Secondary burn not igniting

Hey david, I saw your two recent videos, and I think your probably realizing just how efficient the burn tunnel mode can actually be. The flame your showing is just is hot as you had obtained in previous videos. Your really not seeing a 'rocket' effect tho, your only seeing the burn tunnel effect. To obtain a 'rocket' effect I think you still must have a heat riser component in the stove. And the forced inlet air is not really a 'rocket' thing either, as they are normally naturally aspirated. But it certainly sounds like a rocket!!

When you buy your firebrick, there are the full size brick (about 2" thick), and there are some half-thick brick (about an 1" thick) available, oh and a tile wet saw will make quick work of those fire brick. Since your still experimenting, you might try configuring the primary chamber floor with brick lining of course, and utilize the "V" bottom to create part of a new burn tunnel in the primary chamber. A horizontal flat brick roof over the "V" configured brick floor could give you a small size triangular shaped tunnel with an opening in the primary firebox near the front of the stove/forced air inlet. This triangular tunnel could run horizontal toward the port in the floor, of the primary chamber. When you have the flame pass into the secondary chamber, make sure you direct the flame thru a new similar sized brick tunnel in the secondary chamber. Try Try Try to keep your burn tunnels of similar size for the flame to run thru. If you just dump the flame from the primary chamber to the secondary chamber and there is a vast difference in the size of the tunnels that might promote the fire to prematurely self extinguish, due to the pressure drop.

You might construct a diamond shaped burn tunnel by using the "V" brick floor & adding an "^" configured brick burn tunnel roof over it, thereby doubling the burn tunnel size.

Since it seems you really want forced inlet air, I would think a small triangular primary burn tunnel would be large enough to start. If it seems the triangle simply isn't big enough to suit you, you could easily reconfigure the burn tunnel into an diamond shape, thus doubling the size of it. I would expect with the larger the burn tunnel, the faster the wood consumption. So the triangular shape might be a good place to start. Also a flat floor of the primary chamber (created by a triangular burn tunnel) is less likely to get damaged while cleaning or throwing a new batch of wood upon it. The diamond shaped floor "^" would be a problem with the bricks getting whacked while loading the thing with wood.

How you configure the secondary chamber should be interesting to see, but I would try to keep my burn tunnel square inches consistent thru out the stove.

Don't worry too much about those coals or ash falling in the secondary chamber with a proper burn tunnel those will be mostly consumed. As you have an access door, all you need is a fire place shovel to clean it out now & then. When you do place your tunnels, make the floors fairly smooth at brick joints so you can shovel out debris without chipping the bricks too much.

james beam

Hi James, and thanks for your comment.

I have read through it a few times, and am not understanding how the tunnel in the primary chamber will work. Do you mean build a tunnel over the opening to the secondary burn chamber, or are you talking about building a tunnel from where the air is injected all the way to the opening?

I drew a picture of what I am thinking. Basically I will put a grate over the opening to the secondary burn (even thought it is not a secondary burn, but just the continuation of the primary burn). Then another grate up a little higher to hold the wood up.

Basically coals, will fall into the air/burn path, and burn causing heat that will burn the wood on top. The gas produced from the burning wood on top will be forced down into the air/burn path to create more heat, and the secondary burn. If I create a tunnel in there, I don't see how the coals will be burned up, or where they would go...

Hey david, ya I was just throwing out there another funny idea, and sometimes I don't explain things verbally as well as I should. And the 'triangle' thing and the 'diamond' thing was wrong because the valley of your primary is not a "V" shape at all. (I forgot about that)

So let me try to sort out which direction I would like to see happen with a new diagram, but of course this is your experiment so as I said earlier in this thread: " heck I'm just throwing some of my funny ideas out there for this set up, so take most of what I'm saying with a huge ~dose of salt~, do what YOU think is best."

From the new diagram you may see why I was hoping for lots of brickwork early on in this thread. So since you are headed in the brick direction now, perhaps this configuration will cause the longest flame travel possible. Also you will notice I threw in the diagram (2) charcoalizing chambers in the secondary chamber, this may still be useful to you for one major reason, I don't like the idea of splitting the exhaust in the secondary chamber, I would like to see you keep the burn tunnel consistent in volumetric size & air speed thru out the stove, until it finally dumps at the chimney manifold, then the pressure drop won't matter because you have already obtained all the heat from consistent air flow of the brick structure in the stove.

I really think naturally aspirated operation would be the most economical, and quiet, but I'm not sure how you would set that up. I wouldn't rule out the forced air pumps for use in quick start/warm-up of the stove. I suppose the forced air idea might extend the flame length in the burn tunnel maze, which may be measurably more efficient. I just don't like relying on the electric blower in the event of power failure for example.

Please notice that the venting of the secondary chamber might be plumbed with a port on the access door and routed to the primary chamber (vent the syngas from the charcoal to the primary chamber). Also notice that I wasn't sure how to stack the brick in the lower chamber, because I'm not sure of the height of the secondary chamber, so you might use a 1/4" plate as a divider or a course of 1" thick, or 2", or even 4" thick of brick but the main thing, is to build the burn tunnel area consistent in size throughout the stove.

james beam

OK, that makes more sense now. So out of curiosity, is it better to have a small long burn channel, or a larger shorter burn channel. If it is small, the flow will be faster, but longer. However I am not sure if that is better than a lager channel where the flow is slower. Larger would obviously be easier... I would guess there is probably an optimum size depending on the burn and air flow, but I don't know how to figure what that would be.

I am not sure I want to use up more space in the primary burn chamber, and am thinking I have a lot of space under the V area on each side of the secondary burn chamber that is not used for anything. I could use instead. In fact I could use the whole 6"x2'x2' area in under the primary burn chamber, and the v area. I am just trying to figure out a good way to do that. When I think of a good way to utilize it, I will post a picture. Or if you have a good Ideas.... I have some, but I also want to make it so it is easy to clean out too.

Hey david, I would say for economy reasons of firewood consumption, and to obtain an extended time of each batch of firewood, the smaller burn tunnel might be more useful. The idea being if we can stoke the primary chamber very full (a batch), and only allow to burn what the burn tunnel size determines. This gets more complicated for me to understand when your using 'forced air'. The main thing to consider on the air intake (whether it be force or naturally aspirated) -- what could the most efficient ratio of syngas to air be? Generally in gasoline engines, that ratio is 15:1 (air:fuel ratio) but of course we are using wood syngas which has a different ratio, but I would still strive for something on that order of 15:1, and then adjust as necessary until you get the longest length flame (highest BTU's) thru your system. Generally the air to fuel is considered efficient, when the exhaust is clear in color.

So then, the burn tunnel size will determine to a great degree how fast the batch will be consumed. And also, the inlet air will determine to a great degree how efficiently the fuel is burned. Naturally as you have already learned 'the hard way' the moisture in the firewood is another variable, but easily controlled by always air stack, tarp, & season your firewood from the rain or snow.

