Plans for staying warm

It’s going to be a while before I get the sun porch done and we can get our rocket mass heater built.  In the interim, I must have a less expensive (and quieter) way to stay warm.  Toward that end, I’ve been researching sawdust burners.  We can get sawdust free if we shovel it.

The premise of the sawdust burner is to use a low/no cost waste material to supply heat in a stove that can be hand built quickly, easily and inexpensively.  The plus for me is I can disassemble the stove and cart it outside for the summer months.  A 30 gallon barrel of sawdust should burn for about 8 hours.  With extra 30 gallon barrels pre-filled with sawdust I can quickly replace a spent barrel with a fully stocked one as needed and filling the barrels outside would keep a good part of the mess out of the house.

In one of my forays on the web I ran across a video of a sawdust burning heater built in England.  You can watch the video here.  The model in the video is available from British Hardwoods Online for about $500 US.  Shipping inside England is about $75 US.  In an attempt to get a real clear idea how the stove was built, I did some searching and, through chance, ran across an old open source plan for a “double-drum sawdust stove“.  The plans are available (free) online at VITA.  Do a search for double-drum sawdust stove and you should find the link.

The design shown in the video is a takeoff (improvement) of the original double-drum sawdust stove design. When comparing the plans to the video, take special note of the difference in location of the single exhaust exit from the outside barrel near the bottom, the lack of damper on the chimney (not needed or advised) and legs instead of a “false floor” in the outside barrel. The inside barrel’s three legs hold it above the ash drawer and allows air to circulate around inside the bottom of the outside barrel facilitating the exhaust up the chimney.

These relatively simple changes improve the performance of the design over the original.  With parts and self-labor, this stove, with the aforementioned design changes, can be built for about $100 US.  As we build I’ll keep close account of what we spend as opposed to what we can salvage so I can share the result at the end.

Wadly is embracing the task of accumulating the necessary 55 gallon and 30 gallon drums.  I will acquire the stove pipe, sheet metal, metal drawer pulls, adhesive and gasket material.  In addition I’ll need to buy a 45° and two 90° elbows.

Rather than weld legs on the barrels, I’m going to use three fire bricks to hold the inside barrel off the bottom of the outside drum.  I’ll buy (hopefully used) stainless drawer pulls for the handles on the lid and drawer.  If I can’t find the pulls I want I’ll build some out of 3/8 mild steel rod.  I’ll fold, spindle and mutilate a piece of sheet metal for the drawer and I’ll use the cut-out piece as part of the vent control on the drawer face. I’m a bit fuzzy on this part, but I’ll get there.

I want to be able to install temporary fire proof wall covers for the corner where the burner will rest.  I’ve got plenty of fire brick to make a base on which to set the burner.  I can mortar them in with a clay/sand mortar which will make them easy to take apart and clean for reuse or I can build a 2×4 fence and set them in place therein.

I’ll supply pics as we build/test/build/test so you can see what works and what doesn’t.

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9 Responses to Plans for staying warm

  1. Gierkink says:

    Hello,

    I saw a working stove in 1990.

    Last year I found the open source plan you mentioned.
    I want to build a stove myself.

    I studied the open source plan of the double drum sawdust stove. I wondered how to create the false floor and the fact if it should be airtight.
    On the internet I met Stephen Burlingame, who made the stove with a false floor (his answer to my question : ‘The false floor is air tite because I lucked out. Have you ever seen the type of can opener that cuts the lip of the lid and not the lid it’s self? this was the type of barrel opener I used and when the lid dropped I noticed how tite the lid was to the inside of the barrel so no brazing was required. Just a little bit to attach the legs to the lid’).

    I was also familiar with the British hardwood solution from their youtube video. Your comment ‘The inside barrel’s three legs hold it above the ash drawer and allows air to circulate around inside the bottom of the outside barrel facilitating the exhaust up the chimney’ interested me, because I wondered if fumes escape through the drawer opening.
    I also wondered what the opnening in the lid is for.

    I hope you can answer me.

  2. Nori says:

    I need to make one correction. The poster of the British Hardwoods YouTube video was kind enough to reply to my comment to him regarding the stove.

    my comment on his video Plans for a double barrel sawdust stove are available (free) online from VITA. The design shown in this video is a takeoff of that design. Take special note of the location of the single exhaust exit? from the outside barrel, the lack of damper on the chimney and the lack of a “false floor” in the outside barrel. All these improve the performance of the design. This specific model is available from British Hardwoods Online. With parts and labor, this stove can be built for about $100 US.

    His inner barrel does not have legs. It sits on a false floor as does the barrel in the original double drum design.

    his reply to my comment Thanks for your comments. This stove has got a false floor and the damper is normally fitted to the flue, not the stove itself. The use of 2 flue outlets is of no benefit as the outer barrel transfers much less heat when using an outlet at the top.(we know we have built one). With parts and labour this stove would cost over £200 to build yourself here in the UK. Maybe steel and labour are cheaper in the US.

    I didn’t see an opening in the lid. Where did you see that?

    Where did you read anything about the false floor needing to be air tight? It’s not in the original instructions for the double drum stove.

    It’s important to understand how this stove works. The double drum stove uses three physical forces for moving the air through. The first is the updraft caused by the fire. The second is the down draft created when the hot gasses cool as they circulate against the outer barrel, become heavier and fall. The third is the rise of the still relatively hot flue gasses in the chimney. These three engines keep the gasses moving through the system to prevent smoke backing up through the stove into the living area.

    I am not saying having the burn chamber air tight/separated from the ash tray is a bad idea. I’m just not certainly it’s completely necessary based on what I’ve seen and read.

    I hope this helps.

  3. Gierkink says:

    I didn’t see an opening in the lid. Where did you see that?
    http://www.youtube.com/watch?v=jMdRRhVJorY
    at 2:14 when the lit is put on to the barrel (after the filling).

  4. Gierkink says:

    I think too that the false floor should be airtight
    (like Stephan said).
    Just to keep the 3 air forces do their work.
    A shame the original instructions doesn’t mention
    how the false floor is constructed.

  5. Nori says:

    The original instructions did! The floor is a circular piece of sheet metal with a hole cut in the center. Holes are drilled in the outside barrel and rod is run between the holes. The circular sheet metal floor sits on that and holds up the inner barrel. The only brazing that takes place in the original design is to the rods where they stick out of the barrel and the stove pipe pieces where they meet the barrel.

  6. Nori says:

    I don’t believe that’s a hole. If there was a hole there at one point, and there might have been for using a temperature probe, the hole has since been plugged. JMPO, of course. With a hole in that spot you’d have smoke and flame spurting out of the stove. Not good.

  7. Nori says:

    Ours isn’t air tight and it works just fine. That doesn’t mean it can’t/won’t work just as well or better with an air tight floor. I just don’t think it’s essential.

  8. Nori says:

    Thanks! Only the link I’d already posted is pertinent to this project. The others take a lot more work to build and feed, which is not a value added task.

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