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Project woodstove

Discussion in 'Mini Lounge' started by spaner, Mar 17, 2013.

  1. spaner

    spaner Well-Known Member

    A lot of smart guys here, and I thought I'd ask for some opinions.

    Just a little project for my dad and I this spring. Just a very little stove but, we want to design and build something that has all the bells and whistles that have ever been thought about; ever.

    No fans though.
    HI burn, for pre-heat, slow bake for continuous burn.
    Baffle design.
    Soap stone bricks.
    Plate VS Cast.
    Door and Seal design.
    Air feed plenums, for lite, burn, and bake.
    Air feed position plenums from below to the top of the fire.
    Rocket stove air flow integration.

    Stuff like that...:pop:
  2. Jim Nelson

    Jim Nelson Active Member

    The most efficient heating devise is the Big Green Egg smoker and grill which is patterned after the Japanese kamado.Flat out simple and works to perfection.The worst heating devise I've ever seen is the Country Comfort insert in our fireplace.
  3. spaner

    spaner Well-Known Member

    Thanks Jim, I had a look at that. Covers the heat soak idea. Better than cast, not as good as stone though.
    The idea is to bake the wood, at 400+ and have very little heat radiation. The heat is to bake the wood, to burn the gases that are released. So, HI-heat, without a lot of wood. Ceramic is a good idea for that application.
    We do have soap-stone from an old wood stove though.
    I'd like to see 400+ in the stove, and 100 or less at the flute. A matter of proper baffling maybe. Not a lot of info out there for a well designed system. Maybe cu'z you can just go out and cut the wood?

    Air flow design is another consideration. I can burn butane in an open flame, burns orange. Properly fed, it burns blue, force fed, it can cut steel.
  4. Jim Nelson

    Jim Nelson Active Member

    I experimented with making my own charcoal one time using a 30 gal drum inside a 55 gal drum.I used dry eucalyptus and oak for my wood and was really surprised at the amount of moisture still in the wood that was released as steam when it got hot.This creates a big creosote problem in your flue so if you're going to "bake " the wood it needs to be a consideration.I had a brother in law who was a stone mason and built hundreds of fireplaces,he would not use stainless pipe,only the glazed flue tiles.I'm sure you will get it figured out,you already know that air flow is the most important factor which puts you ahead of a lot of people.It's a shame there are so few craftsmen anymore who care about these kind of things.
  5. spaner

    spaner Well-Known Member

    Fewer and fewer around every day, and most older guys that retire don't bother with internet and forums.
    So far, I think we're going to build it backwards.
    Door, backwards brick baffle, with front flute. Seems to make sense for all the considerations involved.
    Air flow from the top of the door plate for slow coal burn. Not unlike a glass wash application.
    Really need some more general info though.
  6. spaner

    spaner Well-Known Member


    This is our first design run.
    A little too big we think though. Probly good for 1000sf.
    I need something for 100sf; that will burn for 10+ hours, after pre-heat and bake has been set.
    This is like 20" x 20" x 12" ISH. Hard though, to design small, without cutting the bricks.
    Standard size.
    Still thinking, cad still running. Speak up if you know something.


    PS. secondary air, right at the end of the baffle. 3" FLUE. No dampener.

  7. firejonny89

    firejonny89 Member

    Looks good I got a few questions for u on a different subject ill post those up on that thread or pm them to u in a few
  8. spaner

    spaner Well-Known Member

    Spring bump.

    As my dad likes to say, "costs nothing to continue to learn and design. Later, the build costs will be less, and the performance/reliability...better. Take your time, but keep at it". :pop:

    Dad's been asking a few old timers about their experiences with wood stoves, and I've been searching and studying everything that I can find on the net. Forums, generalized information, and opinions begged from a few old timers that actually post their experiences about trap-lines and all that.

    BTW, I have lived on reservations, and know what an adoby stove is.

    There really is not a lot of information out there on this subject. It's really surprising to me. A steel box with a flue, that burns wood, seems to be just fine for most people. Willing to spend a few more dollars for a high quality commercially designed and home insurance approved unit; off the "Show Room" floor? Baffles and B-vent enter the design, not to mention glass. Which just screws everything up (pure crap and exactly opposite to the efficiency question, of the design). Have a good friend in-the-know? Maybe you get to incorporate a wood-gas-burn design consideration. What about a burn-air-channel base-plate?
    Now we're talk'en MONEY. A currently offered "Sea-Worthy" design, is selling for $4500 bucks. A Stainless Steel sewer-pipe and a glass door incorporation (to observe the burn, and enjoy the performance)...crazy; LOT'S-O-CASH to throw away, for no reason what-so-ever.:sly:

    Man has been burning wood for heat since the beginning of time. You'd think that by the 21st century, the system would be computer controlled or something. Perhaps, at least, a mechanical high-performance fail-safe design, incorporating a "get all you can out of the system design"....at the very least.