I think your primary chamber is quite large and if you don't want a burn tunnel in the primary chamber, no problem. But I should like you to know, that if the burn tunnel was in the primary chamber, bringing the burn chamber forward as I tried to illustrate in the diagram, then you have the ability to easy adjust the size of the entrance to the burn tunnel, while in use, by using a loose brick to move upon the burn tunnel inlet, and either restricting or opening the amount of fuel & air that shall go forth thru the burn tunnel after the access door is shut. I imagine opening the primary chamber access door, and the hole to the burn tunnel is right there, the flames should lick down that hole (especially when the access door is closed). This flame travels horizontally thru the burn tunnel toward the back of the stove. This will cause the smooth flat, easy to clean floor of the primary chamber to become very hot, promoting continued combustion of the batch above it, this also promotes easy clean out above the floor, albeit the ashes and fire brands have no valley to collect in. The burn tunnel itself is self cleaning by the volume of hot gases flowing thru it. (I'm sure you could occasionally use your blower air to clean the burn tunnel, if it becomes necessary.) The value of the heat, stored in the brickwork (also known as mass) will eventually transfer to the water passages. I cannot see too much heat becoming wasted to the chimney, especially if the burn tunnel is of the small size.

If you go for the larger size flame & burn tunnel, you might have a slower flow rate of the flame, and that could be adjusted at the back of the stove, at the port, by possibly configuring a few brick around the large port of the primary chamber. (kind of hard to adjust once you have a batch of wood over it & on fire) But once you get your port sized as you like, no further adjustment should be necessary, tending your batch of firewood toward the back of the stove is probably easier than pulling it toward the front. I would want some brick around that rear hole in the primary chamber so that the steel around the port is not eroded from the intense heat. This intense heat is entirely dependent on the inlet air size, which controls the air to the whole batch, and controls the speed of the flow in the burn chamber. If you have various forced air nozzles to promote a supercharging effect, that too could lean out the flame to optimum BTU's or even become too lean and therefore all the available syngas, becomes self extinguished. (as I think we have learned from your previous experiments)

Again the access doors should allow easy cleaning both primary & secondary chambers. Either small or large burn tunnel, I would not expect a flame length to be much more than 2-3 feet. But the spent hot gases beyond the tip of the flame are still extremely hot, and with continued length of burn tunnels you should expect to reap that heat also. I don't think I would make the burn tunnels complicated in the secondary chamber, we don't want to lose the flow pressure, nor make it difficult to clean. There again even your chimney is designed to absorb as much heat into the water as possible so whatever is obtained before the flow gets to the chimney is all we can expect. As for the charcoal chambering, those could easily be filled with dirt to act as mass, there are dirt mixtures with vermiculite and other substances that help promote heat absorption. I'm sure you could come up with some interesting ways to utilize those side chambers, I just thought the charcoal making might be fun & productive.

I think you can dry fit brickwork for experimental purposes, then after some testing, when your happy with the best set-up then wet fit the brickwork for nearly permanent & proper sealing. Don't use concretes or something that sets hard, the clay slip is the way to go, as it holds & seals the brickwork, but mainly because if you have to tear it out for repairs or whatever, it is reusable and turns to powder. If you do make a burn tunnel in the primary chamber you could even coat the new brick floor with wet clay slip (which will make it easier to shovel while cleaning, because of a thin layer of clay slip over the brick will avoid running your shovel into the brickwork and chipping it)

james beam

James thanks for that information... That will help a lot. I plan on doing some more work on this next week... I still need to get more firebricks though, but I think this is going to work.

I will update you with what I end up doing.

I did some more testing today. I still need to get more firebricks, and make the tunnel,but it is looking very good anyway.

http://youtu.be/miuBxgSfy_c

I am also building a wood shed, so I can get store some dry wood.

I did some more testing today.

I also made a video of the inside of the boiler without wood and fire, so you can see what I am running in there now.

After I ended the video, the secondary burned died down again, and I found as the burn slows, it will still produce a clean burn as long as I turn down the air. However by turning down the air, it cools more, and I need to turn down the air again, until eventually I have it shut off, and it dies. If I don't turn down the air, it seems like it is getting too lean, and the flame goes out.

I am thinking I may need to move the air injection up higher so it actually burns through the wood, and not just at the bottom. It seems there needs to be just the correct amount of air burned in the primary area, so the mixture is correct in the secondary burn area. I am just not sure how I can keep this working all the time.....

anyway, here is the video

http://youtu.be/yMPznkTAJqE

hey david, glad to see your getting your wood shed built, and hopefully your getting your firewood very soon for the next winter or two. It seems firewood is about as cheap as it gets at this time. Triple consider any sparks that could come out of your stove and get swept into your firewood storage.

As for your stove, you seem concerned that mixing the air & fuel ratio is tedious. I think this is where brick will come in handy for that primary chamber that wants to cool off too fast. Now that you see the embers & fire brands are 95% consumed in the burn tunnel...would you consider removing your V shaped steel floor completely?

I know you want a really big primary chamber, so why not build your extended burn tunnel and the floor of the fire box completely out of brick?

With the V shaped steel floor out of the way, could that open you up to some new ways of configuring your brickwork where you might even have a brick 'mini heat riser', an accessible clean out area, and still keep your forced air set-up for 'instant rekindling'. This is just another one of my funny ideas yanno, but all I'm saying is don't let your V shaped steel floor control your experiment, and the firebox size. If you want a really large firebox, maybe lowering or removing the floor would give you the single extended brick burn tunneling maze that I think you need, and still give you a large firebox. Fire wants to follow a smooth tunnel, whether it goes this way or that. Personally I would want my ash to end up in an easy to remove drawer.

I guess that is all the funny ideas I have for now.

james beam

I would consider removing the v shaped floor, however it would not be very easy since it is 1/4 inch steal welded air tight all the way around. Also I wanted the v shape to funnel all the wood down to the burn area. If I remove that, then it will not be able to utilize all the wood in the burn chamber.

I still think I like your idea of making a tunnel in the primary area, then continue it into the lower section.

I also really like the idea of having a drawer the ash falls into, but I can't figure a way to get all this to work together....

Sorry, I didn't have much time this week to work on the boiler. My daughter had to have her appendix removed. She is doing good now.

Hopefully I will have some time next week to do some more testing (however I have to replace the head on my car, so I am not so sure how much time I will have). But I will update you when I get a chance to do more. I think I am going to do something like diagrammed earlier by James, by creating a tunnel with firebricks in the primary chamber. I just need to figure out a way to funnel all the ash and charcoal down to the intake into the tunnel to get a full burn.

Here is what I want to try...

