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Thread: Building a Flue Pan

  1. #1
    Join Date
    Jan 2008
    Location
    Frankford, Ontario
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    Default Building a Flue Pan

    In a previous thread http://www.mapletrader.com/community...ead.php?t=4532 I posted my home made brake for bending flues. Now will post the process I followed to make a flue pan. It is not done yet - so this will be a work in process.


    Design.
    I bought a 4x8 sheet of 20 gauge mill finish stainless for my pan, and I wanted to use it to the best advantage. I had a 9" strip sheared off the long edge, leaving me with a 39"x96" and a 9"x96" piece.

    The pan is 39" long x 19" wide, with 9" sides and 6@5" flues, 2 in each of 3 sections.

    I carefully marked both the top and the bottom side of the sheet at every bend location - some marks are on the top, others on the underside - along both edges of the sheet. I have a sketch somewhere that I will scan later and attach that shows the design.

    First - Pictures of the brake (again)
    The brake is primarily made of 3x3 angle with a 3" x 1 1/2" channel for the bed so that the flue can slide over it for the next bend. I have 2 hold down bars - one a 3x3 angle which permits overbending, and the other a 3/4"x 2" bar to fit down in the flues. The first shows on 2 of the pictures, the second on the last. Since this picture I modified the 3/4" bar to add a strip of 1"x 1/4" flat bar offset towards the front to provide some stiffening and allow a slight amount of overbend. It helped but was not enough - see below for the solution.
    Attached Images Attached Images
    Last edited by Big_Eddy; 04-30-2009 at 02:23 PM.

  2. #2
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    After a lot of bending and a lot of flipping of the sheet, this is the end result. (Sorry about the bad lighting - only picture I have of this stage)

    Note how the previous flue is now over the 3" channel so that we can bend up for the flat. Then we lift the tail up and bend the next down leg. Flip the sheet, bend the bottom flat, then again lift up the tail to bend the up leg. We had to do it out in the driveway, not enough clearance in the garage.

    We had absolutely no problem bending 39" of 20 gauge stainless in this brake. It did not take a lot of effort, and there was little if any flexing of the brake. I did add a stiffening triangle to the front member prior to starting, but I'm not sure it was needed. The only issue was the lack of overbend created due to the tall narrow flues.
    Attached Images Attached Images
    Last edited by Big_Eddy; 04-30-2009 at 02:27 PM.

  3. #3
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    Jan 2008
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    Frankford, Ontario
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    Because we were bending narrow flues and the hold down bar prevented overbending, after springback the end result was more like this \_/ than the |_| we were looking for. I made a tweaking tool to tighten up the bends. I can't find my picture of the accordian - I will add it later if I find it. The tweaking tool is nothing more than a T made of bar stock for the inside of the flue, and 2 pieces of square tubing on the outside. Using nuts and bolts on the ends and a big C clamp in the middle, I squeeze each joint closed to square them up. You'll see in the picture how the upper bends are tight while the bottom ones had not yet been tightened up.
    Attached Images Attached Images
    Last edited by Big_Eddy; 04-30-2009 at 02:28 PM.

  4. #4
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    Frankford, Ontario
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    Default Ready for welding

    To weld on the flue ends, I clamped the material to a piece of light plate, to ensure the pan stayed flat, then cut sections of stainless to fit the ends. I purposely cut each piece a bit long and allowed it to hang down (upwards) when I filled the ends - to ensure there will be no gap later when we go to put the end on the pan itself. I considered trying to cut one single end piece, but decided I'd rather weld more than try to cut a complicated shape like that. Note the high tech "jig" to ensure that the flues stayed straight. That stayed on each flue during welding too to try and reduce movement.

    Welding was TIG using a Miller Maxstar 150 STL set at 30 amps, but controlled down from there. 0.020 Stainless Mig wire was used for filler, but whereever possible I avoided filler by fusing the joint. Tight fitup is critical and weld in short sections skipping around. I'm a proficient welder, but this is at the edge of my abilities. Back gassing is needed to avoid sugaring. I ended up using LOTS of argon as it is hard to tape off those flues from the underside.

    Once the flue ends were welded on, I bent up the sides of the pan ready to add the ends to it. And that's where I am at so far.
    Attached Images Attached Images

  5. #5
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    Jan 2008
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    Hopkinton, MA
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    Default

    That is the best how-to for making a DIY flue pan I have ever read. I'm especially blown away by the simplicity and genius of the tweaking tool. I've got to show this to the guys in my class. I'm going to save this and give it another whack some day. Thanks for sharing it!

    Sean

  6. #6
    Join Date
    Jan 2009
    Location
    Ayer's Cliff Quebec
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    Default

    Should have told me what you were doing and I would have bought shares in a vise grip factory. Pretty neat work. Time consuming I bet. What is a sheet of SS worth. I would be happy with a flat pan right now and then figure out how to put tube flues on it later. I am wondering if a person could get 1/2 or 3/4 SS tubes and then bend and weld the ends to the pan. Hope I don't get old to fast and forget all these ideas.
    maybe 50 taps for 2011
    Finally ready to boil when I get enough sap
    I just might be crazy.( make that I know I am)
    Trees all tapped except the ones with 5 feet of snow.
    Enough rabbits to keep Elmer busy..

  7. #7
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    Jan 2008
    Location
    Frankford, Ontario
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    Default

    Ken - that's only half the Vise Grip collection - once you get welding you will end up with a continually increasing collection of clamps and Vise Grips.

    Sheet of 20 gauge mill finish set me back a bit under $250 CDN. I didn't shop around too much, and only have one metal supply business in town, so likely could have done better in time, but I had it in 2 days and I've always had good luck with this vendor. They quoted me a cost to shear it, but waived it when I picked it up.

    Bending up the sheet took place one afternoon while the FIL and I were chatting and boiling sap. We were not in any hurry and probably spent 2-3 hours total. That includes tweaking and making the tweaking tool.

    Probably have another 2-3 hours into welding in the ends of the flues - haven't been keeping track. With work and the kids, I fit it in when I have spare time, tacking them in one time, welding them up another.

    I have one end cut, fit and mostly welded in place - another hour or so into that. I expect to have 10-15 hours into it when I'm done - certainly not a production pace, but even at the rate I'm going, expect to have it done before next season plus a syrup pan and arch to go with it.

  8. #8
    Join Date
    Feb 2004
    Location
    Porter, Maine
    Posts
    383

    Default

    No one can ever say you an't clever. But wow what alot of work , but I'm sure it'll be worth it. Theres nothen like doing it your self.

  9. #9
    Join Date
    Mar 2009
    Location
    Steuben Co. NY
    Posts
    93

    Default Thanks for sharing

    Eddy,
    great ingenuity and really fine description as well. I've never seen a drop flue pan and I really am intrigued about following your approach.

  10. #10
    Join Date
    Mar 2009
    Location
    ANDOVER, VT
    Posts
    588

    Default

    ok guys call me stupid, but i have been reading about these drop flue pans a have a question. how in the world do you know if the sap your boiling in the bottom of the flues isnt turning to syrup with out you knowing it?? and also how do you draw off this pan, because the heaviest sap is going to be at the bottom "right" and if so how does it make it you to your draw off valve?? sorry for the stupid questions, but im new at this and this one was killing me.. thanks m.r.
    2014-1380 total
    vacuum
    RO
    filter press
    auto draw
    pre heater
    3x8 raised flue.
    Polaris ranger SAP HAULER



    http://s712.photobucket.com/albums/ww123/jtrap/

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