    Nope. Very little "hard-core" information actually exists.

    Strangely enough, the advances in the technology strictly exist in the "rocket-stove" phenomenon.
    A high flow heat sink, wood burning contraption; designed to produce the highest of heat, with the lowest of energy input, in the shortest of time span. As in, heat a can of soup to 100 degrees C, with 5 grams of birch, in 5 minutes. A quick lite (easy), very fast burn (pumping)...big bang, for no bucks...and all soap stone encompassed; the flue as well...

    So, this is where we jump back in. What we want, is to have a very small stove to heat a very small space, for a very long time, with no consideration to "feeding it" in the performance interval. Which is 12 hours; minimum.

    Let's say it this way:
    A small stove, tiny.
    That, once set, all preheat considerations are fulfilled, and it is "loaded" for the long-term; at least 12 hours.
    The stove itself, encompasses less than 1800 square inches, and is considered adequate to "maintain-heating" for a minimum of 100 square feet of living space.
    OAT...-30 degree C.
    IAT...20 degree C.

    The stove is constructed of 1/8th plate steel, utilizes a commercial cast door, and uses 14 bricks. A "14-brick-stove". The standard soap-stone we are using are 9.0" x 4.5" x 1 1/4". The 1.25" varies a little, while the other dimensions seem to be pretty dependable.

    Incorporating what the two of us know, and have recently learned, we finalized this design which includes:

    Thermal insulation against heat loss. Very little surface area of the 1/8th steel plate is designed as direct-stove-to-cabin radiation.
    The best thermal insulator available is incorporated. Soapstone.
    A Thermal Mass concept is incorporated.
    A lower "burn-plate", or "Base-air & Flow rate control"; is incorporated.
    Secondary Air, flow-rate and control. The "Wood-Gas-Advantage" given great consideration to both location of oxygen feed, and control rate for long term slow burn of the system by means of the wood bake to extract the maximum efficiency of a slow coal production and burn concept.
    (The wood is baked from the wood gas burn, which actually occurs above the wood box)
    Baffle design, given great consideration as to location, fixed angle, and anti-deformation requirements.

    By the time the exhaust reaches the flue, the requirement for an out-flow dampner has been eliminated.
    7 foot of 3" B-vent equates to both minimum flue radiation and system heat retention, while providing adequate system flow.

    So we think...


    It's not something that we really need to get done right now, but rather, it's a project that we have found to be both interesting, and challenging.

    The mini-stove measures 10" x 12" x 15" approx.
    We think that we've nailed down the design, and are just working on reducing the build cost through measures like "seam weld elimination" by incorporating press brake folds into the construction design.

    The project gives us something that we can both contribute to, and later, that we can both benefit from.

    Also, it's just something that we can do together, that we both think is fun...:p
  9. spaner

    spaner Well-Known Member

    I have a few different writing styles and sometimes I think that I come across as, too confident.
    Like a blog style description of the-way-it-should-be-done.
    This is not my intention here;

    We are looking for input for the project.
    When you consider the concepts involved in building something-from-nothing. The-sky's-the-limit.
    Who's to say that one way is better than another? Most times it comes down to experience. A 100 years ago, I'm sure that there were a few guys that had their "stoves" all tweaked-out to produce the exact attributes that we, and most others would desire in a small-space-heating-wood-appliance. Cu'z they used it, and tweaked on it, their whole lives. Nothing like being able to sleep through a cold winter's night having the wood stove tweaked just right...

    What ever happened to their designs? Probly the fact that "big-energy" came along and quashed any real advantages to wood burning technologies took care of that. So, if you go back a step now, to the "old technology", you end up being only able to buy the crappiest of efficiency systems; geared and directed to the nostalgic (glass viewing doors) or the cottage-life type, ignorant of the difference. (These buy the $8.75 dollar packs of sticks on the way out of the grocery store)...:sly:

    Maybe you can contribute something simple. Like a nice little valve to allow air into the stove for the secondary air plenum. Like a thumb screw valve from the plumbing store for $5 bucks; something like that would be considered a great contribution...:)

    As far as experience type information is concerned. We have had quite a few old-timers say that the best, and simplest modification to any stove, is to have a 5-gallon water pot placed on top of it. Yes, humidity control is a bonus, but really, what we're talking about here is the addition of a "heat-sink".
    It absorbs heat slowly, in the first half of the burn, and then radiates slowly, in the second half of the burn. Not only does it extend the heating cycle, but it smooths it out; giving a more linear radiation cycle. A constant heat, for a longer time span.

