Joshua Myrvaagnes

I just used a shovel and levered them apart, but maybe it only worked because I luckily had two buckets where there was just a little bit of lip in between that I could access.  There’s so many different kinds with different lips, but it might not work for all situations.


I didn’t know it was a vacuum effect!

It does roar, but I don’t think I can upload a sound file here.

Also, the feed tube has now cracked a bit on top (top front brick declared independence from the one below). I think it neeeds more of a buttress and one that is not too much of a tripping hazard—maybe a whole solid mass…it’s too tempting to try to jam a piece of wood in if things aren’t burning very hot and the tensile strength is not great. And my friend is very hard on most of his tools and such.

Still really could use help

Andrés Bernal wrote:

I would like to understand better why all-masonry works at all.  or how much of a difference it makes to have a metal radiant barrel top to shed heat rapidly, whether into a cob hat or to warm up your ceiling.  And suppose you had to have a “refractory“ surface to meet code, can you get away with having a thin layer of that and then an air space and then a cob hat above that?

Plugged after use: aluminum tray mashed flat, bricks holding it down. The firebox is smushed up against the lip of cob surrounding the barrel manifold, so a brick won’t fully seal it. A little air can probably sneak past. The mortar has fallen out of the space between the nearest brick and the ones on either side of it.  I should stick some cob in there.

Regarding using AI, I agree that it’s better to talk to actual people. But sometimes AI can at least throw out some possibilities that I haven’t thought of, if I’m not able to reach a person. Then I can reality test those possibilities. But so far, it has not scored any victories here.

In terms of the amount of ash that this produces, he would get a lot of ash out of the feed tube, several gallons a season. That was true with the liberator, as well as with the Repair.  When cleaning out the pipe in the bench, there was only a quart or two of ash. It was nowhere near enough to block airflow or make starting the rocket mass heater difficult.

So, I think it would be worth making it a little less ashy, by moving the feed tube in 1 inch, and I’m wondering if it’s really necessary to widen the 6 inch channel and have a larger chimney.

The reasoning for the 6 inch bench was that, by some law of physics, the air is actually smaller once it has cooled, to a significant degree.

In some ways, it seems like the problem was too strong a draw.

The baffle experiment seemed to have no effect whatsoever.  (other than baffling me, as I have said, and I promise that’s the last time I’m going to make that stupid joke.)

Information about the house:

1800 ft.², two stories
Has blown in cellulose insulation in the roof spaces, whatever the state program would put in with their rebate thing
Cellulose in the walls??
The attic space over the kitchen (adjacent and open to the sunroom, where the rocket mass heater sits), weirdly, has zero insulation, it’s just an empty attic. The state rebate program would not put in insulation there unless it was certified to be rodent proof, and the exterminator was going to charge $2000. for a $300 rebate.  So that is still uninsulated.

Zone is 5A, temperatures last winter in the northeast were brutal, for long stretches of time, but still, I doubt it was as cold as a Montana winter.

Another piece of information: the liberator, which this Repair of a rocket ;Mass heater replaced, would make clicking sounds when it got up to temperature, and the new barrel does not make those sounds.

thomas rubino wrote:Well, that changes things.
Don't make any changes there.
The fact is that he has an 8" stove, transitioning through a 7" reducer to a 6" piped system, with numerous bells.
We need pictures.

Well, I measured the bottom of the burn tunnel, and I got 25.5 inches. Which would mean that the roof should be 10.5 inches, I might understanding, (subtracting 7.5×2.).  Confirmed by awkwardly sticking my hand in there and measuring the roof directly. That is well within the range of what should work.  Shortening it by another one and a half inches doesn’t seem like it’s going to make that much of an improvement, so I will just put that in.

Can you clarify what you meant by “ what sort of transition area is the barrel dumping into“? There’s a pipe, 7” diameter, to the stratification bell.

I think I will focus on putting more Cob on the side of the first barrel, but there’s one more question.

Is it much better to have no Cob on the very top of the barrel, at least in the center of the top, for rapid heat shedding to create a strong draw? And if that’s so then how come a Cob hat doesn’t mess up the draw?  Another words, if the Cob had retains a lot of heat, then there’s less of a rapid cooling affect there, right? And if that’s the case, then how come other designs like the cyclone (thick mass all over the top, very little possibility for shedding Heat) could work so well, too well in fact? ( I would love to have the problem of a cyclone.)

I have put a thin layer of Cob over the top of the barrel, for this purpose: to make a flat surface for the big tub of water, sitting up there, rather than having a gap. I noticed that when I had spilled water in between those two metal areas, there was much better heat transfer into that tub of water, and it heated up way more than without that bit of water. So I’m thinking conductive surface between their works better than just radiative.  (Pouring water in there every time you operate the rocket mass heater doesn’t seem like a safe idea.). Can anyone clarify this matter of the heat shedding?Thanns

Joshua Myrvaagnes wrote:Thanks for this post, I’m reading it again and I think finally understanding it better.  I’m not sure I’m understanding how you would most easily change the length of the burn tunnel by moving the riser within the barrel, however, since that means taking everything apart, but I I’m assuming that I can leave the manifold intact, have the riser be closer to one side of the barrel, lopsided in other words. No need to rebuild the feed tube at least. If I misunderstanding, please let me know?

My friend had had an inexperienced builder, who did really good work in a lot of ways, but missed a key element here and made the one mistake that really undermine the workings of everything it seems. Live and learn.

thomas rubino wrote:Yes Josh;
A 33" burn tunnel is much to long.
That makes the roof of your burn tunnel 17" long.
Glenn has 8=9", I prefer 10", but have found 12" to work, but no more than that.

Your buddy is asking that slowed down 8" J to push through 6" pipes, again, not to specifications.
A recipe for an ash-plugged system.
I used a 2.5" gap on my 8" for seven years.
I also had a 48" riser. I recorded a 1100°F reading on an 8" glowing red circle on my barrel top.
The riser can be within an inch of the barrel on one side.
What kind of transition area is the barrel dumping into?

You asked why a long burn tunnel is bad.
To create the temperatures at which J-Tubes are recorded.
You must allow the gases free easy movement, although it looks like your J-Tube is burning properly, I assure you it is not.
The core portion of any RMH must be built to specifications if you expect it to work like we say it does.

In your example, the gases are slowed by their horizontal travel. When they reach the riser, they cannot get the 1800°F temperature that it is touted to reach.
This allows Ash to reach the transition area and enter the pipe system.
Increasing the riser height to compensate does not solve the problem.
After the riser, he is asking for 8" of hot gas to travel through a 6" pipe.
It fills with Ash, slowing it down to the point it will not light properly anymore.
I know this to be a fact, as my 15" burn tunnel roof, plugged with ash by mid-winter...
Prior to that, I thought I had a Bad Ass Rip Roaring J-Tube...  I did not.

I believe it needs a rebuild to "factory" specifications, if he wants factory high-performance results.