Sorry, these pictures are not great, but hopefully you get the idea... Basically the burn will start in the tunnel, then at the back of the tunnel, it will split to both sides, and go down to the lower area where it will go down each site to the front of the stove. There it will leave the tunnel, and travel to the back, and up the chimney.

Davi Willis : Life is what happens to us while we are making plans for tomorrow ! the way It worked out is better than taking the appendix out of your car, And your
Daughter needing her head changed ! Good luck with All your Tomorrows and your Kids tomorrows ! Keep them coming !

For the Future good of the Crafts ! Be safe, keep warm ! As always, your comments and questions are Solicited and Welcome ! PYRO AL

So I did some more testing this week. I did not make a video. However I created the longer burn tunnel in the top section, and it did not seem to make a difference.

I have been doing a lot of reading on gasifiers, and I wonder if the problem is that I am not forcing all the smoke to travel through hot coals to convert all the co2 to co. Because of this I have too much inflammable gas, and it does not burn as well. So... I am thinking I need to turn it into a downdraft with a bed of coals at the bottom where all the exhaust has to travel through.

I am still trying to come up with ideas on how to physically do all this, but wanted to know your opinion on it.


p.s. my daughter has fully recovered from getting her appendix out, and my car is running again after fixing the head.... now I need to replace the exhaust system since my muffler just fell out...

David Willis : Glad to know that your Daughter is better now ! The corollary of the tomorrows plans rule - there is no such thing as a convenient crises !

A few weeks ago, we had a member of the Grammar Gestapo, Make a comment on the proper use of Than/Then ! I hope that I am still within the 'Play Nice'
guidelines when I mention you reversed the order of CO carbon monoxide- flammable ! and CO2 carbon Dioxide- Non reactive , Your muffler probably fell off
while you were standing on your head, looking at your Cars exhaust system !

I don't mind being corrected, however in this case I think I have the order correct, even if my wording may be confusing.

I was just saying I think the problem is that I am not forcing the gas through coals to convert the non-flammable co2 to flammable co


Edit: I got it backwards this time and had to correct it....LOL

I did a test tonight and it seems to work very well. It fired up quickly (the secondary burn started up in about 5 min on its own and did not go out until I shut the air off. It then reignited back up when I turned the fan back on after being off for 5 min. It only smoked a little for about 1 minute before the secondary burn ignited a nice blue flame.

I will do some more testing on Monday, and take some videos of it, but that may of fixed it.

david willis wrote:So I did some more testing this week. I did not make a video. However I created the longer burn tunnel in the top section, and it did not seem to make a difference.

I have been doing a lot of reading on gasifiers, and I wonder if the problem is that I am not forcing all the smoke to travel through hot coals to convert all the co2 to co. Because of this I have too much inflammable gas, and it does not burn as well.

Hey david, part of this problem that you describe is quite probably because your stove is a boiler, and the heat sink of the water is not allowing high enough temperatures, to somehow break the CO2 (non-flammable) into CO (flammable) & other components. Most gasifiers are not producing syngas from the colder boiler type hearth. Most gasifiers make their syngas from charcoal, derived from dry raw wood. Typically a gasifier set-up converts the raw wood into charcoal using a closed hopper full of small chunked very dry raw wood, and the syngas is drawn or sucked thru syngas collection nozzles located at the bottom of the hopper located in the midst of the charcoalization burning zone of the hopper. Initial combustion air & flame is introduced at the bottom of the hopper to cause the conversion to charcoal of the dry raw wood. As the charcoal is consumed by fire, the nozzles collect the production of syngas that was given off from the charcoal. This is more properly called producer gas, and is often distilled, filtered, and cooled before being used which helps separate/convert the producer gas into gaseous fuel that burns.

Some actual temperature readings (secondary chamber) might help to realize if that truly is what is being emitted (too much CO2 produced in the flue just downstream from the flame tip). Or perhaps that is already a known result, and you don't need to show the temperature reading? (because it won't further burn, it must therefore be mostly non-flammable CO2 & other non-flammable gases?) Remember CO2 is a pollutant...consider your new wood barn full of wood, and all of it being converted into CO2 and other things & heat,~~~not a green result at all!~~~

david willis wrote:It only smoked a little for about 1 minute before the secondary burn ignited a nice blue flame

So I guess I will ask the obvious: is your latest configuration, approximately what you shown in your last drawings? [Where you have the flame travel thru a burn tunnel in the primary chamber, then split the flame/smoke thru 2 separate side passages, down both sides into the secondary chamber, and have the flame/smoke collect in the middle of the secondary chamber, and finally exit out the chimney?] And this configuration finally produced the blue flame in the middle of the secondary chamber? Was the blue flame observable in the primary burn tunnel with the primary door open?

You really haven't said anything about what changes you made to obtained a blue flame.

I don't know at this point what you have set-up, but if you got a blue flame somewhere in the secondary chamber it is probably because you used the brick insulation/burn tunnel to increase the flame temperature, and possibly due to afterburn air being pumped into your flame to get a lean mixture?

james beam

Sorry I did not give much information last night, I was just excited that it worked. Let me try and explain it.

First it was not using a burn tunnel. I tried that this last week, and I still could not get the burn to stay clean. My guess is from having too much non combustible gasses, but I don't know for sure.

So this is what I did. First I made a mixing tube which will create a vacuum to pull in fresh air. This consists of a 2" pipe going into a 4" pipe, with a 1 1/2" pipe feeding fresh air into the side (going in at an angle to produce a swirling motion). The 2" pipe is turned down to pull gas from the bottom of the primary burn chamber, which is surrounded by hot coals. I did this so that all the wood gas is forced though coals before it is introduced into the secondary burn. I hope this description along with the picture makes sense.

I also noticed the flame started blue with a mix of orange, then changed to almost totally clear with just a slight orange to it.... I am not sure what that means for sure, but the burn was very clean out the chimney.

With this setup, I was able to keep the burn going with my fans (the fans only feed the primary burn) on full, or turned way down. With the fans way down, I got a much slower orange burn though.

Remember CO2 is a pollutant...consider your new wood barn full of wood, and all of it being converted into CO2 and other things & heat,~~~not a green result at all!~~~

I am not doing this to be "green", but am doing it to gain energy independence. However to me it seems like it is basically not creating any pollutantce, since I am growing my own trees which will be converting co2 to o2 for the life of the tree, then will basically do the opposite when I burn them. To me this seems much better than burning propane, or even electricity... but maybe I am wrong.

hey david, hurray! so far so great! Blue & even clear is outstanding! I never could of figured this out from what you had posted previously. Thanks for clarifying in your latest post.

From your latest post, I can see your now on a much better strategy of collecting the wood gas, collecting & delivering into a new 2" pipe/nozzle, and controlling the inlet air flow by the 1 1/2" size of the inlet air pipe & variable pump volume. I really like the fact that you introduced the inlet air into the 4" mixing chamber, at an angle, creating/controlling both the vacuum for the wood gas but also your finally getting a good amount of fresh inlet air where it needs to be: in the 4" mixer. ~~where you able to see any flame swirling caused by your set-up?~~ I also like the fact that you simply need to pile the hot coals around the 2" U shaped wood gas collector, and hopefully just stack fresh wood on top and let the thing work.

