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Pocket Rocket indoors, design question  RSS feed

 
Jon Atkinson
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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
 
Jon Atkinson
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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?
 
Roger Merry
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Hi
Couple of questions - you're using the 2.75" pipe as an exhaust yes ?? Dropping from 6" to less than 3" is a hell of a drop I've kept to the same diameter all the way through the system (5") until the last 6 feet as it exits the building where it's 4".

Strikes me that you're so near having all the stuff for an RMH it would be better to build that even if you add the mass later. I got all the stuff for mine from a scrapyard - cost about £20

Have you got photos ??

Roger
 
Jon Atkinson
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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.
 
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