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Post by Donkey on Mar 21, 2012 15:14:52 GMT -8
Ah, but in a rocket stove, you get gas movement out of heat differential. The difference in temp (and density) between the heat riser and the barrel allows flow without a chimney. Anyhow, there will be plenty of heat left over to drive a chimney attached to the bottom. thewongs, I'd move the exhaust down as far as it will go. With the lid closed, you've got a fast radiant heater there.. Maximize by making the chamber as large as is practical and the exhaust as low as possible. Remember the "stream profile" thing.. It's important. You might be able to reduce pipe size if you can dump enough heat.. I'd do the experiment by building your gizmo straight system size and trying it with a reducer on the end. You can try it reduced or standard and see what works (or not).
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Post by Donkey on Mar 21, 2012 14:57:36 GMT -8
Cool babe, It's just that you didn't say hi first, just dropped youtubes and boogied.. Looked a bit like spam. Welcome to the boards.
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Post by Donkey on Mar 20, 2012 18:42:19 GMT -8
In theory, all same same is good. In practice, it's simpler and more effective to provide a larger area at that point, then reduce. Peterberg describes how to math it on the helpful hints thread.I'll quote his opening shot: There's a difference between a stream opening and a stream profile. The main culprit is the gap between insulation canister and barrel. When you're only looking at the opening in the side of the barrel, it's easy to think you have to make the opening the same as system size. This is utterly wrong, because the gases are not streaming straight out of the opening. Instead, it is coming from left and right, and from the top. Moreover, in the corners two streams can't pass there at the same time, so you have to compensate for that. Maths can help here. Start with system size area, divide it by the gap between inner and outer barrel, add twice the size of the gap for the top corners and you've got the length of the stream profile. The profile length consists of the top rim and sides of the opening. For example: system size of 8" equals a little bit more than 50" square. The gap is, say, 2" wide, which will get us at 25", adding the gap twice will give us 29". Presuming the opening is one foot wide, the height need to be half of 17", which is 8.5 inches. The open area in this instance will be about 90" square. The resulting opening in the side of the barrel will look enormous, nevertheless this is absolutely the correct method. The recommended gap is smaller than in my example, so the profile length will be even larger. P.S. The top rim is rounded, so you have to measure it along the contour, not as a straight line.
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Post by Donkey on Mar 19, 2012 19:09:38 GMT -8
2 possible issues: The exhaust at the bottom there, pretty likely that there's not enough space for proper flow. See the helpful hints thread. It's unlikely that just sticking a stovepipe in the side there will do it. This one is the one I'd check first and my bet for the problem. It could also be the gap above the heat riser is too tight.
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Post by Donkey on Mar 19, 2012 9:19:25 GMT -8
Nice test.. Supports the P-Channel very nicely. Your filters and my nose agree..
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Post by Donkey on Mar 18, 2012 9:58:22 GMT -8
No.. The bench is NOT made of fireclay, not unless you find it in your soils anyway. The only place you might need fireclay is inside the firebox itself, in contact with the hottest conditions.
Red clays that set in very wet conditions for a long time will loose their red coloring.. Normally, the clay will turn grey or black, sometimes it will go white. The red (usually more orange) comes from iron oxides (rust) in the clay. Under water, the oxide will be driven out (by some chemical process) leaving behind just the iron which is black. Over time, the iron can be leeched out, leaving behind white. So, just because your clay is white, it doesn't make it fireclay. It's a likely candidate, just not proof positive by color. The only way to know is to put the stuff in a fire and see what happens. The clays here at my place are NOT fireclay, more like brick makers clay. It does just fine inside a standard rocket stove. In my foundry however, after a while it turns into a slushy, liquid and when it cools it looks like glass. Clear indication that it isn't fireclay.
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Post by Donkey on Mar 17, 2012 16:48:50 GMT -8
Oh, I forgot to mention... Of course at some point, you'll want to throw your test into a fire. Let 'em sit in the fire for a good long time, maybe overnight. The point is to subject each test to more abuse than you think it will ACTUALLY receive.. You want to be able to say "If they survive that, they'll do fine".
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Post by Donkey on Mar 17, 2012 16:43:30 GMT -8
There are several tests you can do. First, take your candidate soil and fill a mason jar 1/3 full with it, add water to just below the top, screw on the lid and shake it up really well. Set it someplace well lit where you can watch what happens next. Rocks and sand will drop to the bottom right away, silt will swirl about for a bit then drop out next, clay will want to stay bound up in the water but will slowly settle on top of the rest and organic matter will tend to float. It's helpful to mark the jar with a felt-tip as each material seems to be done dropping out, no point marking a clay line (below fine, but not above) it can take hours or days to finish depending on the clay. This test will tell you that you have clay in your soil but it won't tell you anything else. While yer watching the jar, take a goodly handful of the same dirt, wet it and kneed it around in the hands. You should have a sticky clump that doesn't come off the hands (or anything else) easily. Take that clump and roll it into a long worm, a good long worm that can hang off of your palms and then be twisted over on itself without breaking indicates high clay content. When the worm tears, it should separate begrudgingly and leave ragged edges. Smash the clump in your hands, you shouldn't be able to wring water out of it and when gently squished between the fingers the surface will not get shiny. If you can wring water out, it's an indication that there is a lot of silt masquerading as clay. Silt and clay feel quite alike as they have similar particle sizes but they are very different materials. Clay holds onto water, silt does not though both feel sticky and slick in the hands. Silt can be easily rubbed off, clay sticks and smears.
