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Thread: getting heavy fog?

  1. #1
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    Default getting heavy fog?

    I looked up the professional ones to understand how they work and I don't see much than just an extra insulated container in the front where ice goes, and also a fan in the back helping the fog which apparently comes out from the left area on the back be blown to the front.
    (warning, images are watermarked)
    http://i.imgur.com/ck4SWsM.jpg
    http://i.imgur.com/84SuFGG.jpg
    http://i.imgur.com/LUNDsQt.jpg
    http://i.imgur.com/O8v7t13.jpg

    So I did an experiment by putting a polystyrene box almost the exact same size in front of my ordinary 1500W fogger, putting a fence 1/3rd from the bottom so ice wouldn't completely obstruct the fog's path (as in the real ones) and filled the whole box with ice.



    My experiment didn't end up well. if I lower the fence which holds the ice, the fog stays on the ground but doesn't blow far enough to cover a decent area (creates only like 3 sq m), if I put it higher, it blows far enough, but the fog slowly goes up (isn't chilled enough).
    I also tried getting rid of the fence and blowing the fog through the ice itself, but it obstructs too much and very little, 'more compressed' fog gets out and lays too low on the ground (few cm in height), rest of the fog gets trapped in the foam box in the gaps between the ice pieces.

    I also experimented with the exit hole location and size, doesn't seem to change anything.

    Does anyone whos done this himself have an idea what I'm missing? because I think right now to me my design is pretty similar to the commercial ones.

  2. #2
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    You need a longer path for the fog to travel through the ice so it will get colder (and thus hug the ground better) plus a fan to blow the fog out. Google "Fog Chiller" and look for the ones that have been built into a 55 gallon trash can. That's the style that you want. They use the flexible clothes-dryer hose to carry the fog and a 4" fan to blow it.

    Adam

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    Yeah, I've built similar things and experimented a bit with them too. I made almost like a round "cage" cylinder to go through the cooler so it was surrounded by the ice. The one mistake I made that I learned later is you need a bit of distance between the for machine and the inlet for whatever you built. I used an F100 fogger which has basically the same diameter output as the dryer hose buffo mentioned above. I clamped it directly to the fogger but, I later learned it requires a gap. I also tried an in line fan (like a duct fan) but it pushed too much air too fast and it didn't stay on the ground either.

    It was a bit of a frustrating messy experiment at the time and I never got the results I wanted. Yet. I've thought about going with a commercial unit but, the really good ones. I mean REALLY good ones.... are just shy of $6,000. They're awesome though! I played with some at PLASA a couple years ago.

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    Buy a cheap used Le Maitre Pea Souper and do it properly
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  5. #5
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    Another thing you can try is dry ice. The chillers that are designed around a trash can and 15 feet of dryer vent hose are meant to use regular water ice, but if you use dry ice you can get away with a straight run through a standard Styrofoam cooler using a rolled metal screen to form a cylinder for the fog to pass. Typically people use something like chicken wire wrapped in window screen to form the fog passage, but I've also seen 1/4 inch stiff wire mesh used. The colder temp of the dry ice allows for a shorter passage through the cooler.

    Adam

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    Quote Originally Posted by buffo View Post
    You need a longer path for the fog to travel through the ice so it will get colder (and thus hug the ground better) plus a fan to blow the fog out. Google "Fog Chiller" and look for the ones that have been built into a 55 gallon trash can. That's the style that you want. They use the flexible clothes-dryer hose to carry the fog and a 4" fan to blow it.
    I'm sure that design will work, Adam. I've seen videos of such builds. I think what's keeping me experimenting with the polystyrene box is that's how many ground foggers seem to do it, so I'm just curious what is the missing bit in my replication. I'm unable to leave something until I get it right even when I have alternative options which is a bad thing...

    Quote Originally Posted by Bradfo69 View Post
    Yeah, I've built similar things and experimented a bit with them too. I made almost like a round "cage" cylinder to go through the cooler so it was surrounded by the ice. The one mistake I made that I learned later is you need a bit of distance between the for machine and the inlet for whatever you built. I used an F100 fogger which has basically the same diameter output as the dryer hose buffo mentioned above. I clamped it directly to the fogger but, I later learned it requires a gap.
    I think your fogger was just shooting fog farther than mine and that's one way to slow it down. Mine doesn't shoot that far though maybe cause it's chinese. I tried cutting a hole in the box from the side so the fogger would shoot to the side of the back of the box not the front where it comes out, but it slowed the fog flow too much. Same with putting an ostacle in the middle of the box. I might be wrong in this but my theory is the fog when not flowing fast enough cools too much and compresses, so less fog appears to be coming out too. Could explain why they put an extra blowing fan in the ice chilled type fogger I posted.

    EDIT: By the way, what even is this? https://i.imgur.com/O8v7t13.jpg
    I would expect an oedinary wire mesh.
    Last edited by blue; 04-28-2015 at 09:58.

  7. #7
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    Quote Originally Posted by blue View Post
    I think what's keeping me experimenting with the polystyrene box is that's how many ground foggers seem to do it, so I'm just curious what is the missing bit in my replication.

    Dry ice. Dry ice is what is missing. (At least for a Styrofoam cooler based chiller.) It's hard to get enough cooling using water ice, unless you have a longer path.

    Another thing that probably helps the commercial units is they've modeled everything so the fog output is exactly slow enough to work with the cooling chamber they've built. Then too, it appears that they have louvers built in to that ice shelf, so it's possible that the fog passes closer to the ice and/or contacts it for longer periods. Plus the unit likely only produces true ground-hugging fog when used in short bursts.

    Adam

  8. #8
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    I built one last year for Halloween.
    I used a large Styrofoam cooler. The type the ship sea food or frozen steaks in. Then I bought 3" flexible aluminum duct. It's almost smooth. The Mylar type used for dryers isn't going to transfer the heat from the fog good enough and has too many ridges slowing down the flow. I then twisted the entire 6 ft section of duct around the inside of the cooler. Seal the duct to the holes you cut in the cooler so it is water tight. Filler the cooler with ice and then I add water to help with the heat transfer. It lasted all night for the trick-or-treaters. My fogger was set for a few second burst once a minute. This was enough to cover my front yard. Keep in mind outside air temperature and wind will affect the fog a lot.

  9. #9
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    A side question about dry ice. Isn't it producing fog itself in some other types of fog machines? Is it just used as a better chiller material than ice for this kind of machine or am I going to produce the less safe fog mixed with the glycol fog by using it?

  10. #10
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    Re: Dry Ice

    This is why I suggested a proper dry ice kettle like the Pea Souper. Yes, its the dry ice itself which creates the fog when lowered into the water. for large amounts of heavy fog you need to heat the water to stop the dry ice cooling it too much. But essentially its just a way of lowering the dry ice into the water in a controlled manner and an output spout to direct it.
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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