Jon Atkinson

Patrick,

My brother-in-law and I built a rocket stove, more like a hobo stove, from a 55 gal drum for his shop. It took about an hour using some of the stuff we had laying about. He only needs heat out there once a week or so and when he wants it he doesn't want to wait for something like an RMH.

Essentially all we did was cut 2 holes in the top of the lid to fit 6" galv stove pipe, we shoved a 3 foot (or is it 30"?) section in until only a couple of inches were sticking up, this is the feed tube. We then filled the bottom of the barrel with several layers of old patio pavers until there was only a couple of inches between the bottom of the feed tube and the pavers. We also used some pavers on their side to protect the side of the barrel from overheating. We only did one row of these, the top 1/2 of the barrel is left alone. We hooked up a 6" flue and piped it outside, ideally we would have used a 4" but this is what we had. We experimented with it outside before we brought it in to verify that it worked well.

It took us a little while before we figured out the best way to fire it up, but since we got the system down we haven't had any smoke issues while lighting it, and nearly none when it's burning.

We use old 6' fence boards, usually split into a few thinner pieces, and just stick them in. The only times we've had any sort of issues is when we've had it burning for a long time and it was really hot. On those occassions the radiated heat will start the wood on fire close to the feed tube opening and then it will creep up the wood against the draw. Usually we can just give the wood a jiggle and it'll settle far enough into the feed tube that it's fine. To be on the safe side we've started sawing all the boards to 3 feet, just in case.A single 1"x6"x6' board takes about an hour to burn when we first fire it up, it takes about 1/2 an hour when everything is good and hot.

The design is good but it does take a little while to really start putting out serious heat, which could be due to several factors, and I'm planning a few upgrades that could really help. One drawback is the feed tube needs to be replaced every now and then because the bottom burns away. Replacing it with a good thick piece of steel tube should fix that. I'm also thinking about using the pavers to create a feed tube. All sorts of ideas to play with. I'll see if I can find some pics.

Read, learn, experiment, have fun, be safe.

Jon

I've been fascinated with strawbale buldings for a long time and I plan to build one if I ever get a little piece of land.

Anyway, I wanted to relay a story that some of you may have heard. In Minneapolis in the late 90's an architect and builder decided they wanted to showcase strawbale construction. They built a beautiful 2-story post and beam with bale infill. The interior was well finished, tongue and groove pine ceilings, hardwood floors, it was really nice. And it was all donated to an under privileged family.

I was touring the site just prior to completion and I noticed they used EIFS panels for the exterior. I thought, that in itself isn't so bad if it's implemented properly, except there were huge gaps between the panels, no waterproofing or vapor barrier underneath, and many of the panels had corners broken off with straw actually poking out. I pointed this out but nothing was ever done about it, I didn't have any official capacity. In four years time the house was infested, mold-ridden, condemened and demolished. All because of a simple fix that would have prevented all of that.

I'm all for strawbale buildings but it requires common sense. There have been a few other locally built buildings that have met with better success.

BTW: bales are going for anywhere between $4 and $7 each within 10-50 miles of downtown. Square bales are getting increasingly harder to find around here as the big rounds become more prevalent.

Thanks Roger,

I knew I'd probably have issues with the small flue, I've been hunting around for a 4" piece of stove pipe and found a short-ish one at my dad's and we'll be putting that on this weekend. Choking down the intake by covering the feed hole helped some, and when we dropped some flaming newspaper down the flue it started to whistle but as soon as the newspaper was finished it went back to it's normal smoking. We have some 6" that we can use as a flue until we get it piped outside and necking down to 4" sounds like a good idea. I know there's a relationship between volume of the system, pressure, heat and velocity of the incoming air and exhaust, I'm just hoping with some minor trial and error we can hit upon a good formula.

The reason we haven't gone to a full RMH is due to space and the need for some additional materials. The pocket rocket is intended to provide us heat while we create the area needed for the RMH. Collecting or purchasing the extra items ro the RMH will take a bit of time, but I'm hoping we can have something in place next spring. I'd like to stay away from using clay or anything that requires water, we were thinking using sand but, as I read here, it seems to insulate itself rather than transmit the heat well. If anyone has suggestions on this I'd like to hear them. I've read the 2 portable RMH posts and I'm gathering ideas from both of them.

We didn't take any pics mainly because I enjoy the doing and leave the picture taking to my friend and he didn't have his camera, and it was cold and wet. We'll need to disassemble the whole contraption before moving into the barn anyway, so we'll take pics then.

Wow, I really need to learn to be a bit more concise.

So, we celebrated the first major snowfall of the season with a couple inches of fluffy slipperiness, we also created our first pocket rocket. We had a 55 gal drum, a 30" piece of 6" stove pipe, an old portable basketball hoop post (about 2.75" i.d.), and a buch of old concrete pavers. We stacked pavers in the bottom of the barrel until there was about a 2" gap at the bottom of the fead tube, took about 6 alyers. Then we filled in the edges with some of the broken bits and put a vertical layer around the edge. After cutting holes in the lid and adding the feed tube and the exhaust we fired it up. It worked but not quite as rockety as I'd hoped. The flue was warm but not hot, I could touch it briefly when it was going as well as we could get it. We're going to be changing to a 4" flue to see if we can get it really roaring.

