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  • DIY air cleaner

    This is some shadetree engineering.

    I got interested in the air cleaners you can buy--I use a shop vac for DC so I miss a lot of dust. Well, after not long researching it, it occurred t me to DIY one of these.

    I had a big fan that I got free in a discarded server enclosure. It's a 10-inch, 110VAC fan made by Comair Rotron (big name in high-perormance fans). I looked up the model number online (it's a Caravel CLE2T2) and was pleasantly surprised to find that it's rated 450-550 CFM. That's comparable to the lower end Delta air cleaner.

    So I figured that furnace filters were the way to go. I built a (not-quite but almost square) box from 1/4" ply I got from the BORG cull bin. I sealed the corners up with aluminum tape I had previously grabbed at a salvage place. The most expensive part of the project was the high-end 3M furnace filter, and I used a $2 off coupon on that. So I have about 15 bucks into this system.



    I decided to use 20x25 furnace filters, so they're interchangeable with my furnace. I keep a small stock on hand anyway.



    There's a kind of shim at the bottom--I just shoved a scrap of 1/2" ply in to take up the slop. There are actually 2 filters in series--the inner one is the fancy-pants 3M one rated for umpty microns or whatever. The outer one is a cheapie for prefiltering. They are just stacked. Air is getting drawn in like crazy.



    And it's blowing out like crazy too. I put some ribbon on just to give a visual on how much this project blows.



    The corners are held together by cleats made of scraps of western red cedar (I love that pencil sharpener aroma when you cut it). The frame on the high-dollar filter is stiff enough that I can get away with only supporting it at the corners.


    It's not terribly loud either. Comair Rotron makes fans with notched leading edges on the blades. This thing just hums quietly.

    Thanks for looking.
    --Rob

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  • #2
    Cool project! It'll server you well, and for only $15!

    JR
    JR

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    • #3
      Very nice!
      John Hunter

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      • #4
        One of the recent woodworking mags (I think it's Wood, October issue) reviewed different commercial air cleaners and included a box fan with a furnace filter taped to it. One of the interesting conclusions they had, besides the box fan doing almost just as well as some of the commercial cleaners, is that the higher volumetric rates don't "clean" as well. Their supposition is that the higher rate kicks the dust around more, making the dust settle in areas away from the fan. They also concluded that you can have a high volume rate as long as the exhaust is diffused out (larger area) to decrease the speed.

        In any case, I promptly taped a furnace filter behind my box fan instead of dropping a couple hundred bucks on the Jet air cleaner I originally had my eyes on. I plugged it into a timer, and I've been pretty happy with it. When I get around to it, I'll build something like your box.

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        • #5
          One other angle I forgot to mention: my 5-year-old daughter helped build it. She got to use a power screwdriver to put the screws into the holes I had drilled for them. She thinks she's pretty big stuff now.
          --Rob

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          • #6
            Rob,
            I have a couple of such fans lying around, so i am very interested.

            How does this work anyway? I could not get a full picture in my mind - where does the filter go, and how do you hook it up to the tool you are using (the tablesaw, i see in your photos).

            (As you can tell, the 'newbie' below my name is well earned )

            - radhak
            It is the mark of an educated mind to be able to entertain a thought without accepting it.
            - Aristotle

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            • #7
              Great idea. good planning. Wonders can be done with fans. My first real spray booth was in a part of the shop that had four windows, one above the other about two feet, and the same about four feet away. They exhausted to the rear of the shop. Picked up four explosion proof fans at a flea market pretty cheap, and mounted them in the windows. Inside used a hospital sliding drape setup with long duck canvas material that finished 12" from a 16' ceiling which I set rows of small furnace filters across to trap dust from incoming air as a plenum. It worked fantastic. Eventually had to do the same thing outside, by making a horizontal hopper sort of funnel shaped out of CDX that had a verticle stack that filters were made to drop in on cletes. At the time spray booths for that size were very expensive, so ingenuity was a must.



              "I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

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              • #8
                Originally posted by radhak View Post
                Rob,
                How does this work anyway? I could not get a full picture in my mind - where does the filter go, and how do you hook it up to the tool you are using (the tablesaw, i see in your photos).
                I considered several possibiliities in designing this--this is just what I figured would be easiest and cheapest to build.

                So to answer your last question first, it doesn't hook to a tool. I use my shop vac for that. This is getting hung from the rafters in my shop (I have a 9 foot ceiling!). It just pulls dusty shop air through the furnace filters.

                In order to do that, the arrangement is just a box, where one end is two furnace filters stacked. The oppopsite end of the box holds the fan, which is set to blow air out of the box. Doing hte cutout for that fan was the trickiest part of the build--I don't have a jigsaw so I used a Dremel tool with a bit #561 (like a rotozip bit, a spiral cutter). I cut freehand to just inside the circle I made by tracing the fan on the end.

                To get the dimensions, you pick what size furnace filter you want to use. Measure it, becuase the size doesn't equal the actual dimensions as I found out. This gives you two dimensions of your box. The third you can pick. I couldn't see any advantage to bigger, so I cut it to fit the scrap ply I had on hand. Add a half inch to one dimension to account for the thickness of your ply, and cut one pair of opposing faces to the longer dimension. The end will be the size of your furnace filter. You can use the filter as a gauge block to set up your fence to avoid measuring.

                I clamped chunks of scrap 1x2 cedar to the inside faces of the top and bottom, so that the ends were 2" from the long edge, and the sides were 14" in from the short edge. Then I drilled and my daughter screwed them to the ply. With all four of those cleats on, made the right angles between box sides by clamping up the arrangement on the floor, then drill and screw.

                I then clamped and screwed cleats 1/4" in from the fan end, and screwed the end of the box holding the fan into those cleats. Tape up the corners, I don't see why duct tape would not work (I used aluminum for looks).

                You can get to the insides of the box since the filters just pressure fit in. I drilled a 3/8" hole to run the fan cord through, do whatever works for you, but tape it shut to avoid a leak. Strain relief on the cord isn't a bad idea either--I considered a strain relief busing from a computer PSU, but I skipped it and did the old knot trick.
                --Rob

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                • #9
                  And to think I spent all that hard earned money of mind for a commercial one. Looks like it should work like a champ. Good going!
                  May you die and go to heaven before the Devil knows you're dead. My Best, Mac

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