Marcel's Pompeii Oven photos Part 5 chimney

[Marcel]

#59

(M) The first image, #64, is a very rough elevation sketch to help visualize the oven after the gable house is added. The chimney pieces are not in scale and are far too wide. They are in reality, 8"x8" and 12" high. I drew them vertually square.

(M) I would like to have a 90 degree peak but I may settle for a flatter roof if it means I can forego one of the clay liner sections:





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(M) The second image, # 69 shows aluminum foil (since removed) that was used to prevent the mortar from dropping between the horizontally laid bricks on each side of the first clay liner:



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(M) The third image, # 70, shows where the cement board will cover most of the new brick work. That place is just in front of the new brick throat, and on top of the new sleeping soldiers. It also shows a 3- 1/2" piece of plate steel about 12" high that has mortar behind it and adheres to the 5 brick high vertical side of the throat:



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(M) The fourth image, # 71 shows that the splayed sides of the throat had the leading bricks split so that we'd later have room to build an arch outside the cement board. You can see the grout line that separates the full from the split bricks.

(M) Also, note the thin layer of mortar which keeps the leading bias cut cooking floor bricks from moving. There will ultimately be stucco against that edge so the faces of the sleeping soldiers you see will be covered.

(M) My main concern is that the 2 pieces of 1-3/4" x 20" x 1/4" flat steel will be sufficient to support the weight of 4 more 20 pound clay liners! We originally hoped to use the wider steel that you see imbedded in the preceding image #70, but Mary wisely wanted the chimney as close to the dome as possible, and also wanted to allocate more space in front of the entry:



Ciao,

Marcel

[paulages]

My main concern is that the 2 pieces of 1-3/4" x 20" x 1/4" flat steel will be sufficient to support the weight of 4 more 20 pound clay liners! We originally hoped to use the wider steel that you see imbedded in the preceding image #70, but Mary wisely wanted the chimney as close to the dome as possible, and also wanted to allocate more space in front of the entry:

as much of a pain in the ass as it was in some respects, this is one area where the arched entry is a superior design, i believe. unless the chimney weight becomes heavy enough to actually crush the bricks in the archway (it would probably take a very considerable amount of weight), it actually helps hold the arch bricks in place, strengthening it's own base.

that said, i have no clue about how much weight your metal will take.

would it be possible to widen the footprint of the first chimney section closer to the vertical walls on the sides?

[Marcel]

#60

Originally Posted by paulages

as much of a pain in the ass as it was in some respects, this is one area where the arched entry is a superior design, i believe.

(M) I agree.

(P) unless the chimney weight becomes heavy enough to actually crush the bricks in the archway (it would probably take a very considerable amount of weight), it actually helps hold the arch bricks in place, strengthening it's own base.

(M) Again, I agree.

(P) that said, i have no clue about how much weight your metal will take.

(M) I'm not afraid of the steel breaking, but of it bending and thereby weakening the chimney.

(P) would it be possible to widen the footprint of the first chimney section closer to the vertical walls on the sides?

(M) Not without getting a different size flue. The bricks I placed on the foil on each side of the clay liner are there primarilly to close that space and force the smoke up the chimney; .... or into my face

Ciao,

Marcel

[Les]

Marcel – I would be concerned. There is going to be a considerable amount of weight on the steel. Paul could probably give you the temperatures that the vent area is going to be exposed to. If they are high, you may have a problem. It doesn’t take a lot of heat for iron to get soft. If you were using an angle iron it would be safer (IMO). But…. If it works let us know, this will be a huge learning curve for us wannabe brickies.

Les…

[paulages]

by the way, marcel, do you think the trumpet in your chimney will help or hinder positive ventilation?

[arevalo53anos]

Marcel/Les:

I had posted the graphic below in other threads.
These is one in which the chimney entry (or the junction between the flue liner and the chimney) was registered.
It is the green line in the graphic. The temperature value exceeded the 1000°F (nearly following the dome ambient temperatures).
May be this help you to figure out the vent area.

Luis

[jengineer]

Please explain the purpose of the Alto Horn out in the elements.

[Marcel]

#60

Originally Posted by paulages

by the way, marcel, do you think the trumpet in your chimney will help or hinder positive ventilation?

(M) Paul, if I may be permitted to toot my own horn, I think it is noteworthy that the famous Pompeii oven builder, Louis Armstrong used just such a baritone horn in his chimney and it enabled him to get in quite a few hot licks.

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(M) Les, although I have some anxiety concerning the steel lintel chimney liner supports I should mention that I no longer will clad the liner pieces with brick. Since 5 liners will weigh under 125 pounds I'm fairly sure that the steel will support that weight when cold! The average indoor fireplace I've seen uses a steel lintel over a greater span to support far more weight. Those fireplace lintels of course never approach the 1,000 degrees F. that Luis measured so I may be unrealistically mollified.

(M) Luis, your graph is both bad news and good news for me. The bad side is the high temperature you measured in the vent. The good news is that it rapidly dropped. I suspect that initial high temperature was caused by building a very hot starting fire as recommended by several experienced oven users. I tried to find some basic Info. on the internet about the relationship of temperature in steel to it's malleability but most of what I've seen is too technical for a non-engineer.

(M) In a few days, if the weather is dry, I will light a few low test fires with the clay liners unmortarted. I'll measure the distance during the firing against the 12.5" height when cold. If there is a significant drop I'll go back to the drawing board and also advise everyone of the results. I hope to be objective enough to admit a mistake as many "Newbies" may be helped from my experience.

Tootle oo,

Marcel

[paulages]

I tried to find some basic Info. on the internet about the relationship of temperature in steel to it's malleability but most of what I've seen is too technical for a non-engineer.

i have a motorcycle workshop i share with some sculptors and blacksmiths. i've talked to them about this subject before. i'll ask them if i see them soon enough to get a helpful answer for you.

[Marcel]

#62

(M) The next image, # 73, shows an unfinished attempt to cover the dome, first with aluminum foil, and then with perlcrete. The perlcrete tends to slide off the foil in the vertical plane. Paul suggests, and I will try, to lay down a layer of chicken wire before adding more perlcrete. This will be done in order to give the perlcrete some "footing". If it doesn't work, I'll need to remove the foil in those vertical areas.




(M) I dropped in on my potter friend today who is drying the chimney cap in advance of the kiln firing. I am knocked out by how great it is turning out. The rain cap roof part is removable.

Ciao,

Marcel