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Added a baffle to Grandma Bear Fisher Stove (updated with 2ndary burn idea)

Post in 'Classic Wood Stove Forums (prior to approx. 1993)' started by pen, Dec 19, 2008.

  1. jacksnipe

    jacksnipe Member

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    I would assume this is a top outlet stove model, if so, How high above the brick retainers does the baffle plate sit & what is the length & width of the baffle plate. Wait until the stove cools down before you do any measuring...
    Pen Mentioned something about a bent lip on the front edge toward the door opening, is this to help keep the smoke down in the firebox.

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  2. pen

    pen There are some who call me...mod. Staff Member

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    Yea,

    Just a lil' woman who has no problem with a wood stove and will stick her head into one jeopardizing life, limb and camera for "the shot" just to keep the conversation going!

    That's pretty good as well as above and beyond the call!

    pen
  3. Yamaha_gurl

    Yamaha_gurl New Member

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    Top outlet you mean stove pipe going straight out the top correct? If so, yes.

    I will measure tomorrow morning...I never have coals for overnight burns :(
  4. pen

    pen There are some who call me...mod. Staff Member

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    Well, I think I am changing my mind as we speak about what I am doing with this baffle.

    I found aspot on the stove that is "glowing" with a normal burn style fire going on.

    I am afraid that by building my baffle as far forward as I did (bringing it into the front shelf) that I am forcing too much heat to go along that front top plate on its way to exit.

    I happened to be up early this morning wandering the house and went down in the basement to relax by the warm stove. For some reason the little blue light on the satellite box wasn't on (must have had the power flicker) and I can just barely see glowing red on the center of that front part of the top plate.

    What baffles me (pardon the pun) is that when I move my stove top thermometer to the area it is only registering about 700 degrees. I know it is accurate to 600 as it was compared to a IR thermometer just recently. Does metal cherry faster or at a lower temp if it has been heated continually over the years?

    I can't in my mind see how my setup is stressing that top plate anymore than what yamaha_gurl showed us with her baffle in her honey bear, but I perhaps it is.

    I am going to try removing the smallest (width-wise) firebrick form the front of the baffle and pulling the bricks together, making a bit of an escape on either side of that front row.

    I'll just need to wait for the old girl to cool and the experimentation will begin all over again.

    I am absolutely dumbfounded how that 1/4 in steel top plate has some color too it yet will only read about 700 on the thermometer. I hear some of you guys pulling 750 on a stove stop?!? Why is mine turning into a light bulb and yours isn't? I would think that your top plates would be subjected to a higher degree of a beating considering the secondary burn.

    Who knows, maybe I shouldn't even be concerned. After all, that top plate isn't really going to go anywhere. And its not like I have a stove that is assembled with gaskets like many others to be concerned about warping. The stove pipe temps are staying right in range too. Ah, there I go trying to rationalize again.

    Any and all thoughts for the sake of discussion are welcome and encouraged of course.

    Damn this irritates me as the results have been so good. ugh.

    pen
  5. pen

    pen There are some who call me...mod. Staff Member

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    I believe I follow what you are saying here in that using the baffle with out secondaries may result in unburned wood gases going up the chimney. Perhaps my baffle is too efficient and I would be better off removing one of the front brinks to allow the fire to cool a bit and not out-gas so much.

    Are you just making an observation here or would this have any effect on my situation with the stove turning into a small lightbulb ?

    pen
  6. pen

    pen There are some who call me...mod. Staff Member

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    I wonder too if this could be a result of it being -10 for the last two night. Perhaps I haven't seen this before because I haven't seen this hard of a draft draw?

    That could create a catch 22. If the increase draft is causing me to overburn, I could reduce draft using the damper, but that would keep more heat in the stove also!

    Maybe I am just running too much primary air for this cold weather, but didn't think about it as my chimney temp is staying about 400-450 (where I like it) and I am still getting the burn times I expect.

    Who knows.

    pen
  7. Yamaha_gurl

    Yamaha_gurl New Member

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    Sorry Pen, can't help you out there, and I can't measure anything cause bf woke up before me and started a fire %-P
  8. jabush

    jabush Feeling the Heat

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    I think you are on the right track as far as removing one of the thinner bricks and allowing additional space at the sides of the baffle to let the hot gasses escape.  Right now you are focusing all that hot gas on one part of the stove.  If you open up some space around the baffle to disperse the heat a little, the glowing may stop.FWIW...I routinely run my stove top thermo up to 700+ (with stack temps in the 800-900 range)in preparation for overnight burns, and I've never noticed any glowing. There is however a very slight warp on the back panel of my cabinet, which is where all the hot gasses are forced around the baffle.
  9. jabush

    jabush Feeling the Heat

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    I think this had to do with the high demand for these stoves when they were first made. Bob Fisher subcontracted to many fab shops around the country to make the Bears. I imagine some shops included the baffle and others did not.
  10. bokehman

    bokehman Feeling the Heat

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    750F. Obviously if you modify the stove and change the air currents inside you will change the areas that get hottest but I wouldn't worry about it and I certainly wouldn't remove any of the baffle that's making it run so well.
  11. jacksnipe

