Dirk Dorme

I would like to install a 'natural' pond, using clay and gleying it with ducks. Aka, let them 'seal' the pond by letting the ducks drop their manure to block the water from leaking. Now, that is the theory. I would not like to install a pump, simply dig a whole, add some clay, gley it and move along.

I will install the pond in a section where it would not bother too much that it is not a clear pond,  however I do wonder whether the quality of the water will not be very very bad due to the manure of my ducks. Aka, will the nitrate and the rest not build up massively and thusly poison my ducks? And suppose that I add plants, will they not perforate the 'seal' as such?

Does anyone have some experience with a natural ponds, leakage and gleying ponds? Or should I  best dump the whole idea and use an epdm or the  like? Should i use banks to allow certain plants to  grow, should I make it large enough (aka how much m2 per duck)...? I realize it ain't an exact science, but any advise is more than welcome.

Alden Banniettis wrote:Dirk, bells do not operate on draft.  They operate on gravity.  The exhaust from the firebox stratifies in the bell and the cooler gas drops down.  As this goes on and on, the cool gas escapes from a low exit at the end.

Again, I do apologize if I'm not getting it, but...

If the operate on gravity, I assume that means that the cooled gas/air which is lighter that the hot burming gas, will flow to the exit. What I do not get then is that a chimney would aid the cooler/heavier air will exit a vertical chimney, or even more that a vertical chimney would help the air flow to exit. I would think that a clear exit that does not go up would then be better.

And I thought that the clash of temp would increase the flow, but maybe not. If not, and if the difference between the secondary burning chamber and the exposed barrel is not the key, than the barrel could indeed be integrated in the mass of the sofa.

Thanks for the reply.

The chimney makes sense. Will add a chimney indeed.

The bell is not so clear to me. I thought the draft was pushed by the temperature difference between the heat riser and the bell as such. An exposed bell allows the heat to drop dramatiically, hence create the draft towards the exhaust. However, inserting it into the 'sofa' would that not hinder the necessary heat difference?

Thanks for the feedback. And sure, I will take pictures as I build along.

The feed is indeed a J feed, of either 6'' or 8''. Given that I worry that my 6'' might not push enough, I thought of having a 8''. The dimensions are as follows:
- Feed of 8''
- tunnel of 16''
- masonry bell with metal top to cool the air down
- exit 1 total length of 59''
- exit 2 with total length of 59''

Both exists are connected. I can close exit 1, and let the flow pass through exit 2. Both exists do not have a chimney indeed. Would that be a problem?

Would you make the duct longer? I thought you could not make the duct too long, for the bell would not have enough power to push the air through...

Hi all,

Following this thread and some of the mods there, here's my design which I surely could use some feedback on. In any case, I will report back on whether it worked.

In short:

it's an outdoor rocket mass heater

maximizes exhaust

The image might explain a bit more.

The Top View shows that there are two exhaust sections.
Section A: the main exhaust, which is already rather lengthy given the sizing of the stove.
Section B: the secondary exhaust, which is (as shown in side view) raised to heat the back of the outdoor 'cob sofa'.  This exhaust passes through the bell, which is supposed to heat the exhaust and create an additional pull
Bypass starter: is an opening directly into the bell, to start the RMH and is closed once heated enough to push the RMH

As one can see in the side view, the idea is to insulate the bench entirely except from the seating part and the back. This is to maximize the heat going to the seating area when outdoors.

What I'm concerned about is the dimensions of CSA and whether it can push/pull enough air to bridge the length of the first exhaust. Honestly, I hope the second works, but that is less crucial. It would be simply be cool to get the second going as well. If the first would work, I already would be happy enough.

That is a brilliant idea! Indeed, the increase the pull, simply heat up the chimney. Simply smart.

Hi there,

I am thinking of building a rocket mass heater as an outdoor warmish sofa for colder autumn and winter days. As such, it will be built in de garden, and will only occasionally be heated. The first and most important feature is to heat the thermal mass. I will insulate the bottom and sides, to maximize heating through the top.  I'm looking at a reasonable sized rocket mass so it does not take over the garden entirely, and am thinking about the following dimensions (of the excellent book "The rocket Mass Heater: builder's guide":

consistant cross-sectional area (csa) of 6''

feed of 12''

burn tunnel of 18''

heat riser of 40'''

However, I want to maximize the heat exchange of heat from the exhaust to the thermal mass. Therefore, make the exhaust as long as possible. Longer exhaust requires more push from the barrel, so there are two solutions I am thinking of:

'regulate' heat exchange of the barrel: since I'm talking about winter, I should not worry too much

create an exhaust that I can vary in length.

As you sometimes see a bypass towards the chimney to start up more easily, one can imagine one or more bypasses in the exhaust itself to lengthen or shorten the exhaust. If I think that the exhaust can take it, I could open a valve to an additional second exhaust tube (or even third). If I notice that it does not work (for whatever reason), I could close it as such. Advantage is that this does not have to be airtight valves.

Would that make sense or am I missing on some details or basic understanding of the RMH.