I think you should come up with a name of your new multi manifold/mixer assy. I included some silly questions for you david, if you care to answer them.

Q. #1 Is the 1 1/2" inlet air pipe plumbed directly to the air pump/ outside air? ~~your drawing kind of shows that pipe not making it directly to the outside of the stove, so I'm curious if it connects directly to the pump/ outside air. (your previous 'exh. manifold' did NOT directly connect to outside air, this is why I ask)

Q. #2 Without changing your 2" U shaped wood gas collector, would it benefit your set-up at all to add an additional pipe that is perforated, and lays underneath the hot coals (like a manifold rail that is connected directly to the 2" U shaped wood gas collector, runs horizontally, and lays in the base of the V shaped trough)?

Q. #3 Is the fire easy to tend, by simply pushing a pile of hot coals over the 2" U shaped wood gas collector?

Q. #4 Are you happy with the new size of the 4" mixer, as being small enough to actually conserve wood fuel?

Q. #5 Will you expect to fill the secondary chamber with brick/dirt to capture heat, but also insulate/slow the cold natured water passages from too quickly absorbing the heat of efficient combustion?

Q. #6 Do you expect to load a single batch, burn hard & fast, and gain enough heat to keep the home warm without any other fire tending? (is the water/house capacity somewhat matched to the size of the wood batch) Or will you possibly keep a continuous fire tended for home use, but may be less fuel efficient? (I ask this because your 'mixer assy' is more efficient now, but it seems smaller than the port you had before...which should have an interesting effect on tending the fire.)

Another funny idea: could you make a 'shower head', something 4" round, 1" thick fire brick, with many holes drilled at angle thru the brick. This type 'head' might cause the flame to increase in temperature due to the brick becoming quite hot, perhaps acting somewhat like a catalyst.~~~just something funny to think about. hahaha

james beam

hey david, hurray! so far so great! Blue & even clear is outstanding! I never could of figured this out from what you had posted previously. Thanks for clarifying in your latest post.

Yes, I would have been surprised if you figured it out with my other post. I was just excited and wanted to let you know it was working.

~~where you able to see any flame swirling caused by your set-up?~~

No, I could not see the swirling. the volume of the gas coming out was fairly fast, and the air being sucked in was less than I expected (it is vented to the outside air, and I could hardly feel it sucking in air, except when I lit a flame at the opening it sicked it in with enough flow to put out the match, so it was pulling in air). I put it at an angle to swirl it around and help mix air on all sides of the gas, but I am not sure if it did that or not...It is just too hard to see. I will get a video of it next time

Q. #1 Is the 1 1/2" inlet air pipe plumbed directly to the air pump/ outside air? ~~your drawing kind of shows that pipe not making it directly to the outside of the stove, so I'm curious if it connects directly to the pump/ outside air. (your previous 'exh. manifold' did NOT directly connect to outside air, this is why I ask)

Yes, it pulls from outside the boiler completely separate from anything else. It also goes through a very hot area of the primary burn, so it should preheat the air very well. The idea for this is so it will pull the air it needs, but no more or no less. I did put a blower on the the pipe while it was burning to force more air it to see if it would do anything, but it did not change the burn in any noticeable way.

Q. #2 Without changing your 2" "U" shaped wood gas collector, would it benefit your set-up at all to add an additional pipe that is perforated, and lays underneath the hot coals (like a manifold rail that is connected directly to the 2" "U" shaped wood gas collector, runs horizontally, and lays in the base of the V shaped trough)?

I really like that idea a lot... I think it may help to keep a good even flow through the coals, and should help.

Q. #3 Is the fire easy to tend, by simply pushing a pile of hot coals over the 2" "U" shaped wood gas collector?

I have not done much testing, but it seems very easy. I had cleaned out all the old coals to put in my modifications, and when I was done I just but the coals back in (around the gas collector), then put a few more logs on top. Then to start it, I just lit a piece of paper then threw it on top of the coals (with the fan on). I let it burn for a couple minutes, then shut the door, and in a couple more minutes it was burning clean. I have not burned it long enough to have to add more wood, and see how it reacts to that. Hopefully it keeps producing enough coals to keep it working.

Q. #4 Are you happy with the new size of the 4" mixer, as being small enough to actually conserve wood fuel?

With the amount of testing I have done so far, it seems perfect. It seems to slow burn the wood on top (smoldering it), but then finishes the burn clean in the secondary burn. once it is lit, I can even turn the burn down to a really slow burn, and it still keeps the secondary burn going (at least it did in my short test run).

Q. #5 Will you expect to fill the secondary chamber with brick/dirt to capture heat, but also insulate/slow the cold natured water passages from too quickly absorbing the heat of efficient combustion?

Yes, it seems to work without the bricks, but I will add them in to help it burn even better.

Q. #6 Do you expect to load a single batch, burn hard & fast, and gain enough heat to keep the home warm without any other fire tending? (is the water/house capacity somewhat matched to the size of the wood batch) Or will you possibly keep a continuous fire tended for home use, but may be less fuel efficient? (I ask this because your 'mixer assy' is more efficient now, but it seems smaller than the port you had before...which should have an interesting effect on tending the fire.)

I plan to set the fans on a thermometer to keep the water in a set temperature range (between 140-180 deg F). I will be heading my house with the water, but I think even on the coldest days it will have to shut off at times, but it will not burn too hard & fast with this new design. I am hoping that I will only need to load it twice per day, but it will depend on how cold it is, and how efficient it burns, as well as how much heat is lost to the cold air. I am afraid I will loose a lot out the chimney. I guess I just don't know the answer to this for sure until I start using it.

I still need to put in the firebrick, and put baffles in (so the hot air does not just quickly go up the chimney without heating up the water).

hey david, some good answers~~~tyty, it seems we are back on the same page again. Can't wait to see your new video when you get it made. Oh yes I was pleasantly surprised by your latest modification. Way2go!

davidwillis wrote:I still need to put in the firebrick, and put baffles in (so the hot air does not just quickly go up the chimney without heating up the water).

hey david you want to be careful with the word: baffles! LOL ~~~As those things can damage your natural draw thru your system. Check out this thread, scroll to the pixs at the bottom of p.1, and it will show some pixs of intentionally installed stone baffles, which upon testing was found that a series of baffles like those slowed the flow of hot gases until flow actually stopped. The stove builder, temporarily blocked off the baffled area with a piece of sheet metal, just to realize that the baffles installed caused some serious flow issues until corrected. https://permies.com/t/17748/rocket-stoves/st-RMH-build

I think if you decided to put an extra rail on the wood gas collector, you might find that you can get quite a good pile (a windrow looking pile) of hot coals to cover it, and then stoke the thing full of dry raw wood over it all. But as you have it now that is just fine too.

davidwillis wrote:No, I could not see the swirling. the volume of the gas coming out was fairly fast, and the air being sucked in was less than I expected (it is vented to the outside air, and I could hardly feel it sucking in air, except when I lit a flame at the opening it sicked it in with enough flow to put out the match, so it was pulling in air).

