Marc, if you can get that thing to burn consistently clean, or just cleaner, you be sure and post up how you did it.
You betcha. The large central air passage has already made it much cleaner. I'll have to clean off my kettle from the first as-stock burn and give it another shot, but so far so good, though.
Excellent work guys and has given me a few things to think about. Firstly these are primarily designed to burn small sticks and twigs etc in places where wood is burned on open fires. The up draught in the main chamber will therefore be much greater with lots of little sticks. Trying to burn kitty litter, pellets, will reduce the optimum main up draught. The addition of the central tube is mimicking a more open fuel base? Perhaps a perforated tube would increase air into the fuel bed. With regards to the pot stand, the design images show a 'chimney' type stand with holes. The versions we seem to have are pretty much open after the main chamber, with variations of pot height. I'm considering a possible replacement along the lines as described previously. That also has vent holes above the escaping flames. Above is only a few thoughts, so would appreciate any views if I'm going in the wrong direction here.
I saw a stove of this type equipped with a computer fan to force air into the combustion chamber causing it to burn with a mostly blue flame, very hot. It seems that these stoves would benefit by getting all the air they can, and Marc's tube experiment seems to confirm that.
Thanks folks, appreciate the insights. I'll definitely have to try mine with sticks, as so far I've only burned wood stove pellets. I could claim "consistent fuel source" to remove fuel variations as a variable as far as the outcome of the experiments, and there's some value to that, but the truth is that I've used them out of sheer laziness and expediency. The stove experiments have been something I can set up and then walk away while I take care of other projects. I can also try an extended chimney relatively easily. Perhaps even additional air inlet ports in the lower parts of the chimney.
Tried with sticks today. Plan was to do so yesterday but a sudden downpour soured that plan. Attempted again today with poor results due to still damp sticks and not being willing to look for dry ones. Eventually got it burning but had to add dry pellets and use the torch to get it to take off. Even so, the attempt was educational. Previously I'd only regarded these gassifiers as a novelty. The gassifier stoves I'd built before were in an attempt to burn wood pellets in a standard wood stove. They gassified and ran well and had I added a pot support they'd have worked great as a stove, but when placed in the wood stove they didn't do too well for producing heat and I abandoned both the project and any thought into the matter. Today's experiment really pounded home the economy of work, time, effort, and fuel that a wood gassifier stove represents vs. just an open fire. A smallish double handful of kindling size sticks would have boiled several kettles. Try THAT with an open fire or even a very small "three rock" stove. One kettle at most. Along the same lines, I've read of people switching to Speedster and Trangia stoves because they can boil their kettle with just about the meths it takes to prime a kero burner. I think I need to look into this as well.
@Marc if you really want a "consistent fuel source" for testing stick burning, you could use cut lengths of dowel, or even pencils. Obviously, this would only be used for testing! ....Arch
Thanks for the suggestion. I'm not THAT concerned with a consistent fuel source! After things have dried out sufficiently(sometime in July I figure) I'll gather enough fuel for several good burns w/ natural fuels.
@Marc Out of interest did you try a pot on top to see if the sooting had gone which we're getting with the pellets? Fire bed a lot more open so hopefully more oxygen passing through, interesting about the efficiency again. In supermarkets in the UK you can buy small bags of 'kindling' basically standard soft wood sticks for starting log/coal fires and have yet to try them in the stove. I would like to see what the consumption rate would be. I suspect like most I have a fine collection of wood off cuts hanging around in the might come in useful box that will be 'useful' being burned. Then as you say the naturally collected fuel including possibly pine cones etc etc. Still investigation changes in the pot stand to something resembling the 'chimney' type as shown previously, I happen to have a donor sheet of stainless if I can find a way the form the tube.
Consider, a taller stove to create a chimney effect to increase draft, drawing in more air for the combustion of the same amount of fuel. The fan equipped stove I saw operated drastically more efficiently, so it must be a question of how much air can be supplied to a given amount of fuel to affect efficiency. Perhaps an extension, preferably sealed to the top of the stove ........ how much to achieve the desired airflow? ..........a foot, two feet, does it become absurd?
