the rocket mass heater in the solarium at wheaton labs

right now, this very morning, the permaculture bootcamp is building the solarium here.  We start with this:



And then add this



And below is a crappy drawing of the new solarium space, with the proposed rmh.

the bench will be about 7 feet long and no wider than 3 feet wide total.  

8 inch system with a puppy burner core.  Pebble style.  

I would like the heat shield of the barrel to be brick.  Maybe even dry stack brick.  We do have heaps of that orange brick that we don't want for anything anymore.  Maybe they can be stacked like this and won't need further support:

puppy burner style shippable core

The manifold will feed an 8 inch duct that will rest on the cement slab.  I would like to add stratifcation elements of some type (open to ideas here) where the green dashes are.  

The yellow arrows show where the duct goes slightly uphill.  The idea is that the duct on the right might be about five inches higher.  This is in hope of facilitating the stratification transition to the 4 inch stove pipe for the vertical exhaust.  I would like there to be a 4 inch "T" below the 8 inch duct which quickly transitions into a "U" for the vertical exhaust.

Hi Paul,
Have you seen the hybrid heat extraction system that several people did a few years back? It consisted of merging tubes and a bell in the bench. The tube leaves the manifold, then dumps its exhaust into a bell (stratification chamber) at the end of the bench. Another tube next to the first then picks up the cooled gasses and continues its merry way back alongside the first and then to the vertical exhaust.
This eliminated the end 2  90's thereby not having as much friction on the gasses and better draft.

Donkeys video. Around the 3 minute mark:
rocket bell retrofit

So going from either a 6 or 8" J tube to a 4" vertical chimney is not asking for drafting trouble?

It seems that while I was thinking i was inventing something, it has already been invented.  But, yes, I am thinking of something a bit stratification-esque like what is in the video.  I suppose the next question is whether we want to do something with brick or tile - or something with duct and cob.  

So going from either a 6 or 8" J tube to a 4" vertical chimney is not asking for drafting trouble?

CSA for 8 inch vs 4 inch:

8 inch csa ...   pi * r^2 = pi * 16 = 50.24

4 inch csa ...  pi * 4 = 12.56

So we embrace that a 4 inch CSA is one quarter that of an 8 inch CSA.  

And an 8 inch batch box burns about five times more wood at once.  

And ...  the vertical exhaust gasses should be much cooler ....

The idea of the smaller exhaust is something I have talked over in great detail with ernie, erica, peter, donkey and mud.  It is a worth experiment.   Lower cost; slow the system so we can extract more heat; less exposure to the cold when it is not burning.  Overall, I think it might add about 10% to the efficiency.

I'm thinking this needs a bypass built in.  
I think your gonna need it.

thomas rubino wrote:I'm thinking this needs a bypass built in.  
I think your gonna need it.

Why?

I've done my time with a first class bypass and have come to the conclusion that they are excellent if your human discipline is excellent - and mine is not ...   and nobody's is.  

Well, I can't argue with your reasoning about discipline.

But in answer to your question,    Smoke-back

But if Ernie & Donkey and the gang think it will work, then it is certainly worth experimenting.
Looking forward to see the outcome.

The rmh in the fph has a powerfully strong draw.  It uses a puppy burner core.  One of the changes coming up is to replace the 8 inch exhaust on that with a 4 inch exhaust.

So rather than having a bypass, have a really good design.  This means

  - puppy burner core
  - vertical exhaust kisses the barrel

A 6" chimney for an 8" J-tube core will work - I have that and it draws fine. A 4" chimney is definitely an experiment, being a quarter of the cross section compared to the 8" core. I would be prepared to enlarge it if it turns out to be too much constriction.

I can't find any other reference in the forum for "puppy burner", and the video doesn't explain what it is that makes it different from other J-tubes. I see firebrick splits being glued/caulked into place. What is this concept?

Oh!  I left out one bit ...

The 8 inch exhaust has 4 times more CSA.  

An 8 inch batch box burns 5 times more wood.  

And the vertical exhaust gasses are much cooler than the rest of the 8 inch system.

Glenn Herbert wrote:I can't find any other reference in the forum for "puppy burner", and the video doesn't explain what it is that makes it different from other J-tubes. I see firebrick splits being glued/caulked into place. What is this concept?

It is a molded ceramic fiber shape that is available for purchase.  It is used for small pet crematoriums.  And it is what is in the fph rmh.

Hi! I've been recruited to make a FreeCad model of this RMH for the jamboree in October.

Paul: For the construction of the bench, do you intend it to be constructed in the same way as the bench in the FPH? Any lessons learned there to apply here?

I'm thinking more like the bench in the classroom.  Bricks on pea gravel.

Thanks. That's one I've not been real up-close and personal with. I'll see what I can find in the RMH DVD's.

And because I'm frustrated with how slowly I'm learning FreeCAD, here's a quick SketchUp model of my understanding of the thing:

(edits, the image)

:)

I think the wood box would include the core.

In your drawing, is the purple box 7' long?

paul wheaton wrote:...I would like there to be a 4 inch "T" below the 8 inch duct which quickly transitions into a "U" for the vertical exhaust.

I don't understand this part. Probably because I've not handled enough stovepipe in my life yet.

Does this sketch accurately describe what's happening?

The part that you sit on would be 7 feet long.  So the whole box will need to be longer.

Your sketch is spot on!

Mud and I are on the phone and this is our new idea for the strafication from an 8 inch duct to a 4 inch vertical exhaust

Some minor modifications ....

now all of the 8 inch duct is perfectly horizonal about one inch off of the cement.

There are two cleanouts.

The burn tunnel and wood feed are surrounded by sand.