How exciting, so your outside air is naturally aspirated and not hooked to the blower~~~whew I thought you had it hooked to the blower. But as you have seen, a lot of air pressure really isn't necessary for the thing to draw properly & mix properly, and get very hot! This is important because getting the mixture right is absolutely the most important part of economical, efficient operation of the unit. As you know, I like the naturally aspirated whenever possible,

davidwillis wrote: I did put a blower on the the pipe while it was burning to force more air it to see if it would do anything, but it did not change the burn in any noticeable way.

but for testing purpose, I'm glad you tried the air pump charging on that inlet air pipe...yanno just for fun. I think it is part of the experiment to know that charging the inlet air did not improve things much. The thing about a naturally aspirated air inlet is that you could easily adjust the air flow/mixture from the outside of the stove, with a simple valve of some sort. (not unlike adjusting an cutting torch)

But really why would charging that inlet air help in the mixer? It would only serve to change the mixture ratio, but the main thing about 'blue burning charcoal' is that it burns blue with very little air in the process, yanno while making charcoal, there is no air allowed in, except 'just enough' to keep things processing along well.

davidwallis wrote:With the amount of testing I have done so far, it seems perfect. It seems to slow burn the wood on top (smoldering it), but then finishes the burn clean in the secondary burn. once it is lit, I can even turn the burn down to a really slow burn, and it still keeps the secondary burn going (at least it did in my short test run).

That is some of the best news, I'm glad you chose 4". You might think about your next batch, and measure how long it takes to burn the batch, could be a good statistic to know later.

james beam

Ok, I just made a video. The previous test I did was in the evening, I don't think you can see the blue flame during the day.

http://youtu.be/C1QZ7uEDsUU

sorry, I messed up on that last video... here it the fixed version... It is uploading now, but should be ready in 15 min.

http://youtu.be/rqCKFTGKZhs

hey david, as your considering your secondary chamber, you might give this pdf file a read: http://www.woodstove.com/pages/pdffiles/Catalytic%20Combustor%20Tips.pdf

It seems they use their catalyst in the 500-1000 F degree range, to further chemically change wood smoke, and claim further combustion of the exhaust. These things might be incorporated as part of your secondary area. I think it is neat that your really only using a 4" mixer which has drastically reduced the size of any secondary burn passages. I would imagine you have already cut your wood consumption by half, as compared to your original large hole set-up. I think you will see increased performance when you get your secondary chamber/burn tunnel built, because as it is now, I think your pressure/flow is lost as the flame transitions into the secondary chamber. I think this because, consistent flow pressure thru the whole system should be considered for overall efficiency that you can reasonably build into it.

From your latest video, you had a temperature guage, but could you monitor & post some flame temp. readings of the secondary chamber flame itself, when you have the secondary chamber door open. This temperature might tell you if your flame is truly blue, without it being nighttime!

LOL ~~I'm guessing your temp is at least 1500 F! whoooooohoo~~ just a wild guess

So the funny idea of the day is: could you incorporate a catalyst type grate in the secondary chamber flow/burn tunned, to maximize the efficiency thru the chemical changes that the catalyst will cause. The thing is... about the catalyst (as read from the article above) they have a way of physically removing the catalyst from the flow to extend the life of the catalyst, and protect the catalyst from thermal shocks. I think you would have to place it in the tunnel down stream quite a ways from the mixer, as the catalyst does not like being over heated. I think if you could find an old automobile catalytic converter, you might could plumb that in the secondary chamber, and easily put a slider valve on it so that you can close it off temporarily until exhaust temps. get in the range of the converter.(while stoking up a cold stove for example, or throwing a bunch of wet wood in a hot box)

I want you to burn this thing as cleanly as possible, which means converting as much CO2 as possible, you may have a mostly clear exhaust now...and that is great! But if it was simply the addition of a catalytic grate, to make the thing even better (considering your really only running a 4" flue)...I think it should be worth a try.

Remember there are others out there that are truly interested in your set-up, your experiments, your innovations, and your reproducible test results. If you can take the next step and install a catalytic converter on what is now a very efficient wood boiler, you might step-up with other leaders in sustainable wood boiler performance. As noted in the article, the catalytic converter extracts heat from the typical wood stove exhaust, thus saving fuel & your environment.

I won't say anymore about catalytic converters, unless you attempt to install one, and then I may be able to help somewhat.

I hope I have been constructive with criticism & most ideas thru out this thread, and well....funny ideas are 'just funny ideas'.

james beam

Thanks james. I started reading the article, but I am just too tired tonight to stay focused on it (I finished my wood shed, and got another load of wood, and I am tired).... but I will look into it.

From your latest video, you had a temperature guage, but could you monitor & post some flame temp. readings of the secondary chamber flame itself, when you have the secondary chamber door open. This temperature might tell you if your flame is truly blue, without it being nighttime!

The monitor I have will not read the flame temperature, but will read off a surface. However it maxes out at 1,000 deg F. So it maxes out when I go to any surface near the flame. And I don't have any thermometer I can put in there to read that high of temperatures.

The best way for me to measure that temperature is by the color

Color

752 Red heat, visible in the dark
885 Red heat, visible in the twilight
975 Red heat, visible in the daylight
1077 Red heat, visible in the sunlight
1292 Dark red
1472 Dull cherry-red
1652 Cherry-red
1832 Bright cherry-red
2012 Orange-red

If you see my video when I show the exhaust mixing unit, it looks like it is in the 2000 range, but that does not really tell me what the secondary burn temperature is.

Ok, I read through the catalytic converter details, but it does not sound like it would work or help with my system. It says it will make chemical compounds in the smoke combustible at lower temperatures 500-100 deg, instead of needing to be over 1000 deg to burn break down. Since mine is already burning, and I am sure it is well over 1000 deg, then I don't think this would really do anything for this stove.

On my next burn, I will get some reading near the outlet of the secondary burn just to verify it is over 1000 deg (since that is as high as my thermometer goes).

I thought I would post an update if anyone is interested. I have finished building my shed around the boiler, and did a real live burn, heating my hot water and in floor heat. It worked great, and I found with the insulation and hot water around the stove, it would keep enough heat in the coals to ignite again even after sitting for over 12 hours. Anyway, I posted a couple more videos on youtube.

http://youtu.be/aw4EI9KJJJg This one shows the burn
http://youtu.be/aC6kQrE5ocw This explains the secondary air injection.

