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Post by miklas on Feb 17, 2011 22:05:00 GMT -8
Hello, I found this plan and photos online here: acbagnetwork.ning.com/profile/TonyFillingham and I was going to try to build this big 55 gallon barrel rocket stove using about 9" flue tubing or so. I was looking for advice, I read on here that the shelf for the fuel has to have the bottom third of the area of the horizontal tube. Also the drawer of these plans says that the area under and around the vessel--the gap that that the gasses go into has to be the same area as the flue. Is this right? Anything else I should know--does the L joint of the stove have to be a certain ratio between the flue and the tube that you feed the fuel into? Thanks  |
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Post by Donkey on Feb 18, 2011 10:28:44 GMT -8
That's an Aprovecho style cooker. Typically (if memory serves) the thing should have the same area all the way through. I know that they spent a HUGE amount of time over there figuring out the EXACT gap size around the pot (in your case barrel). One thing I'd do is make the jacket around the barrel higher. You want the heat to stay against the barrel for as long as possible. I think you should go here and check out the "Institutional Stove", it's along the lines of what you are doing. They've got an online design tool there for just this sort of occasion. |
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Post by miklas on Feb 18, 2011 21:21:47 GMT -8
Thanks very much. ^^ The link you provided says the skirt should be about three feet tall, looks like about double what is in the plans I provided. I was sort of hoping that I could just roll out of bed in the morning and cut a barrel in half and make an L out of 8" stove pipe and have a shop weld it into place with some iron bars at the top. But the stove the tool came up for me didn't seem too complicated, but since I don't have any welding experience, I'm trying to think if I can cut all the materials to size and then bring them to a shop. Seems you can insulate the chamber with vermiculite, though the plans don't seem to say how thick the layer should be. I have some 8" stove pipe which would give about 2 1/4" of insulation inside the combustion chamber. Thanks again, I think you provided me a better option if I can do it . |
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hpmer
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Post by hpmer on Feb 19, 2011 7:40:23 GMT -8
I'd make sure you insulated the guts of the stove with some sort of maybe perlite/cob or ash/clay mix since the stove pipe isn't going to last very long.
I made a 4" cooking stove and the pipe lasted maybe 25-30 hours before being consumed and my loose insulation started coming into the burn chamber. I then made a 6" stove out of institutional grade food cans and it didn't make it more than 8-10 hours.
An 8" stove will be even more powerful so plan on some sort of mix that can harden into the shape you need even after the stove pipe burns out. That, or plan on rebuilding the thing on a regular basis.
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hpmer
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Post by hpmer on Feb 19, 2011 7:52:14 GMT -8
Another suggestion is to add another elbow to the end so you can feed it vertically, especially if you are not going to have it elevated. You want to have just the tips burning for most efficiency and the horizontal feed requires almost constant attention, pushing the sticks in manually as they burn. With a vertical feeder gravity takes care of most of that, and you can focus on what you're cookin'.
In my case it's maple syrup. Season's almost ready to start and I just finished my lastest and greatest stove. Built it in a oval wash tub for portability, but it's almost too heavy to move around. Made the feed tube and burn tunnel from a mix of perlite from Walmart and furnace cement from Home Depot in I think a 5:1 mix. The heat riser was made using a form and a mix of ash/clay in I think a 2:1 mix.
Can't wait to start boiling sap!
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Post by miklas on Feb 19, 2011 13:08:21 GMT -8
Aie, was afraid of that, I have the black stovepipe which is supposed to be pretty durable, but that's a good suggestion about using a mix for when it burns out. Or maybe I could just use better sheet metal. Or do both. Thanks for the suggestion about the feed tube as well. I guess you're going to burn maple in your new stove? I was wondering about the "build your own stove" plans--the circular metal option doesn't seem to have so much of an "L" shape as an "I"--there isn't really a horizontal tube where the fuel sticks out, it's an open shelf. I assume this is okay, but I thought it was sort of against the rocket stove fundamentals? |
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hpmer
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Post by hpmer on Feb 19, 2011 19:06:03 GMT -8
The "magic" of the rocket stove is the insulated burn tunnel and heat riser that allow the temperatures to get super hot and burn the fuel most efficiently. Smoke is essentially unburned gases, and with a properly built stove there is little to no visible smoke.
I burn mostly split tree limbs and branches, some maple, ash, birch etc. My new stove is a square 6" system which approximates a 7" round system.
The shelf in your system is to allow air to pass under the fuel and pre-warm it before it enters the combustion area.
