Using 8" pipe for J-tube. Question:

Morning all. In building the J tube, would a ninety degree elbow from the tunnel to the riser be better than simply butting the two pipes together? I'm building one from eight inch heavy steel pipe and was curious. I can cut and weld the horizontal to the vertical using two forty fives, or use the eight inch elbow. I thought the elbow would feed more smoothly, but I figured I'd ask. Any input?

Don't use metal, it's doomed!

I think that any time you can smooth out a rough edge or ease a change in direction it helps, but I'm still a rookie. I have worked in a fab shop and know welding pipe is way easier and more reliable than trying my hand at any type of masonry, but I've been convinced metal anything won't last. I believe it is referred to as carbonizing when steel gets superheated over 2000F, ot there abouts, and the molecular structure changes and the integrity of the steel is lost. Kind of like a piece of creosote, brittle.

However, the question begs, what is so wrong with using steel pipe and building your masonry around it? You have instant (but not permanent) structure and if you use it as a disposable form, is there any danger in that? I know steel is expensive, but that idea goes for any consumable material you could use for the initial form inside the burn tunnel and heat riser. I have been wondering why you couldn't form your burn tunnel and heat riser out of black stove pe and let it burn out?

Any thoughts? Sorry if I hi-jacked your topic.

time temp and turbulence
you want the turbulence its good for the burn. mixes the air gas makes a nice clean fire.

why are you trying to make a steel stove? its not as easy as stacking bricks and you cant really reuse the materials after you cut them up.
I just dont understand the insistence that metal is somehow better than masonry. each does a job well, its not so good to try and make them do the others job.

I went ahead and built it. I used a ninety degree cut and weld instead of the elbow I was thinking of using, for the reasons already stated. I think perhaps the "doomed" comment is from the assumption that I'd be using stove pipe. Not the case; I used 8" steel pipe, roughly 3/8"s thick. Another couple reasons I used it- it was free. I've got hundreds of feet of the stuff. I am also more comfortable welding than relying on my mediocre masonry skills.
The proof being in the pudding, I ran a test fire yesterday. It worked beautifully. We'll see about the durability. I'll report back.

Kilgore, building that large in steel allows you to line the steel with refractory materials or you can also try one of the ITC products...

I build metal combustion units too, but I use high tech liners to protect the steel, and to be able to reach proper temperatures.

Some people use stainless steel, I've found that to work, but think refractory liners are a better value.

Search for ITC under kiln accessories, ceramics/pottery supplies: expensive, but you don't lose CSA like with a liner

Hi this message is regarding building with 8" thick walled steel tubing.Kilgore could you post a photo ofyour design? I am looking to boil sap (maple) and do not have a lot of time but have the pipe and the need to get things working.
Thanks David

I need a 36" l x 6" id cast iron or steel pipe for my rocket stove liner.Anyone here have any for sale?

Well...I built it.
The damned thing WORKS! I'll see about posting some pics later, right now I'm just happy to have had the experience, and I'm looking forward to building another one.

Kilgore, been there done that. With steels up to 1cm thick. They all burn after a while. There's only one thing i've been impressed with for the heat riser, aluminized steel. The layer of aluminium turns to alumina, after only few minutes of burning. Alumina can whistand 2300C° iirc. But it's no good for the burn tunel.

Check thoses two pics of a gas bottle. The feed tube is 1cm thick. And delaminated up to the point that it wasn't useable anymore in 14 burns.

http://scontent-b-mad.xx.fbcdn.net/hphotos-frc3/542145_2129483974087_1024853031_n.jpg

The dip at the top of the bottle, where the heat rised was bolted is from melting the metal.

http://scontent-b-mad.xx.fbcdn.net/hphotos-frc3/550186_2129483854084_1054008007_n.jpg

I can see where that failed, and I'd like to know more. Was the entire thing insulated with clay mix? The small tube, this was the feed end? Was this a mini rocket?
I've had 13 fires in mine to date, for five to eight hours at a time, not including the current one I started at seven this morning. I'll tell you what- I'll take the barrel off when I get more cob ready and inspect the tube, report back.

Here it is in action. I think I've attached a picture, never tried before.

One issue I am having is incomplete fuel consumption. There seems to be charcoal left after a few fires.

Would adding insulation (clay/perlite) to the vertical pipe inside the 55 gallon drum increase the burn efficiency and eliminate the charcoal issue?

KB, this was a four incher with cyclonic action. The flame would enter the bottle tangentialy, and turn in it before reaching the heat riser.

Well, your heat riser in the barrel must be insulated.

At least 2 inches of rockwool, 1 inch of superwool, four of clay perlite. Or vermiculite. Any of the four products should do fine.

You can use smaller wood and a little more of it, that will automatically raise the burn temps for more complete combustion but you will be flirting with distraction !

Robert E. Lee said that in order to win wars you must be willing to lead men to their death, and it was a good thing war was so bad it kept men from loving it to much!

This is the problem that PYRO-maniacs have had for eons, we kill the things we love. J-tube RMHs require complete combustion or they will become constipated, and
need frequent digital manipulation to evacuate the area or suffer impaction, and even more digital manipulation! Replacing your present vertical tube with Clay/Perlite
will help, how far are you willing to go ! For the Craft ! Big Al

Thanks. I'll try to modify it, adjust wood input.

And Al- Cake said it best: I'm going the distance.

Took the barrel off today, inspected the riser. Roughly twenty burns of a minimum of four, five hours, with several eight and ten hours burns, no scaling or damage to the metal riser. Added insulation in the form of clay and perlite and put the barrel back on. Everything seems 10x10.