more DSR pics (double Shoe-box Rocket

Note the opening to the left of the tank, exhaust gases travel counter clockwise around the tank once the insulated top is installed

Two water connections to the tank, hot through the upper pipe, cold through the pipe that exits the enclosure botom


I prefer to think of the junk you see as a parts depository, the stove pipe comes up in the center of a poured concrete 2′ wall from the basement, runs horizontally, then down to the ground

The wider area of the pipe after the angle pointing down houses a small fan,

Though it looks solid from the sides, there is actually quite a wide openiong for the exhaust to exit. This configuration keeps the fan dry, allows for a small amount of falling for the exhaust as it cools, and protects pretty well against strong wind


sThe tank enclosure has an insulated   top and sides, with just enough room to circulate exhaust around and over the tank to transfer as much heat as possible to the water.

5 thoughts on “more DSR pics (double Shoe-box Rocket”

  1. Hey, nice build.
    I love the way you diverted the exhaust and used a cheap fan to do it.
    Have you gotten any weird condensates from the wood smoke?
    I know you managed to boil the water in the tank to steam and still have 100 degree exhaust, but it looks like the water lines are made of PEX pipe, and that they run directly into the bell.
    PEX has a temperature rating of about 200 degrees F, so is it even PEX I’m looking at?
    I want to build outdoors and bring the hot water or better yet, steam , indoors, so I’m very intrigued with your work.

    1. Hi, sorry to be late in responding, yes, that is pex pipe going into the bell, and it is not without problems, but not totally because of temperature. Past experience tells me the pex will only blow at high heat if it is under extreme pressure, and the 200 number is likely pretty low. I have not generated much steam with this setup, and the internal routing of the exhaust stream takes it all the way around the tank before coming in contact with that area. But for safety sake I did wrap it in ceramic fiber as insulation, an extra safeguard. The next rebuild will use cast iron fittings inside the bell.

      The only problem I had with the Pex was a mechanical one related to the tight quarters and heaviness of the tank snapping a short section of pipe in two during the setup phase.

      I don’t know if weird is the right term, they are simply wood condensates, and lots condenses on every internal surface the exhaust comes in contact with except for the final leg going up and out which only has a light black film. Likely most of that is from start up and ember phases when efficiencies are lowest

  2. Thanks for the reply!
    Good to hear, about the temperature performance of the PEX.
    I aim to make a lot of steam at low pressure, so it still might not suit my needs.
    The question about the condensates was because of the downward path of the final section.
    Because of your fan, you could potentially cool your exhaust till its heavier than the surrounding air, or even condense some of it.
    Sounds like you have deposits much further upstream in the system.

    1. If you’re trying to generate steam, a tank system like this would not be too good. The bulk of the water tends to keep everything equalized, so while you can get hot water at about the same temp, the flash point is unlikely to be anything you would want to reach at that volume, even if you were getting it hot enough, there would be a danger of a sudden flash which is where explosions and other troubles start.

      I ran a conventional RMH with a regular heat riser and 55 gallon barrel wrapped with 1/2″ copper, I also gave a thought to trying to generate instant hot water using thinner diameter copper . That system might be better suited for generating steam, (I did it quite frequently by accident in the early days before the thermostat pump control)but again, playing with steam is not for the feint of heart, you may need heavier material than copper . Be aware that system ran dry at one point and melted a solder joint on the coil, The ordinary mass heater has some real power, especially with a well insulated properly sized heat riser. (much less soot also.)As far as the pex goes, my lines were exposed to a fair amount of steam under low pressure, but I would not reccomend it as a regular practice. My steam episodes were accidental, not deliberate, and under no pressure the pex did distort, so eventual failure would be likely. You may want to go with steel/iron to avoid longer term breakdown of materials.

      As far as the deposits, when the exhaust is dirtiest, the water tank is coldest, and with a fairly large surface area exposed to the exhaust, almost all the condensates are falling out of the exhaust. In fact, I am still pondering how much danger there might be from the soot and all suddenly igniting inside the stove if that end got hot enough. It certainly is a good reason to keep it a little cooler(300F) there.

      It’s been a while since I opened the stove, and I may just let it go till rebuild time over the summer. But I will publish what I find,both here and at donkey’s

    2. I need to update my reply and relate a recent pex failure on the hot water side of the water tank.

      I had been heating the tank for some time under pressure, and started to take a shower, but because the water was very hot the hot water tap was turned way back till it was just slightly on. Meanwhile the fire was still heating, and a couple minutes into the shower I heard the sudden release of pressure, which stopped the shower, and I quickly turned off the supply line. closer inspection found a split in the pex where it first comes out of the tank. There was very little damage otherwise, and quickly turning off the water supply meant there was little cleanup. I replaced that area of the line with steel fittings, but it is my concern that this could be an ongoing issue that will require closer monitoring in the future.

      The evidence suggests that running the hot water softened the pex and the pressure (even though it was not extremely high, I was showering remember) caused the pex to fail. Using my previous system it was easier to vent steam with no pressure, and the times when I did have pex failure were always under pressure

      My monitoring is still somewhat primitive, but I do have a couple of places now where it is easier to track approximate tank temperatures and I’ll install a pressure gauge on the system to get better numbers.

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