It's good to have a lot of clay in your soils, but high clay content (when making cob) is not necessarily ideal. Good cobbers soil has a high amount of sand in it, if the soil is really high in clay (like mine) you'll need to add quite a bit and it's a lot of work. Best to find "readymix" with a lot of sand already in it. The best test of the quality of your material is to make test pucks or bricks and let them dry out completely. Once they are dry, look them over. High clay content soils will crack, more bigger cracks indicate a lot of clay and/or very expansive clay. Crumbly, easily smashed into dust means high silt or even too high a sand content. The ideal is a piece that dries hard with no cracks, something you can't crush with your hands and feels rock-like. Better to have too much clay than too little, a mix can be amended with sand but if you don't have the clay, it's a bust. If your tests show good for clay, start experimenting with how much sand to add (assuming) make more pucks/bricks, make them the same size and label them well. First puck will be the un-amended soil, second puck add a ratio of sand, add sand and make several mixes changing the ratio as you go. Use easy ratios, 1part this, 3 parts that, 1/2, 1/1, etc. Carry on till you just know that you've added a stupid amount of sand. Set them all out to dry then (when they're done) test them to destruction, select your favorite results and make new tests using straw, do the routine again and repeat.
This'll give you an idea of what you've got and what you can do with it. You can read all about it somewhere, but nothing beats fooling with it yourself. The higher sand mixes will have higher thermal mass and tend (depending on the type of sand) not to crack around hot parts of the stove. Higher straw content will tend to have higher tensile strength, higher sand better compressive, and so on.
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Post by Donkey on Mar 13, 2012 10:06:11 GMT -8
Well.. I've never been quite satisfied with my stove at home.. Looks to me like this might be just the ticket to change that. I'm re-thinking this statement.. My stove is pretty good at turning wood into fire, which is what this nozzle helps to solve. It might help a little though, and I'm considering it. Actually, what my stove lacks is enough thermal mass in the right places and a quick radiator (barrel or some such).
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Post by Donkey on Mar 13, 2012 6:53:46 GMT -8
Well.. I've never been quite satisfied with my stove at home.. Looks to me like this might be just the ticket to change that. I'm excited about this and look forward to your results.
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Post by Donkey on Mar 12, 2012 19:17:58 GMT -8
Hmm.. 133C does change the equation somewhat.. Still, there's some head-scratching, hair tugging and elbow grease involved to make that one work. For small footprint solutions, have you explored the bell stove concept? Dunno how that would entirely heat yer old house, but bell stoves are VERY versatile. Definitely worth a look.
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Post by Donkey on Mar 12, 2012 8:19:04 GMT -8
Mostly, safety issues fall into the category of inexperienced users. Covering the feed to shut off the fire, then lifting the lid to see how it's going, the works can fill with flammable gasses which can ignite explosively when in given air. The most common is placing really long sticks in the feed, which can hang up and fail to slide down, when the bottom burns off, the sticks will over-balance and fall out of the firebox onto the floor of your home. The rest of the safety concerns come from inexperienced builders. Using river rock too close to the heater core or (my personal favorite) placing water heating coils in the barrel where temperatures can flash water to steam. Problems can come from placing different materials with different characteristics against each other and not allowing for differential expansion. The stove will crack and though I haven't seen a problem yet (my stove suffers from this) my assumption is that it's a real issue.
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Post by Donkey on Mar 12, 2012 7:57:39 GMT -8
To my knowledge, salts have not been tried. It's a complicated solution that (in analysis) presents more problems than it solves. Water storage HAS been tried with various results. Seems to me that water storage suffers the same, more problems than solutions.
Solids as storage (rock, brick, sand, concrete, cob) is simple, effective and safe. Neither of the above solutions tend to accomplish all three. Not to say it isn't possible, just hasn't been done satisfactorily yet.
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Post by Donkey on Mar 10, 2012 11:56:22 GMT -8
Aha!! I finally got the book. Page 42.. Interesting stove, but NOT a rocket stove, mate. You might want to ask your question of the folks over at Aprovecho.. It's their gizmo after all.
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Post by Donkey on Mar 10, 2012 11:36:53 GMT -8
Well, I'm having a hard time downloading the book, I keep getting corrupted files. Also, for some reason, I can't load the large version of the image you posted. Grrr! Can't very well answer the question without some idea of what yer talking about. I'll try again in a few minuets, but first a stab in the dark kinda comment.. With standard rocket stoves, I don't think anyone's really quantified how much heat is stored/produced by a given amount of bench (assuming that's what you are asking). The very little bit that I can see of the small version makes me think that you are NOT building a standard rocket stove, perhaps even not a rocket stove at all.. ??
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