Hey David, ~~~Wow!! I'm very proud of your ingenuity, ability, & craftsmanship on this project. I still can't quite believe it, except that I saw your latest performance videos, I'm completely impressed! I like the tricky flapper valve/solinoid you installed on the air blower. I like the fact that you decided to use the 2" size collector nozzle, which seems well matched to the size/capacity of your household use system. It is the 2" collector that demands conservation of wood fuel, and your innovative 4" cyclone mixer demands efficiency & delivers something close to a what I would call 'a rather large cutting torch'. hahaha

Hey David, don't get me wrong, I like your present set-up just fine, but just for fun, I have another funny idea for ya, so hang on~~~ since you effectively have a single burner in the secondary chamber, which is effectively blasting straight down into your brickwork, not exactly the optimum location for your heating flame.

Do you have a water jacket on the underside of the secondary chamber?

So the funny idea is to get the flame introduced closer to the water jackets in the sides of the boiler, actually blasting the flame upon the water jackets. (I just feel like you are losing the heat transfer from the brickwork, thru the 'open areas' and then finally into the water jackets in the sides of the secondary chamber)

The thing is that your cyclone mixer, as it is now, it is at a proper fuel/air mixture no matter where you direct your flame, so maybe a redirection of the flame (toward the water jackets) might yield improved heat transfer to the water.

So the funny idea is to make another cyclone mixer/collector nozzle assy. and throw that in the bottom of the box along side your original one, but direct the flame from the auxiliary mixer into the sides/water jacket. I think the efficiency of an auxiliary/water jacket flame could be calculated based on wood consumption, batch times, and straightly compared to your centrally located flame. Or perhaps plumb the side water jackets thru a heavy pipe(s) closer to the flame. Of course IF you already have a water jacket under the secondary chamber, my funny idea become moot.

I hope you updated/post this tread from time to time, with the wood consumption figures, I think that consumption is directly a testament to your machines overall efficiency. For my 'regular' wood stove, I typically use 1 wheel barrow of wood/24 hr. period, I think your consumption might be less than that, and you get hot water out of the deal, there is the other advantages of having your wood boiler outside by the woodpile, and infrequent tending...even if you do require electricity to run it.

james beam

James, Thanks for your kind words. I will keep you updated with my wood consumption, since I have never had a wood stove (except when I was a kid), I don't really know how much I expect to burn. I figure I have got about 3 cords of wood, but I feel like I will need to get some more. Also some of it is green (I got it from our local garbage dump where tree trimming companies drop off scrap trees for $5/cord).

ohh, yes I do have water under the secondary burn chamber, so the only loss of heat will be through the doors, chimney, and any that is lost from the water through the insulation (which about 8-10 inches thick). I heated up my tank on Saturday night to 165 deg, and even using it to heat my hot water tank a few times it was only down to 130 deg This morning (about 36 hours).

Hey David, OK thanks for reminding me that the water jacket is included in the floor of the thing. I think your single burner is simplest & enough.

Did I notice your horizontal 1 1/2" intake air pipe sagging/bent in the video? I think it was sagging due to the extreme heat in the coals area, or the fact that your just throwing in those heavy logs onto a heat softened pipe, that pipe could possibly rupture/collapse with continued hard use, perhaps a brick support/protector might help with that. I know it is early in the season, but you might try producing another duplicate cyclone mixer with air intake pipe to have as a 'back-up' just in case the one currently installed fails for any reason. Remember during the coldest season, you are going to work the thing very hard, somewhat continuously.

I love the current set-up, as everything has easy access for maintenance. Just for fun, you might consider while making a 'back-up' cyclone mixer/air intake assy. by changing the size of the air intake pipe, to change the air:fuel ratio. Funny I know~~~but you know me, always jacking with stuff.~~~ What I have in mind is a 2" U-shaped updraft collector [same as you currently have], but the naturally aspirated 1 1/2" air pipe might be increased to 2". As you know David, the more air introduced into the cyclone mixer should yield an leaner fuel:air ratio, and perhaps yield the blue or even clear flame. You might try again, supercharging the present 1 1/2" intake air pipe with your other blower experimentally... expecting a leaner burn.

Does your intake air now draw more fresh air that previously stated in earlier experimentation: "will blow out a match"? (in this case I imagine your preheated air is extremely hot, and therefore the Oxygen content is extremely diluted, ideally I would want cooler intake air, because 'the denser the air, the more Oxygen is available for combustion')

Of course there is a trade-off with leaner/hotter mixture ratios, the maintenance & component failures will increase, but you get better fuel consumption, and better air pollution, faster thermal conversion into the water jacket~~~which seems worthwhile goals.

What is the exhaust temperature at the top of the chimney? I would consider putting a rain cap/spark arrestor on those stacks, internally rusted pipes are not your friend!

Is there a thermostat/regulator of some type that you intend to use, to prevent overheating the house? How funny an idea would it be, if you were to plumb in an auxiliary radiator into the woodshed, thereby redirecting/bypassing all unregulated [excess] heat away from the house and into the woodshed. This 'woodshed radiator' could be coupled with a fan, could come in quite handy for drying that $5/cord green wood, but also, used to dehydrated food stuffs, or laundry, or just be a fun place to hang out.

I don't know if it would be worth trying to configure a secondary chamber, 'charcoalizer area' at this time, (because a pyrolysis vent would have to be addressed...wouldn't want to waste the syngas production from charcoal making, out the chimney) but I think you can see the potential now for your wood boiler, and a good amount of charcoal on hand would be very useful.

I think a project summary should be made with pictures/diagrams, proper component names, & working specifications should be useful so that others can try to duplicate your results, with very little 'trial & error', & I think it is necessary for this & your website http://www.independenthomeenergy.com/projects/wood-boiler/control-system/ also.

james beam

Did I notice your horizontal 1 1/2" intake air pipe sagging/bent in the video? I think it was sagging due to the extreme heat in the coals area, or the fact that your just throwing in those heavy logs onto a heat softened pipe, that pipe could possibly rupture/collapse with continued hard use, perhaps a brick support/protector might help with that. I know it is early in the season, but you might try producing another duplicate cyclone mixer with air intake pipe to have as a 'back-up' just in case the one currently installed fails for any reason. Remember during the coldest season, you are going to work the thing very hard, somewhat continuously.

That pipe could be bent from the heat, logs, or it could be that I did not weld it strait... I am concerned that the heat may burn/melt the parts of the pip or mixer, because it gets very hot. This winter will be an experiment to see how it holds up. However I have it all welded in, so even if I have a spare build, it will not be an easy change. It may be something I will have to redesign in order to hold up to the heat.

