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Re: Makings for a new Stove

Posted: Sun Apr 08, 2012 5:34 pm
by Paul B
These are pellet burners, the parts can be assembled into stoves, large and small. Some of the little cans have false bottoms, to suspend the fuel/fire for ventilation. Some burners produce a fair amount of blue flame; others have more air holes and produce a 'candle flame' that shoots up and is more pure yellow. Less air, the fire 'sits' in the top of the burner, a lot of blue in the top of the can, but the tops of the flame are more yellow. More air, a tongue of yellow shoots up - I've made some flame spreaders or gas wicks, which collect a lot of soot, the good part being this soot doesn't make it to the pot. Haven't studied on the loss of efficiency, yet. Probably the right way to use this shooting yellow flame is to have a tall enough chimney the flame doesn't quite reach the pot bottom. Seems like the contained, largely blue flame needs little air intake, which means that flame-out will be very smoky - might as well just quench the charcoal. The shooting yellow super candle flame is difficult to manage, requires a very tall chimney, but there is little to no smoke at flame-out. Also, the start-up at lighting is quicker. So there is the possibility of getting a fast boil, to be followed by simmering with the charcoal. But this seems to involve fiddling with chimneys; not exactly light and forget, but not a terrible chore, if you're in cooking mode. Anyhow, next thing to try is, can there be an in-between amount of air intake, that won't have the exploding runaway yellow rocket flame, but will still burn the charcoal to ash.

This is perhaps the most practically useful way to use the charcoal chimney: ... _00054.jpg ... _00053.jpg ... _00052.jpg ... _00051.jpg

The pellet burner can does a nice job of making a lot of blue flame, though there is enough yellow htat it comes out sorta purple looking. There's 9 holes in the bottom, a row of 8 or so jets about 1/3 of the way down from the top, and about as many 3/4" holes as will fit, around the top. Slow to start, but once it gets started, there's a nice flame cap, and the variation from least to most flame is small. Early and late in the burn, the pot can sit right down on the grate, or even on a cross-piece directly on the burner can. Even at maximum heat, it only requires the insertion of a short can+crosspiece to keep the pot above the flame; but close enough for good heat transfer.

And, of course there are various options for wind-screens, which are also draft producing chimneys, sometimes with the pot inside the chimney, sometimes on top.

(yeah, I didn't edit these pics, re-size, etc. Maybe I'll come back and edit this post later. Right now I'm distracted, because:

Much to my surprise, when I opened the front door this morning, there were two boxes from Stovetec. I thought I better make this report before I opened those boxes.... :P

Re: Makings for a new Stove

Posted: Sun Apr 08, 2012 11:41 pm
by zelph
Paul, what sucess have you had with twigs and getting the blue flames?

One of the nice things about pellets is how dry they are. That's why they burn so nice and clean. all the nasty stuff has been compressed out in the form of moisture. There is an extreme amount of heat generated in the compressing and squeezing the wood paste through the tiny holes.

You'll have plenty of fun with the Stovetec for sure. Be sure to stop by this fall and show pics :mrgreen:

Re: Makings for a new Stove

Posted: Mon Apr 09, 2012 3:39 am
by Paul B
I've never seen really prominent blue from twigs. then again, I recall at least one 'woodgas' stove video that did show a lot more blue, and that quiet but slightly pulsing blue - purple bubble of flame. This was after burning enough twigs to get a substantial bed of coals.

Anyhow, I think I need to sleep on this and make more comments in a day or two.

But, I've been surprised, and very pleased, at the subdued, quiet, yet healthy blue tinged with yellow that pellets can produce, if the bottom air is not too big, but at the top there are BIG holes - seems like the air that pours in from the top sort of holds this blue pillow down, not rising above the lip, and the top of the fire chamber is bathed in fire, but it looks a bit like water in an aquarium.

So, I look forward to camping where there is 'real' wood, naturally dried twigs.

I've lit up the Stovetec 2 door a few times, and done some cooking, already. First off, I just lowered one or another of the smaller diameter pellet burner cans down the chimney, to rest on the grate. There's still a similar issue to the charcoal chimney - Burn blue, but quench the charcoal before it smoke-bombs, or accept a runaway yellow light sabre, but the end product is ash. Then I made a screen floor on top of the grate. Initial impression: inserting a pellet burner can probably offers more choices about what kind of burn - but having a layer of charcoal covering the entire cross section of the burn chamber makes the charcoal - simmer work way better. The concept of 'rocket stove' includes more or less constant adding of fuel - and, actually, that's the primary nature of pellets, too. This is all going to be very good; what I've learned about pellet burners will generally transfer to the Stovetec, though the different environment will produce somewhat different results.