Took the top piece of the stove w/ pot support to the grocery store and started comparing to cans. Got some weird looks, but found that a large chili can would fit and extend the "chimney" by 8"/20cm or so. Full load of fuel, no central air passage added this time: Can-chimney in place: The can snugly fit over the pot rest, with the legs folded in: Ignition! Burn well underway, gassification started: Flames reaching 1ft/30cm+ above the chimney. Faint black smoke and a tinge of soot in the air - turned on the exhaust fan. Interestingly enough, it did not burn as cleanly as without the chimney. Until it got down to this, just charcoal at this point. Pure blue flames and a ferocious amount of heat, burn your hand even when held two feet above the chimney. Note: While I'm not exactly svelte, the belly shown in the pic belongs to a buddy who was over. He thought this whole process was quite amusing. I'll try with the central air tube and see what happens. Current theory is that while the chimney increases the flow of air, it also increases the flow through the fuel bed, in this case richening the air fuel mixture rather than leaning it out.
This is great, keep working on it. I couldn't figure out just where the air was directed on the stove I saw with the fan forced air. Was it through the fuel bed, fed through the upper air holes, or a combination of the two? In high school I was friends with a combustion engineer, who took me under his wing. I wish he was around now, as I have some questions for him.
'Lightbulb' @Marc your images of flames out of the top of the chimney suggests there is just TOO much fuel trying to be consumed in a device never designed for the quantities of pellets in the fuel bed. It"s producing far too much gas that can reasonably be burned however much air you can introduce, or if you could it would probably melt your pots. The portable pizza oven I have uses just a small handfull of pellets which raises oven temp to 400 deg+ but has a hopper system to add more pellets on a small and often basis. Couple of table spoons at a time every few minutes. Also you have noticed the efficiency of the charcoal residue to produce quite large quantites of heat as well. Think what charcoal was actually used for in smelting.... Not only do sticks allow a more open fuel bed, the fuel amount isn't as great for the available oxygen supply naturally introduced. Another possible analogy might be steam locomotives, optimum fuel consumption from regular addition of coal by the fireman. ETA Yes you can load the stove to run for 30 mins unattended but you have to live with the inefficiency and sooting this produces.
@dogface Are you thinking something like the Zip Stove? @Simes That's a good point. I shall make a greater effort to source proper fuel. My pellet stove combines the fan forced draft that Dogface mentions along with the steady small fuel loading you mention. Burns with great efficiency and no smoke as well.
@Marc I don't believe were looking for 'proper' fuel particularly, it's just knowing what amount of 'what fuel' works best. Possibly the less is more principle. Now we've lost the snow I'll try the stove again with a smaller quantity of pellets to begin with and try adding as appropriate. Need to identify a suutable 'shovel'
Well, I was thinking for my application, as you say it IS meant for sticks and such and not for pellets. For a suitable "shovel", perhaps a spoon stuck on a long stick?
Or one of these. https://www.amazon.co.uk/gp/aw/d/B0...4567&sr=8-5&pi=SL75&keywords=metal+food+scoop Long stick optional I would say. The pizza oven came with a scoop to add the pellets to the hopper, a scoop every 5 mins seemed to be the consumption rate. I've never done a weight per min calc as that would be really sad. Just pour in and make pizzas. The youtube stuff on lixada on pellets the guy just filled it up and set it off to see how long it would burn for. Never considered the actual practical issues of using it in that way at all. With a wide pot like the DO a chute arrangement might be useful if you didn't want to be taking the pot off every 5 mins. As I found letting the fuel bed get too low risks putting the fire out completely with new pellets.
It has not been said. This is a clone. Do you have access to another brand? Bush Buddy, Solo, etc. You may be starting from a negative position with this stove, and therefore misjudging the gasifier stove in general with this poor copy. I have an Eagle Stove, it has the fan like @dogface references. @presscall did some testing a few years ago with a fan assisted stove. He said it ran ok without the fan, as when the battery is dead. Ken in NC
@snwcmpr Ken I appreciate these are all clones and come in a variety of shapes. Saying that the principle behind them is pretty straight forward and would hope that they might perform rather better than a home made variety, and they are certainly cheap enough to have a play around with initially. I was aware of the powered versions, name escapes me for the moment, but is a little expensive unless I was seriously considering it for regular use. As a first foray into wood burners it's an education in itself, I'm certainly having fun. I just had the feeling that filling the chamber chock full of pellets isn't going to get the best out of what we have in front of us. Like any stove it's useful to know how the thing likes working before taking it on holiday with you.
@snwcmpr This on wiki makes interesting reading. https://en.m.wikipedia.org/wiki/Wood_gas Couple of pages down regarding stoves. Is there a definitive history of wood gassifier stoves? Zen only.have a link to a supplier. I've seen programmes with student projects to build similar stoves for 3rd world countries to try an eliminate open fire cooking. I had assumed that the configuration was relatively recent development. Recent as in previous 50 years in regatd to small stoves. Wood gas obviously a source of energy has been appreciated long before.