    jacksnipe Member

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    Pen: I would like to see some results of running the stove with both drafts set at 1/4 - 1/2 open during these extreme cold spells. If the chimney is pulling real hard during sub zero weather this may help or a damper might work also. If we could get these units to run at a 1/2" open draft setting
    during a real cold spell like this & maintain high stove temps, it's all gravey
  12. karri0n

    karri0n New Member

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    Ressurecting this thread due to precaud's thread. Pen, did you ever go ahead with the secondary idea? Is it still in the works, or are you scrapping it, or is it just on hold due to other projects? I'm quite interested in seeing your results.
  13. pen

    pen There are some who call me...mod. Staff Member

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    I removed a brick and allowed about 3/4 of an inch of space along the side of the bricks in the baffle and this took care of overheating the front of the stoves top plate. The stove is burning great, I am using much less wood, and the chimney is not accumulating anything more than normal. With that said, I am very happy with the results and haven't gone any further in playing with the idea of secondary air. Maybe down the road.

    pen
  14. Rebel Wood

    Rebel Wood Member

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    My father in law had an early Grandpa Bear with no provisions for a baffle,maybe later versions did. His stove dated from the mid-seventies. My Hutch Rebel had angle supports welded to the sides to support a baffle. Recent baffle changes have made a huge difference as you describe. Existing, but inactive water coil will be coming out to install secondary burn tube per your drawings. Since I made the stove penetrations 20 plus years ago, and the one is in the perfect location, I have nothing to lose. Pictures of progress forthcoming. Thanks for the inspiration.
  15. jacksnipe

    jacksnipe Member

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    Pen: This is great news to hear that you have tamed the stove down to a milder condition. I will incorporated your update to my final design for the baffle in the fisher insert. I never heard back from the Gal the runs the Honey Bear model on the dimensions of the stock baffle that was originally
    installed in some of these models. I will continue to monitor this thread for futher updates from all users considering this modification in their units.
    I Can't wait for spring time to roll around so I can yank out the insert & install a full block off plate on top & all around the back & sides. I loose way to much heat up the chimney & being a brick fireplace on an exterior wall it's not an ideal situation..
  16. cottonwoodsteve

    cottonwoodsteve Member

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    DYI ideas;
    For air tubes, look at propane grill replacement burner tubes. The holes may need to be drilled out a little
    One of these thin stailess tubes will last much longer than a s regular thick steel pipe.
    They are about $10 at the big box hardware stores.
    If you use regular pipe, use "black" gas pipe. Do not use galvanised water pipe. The zinc coating is poisones when it burns.
    When you get things designed correctly then order some thicker stailless pipe and do it right.
    Regular steel will appear to quickly rust away in extreme heat.
    For long term but still temporary protective heat coatings, use muffler patch with the liquid or cream. The two types act different.
    Experiment!


    Other ideas;
    Also mess with a simular air system on the bottom of the fire. Angle bricks in so the fire and coals shift to the center as things burn.
    This prevents something from just smoldering over in the corners.
    The "in" thinking is burning the smoke after it forms. But you can also burn things better so they don't make smoke in the first place.
    Look at making a pellet stove type system. But make it burn split log size pellets :>)
    Do pellet stoves have an afterburner system? No, they burn the wood correctly the first time and don't have a smokey mess the burn off.
  17. TX-L

    TX-L Burning Hunk

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    Here is what I did last year: http://www.hearth.com/econtent/index.php/forums/viewthread/60745/

    It works pretty well. I don't know that it could pass an EPA test, but it's much better than before regarding burn times and chimney smoke. And it gets HOT, I routinely see stovetop temps of 700 - 800 F for a period of time after I engage the secondary air and shut down the primary. I only use this stove when it gets way below zero degrees to keep the cellar warm. The Quadrafire baffle material looks brand new, not even the slightest discoloration or soot. Pretty amazing stuff.
  18. comstock1869

    comstock1869 New Member

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    I have a neighbor who warped and burned a hole in the side of a Fisher insert stove converted as a free standing stove (home made legs and all). This is a one match per season stove running 24/7 for 7 months of the year warming his 2 story shop building attached to his office. Keeps the place in the 60s. They pack it full of birch. They welded up some battleship plate and it is back in business. This all done with out a baffle and burning gobs of wood.

    Has anyone who has added this baffle figured out their wood savings? Are we talking 25% savings? More? Less? Just looking for an update before it gets cold. I have read this thread and it sounds good for my Fisher Grandpa Bear.
  19. WES999

    WES999 Minister of Fire

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    Nice job on the baffle addition, looks great. My Fisher also has a baffle and secondary air mod.
    I also added a viewing window so I could see the fire. I used a 3" X 3" piece of ceramic glass purchased form McMaster Carr. Here are some pics.

    Attached Files:

  20. Redbear86

    Redbear86 Member

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    thats cool, i was kinda wondering the same thing that comstock was asking did you add the baffle and run it for a while so see how much you've gained with the air tubes? When i saw the whole you cut on the door of that fisher i had to shake my head....

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