Ralf Siepmann

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since Jul 04, 2015
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forest garden tiny house
Northern Germany
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Recent posts by Ralf Siepmann

Reading this thread I immediately remembered this solution of a German enigineer, but it´s only viable if you go large scale, and by this I mean very large scale.

Find an area with massive uncracked bedrock, cut a very big cylinder into that bedrock (the techniques to do that exist in other industry sectors, mainly mining and quarries) , seal it on the sides and lift it by pumping water underneath.

Most information about the concept is in German, but there´s an explanatory article in English HERE
6 months ago
I know this one.
Caper Spurge
8 months ago
Thanks Thomas & Satamax !

There´s a guy with the nick Manuel over at Donkey's who had the same idea independently and uses it in his builds, but he cuts the pipes by eyeball, which is ok when he cobs them in.
Cutout template rolled around the barrel is 44 cm / 17.5 "  wide and 15 cm/  6" (system size) high, circumference/edge length approx 1 meter / 3.3 feet.
More important to me was the intersection depth that is 11 cm / 4 1/3 " (depth 0 means tubes touch but do not intersect).

The nicest thing about this I discovered: when you open the cleanout you can see straight through to the bench entrance an clean super easy if necessary.
And since the combustion unit is mobile you can hook up the thermal battery left or right depending on where you install it.

The build sequence isn´t published yet, I plan to do so here and at Donkey's, but it will take some time. I want to run the stove for some time and get used to fire it under all atmospheric conditions before I declare success.
Here´s a pic of the finished unit. Flue pipe ends sticking out behind the barrel to the left and right not visible here:

2 years ago
Good idea to make this thread!

Brief explanation: a rocket combustion unit on wheels and not much room at the back side of the barrel.
Idea: Intersecting the barrel with the flue pipe. Pipe runs tangential and opens where it cuts the barrel.
Advantages: bigger open space and less direction change of the exhaust gases compared to a 90 degree outlet. One of the side openings is the flue connection and the second is capped as clean-out.
Challenge: get the intersection cut to fit. Solved with an Excel template calculation sheet.

Printout of the actual intersection, according to theory:

Checking my math with cardboard tubes, you should get the idea by now:

Template cut out and layed on target area at the actual lower barrel part, 2" above floor for ash deposit space:

Tubes cut (jigsaw), matched, secured with screws and sealed with high-temp automotive silicone (lack of welding equipment):

Opening viewed through the exhaust/cleanout pipe:

Metal "manifold" with cutout for core:

Transition space viewed from the inside:

"Manifold" in place:

Being built in with cob mortar and perlite/clay insulation:

The finished heater is running its exhaust through bell bench in the 4th week now with no hassles.

2 years ago
Here in Germany there´s company that produces basalt fibres for composites, they sell their "waste" cut to 2.3" for cheap. Maybe there´s the same where you are if you google it.
2 years ago
Hi Glenn, great build !
From the drawings and pictures it seems you actively cool the upper part of the feed tube by channeling the air for the p-channel around the metal collar that´s sticking in the feed.
If I´m right, how well does that work, and does the plate next to the feed still get hot enough to cook some tea on it (as there is a small kettle there) ?

Looking forward to more pics,
best wishes
2 years ago
Hi Abe,

my first thought was: Leave the outside barrel faces exposed, looks like a happy home !

Kidding aside, the main problem would not be the heat conduction of the steel itself but the air enclosed that can move freely and start a convection loop inside each barrel.
It will charge heat from the inside face, rise, move along the top and give it off and cool and fall down at the outside face of the barrel.
To counteract this you´d have to fill every barrel with something foamy aka additional insulation.

Wether horizontal barrel walls could be load-bearing and support a roof I don´t know, but your drawing shows the edge reinforced by something else that holds it up so that´s fine.

I also think that cool metal attracts condensation of air moisture and might cause straw that´s suffed in between to rot, but I´m not sure.

That´s my 5 cents.

2 years ago
Hi there,

I´m just about to finish one in northern Germany, I´m investing every bit of free time to get it lit before the next cold spell.
I dealt with the laws in two ways: Since it´s my first one for testing it´s not in a house but in a 2 room brick workshop that I want to keep warm.
And since all the laws and restrictions refer to stationary fireplaces ("ortsfeste Feuerstätten") I built the combustion unit on wheels. This way it´s more like a big barbecue oven

Here´s a pic of the combustion unit that can be rolled around.
Already tested without mass and working like a charm.

I documented the build with a lot of pictures and some videos starting with the chassis, I hope to put a Youtube video up once the thing has proven its functionality.

The thermal battery however is fixed.

SInce I discovered this kind of heaters I´m totally nuts about them, got both books (Ianto Evans and the Wisners) and Pauls 8 DVDs.
And I´d be happy to connect with other RMH builders in Germany. Maybe there´s a way to get them established here.
And even though my first heater is not completely finished (I just started to mortar the bench after a lengthy chimney liner install) I´ve got the second already planned in my head. This will be more of a micro batch rocket instant heater without mass, for sure on wheels again.

2 years ago
Hi Folks,

yesterday I watched a longer Youtube video about earthen plasters. The guy managed to darken his clay plaster by mixing in finely ground coals left over from his wood stove. Looked good, dark but not pitch black.
This could also be applied to tromb wall plaster.

2 years ago