I love the current set-up, as everything has easy access for maintenance. Just for fun, you might consider while making a 'back-up' cyclone mixer/air intake assy. by changing the size of the air intake pipe, to change the air:fuel ratio. Funny I know~~~but you know me, always jacking with stuff.~~~ What I have in mind is a 2" U-shaped updraft collector [same as you currently have], but the naturally aspirated 1 1/2" air pipe might be increased to 2". As you know David, the more air introduced into the cyclone mixer should yield an leaner fuel:air ratio, and perhaps yield the blue or even clear flame. You might try again, supercharging the present 1 1/2" intake air pipe with your other blower experimentally... expecting a leaner burn.

This is funny you mention that. I have found there are times when the mix is too rich (I could see some smoke even though the secondary burn was burning). By adding a blower to the secondary air line, the secondary burn would get hotter, and the smoke would go away. Because of this I was thinking of running a T off the blower to increase the flow into the secondary burn, I may even put a valve in there to be able to control it.

Does your intake air now draw more fresh air that previously stated in earlier experimentation: "will blow out a match"? (in this case I imagine your preheated air is extremely hot, and therefore the Oxygen content is extremely diluted, ideally I would want cooler intake air, because 'the denser the air, the more Oxygen is available for combustion')
Of course there is a trade-off with leaner/hotter mixture ratios, the maintenance & component failures will increase, but you get better fuel consumption, and better air pollution, faster thermal conversion into the water jacket~~~which seems worthwhile goals.

When the secondary burn is running, it does draw enough to blow out a match or a lighter, but it is hard to know for sure how much air is going through. I would also like to know how hot the air is. Hotter air will help the secondary burn start up, but once it is going, colder would be better, so I am not sure which is best. Everyone else says to pre-heat the air.

What is the exhaust temperature at the top of the chimney? I would consider putting a rain cap/spark arrestor on those stacks, internally rusted pipes are not your friend!

I have not measured the exhaust temperature lately. The pipe is about 200 deg. Thanks for reminding me. I do plan on putting a cap on the stacks, I just have not got to it yet.

Is there a thermostat/regulator of some type that you intend to use, to prevent overheating the house? How funny an idea would it be, if you were to plumb in an auxiliary radiator into the woodshed, thereby redirecting/bypassing all unregulated [excess] heat away from the house and into the woodshed. This 'woodshed radiator' could be coupled with a fan, could come in quite handy for drying that $5/cord green wood, but also, used to dehydrated food stuffs, or laundry, or just be a fun place to hang out.

I have the water temperature regulated by the controls that turn on and off the blower, which has been working great. I also have circulation pumps that I plug in and unplug to turn on hot water circulation through the floors of my house, but I have not regulated it yet, I am still testing to see how well it works.

I don't know if it would be worth trying to configure a secondary chamber, 'charcoalizer area' at this time, (because a pyrolysis vent would have to be addressed...wouldn't want to waste the syngas production from charcoal making, out the chimney) but I think you can see the potential now for your wood boiler, and a good amount of charcoal on hand would be very useful.

If there was an easy way to circulate the syngas back in, that would be a very good plan, but even wasting it, it could be a good way to make charcoal.

I think a project summary should be made with pictures/diagrams, proper component names, & working specifications should be useful so that others can try to duplicate your results, with very little 'trial & error', & I think it is necessary for this & your website http://www.independenthomeenergy.com/projects/wood-boiler/control-system/ also.

Yes, I agree. I have been so busy lately I have not had a change to get that done. I have a lot of updating to do on my website, because a lot has changed since I started. However right now I am trying to get everything done that I need before the snow flies, which includes getting more wood, and finishing my in-floor heat (I only have in-floor heat in 1/2 my house). I want to organize my site, and put the relevant videos on it (not all the testing ones, but the ones that show my current setup). Once I get it done, I think it will be useful.

I thought I would update a little bit, and give some thought I have been having.

The burn seems to be going good, and it is working well, other than the fact that by putting in the cyclone mixer up top, with the secondary air line, and also putting firebricks around everything, I don't have space to fit much wood... And filling the boiler is not as fun as you may think, because when you open the primary burn chamber all the smoke buildup rushes out the door. It is not too bad when it is not running, so if I shut the boiler down for a while before I fill it, it is not too bad.


However I would like to be able to fill the boiler with more wood each fill, so I am thinking alone the same lines as James mentioned months ago....

Basically since I am just burning the secondary burn right in the boiler, there is no real need to separate the secondary from the primary burn area. So I am thinking about dropping the v-bottom all the way to the bottom of my secondary burn chamber, and then place a grate over the top to keep a small secondary area at the bottom. Any wood gas created in the primary chamger would pass through the primary burn, and the coals on top of the grate, and into the bottom where more air will be injected to complete the burn. After then end of the primary burn, the hot air could be directed back to the front (through the area under the v bottom, then back to the front to help transfer the heat into the water.

This will take some work to move the v bottom down, but it would give me a much larger wood capacity, and it may even produce a better burn (at least it may not take as long to start burning clean).

I was also thinking (I am not going to do this now, but maybe later), it would be nice to have a chimney out the top of the primary burn chamber that could be opened when wood is going to be added so you don't get a face full of smoke when the door is opened.


Anyway, here are the pictures of the idea.

Hey david, I'm surprized you would make such a drastic change at this point, because your unit is running so well, and we haven't even got into the durability test of this winter yet. Oh well, hey that is what experimentation is all about, refining till we get the thing the way YOU want it. I'm going to agree and say that because of smoky/dirty/difficult chore required on the current set-up is your main reason for a drastic change. I can imagine cleaning out the valley below the grate (primary chamber) with the horizontal fresh air pipe, & cyclone mixer in the midst of it all, makes it difficult.

Ok at this point I'm also going to laugh out loud, at you, yanno just for fun...I just can't quite get the image of you going back into the house or whatever, blackened with soot, and you take your smoldering safety glasses off, to proclaim: "well I got it stoked up for the night, cough! cough! I need a shower now", just can't quite get that out of my mind. Some how we over looked the reality of the fire tender reaking of wood smoke. Gosh the things we do to save money.

Ok I've got a new funny idea for ya: How about a different fresh air intake pipe for the cyclone mixer...what is different, the intake pipe would be vertical & larger than 1 1/2" pipe. A larger vertical fresh air intake pipe to the cyclone mixer would have to breach thru the roof of the primary chamber and further still protrude out the top and pass thru/clear the upper water tank area to a reasonable height or length where a dry air source is obtained. Now that larger vertical fresh air pipe might not become warped as much under the heat stress, and should not interfere as much with the wood batch, as positioned vertically most of the fresh air pipe is not located in the midst of the hot coal bed. The larger vertical fresh air pipe might be well situated running up the primary chamber side wall (which might provide a bit of cooling due to the nearby water jacket, rather than freestanding directly in the center of the wood batch area...allowing easier wood stoking, & perhaps easier ash clean out.

