I'm building a rocket stove for heating in my garage. With all things considered from last year's research and wondering about the use of my existing chimney I decided to abort any plans to use the chimney with a rocket stove.
In the picture in the link here there is a rocket stove dry stacked showing 7 bricks laid on their side to form the bridge area of the combustion chamber. I have seen 5 bricks also used.
What I am wondering if I could not use perhaps 3 or less for the same thing without affecting the performance of the stove? My garage is cramped for space and if I can save a couple inches in overall length it would help me out a lot.
I won't be utilizing any heat storage other than what the stove itself can store. My plan is to use less fuel to keep the heat output lower and not waste fuel. My wife and I work away from home and instant heat is more up our alley for our requirements.
As long as I maintain a good ratio to the height of the heat riser with the length of the combustion chamber I think I should be ok. IE having the heat riser being at least or more than twice the length of the combustion chamber high.
I think the length of the burn tunnel has more to dowith the space requirements for the two barrels (the one surrounding the heat riser and that encompassing the feed tube) since they are sitting side by side. You'll want to enclose the heat riser with insulation to ensure a complete burn so you'll need some horizonal length, but I thnk minimizing it to what is necessary should be fine as long as the relationship to the heat riser is 1:2 at least.
Are you planning to just use the exit pipe as a radiator to throw the heat off? The stove won't throw enough heat by itself as it really should be well insulated, and especially won't for quick heat.
The shorter the horizontal run the better your stove will work. That part is just to get the firebox out past barrels and whatnot, and the struggle is ALWAYS to short it up as much as possible while keeping it just long enough to do the job.
From your image, it seems like you've got the horizontal run FAR too long. Well what the heck, if it works, it works.. Right??
Hpmer, yes I am up to speed on the items you mentioned and aware of them as well. As to the pocket rocket..........I think the thing they do best is send heat up and out the chimney. I will consider this more though as I will be using heat exchangers up stream from the stove itself.
Donkey, thanks for the compliments on the layout and dry build but that is not my doing. That picture is simply one I found on the ilovecob website that illustrated my question well. It was because of it's extreme horizontal length of the tunnel that raised my question about how long it could be. My build is going to be much shorter.........in fact as short as it can be made now that you have confirmed my suspicions about shorter being better.
I mentioned about heat exchangers being used downstream. Actually I thought about peterbergs double bell system most of the summer and I am going to build it but instead of using brick I am going to build a conventional rocket mass heater with two barrels instead of the usual one. The second barrel will mount on top of the first with approximately 4 inches between the barrels vertically to allow more heat to be given off from the first bell and then a second barrel will form the second bell on top. Being all steel they should throw a very large amount of heat rapidly and by pulling off as much heat from the gasses as possible I can negate the need for an external chimney and just vent it through an exterior wall.
In principle, that post I made just recently on the scaled down rocket stove is very similar in design to what I will now build.
Err... Just remember that bells have the intake and outflow at the bottom (of each bell). Not sure how that would work with one barrel on top of another, though it would be easy-peasy if they were next to each other.
It would be configured exactly the same as peterbergs brick version in the earlier part of those threads. Peter had the bottom and top bells sepparated with paving stones. Mine will be the closed bottom of the barrel/s. An internal stove pipe that passes from the lower barrel to the top barrel will act as the second heat riser inside the barrels.
A normal rocket stove barrel sits over top of the heat riser with the exhaust coming out the bottom of it. Same thing can be done but the exhaust is drawn from the bottom via a chimney pipe within the barrel as opposed to the outside like normal. That chimney pipe then passes out the top of the first barrel - passes through 4 inches of air and then is passed through the bottom of the top barrel to the inside top of the upper barrel. Exhaust then is drawn off the bottom side of the upper barrel. Same smoke path as there would be in a double bell but Peter had his exiting out the top. It is an easy difference to deal with.
LOL, yes I will. I will try to do just that and take pics throughout the process. Something I have been wondering about though. Fireplace cement or mortar are impossible to get here. Seems there has been problems with guys mixing their own ratios and problems resulting later from cracking etc. Building inspectors have since gotten involved and made if difficult to have the fireplaces pass inspection if non standard mixing was used. Hence, there is now a premixed mud that costs about twelve dollars a pint for the stuff. I'm not paying that kind of price. Can you spell RIPP OFF? LOL.....anyhooo. What I have been thinking about doing to get around this is to make a big rectangular frame made out of plywood to make a concrete form. The form would be the height of the top of the feed tube. In which I would pour/fill it with a vermiculite or perlite mix with a portland cement slip just to act as a light coating and give it some formable strength. I have no clay to draw from otherwise I would use a clay slip instead. Question;
Do you think the cement slip will cause problems once it gets exposed to high temps and it surrounds the rocket stove body?
My thinking with the concrete slip is I could dry stack the bricks for the stove within the plywood form work and then pour in the vermiculite/perlite/slip all around it and let it set up well before firing it. Then the stove would be securely held together by the encapsulating insulation shell. And I would not have to shell out for that expensive premixed mortar mix. I think it should work.
Post by mountaindreamer on Jan 22, 2010 22:49:15 GMT -5
I don't know the most about Portland Cement, but it contains a lot of toxic stuff dumped from other industries. My immediate reaction would be not to put toxic stuff by the fire. Donkey can probably tell you way more than I can.
I never even considered the possibilities of a school program. I will look into that.
If I could find enough clay, how much would have to go into the mix for 5 gallons of liquid slip? Would a ratio of 10 to 1 water to clay be enough?
I have a potter just down the road from me and inquired with him before about the dregs of his workings. I know there is a name for them but essentially they are the left overs that have not been fired and could be re-hydrated and used for my purposes. He wanted $5.00 for a small bag that might have held 2 quarts of volume. I thought that was high for scrap material but........not being familiar with the stuff it could be cheap? What do you guys think?
I am also still considering a castable refractory that is readily available.
I wouldn't use portland.. It'll heat shock and break apart. It's also full of industrial flue ash and heavy metals, etc. A result of the clean air act...
It's hard to imagine that you've got NO clay in your soils.. Look again, you might get a happy surprise. Don't expect pottery quality clays, or even brick makers clay, but there's got to be something.
All clays are different so I can't toss out a formula for you to follow blindly. If you use potters castoffs, make a thin milkshake out of it. You want it just thick enough that when you put your hand in, it forms a coating that looks like a glove when you pull it out. Too watery and it won't form the glove, it will run off, exposing skin.
Well Donkey, I am not saying there is NO clay around here but I have not found any. We have lots of what us locals call clay that forms the clay banks surrounding the lake. But that so called clay is silt. According to a local potter it totally crumbles in your hand when squeezed after it has been fired. It has a real powdery feel when dry. It can be extremely slippery when wet. Normally it is real flour'ish and powdery, dusty, yet when in its natural setting as part of the clay banks it will break away in large chunks that will break apart as it rolls down the hillside.
I would like to use natural clay to encapsulate the rocket unit. Problem is it will be at least two more months for the frost to come out of the ground so as to be dug. That puts a damper on building plans. However I would prefer to wait if it meant having a better product when done.