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

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:


1 year 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.
Pictures:

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.

1 year 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.
1 year 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
Ralf
1 year 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.

Ralf
1 year 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.

Cheers
Ralf
1 year 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.

Ralf
1 year ago
Hi Scott,

I will leave the evaluation if your new design will work to someone with more practical experience under his/her belt.

My feeling is that the top gap would work better with 50 mms /2 inch (it´s not only the cross-section needed but also room for the direction change of the gases).
And if you could somehow construct a round or at least octagon heat riser in that square tube it would leave a little more room for the gases to stream down on all four corners.
It would not harm the upward draft through the riser as long as it´s got 75 mms inner diameter

Just my 5 cents.

Good luck with your build !
1 year ago
This thread got my head spinning

Scott, if you have room for a footprint of approx. 30 x 50 cms I have got an idea:
Your heat extraction bell can be a capped standing steel tube (with removable top lid /cooking plate in case of inspection) of 30 cms diameter, about 1 meter high or more.
Cut an opening low on the side to fit in a rectangular box-like tube of steel plates which protrudes towards the inside of the big tube as well as towards the outside.
The box should be just big enough to contain a small (4 inch /10 cm) batch box (maybe cast of refractory concrete with thin walls) wrapped or embedded in refractory (and shock absorbing) insulation.
Heat riser could be made of 5 cms /2 inch refractory fiber blanket fitted inside a 20 cms / 8 inch diameter steel tube which is fixed near the rear inner wall of the big tube (viewed from the opening of the fire box).
This way you will further shorten the required length you need for the batch box by "shoving" it deeper into the big tube.
Then you only need a door at the front of your batch box "insert" and that´s it.
You´d only have to watch out that there´s enough space to the left and right of your inserted box so that the gases can pass it unhindered on their way down to the exhaust opening.

This would be basically a shrunk version of Peter van den Berg´s workshop heater made of three full-sized barrels stacked on top of each other.
It can be found here.

Ralf
1 year ago
Hi Scott,

there are several reasons why your current heater configuration doesn´t work properly:

1) the recommended ratio of the lengths of feed tube, burn tunnel and heat riser are 1:2:4, So your heat riser is way on the sort side.
2) the area around the heat riser where the gases must come down again seems very narrow, normaly the minmum gap should be 2 inches / 5 cms all around. Not to forget a big enough top gap between riser and ceiling for the gases to turn direction.
3) the use of metal to contain the burning fuel has serveral disadvatages:
It conducts heat away from the fire, thus cooling the burn and limiting its efficiency.
Due to this the feed tube will also heat up and serve as a competing chimney causing smokeback.
With an unsinsualted heat riser the metal wil also conduct heat between the inner (upwards) and outer (downwards) exhaust gas path, so the heat riser gets less hot and produces less updraft and the surrounding chamber gets hotter and produces less downdraft.
If you manage to get hot and clean rocket combustion by insulating the burn area form the outside, metal will spall and disintegrate over time.

However metal is fine as a casing around an insulated burn tunnel and heat riser made of refractory materials,

I understand well that it´s tempting to construct a rocket stove with the materials you have at hand, but if you want to heat with very little wood and no smokeback and a clean exhaust you´d have to redesign your stove qite a bit.
First thing would be that you construct your feed, burn tunnel and riser of firebrick splits. There´s a mock up for a small fire brick core and heat riser that I found very nice in the first few minues of this video 

This fire brick core should be wrapped either in cermic insulative fiber board or put into a bigger metal tube that is backfilled with a mixture of 1 part fireclay and 3 parts Perlite, both serving as insulation to keep the combustion super hot and clean.
Also such a " soft insulation" will protect the firebrick core from shocks while driving with your van.
And the radiating casing around all this should be big enough to not restrict the downflow of the burn gases.

I hope this is helpful.

All the best,
Ralf

1 year ago