If you went that route, ~larger vertical fresh air pipe side wall mounted~, I think such a change would also suggest fundamentally changing your cyclone mixer location as it is now (move the cyclone mixer to the side wall also). Other than the location change, I would also suggest a change to the cyclone mixer, by using the larger fresh air pipe, that should cause a leaner air:fuel mixture ratio. I'm thinking 3" or 4" vertical fresh air pipe side wall mounted. If you use the 4" fresh air pipe to connect to the 4" cyclone mixer, it might resemble a 'typical propane type furnace burner'. The idea being a large amount of air becomes available for the combustion of a much smaller amount of syngas fuel. The syngas collector nozzle size might even be reduced from 2" to 1 1/2", or possibly as small as 1" pipe. The size or ratio of the fuel & air pipes have everything to do with the efficiency, and should be somewhat adjustable, to maintain efficient performance. You might try a google search of: propane furnace air:fuel ratio for clarification. Perhaps my pixs of a couple different propane burners might help.

james beam

this is what I came up with for a possible 'side wall burner'...~~~just another funny idea. But with that funny idea, how about adding an additional opening {not shown in my pix}in the fresh air intake pipe , that might be used occasionally to vent the primary chamber out the fresh air pipe (while stoking the wood batch)...I don't know some sort of large hole or door in the side of the pipe that would be able to open & close & properly seal while the machine is in use.

james beam

haha... I think you may have imagined it a little worse than it really is, but it may be that bad in the middle of winter when this is running 24/7.

Cleaning it is isn't really that bad (at least not yet). The big problem I really see is that it simply does not hold enough wood, and adding more wood is not a fun task (not as bad as you imagined, but I do smell like smoke after doing it.

Also last night I left my in-floor heat on all night, and by morning my boiler was totally out of wood, and the temperature had dropped to 139 deg, and the temperature is not that cold (it got down to about 28 deg F). Even though it did keep the house plenty warm, and heated our hot water tank nicely, I think it will need more wood to keep up through the night when it is really cold.

I think moving the cyclone mixer would provide a little more space, but I think I will need more than that. that is why I am thinking about moving the entire primary burn chamber down lower.

I guess I could always use two cyclone mixers, and put them under the sides of the v bottom area, and turn them sideways.

I also think part of my problem is that I get no draft from the chimneys because I have two. I find one gets started flowing first, and the other one actually flows backwards creating a loop. this is bad in two ways. For one, it does not create any draft to pull smoke out of the primary chamber, and two it pulls cool air through the second pipe cooling the water instead of heating it.

Hey david, I'm sure you can temporarily block off one of those stacks, top & bottom. I meant to mention that a long time ago, but sometimes I dare not mention all the things 'I would do'. Probably the dual stacks are not necessary now that your really only running a 2" fuel nozzle, and we lost a lot of flow & pressure when the 4" cyclone mixer/burner simply dumps into the large secondary chamber.

I would not be against increasing the height of the useable stack, because the taller you get that stack (into the upper air currents) the better the chimney shall draw. From time to time there will be a smoke issue from the chimney, and the taller it is...the least amount of smoke will accumulate near the house doors or windows. Typically a chimney should rise above the peak of a house, I would say an adequate distance above the peak is 4', this may seem like a lot but when the wind is laying dead still or gets to whipping around and swirling, a tall sturdy chimney with a rain cap really out shines a short one.

I think running a second cyclone mixer is probably your best bet, maybe you can plumb it/run it as an auxiliary 'when needed', I would probably build the second one with a leaner fuel:air ratio, but another identical mixer might work just fine too.

Eventually at some point, don't forget about some sort of ash drawer, and often used on the gasified pickups, they use some sort of shaker grate set-up that shakes the ash out of the coals & into the drawer, makes tending easier, especially if you intend on increasing the size of the batch.

james beam

Any member is welcome to jump in on this conversation/experiment...if they can offer constructive criticism, ideas, or experience, all you have to be is... somewhat nice about it.

hey david, I'm still thinking about the lowering the floor idea, and I really haven't come up with anything to add yet, I'll try rereading this tread and see if I can get my head wrapped around whatever it was I was thinking at that time. Ok here goes another funny idea for the moment: modify your existing large front door for the primary chamber. Make a new prototype door that will fit in its place. On the prototype, incorporate a rather large protruding 'hopper', of which the hopper might have a simple very wide opening thru the main prototype door, and the hopper might hold an good amount of charcoal or wood. The hopper should be slanted as such to allow the fall of fuel charcoal or wood to proceed without much tending. The hopper could have a heavy lid on the top of it, to load the batch, open the main door & stoke as usual, then latch the main door, then simply open the hopper lid at top to finish filling the thing with additional fuel wood or charcoal. It may look funny, and probably won't feed all the extra wood (hang ups happen), but it would....get this...it should allow you next time to tend the thing, allow you to open the hopper lid (flip it all the way where it will stay open) and allow most of the smoke to clear the firebox thru the hopper before you open the main door!

james beam

Hey david, Ok 'the hopper in the door' idea is ridiculous, could cause serious trouble for you when you need to tend the fire, I don't think I would try a hopper in the door.

How is the stove operated now? It seems once you get it up to full operating temperature, that you are running it unregulated, hard & fast until the batch is consumed. How about try running the thing hard & fast, with occasional intervals of choking it back, if the blower was shut off temporarily, the fresh air pipe is temporarily blocked off and the batch was allowed time to charcoalize in the primary chamber, then after a time, restarted in the hard & fast mode. I don't know that this would help, just another funny suggestion. I think I remember seeing an wood boiler with a blower to the firebox, that operated similarly, running in cycles, based in regulating output temperatures within an operating range, building charcoal production, but also to extend batch times.

james beam

Sorry, I have been sick this last week, so I did not check here.

I can easily adjust it to run in shorter intervals by setting my thermostat at different ranges. Currently I have it heat up to 190deg, then turn back on when it hits 160deg. I have found it is more efficient when it is running hot for longer, because it takes a few minutes for the secondary burn to heat up. Durring that time it is a little smokey for about 15-20 min before it gets clean.

This week has been warm, and I have really only been using the stove to heat water for showers, the dishwasher, etc. With this, I only have to do a burn every couple days, but it will be getting colder in a day or two, so It will be interesting to see how much wood this really takes.

Also my tube to pull the syngas from the floor under the coals broke off (I only had is spot welded on because I was not sure it would work) and I have been running without it for the past few days. It lights up a little faster without it, but it is not a good of a burn, and still smokes a little even when the secondary burn is going (even with the air turned up to the secondary injection). I am not sure why, other than there must be less flammable gas without it being forced through the coals. Anyway, I will probably weld it back on next week when I am feeling better.

I still like the idea of moving the v bottom down, but I am not sure I feel like going through all the work right now. I may just use this through the winter, and see how it goes.... I just hope I am not out putting wood in at 3:00am....