In hindisght I think we should have moved the barrel into place before we loaded it with the pavers, it was nice to be able to build it in the garage and out of the snow, but it was a wrestling match with 2 largish guys vs. one barrel. It ended in a draw, not as far from the building as we'd hoped but far enough away that we felt safe and too exhausted to try and move it any further.

I think the pavers really helped to store the heat and provide a buffer for the barrel, as the lid of the barrel stayed free of snow for a couple hours after letting the initial fire go out.

A couple questions that I hope somebody will be able to answer; Can I use elbows in the flue of the pocket rocket or will it add to much friction? And will running it outside to the same height as an old woodstove flue be too much distance for good draft? The structure is a pole barn with 10' walls and I think the total flue would end up being about 15-18' total. Would this require the use of a larger flue ro would the longer distance cool the exhaust too much regardless of flue size?

Hi Chad,

The only issue I see is that the heat source needs to be below the cold for the thermosiphon to work. If you put the heat sorce above the cold then the hot will just stay above the cold, it'll have no reason to move down. Whereas, if the cold is above the hot you'll get a constant push from the cold water displacing the warm.

If you're using passive solar to heat the water, you can use a small PV panel and battery to run a pump to circulate it. If the pump is running all the time you may not have an issue with freezing water in your pipes, but if the pump stops and your temps cause the water to freeze in the pipes it could be serious problems. Of course, you could try a hydraulic ram pump, I've never tried one, but I'm sure there are folks here that can give you some good info.

I made a small foundry using waste oil (haven't tried WVO). I start it with a propane feed and then start the oil drip and turn off the propane as it takes off. I use an old vacuum cleaner to supply the air, I still need to attach some sort of voltage regulator because it's way too much air. The oil drip tube runs right down the middle of the air / propane feed tube and ends just short of the end of the feed tube, the high velocity of the air vaporizes the oil before it enters the combustion area. I don't have a thermometer to measure it but it's hot enough to liquify aluminum very quickly. (My nephew dropped a soda can in it on one of the initial burns and it the whole can dripped out the bottom in seconds. Didn't have a crucible in it at the time.) It's packed away at the moment, since I haven't done any casting for a while, but maybe I can dig it out and get some video, or at least some pics.

I'll try to find the link that provided the inspiration. You might be well served looking into what the casting a forging communities do. I see some similarities; making a really hot clean burn, materials to withstand the heat, insulation, make it cheap, make it yourself, recycle.

I had an idea for using a couple car radiators to heat a space, but I haven't had a chance to try it yet. The basic concept was to have a 40 gal or larger water heater tank, preferably with side taps, and run a heat exchange coil from an RMH or a solar panel, then run additional lines to the radiator(s). This would be run entirely through thermosiphoning, so the water tank would need to be above the heating coil, and the radiator would need to be above the tank. Hook up a small PV solar panel and a 12v battery to the radiators fan and you get forced air. The tank has a TPR valve, so overpressure shouldn't be an issue, and pop the radiator cap to add more water or burp the system. I would be inclined to add a small pump or 2 just to give peace of mind and also not need to be too concerned with placement of each component.

I'm not 100% sure about the whole thermosiphon thing. I know going from the heat exchanger / solar panel the water will circulate if the tank is above the heat sorce as the cold water from the bottom of the tank has more density than the hot water from the panel and pushes itself through the system. I would think going to the radiator would be similar as long as there were no air bubbles in the system. It works in my head, but I'd still like to see it in practice.

A friend of mine has an insulateed workshop, 1000 sq ft or so, and we're planning an RMH but we need something to get us by until then. Our thoughts were to use a pocket rocket but I have concerns about the use of elbows affecting the draft and exhaust temps and clearances to non-combustibles, especially from the flue. I haven't seen good edscriptions of indoor pocket rocket applications, and I don't recall seeing any elbows on the ones I've seen.

My idea is to use a 5 gal bucket (or bigger if I can find one), 4" flue with 2 elbows and a 6" feeder tube. I plan to line the bucket with old patio pavers to add mass and help the longevity of the bucket. There's already an 6" wall penetration at about 4-5' above the floor (dirt) from the previous owners wood stove, which he didn't leave. The wall is insulated, steel siding, plywood interior and, of course, the 6" penetration ring. I was thinking that a 4" flue would give some additional clearence at the penetration, but would the elbows slow the draft too much? I'm also thinking about building a small enclosure of block and sand around the bucket. The idea is to make it good enough to get us by this winter while we finish sourcing all the parts for the RMH, and easily removed when the RMH is ready for install.

Thanks