volume of fog. I don't know the physics behind this exactly, but when you allow the fog to interact with the cooler air, it just works better.

    Jeff
     
  7. Van

    Van CBMod CB Mods Premium Member

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    Anytime you use a fog machine and couple it to hose, pipe, or any other ducting material you must include space between the body of the fog machine and and the ductwork. Rosco manufactures a device expressly for this purpose. It allows the hot fog to combine with cooler air which causes a better encapsulation of liquid particles in the air. It also creates what is known as the "venturi effect" in which the fog rushing in pulls an equal volume of air into the pipe. This increases the the over all fog effect and leads to much happiness.
     
  8. chrizEHS

    chrizEHS Member

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    I know its seems basic but someone nearly burned our auditorium down a few years ago by doing this, most professional smoke machines will have a venting gap and then another ring. Avioid the impulse to gaff tape it up to stop the leakage. Some leakge is needed to draw air into the system to force the fog out. Always check it during tech to make sure nothing gets too hot. Good luck smoke is tricky to work with.


    CJ
     
  9. len

    len Well-Known Member

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  10. Adam Brock

    Adam Brock New Member

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    Hello everybody I wonder if anyone could be any help. (I am new to forums so unsure if this is the right place to ask)

    I use a smoke machine which is connected to a PVC pipe which works fantastically but I have issues with the smoke fluid (From what I can gather) condensating and dripping out of the end of the PVC pipe

    Have any of you had this issue before? And what could stop the smoke from dripping?
     
  11. Les

    Les Well-Known Member

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    Do you have a ~2" air gap between the fog machine nozzle and the pipe? If not, try that. Otherwise, maybe something to catch the fluid at the other end. Fog is a particulate and it will return to its liquid state no matter what; it's just that normally, it has more surface area (an entire room) so it goes un-noticed.
     
  12. Mike

    Mike Member

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    I built a 3 1/2' wide ufo. I want to place a fog machine inside and vent it to three or four ports (space ship exhaust) venting it from the bottom of the ship. It will have 3 legs and be about 5' up in the air. I have a light mounted underneath so it will also give the light a tighter "beaming" effect (I hope). Just not sure how to make the fog go around the tubing and make the 90 out the bottom. Help
     
  13. Van

    Van CBMod CB Mods Premium Member

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    The most difficult issue with any application like you are proposing is heat dissipation. You can put a fogger inside of anything. Unfortunately it will overheat and burn itself out without proper ventilation. Moving fog through any small diameter tube is also difficult as it tends to condense on the walls then trickle out as a slippery-wet discharge. I think in some ways a CO2 or N2 setup might be a better solution, but expense and concealment are going to be an issue.
     
  14. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @Mike A few thoughts for you worth every penny you've paid. (Thus they may not be worth much.)
    CO2 has the advantage of being cold and thus wants to sink until it warms up. One of its disadvantages is cost and sublimation, changing state directly from a solid to gas without first changing to a liquid.
    Nitrogen is costly and is usually noisy.
    Here's possibly a workable option for you.
    Consider placing your fogger where heat won't pose a problem, possibly NOT within your UFO, possibly behind and / or below with as little additional hose as required.
    If you can organize a muffin fan or two to create airflow in your pipe, through any T's, bends and any / all fittings along the way to your exit points then you merely need to inject fog into the already established air stream when, and in the quantity, desired. You may find an assortment of suitable fans at an electronics wholesaler, a computer parts supplier or from a discarded computer. Most muffin fans are near silent in operation and most are designed to operate 24 / 7 / 365 thus service life shouldn't pose a problem. I'm envisioning 4" diameter dryer hose with 4" or 4-11/16" fans. If you're using an oil-based fogger you'll NEVER need to lubricate your fan. It'll likely get grungy but it probably won't mind. If you look around, you'll likely find suitably sized fans in AC or DC and in voltages from approximately 6 to 240 volts. It goes without saying, if a muffin fan is sucking rather than blowing, you merely need to flop it over to suit your needs. (A lot of things in life are like that but more than enough said.)
    Toodleoo!
    Ron Hebbard
     
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  15. Les

    Les Well-Known Member

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    I think I ended up in the wrong forum again.
     
  16. Mike

    Mike Member

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    I am thinking about removing the dome light mounted underneath and going with a smaller more compact green led setup. With the dome gone the fog will have a 7" to 8" inch egress. Possibly taking it a step further and lining the inside of the center chamber (where the fog enters) with ice packs. Maybe even a step further and use the extra dense fog juice. This is the first exhaust venting ufo I've built. I'll try this route and see how it does. I'll post a vid once I have a decent configuration.
     
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  17. Mike

    Mike Member

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    Alright, I used a 4" pvc elbow. Packed it full gel ice packs. I think it was too short a run. Fog was a little thicker, came out better (smoother rounded turn helped) still rose just as fast. Installed a high rpm pc fan, didn't make much difference. Apparently physics don't like being defied. I think I'm going to ditch the fog idea in the ship for this year. I'm going to build a chiller and blanket setup for the graveyard. Maybe next year I'll go with a nitrous or co2 setup. Halloween budget is blown for this year. At least my ufo is animated and very well lit up.
     
    RonHebbard likes this.

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