The batch load approach isn't the same with pellets as with twigs, seems to me. Twigs, in a 'conventional' (whatever that means!) stove, just fill 'er up, top light, and give it a lot of air.... Right?
You want maximum air under and around and thru the middle, if possible, the top lit, up draft will help regulate the burn. But with pellets, there needs to be a bit of air from underneath, but if you give it unlimited air, it's gonna go off really fast, and not be all that useful in the process. Control the air, a little to start, a lot more at the top, and the batch load with pellets works, not completely steady, but usable, predictable, pretty long lasting. Haven't figured out how to have the batch load slow burn and still get the charcoal to transition.

Ah! Now this is why I've prattled on for some paragraphs (maybe :shock: ) : Somebody, maybe Paul Anderson, has designed a TLUD that sits atop a charcoal stove, you dump the charcoal into the charcoal stove at the appropriate moment, and, well, "Bob's your uncle!" So, I'm thinking, there's a way, with the new 2 door rocket: Use a nice Blue Pillow slow, controlled burner can, when quench time comes, extract the can, (VERY CAREFULLY!) and dump hot charcoal back into the burn chamber, which has a screen bottom. I think the charcoal transition doesn't take place because the controlled air requirement of the slow blue (ok, purple) isn't enough for the charcoal to keep burning. Or something else, maybe you have a suggestion, maybe I'll learn stuff while trying this idea....

Anyhow, the 2 door rocket isn't intended to batch load burn pellets, but since it works pretty good in the charcoal chimney, it should work even better in the rocket stove; The environment is very well insulated, and there's a lot of control over the draft....

Ouch! There's a storm in my brain....

Re: Makings for a new Stove

Posted: Mon Apr 09, 2012 9:28 am
by zelph
Twigs, in a 'conventional' (whatever that means!) stove, just fill 'er up, top light, and give it a lot of air.... Right?

That is correct. We want 4 cups of water boiled now. We want to eat/drink. We can accept soot and the smell of smoke. :mrgreen:

The Stovetec allows for lots of food and water to be cooked. adding long, large diameter wood is easy.

The stoves that produce nice blue flames need to be protected from drafts to prevent flame lift off and the stove going out. Once the pot is put on the stove thats producing nice blue flames all of a sudden we have yellow flames and very possible flame out.

I think it was a Winarski design that showed the bottom of the stove having an air control device to reduce incoming air during the initial lighting of the stove. We need to remember that those TLUD manufactures for 3rd world countries wanted to have electric fans on them. No way could they pay the high price for them. So they put the fans on them and sell them here in the USA. :o So to compensate for lack of electric fans they make the stoves taller to get the drafting needed to make the stoves work. And then we see the Rocket Stove being most popular, why? Because it's easily controllable. Push twigs in to burn hotter, pull them out to simmer :D that was easy ;)

Re: Makings for a new Stove

Posted: Mon Apr 09, 2012 11:28 am
by ConnieD
Did you get the Stovetec model that has a separate door to let in air under the fire? or the ceramic model?

Re: Makings for a new Stove

Posted: Mon Apr 09, 2012 7:35 pm
by Paul B ... 0061-1.jpg ... _00065.jpg

(O.K. that's it for now! I hit the frustration with a new skill wall. :roll: B u t I'm learning..... :P

I have accepted some reality, and I'm very happy, now, with the charcoal chimney + 4"X7" inner burn can, tuned for semi-blue flame, that isn't too fragile, yet very well behaved. I've tried a few pellet burner cans in the Stovetec rocket (I have the 2 door model, with the heavy grate, meant for both wood and charcoal. A good choice for me, though the 1 door model has it's advantages, too.)
The 2 door Stovetec's insulation must count for something, like keeping the heat inside the stove, and under the pot! Anyhow, some of the tree trimmings I've rescued from the curb, which are still too wet to burn easily, will get started in the Stovetec. Seems like I could easily make a far more ventilated inner can for the charcoal chimney, when twigs are available, it should go Shwissshhhh, just fine. This morning, I ran the charcoal chimney and the Stovetec 2 door kinda side-by-side: First, the C(harcoal) C(himney) was a little slow getting started, but it boiled 4 liters of water, one liter at a time, and was pretty quick, after it got started. oh, yeah, 1 cup pellets + a bit more, soaked in ISO. Ok, maybe it was 'only' 3 + liters. The Stovetec will run on pellets, though it's apparent that's not the primary intention. I tried putting a screen on the grate, and spreading pellets all over the grate, and wasn't real happy with the results. Either wildly jetting flame, or smoke-out, too hard to control. But, the appropriately tuned pellet burner insert, now that works just fine. Turn a can into a sieve, there's yellow flame, but pellets burn to ash. it might be a better strategy in this mode to use a smaller diameter can. A can insert tuned for a more controlled, quasi-blue or at least less wild flame works great, too; but ya gotta quench those charcoal pellets if you don't want clouds of smoke at the end. But, the Stovetec 2 door is much better protected from 'outside' wind - in fact, both doors can be shut tite, or the lower door opened just a crack, and that does to some extent control how hot.

