900 sq. ft. home heating needs

[matt walker]

Yeah Andrew, Manny's got good advice there, and yep, switch the riser from feed to riser side of the mold and back a few times during the dry out if possible.

I think you'll get it, and I'm stoked to hear you are going to give it a go without the hardener. I stopped recommending folks try it after I heard from people who had failures, but if you get that it's tricky but can be done, I think it's a great way to go for an inexpensive process. My home system is really performing beautifully and holding up just fine, so I know it's a viable way to go. Just got to be prepared for a failure or two and not let it get you down. Sounds like you have that part figured out to a T, and I'm really happy to see that.

[hpmer]

Freedom, I've had similar experiences. I just took apart a stove to reuse the mix and found it readily remixed when adding water - all except for the part closest to the burn tunnel. That was hard as brick, and although I eventually crushed it with a hammer, my guess is it's more grog than clay.

I had cracking issues until I started mixing in some fiber. I use cut up spent day lily stalks, or ornamental grass stalks, etc. and those seem to work pretty well. Those would be more in the category of freely and locally available, though you might have something slightly different. I've not used the insulation myself, but Matt's had good luck with it on his stoves.

[freedomlives]

It is local clay. When I dug down in the field above our house, I hit pretty much pure clay once past the (unfortunately) thin topsoil. When using some of it for earth plaster this summer, I just dug down enough to where it was fairly uniform cream-brown/latte color and used that, and that is what I am using for the rocket stove as well. One of the neighboring villages had a brick works, so I suppose they used this clay as well. I don't know if it would meet the technical requirements to be a fireclay though.

I actually planned to incorporate fibers, but the fiberglass I pulled off of some old water pipe didn't easily tear into individual fibers so I gave up fooling with it. It would be really cool if the building store sells loose fibers for incorporation into concrete, otherwise I'll buy a foot or two of fiberglass roll.

-Andrew

[freedomlives]

So far, so good--
I didn't get the fiberglass fibers. I could have borrowed them from the attic of a small cottage, but I was lazy to go up there. Instead I put layers of this fiberglass netting (5mm squares) in as I packed down the clay/perlite. Over the burn tunnel I placed (instead of the thin MDF board) a ceramic tile. This held up through a few burns and allowed for the roof of the burn tunnel to dry/harden before having to support itself. The outside of the mold I have so far left on, though I did remove it temporarily to reduce the height and the whole structure on its own seemed pretty firm-- just not enough that I would trust it to support the heat riser alone.

My heat riser has a 7.25" square inside (MDF form, burned away). I covered the form with a clay rich/perlite mix, then wrapped the fiberglass netting around the half-inch thick layer of clay on the form for reinforcement. In retrospect this would have worked better if I had then layered another at least quarter inch of clay rich/perlite mix ontop of the fiberglass net, as now, near the top and bottom of the heat riser, the rich clay/perlite mix is hard but sort of peeling. Oh well... The outer form I made with sheet metal, 19" diameter cylinder. The whole thing is 31" tall. In between is filled with the clay perlite mix.

Then lots of burning (with a barrel inverted over the heat riser) and lots of steam being driven off. I also piled loose perlite on top of the barrel's bottom to increase the amount of heat going down the sides to heat up the heat riser more. Today, with a bit of help from my wife, I managed to flip over the heat riser, and now I've got it burning a bit more because I felt the bottom portion of it didn't dry out on the outside completely. Its heavy, but I could (in theory) lift it by myself. Also now I'm hoping to burn off (melt off? sublimate off?) more of the galvanization on the barrel, and tomorrow I'll spray it down with hydrochloric acid to get the rest off, then paint it with this silver stove paint (heat resistant to 600°C).

[pa_friendly_guy]

If you have not bought the paint yet I would consider getting paint that is rated for higher temperatures. Rustolium makes paint that is rated to 1000* or 1200*. There are other brands as well. The barrel will definitely get hotter than 600* and your paint may burn off. When I looked for paint for my Rocket Stove Pizza Oven I looked around and many stores only had the high temp paints in a spray can. I did find it in quarts and painted it on with a brush, I felt that would give me better coverage and a slightly thicker coat of paint than what you would get from a spray can. Black and silver seemed to be readily available in quart cans, other colors would have to be special ordered. If your goal is to have an attractive unit with at barrel all the same color higher temperature paint might do a better job for you. If your goal is just to stop the rust the lower temperature paint may work for that. Just a thought. If you already have the paint that go ahead and use it, you can always repaint in the future if needed.

[hpmer]

He's talking 600*C, not *F.

[pa_friendly_guy]

Never Mind, ,,,,,,,,,,,,,,,,,

[freedomlives]

I bought the cheapest stuff actually! 1€/100ml, but it is what is typically used by people here to make a silver colored coating onto the cast iron of their wood burning stoves and/or the stove pipes. The only listed ingredient is 50% water glass (Sodium Silicate), and I suspect the other 50% is fine aluminum particles. Probably not as tough as the spray paint cans of muffler/exhaust pipe paint, but much cheaper, and if a couple of Euros wears off after a year, I can spring next year for the 10€ spray paint cans...

[freedomlives]

After a really long delay and just kind of hunkering down for the winter with the old stoves we have in the three livable rooms of our house, my wife got to prodding me to continue with the rocket stove so that further renovations can continue.

So I moved the core inside, and have made a foundation layer of perlite clay to keep heat from going down to the floor, and then as I was setting the barrel on to get a feel for position, how the smoke will go down, etc. I realized a potential problem:

My barrel is 56cm diameter, the heat riser is 48cm diameter. The difference between the areas of these circles is 832cm^2, my CSA is 400cm^2, so in theory seems good. But now I realize I won't actually have all of that area between the barrel and the heat riser open-- the CSA of the opening of the barrel where it hangs off the core will be only 220cm^2. Half of the system CSA. Does anyone else have this problem? Do your rocket stoves still work?

I could always make another heat riser with a smaller outer circumference, but I'd rather not do that if possible. I don't think I can find a barrel with a wider diameter-- 56cm or so is pretty standard.

[freedomlives]

I guess I found my answer:


I was trying to do like in the last of the three images, but that just won't work. So I need to cut some out of the side of the barrel and build up the bench around it...