    That's what we had hoped to achieve with the thermal-mass incorporation. Cu'z we think that soapstone bricks can do the same thing, only better. The stove is lined as much as possible with the soapstone, so that the burn-box really is brick; the steel just holds the brick in place. Also, we have a "MASS" of soapstone bricks just above both the primary and secondary burn areas. What we think is the position to absorb the highest heat production during the burn cycle.

    But, then again, who is to say how this is to be designed? The thermal mass I mean. What, of a blank-slate-concept, "anything goes" would be the most efficient?
    Should it just be one big block? Like a big rock. Or should it be like a radiator? The radiator concept seems to work best in automotive designs. It radiates heat better than a single block, right?
    So why not here, in a stove?

    This is the single piece thermal mass design:


    And, this is the radiator style design, which actually gets one more brick in there; "a 15 brick stove":


    Again, I ask for your opinions.
    It's all just for fun, but I keep posting this project here cu'z, out of everywhere that I could, this is the place where there is the highest concentration of mechanically inclined people, that I think there ever was, or will be.

    Practical experience counts for a lot. Book smarts, belong in the classroom...:cool:
  10. muddy moose

    muddy moose Member

    I've been thinking of building another wood stove myself. I've never actually built one from nothing but rather just fixed existing ones I've had. 90 percent of our heat in our cabin is from our wood stove . Its a fairly small stove. Burn box is about 8 inches tall 8 inches deep and 22 inches long. Our "T" shaped 1300 square foot palace of fortitude is easily kept warm down to about 10 below zero ferinheit. I pulled the bricks out of the bottom and put sand in as well as welded a plate all the way across the top that has a 2 inch bevel on either side with brick under that. Then on the entire outside of the wood stove......top. bottom. And all sides I made a 2 inch water jacket except the back has a 4 inch to allow easy access to hot water. Just have a plate metal top with a home made hinge so it closes. It burns for 6 hrs with the top flew open, the one in the single wall pipe. Bottom closed. Will.make you sweat at 40 below......and we have single pane windows that we are replacing ..with all vents and flew closed water is just about at boil and the fire will burn for 10 to 14 hrs depending on the wood. Oh......I forgot to mention that instead of brick on the walls inside the wood stove I also put sand. So the only bricks are in the top under the plate because the sand actually melted and became impossible to remove when it came time to clean the stack.........don't know if any of this is usefull or not but so far this has been one if the best I've modified. I also incorporate a dual door seal. The tighter the seal the better. The smoke rolls up the back from the fire. Crosses over the bricks to the front then back acroos the top of the steel.plate tword the back of the stove then up and out. It was a bit of a bugger at first to clean everything out but not any more.
  11. muddy moose

    muddy moose Member

    Oh sorry almost forgot......we burn less than 6 cords of wood a year.
  12. spaner

    spaner Well-Known Member

    Thanks, 40 below here too in winter. I've had a place with single pane before and just closed them up with pink-bat and thermal shrink plastic for the winter. Just one year there though.

    Yea, helpful. Sand and water, not so good for small portable units. I mean something that I can squat, and move to/from the back of my truck, by myself.

    Very good points for medium to large burning system though.
  13. muddy moose

    muddy moose Member

    Yes sorry.....,I missed the portable part. Hahaha I've made a couple out if 8 inch schedule 80 pipe. I happened across some copper plate and 3 inch pipe that I incorporated into my last one. The copper is a great way to maximize the length of time you feel heat. The problem with it is the cost. A piece of 1/4" thick copper plate 4"x6" would still be warm to the touch about 3 to 4 hrs after the fire went out. I always wanted to build a small wood stove out of 1/4" thick copper. Not cost effective at all but I think it would work amazingly
  14. o8k

    o8k Member

    any progress? prototypes? Im always interested in camp cooking stuff.
  15. muddy moose

    muddy moose Member

    OK.....how does this sound.......I've been messing with a small 6x6 burn box. Put BBQ bricks in. One layer. Then above that is another box. 6x6 both 3 inches tall. Small 1/8th by 1 inch vents along the edges between top and bottom boxes. Then a piece of .100 metal set in to direct the air from vents tword bottom of upper burn box. Stuff upper box with wood. Burn the BBQ bricks.......I've gotten 10 hrs of burn from 15 bricks and upper box filled with wood. Sorry I can't seem to post pics.....total size is 10x12x8. 2 inch pipe. I'm trying to make it so I can pack the pieces flat in a pack. Boils water about 30 min after started and does so in 5 min. 4 cups in pot

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