another newbie question about the core

Greetings! I am a Long-time lurker, to much benefit, but now have a specific question that i haven't seen on any of the threads. Not sayin' it hasn't been answered already, just that I haven't seen it.
I just finished temping together a firebrick core, just as shown in Ianto's 3rd ed. book. I burned a test fire in the core alone, with no insulation, and with no barrel. -just the brick J-tube with the brick chimney(riser). I wanted to see how it would perform before I went further. I got a pretty good draft, it seems, with the horizontal fire in the burn chamber. But I also had a lot of smoke and some flames coming back out of the feed tube! I don't think this is normal, and I tried adding courses to the riser to raise the draft, with no luck. Like I said, I built the core just as shown in the book, so I can't be doing something too terribly wrong. I was burning very dry scrap lumber. Do I need to put the barrel on before the core will draft properly?

No I built my j tube or core as you are calling it and burned it on the floor of my garage b4 building the rest. It will actually burn better without the barrel

Interesting, and I'm wondering, did you burn it long enough to warm up the riser? Is the CSA consistent throughout the J? Was the brick layout measured accurately? Watch out for a bit less CSA (restriction) in the riser compared to the burn tunnel, whereas the other way round is not so bad. There could also be unwanted combustion air leaking into the burn tunnel between the dry stacked bricks, assuming that they are dry stacked of course. I packed sand around my dry stacked test core to seal the bricks and it does make a significant performance improvement.

John, Byron, Thanks for your replies. I went ahead and wrapped the riser with insulation and bermed the burn tunnel and feed tube, and got amazing results! Now, all I have to do is figure out how I am going to get my barrel installed on the completed J-tube (core) as my ceilings are few inches too low!

rob hinkle wrote:John, Byron, Thanks for your replies. I went ahead and wrapped the riser with insulation and bermed the burn tunnel and feed tube, and got amazing results! Now, all I have to do is figure out how I am going to get my barrel installed on the completed J-tube (core) as my ceilings are few inches too low!

Well, build a bell instead!

rob hinkle wrote:John, Byron, Thanks for your replies. I went ahead and wrapped the riser with insulation and bermed the burn tunnel and feed tube, and got amazing results! Now, all I have to do is figure out how I am going to get my barrel installed on the completed J-tube (core) as my ceilings are few inches too low!

To keep from having to "shoehorn" a full size barrel onto your core, you could use two cut down barrels and then stack them. I.e. similar to what *Ernie Wisner does, joining the two barrel portions together with a barrel ring clamp, sealed appropriately with high temperature gasket. I'd make the top barrel as long as practical to keep the clamped junction as low as possible.

*Check out the photos on pages 91 ~ 94 in "THE BOOK" [Rocket Mass Heaters, 3rd edition, hard copy, by Ianto Evans & Leslie Jackson]

I see the concept of stacking the barrels, using a clamping ring, and that sounds like a great idea. Is it a different kind of ring than the lid clamp ring? I do not "see" how to use it in this application. Is the ring wide enough to accommodate two rims together, or is there some modification needed to join these two, including a gasket? Also, if I am to make the top barrel to be the proper length, I assume that the method is to cut out a section in the middle, and weld the two remaining sections together, keeping the rim section to join to the manifold section. -is this correct?

Yes I believe you've got a good handle on it Rob. The way the system is described in "the book", the two barrels are joined by their ends that would normally accept their removable lids (joined lip to lip with the standard barrel band clamp). So in your application one option would be to cut your top barrel to length with clamping end intact. Then close the cut end with a welded on lid, or even make one from a disk of heavier gauge steel for a nice heavy cook surface.

Here's another idea that may help you avoid the welding chore. Common 55 gal. drums have two molded in strengthening or stiffening bulges encircling their circumference, one at about 1/3 the barrels length and the other at about the 2/3 point. If the barrel was shortened by cutting it at the apex of one of those molded in bulges it would make for a nicely flared opening to facilitate clamping to the other barrels lip. Best to try this out first with a scrap barrel.

As to the gasket to seal the two barrel sections together, Wisner mentions using fiberglass woodstove door gasket, high heat foil tape, then the original ring clamp (band clamp).

Bryon, Thanks greatly for the amplifying info! My wife and I are very excited about actually putting this stove together in the house. I will try to post photos of our completed project.

All,
I have one more question before I start putting the whole thing together.
I was under the strong impression that if I were to use a 55-gallon drum, I needed to make this an 8" system. Is this correct? I ask this, because I have on hand some 6" stove pipe and components, and for some reason, in my location, 8" parts have been somewhat iffy to find. I would really like to use 6" for this reason.
We live in an earth ship of about 1000 sq. ft. in Montana at an altitude of about 5500', in the mountains. While outside temps regularly drop to -30F or lower, our indoor temps usually range from 50-60F with no supplemental heating, unless there is absolutely no sun for several days, which is seldom the case. So, my heating load is not terribly great, but, 50F is a little chilly for me. In this case, does it seem that a 6" heater would suffice?
Thanks again.

6 is plenty good enough. And they can be fitted into a 55 gal barrel no prob.

Wonderful! Thanks!

Byron Campbell wrote:Yes I believe you've got a good handle on it Rob. The way the system is described in "the book", the two barrels are joined by their ends that would normally accept their removable lids (joined lip to lip with the standard barrel band clamp). So in your application one option would be to cut your top barrel to length with clamping end intact. Then close the cut end with a welded on lid, or even make one from a disk of heavier gauge steel for a nice heavy cook surface.

Here's another idea that may help you avoid the welding chore. Common 55 gal. drums have two molded in strengthening or stiffening bulges encircling their circumference, one at about 1/3 the barrels length and the other at about the 2/3 point. If the barrel was shortened by cutting it at the apex of one of those molded in bulges it would make for a nicely flared opening to facilitate clamping to the other barrels lip. Best to try this out first with a scrap barrel.

As to the gasket to seal the two barrel sections together, Wisner mentions using fiberglass woodstove door gasket, high heat foil tape, then the original ring clamp (band clamp).

That's what I was thinking but it might fit better against another apex (cut the barrel just above one). The clamp has a V shape doesn't it? Been a while since I looked at one.

Interesting idea Bob, and it would give more surface area to work with for sealing the connection / joint. I.e. for a gasket the flat woven tape style woodstove door gasket may just be the ticket.

I've noticed some fairly thin walled 55 gal. drums floating around of late, so working with the thinner material may be problematic. 16 gauge drums are my preference.