Others have used steel pipe for the heat riser with good success, but I think it was at least 1/4", and that is further downstream after much of the oxygen has been used up. I think the best option is masonry for the feed tube and burn tunnel since they hold up better and longer.
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Post by miklas on Feb 20, 2011 0:07:42 GMT -8
Yeah, I don't know much about metal working but 1/4" seems pretty thick and perhaps unwieldy. I guess firebrick is a good option for constructing this ceramic box? One of the stove plans (I think square ceramic) has a few ceramic tiles and then a layer of it looks like vermiculite before the metal shell. I think firebrick is kind of expensive so this might be the way to go. Sounds like you'd use furnace cement to join the bricks? I appreciate all the feedback, it's invaluable . |
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hpmer
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Post by hpmer on Feb 20, 2011 6:41:25 GMT -8
Sounds like you'd use furnace cement to join the bricks? That's an expensive option. Or, you could just use a clay slip (clay mixed with water). Donkey dips his bricks in the solution to lightly coat the joined side which holds it slightly apart from its neighbor. As he says, the mortar is there to keep the bricks apart, not hold them together. |
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Post by Donkey on Feb 20, 2011 17:12:22 GMT -8
You could also get on with the stove-pipe as hpmer suggested. I use clay slip/pearlite and when the pipe burns out it keeps it's shape and works just fine.. Just gotta pull the fragments out carefully, as the mix is a bit fragile and susceptible to bonks. Personally, I like the lighter weight metal/insulation combination(s). They get going and heat up faster than brick.. More mass in the brick needs more time to come up to temp.. 'Course, it's probably just a quibble as the things work GREAT one way or the other.  |
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Post by miklas on Feb 21, 2011 22:33:27 GMT -8
Hm, I'll probably have to hook up with a metal shop either way, so I'm more keen to try the option with the exact measurements and masonry if I can get it. Yeah, they're seemingly pretty amazing, the guy whose plans I posted says he can boil 40 gallons of mash (like beer) in 30 minutes with his rocket stove with only a few pieces of small wood. But I'm preaching to the choir here. ^^
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Post by Donkey on Feb 22, 2011 10:06:01 GMT -8
Ermm.. You may need a metal shop.. OTOH, if it's about the pipe, you probably don't. If you expect the stuff to burn out anyway, there's no point in welding it together. It's pretty easy to cut stovepipe with a pair of metal sheers and sticking it together is as simple as it gets. You don't really even need it to be airtight, at least not the parts buried in mud/pearlite/etc. I've even built the fire-paths out of rolled up cardboard, packed in the insulation and when it was dry, burned out the cardboard. It works, though I've had to clean up the tunnels a bit afterward, wet cardboard tends to sag a bit.. Tip - use waxed cardboard.. |
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Post by miklas on Feb 26, 2011 22:47:08 GMT -8
Hmmmm... but how durable is clay slip and perlite, and can you just stick a metal shelf in there with no problems? I could just screw on the sleeve around the barrel and lay the metal spacers across the top with no welding...hmmmm. Seems pretty cursory compared to the custom plans for the institutional stove, which I think would probably be a better all around stove. Maybe it just seems too simple and I'm not used to it . |
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Post by Donkey on Feb 28, 2011 8:56:16 GMT -8
It's fairly fragile and won't stand up to a lot of banging. It can handle the heat though, and is very easy to work with.
If you plan to use the Aprovecho style feed (horizontal with shelf) you could choose to leave in the horizontal stovepipe. Incoming air will keep it cool, so it won't melt in the heat (stovepipe gets (mostly and worse) eaten from just behind the 90 at the elbow to the top of the heat riser). This will protect the pearlite/clay mix where it gets knocked by the wood.
Most people assume that simple can't work. As a Natural Builder, that deeply ingrained mindset is one of my most present obstacles. I think that our society does that to us on purpose, a necessity for the smooth running of the ever-growth, capitalist thing we've built and currently live in...
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Post by miklas on Mar 2, 2011 22:05:59 GMT -8
Can you repair the area around the stovepipe with more clay slip and perlite mix if you happen to gouge out some at the back or some falls out? Good to hear about the probable integrity of the ends of the stovepipe where the wood goes in. Err and one more question--it sounds like you want to make the L joint of the stovepipe a 90 degree angle, not use one of those multi-sectioned stovepipe 90 degree elbows which is more like a J? Yeah, I've heard simple is better--"the main path is easy to walk on but people love to be sidetracked." |
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