So, are the Stovetec doors pretty much air tight, ya think? 'Cuz the pellets inner can burns slower, when the doors are shut, but doesn't go out. So, maybe the can insert is enough narrower than the ST's burn chamber/chimney, that air can actually be drawn down the throat? I recall, recently, viewing an air flow diagram of the Lucia stove: which showed air being drawn DOWN the inner burn chamber, going out the row of holes that are a bit above the bottom, and rising between the walls, to be re-introduced at the top. Now, after I saw that, I made another tiny Everything Nice, being a bit more attentive to proportions - and dang if the thing didn't burn BLUE ! Oh, yeah, the usual problems - more than a couple un-burned pellets, etc.

Stovetec used to offer 5 or 6 rocket models, 'economy', 'standard' and DeLux, both 1 door and 2 door. (Maybe I don't have that exactly right....) I think, just lately, they only carry the delux, in both the 1 door and 2 door. I caught myself jamming the long sticks into the far side of the burn chamber; that's an awfully good reason for the refractory metal liner!

Now I have the Stovetec 2 door, I am a lot more pleased with my C.C. + insert burner thingee. I think it is a reasonable approximation of the most controlled, most blue flame that is practical in a simple sort of stove. (with pellets, of course). Of course the Stovetec is just better, will do a lot more things, etc. But the C.C. holds it's own when boiling water with pellets is the task. Oh, yeah - I have not tried the big Water Pasteurizer yet.

Nice that both the C.C. and the ST can boil fast, but I'm not so sure the C.C. can easily simmer, while the ST 2 door is just made for that!

I have a few iterations of the pellet burner + stand and wind screen that are small enough to be carried around (Hey, nobody's going on a thru hike with a pellet burner, I get it!) for a day hike or maybe an overnite; but I'm noticing how nice it is to use an alcohol stove, too. And even a simple overnite or day hike, why carry stuff you don't have to?

Which reminds me of my youth: Fill the main bag of the packframe with food, food, and more food, strap a tarp and sleeping bag on the top/bottom, and don't come home till the food's gone! that could be a long time if the fishing's good....

Now, pellets are primarily intended for some sort of mechanically complex, pretty air-tight sorta stove, right? I mean, there's spozed to be some sort of auger or gravity feed, right? Well, I note there's enough clearance between a small to medium size pot and the cook-top, to let a few pellets at a time slide down the throat. Looks to me the ST 2 door may actually be a stable and protected and insulated enough environment to burn pellets a few at a time, a slow but steady rate of loading.
Initial thought, that will either be busy-work, or excessive added complexity. Or, maybe not...
And, I believe I've seen vids of auto load devices that were arranged to pre-heat the pellets, before they get to the burn location. That's the rub, with pellets, and probably why we settle for the less than ideally consistent burns of batch loaded pellets, TLUD style. TLUD works good with twigs or pellets, but while it is possible to start a small twig fire, and build it up, or add twigs to a TLUD twig burner, (Right?) I have not had much success adding even a few pellets to try to extend a pellet burn.

Re: Makings for a new Stove

Posted: Mon Apr 09, 2012 11:34 pm
by zelph
So, maybe the can insert is enough narrower than the ST's burn chamber/chimney, that air can actually be drawn down the throat? I recall, recently, viewing an air flow diagram of the Lucia stove: which showed air being drawn DOWN the inner burn chamber, going out the row of holes that are a bit above the bottom, and rising between the walls, to be re-introduced at the top.

I saw that also. They used a dc motor with reversing swith. Clever aren't they ;)

I actually did that with an alcohol stove.

All pellet burners have to have the entire surface ignited evenly to burn well. We need that entire even surface flaming to get the pyrolysis action to do it's thing. Same applies to a can of small twigs. Entire surface needs to be ignited. Twigs need to be compresssed close to each other for a proper burn.