Collapsible form

[Marcel]

#20

(M) Paul wrote:

(P) " marcel,
if you are thinking of using a lintel, why use angle iron at all?

(M) Why, indeed?

(P) wouldn't a lintel do the job structurally by itself?

(M) Dunno; I never arm wrestled a lintel.

(P) by the way, i believe my brick supplier here in portland has solid refractory lintels. wouldn't look as nice as basalt, and you wouldn't be able to say that your oven contains a piece of the cascade range, but it sure would work nicely.

(M) Plus it would give me an opportunity to see if you had started on your roof yet ;-)

Concatenatedly Yours,

Marcel

[jcdup]

Hi Marcel,

(M) Johann, I would like to see images of your work. Do you have postings on this forum?

Yes. My oven's photos are under the thread "Pompeii oven in South Africa" in the Brick Oven Photos (http://www.fornobravo.com/forum/showthread.php?t=220 (Pompeii oven in South Africa))

Cheers

Johann

[dmun]

From Machinery's Handbook 20th edition:

Values are per unit, per degree F:

Wrought iron:
.00000661

Cast iron:
.00000655

(no value given for Stainless Steel)

Granite (and presumably other ignious stones like basalt):
.0000044

Concrete:
.0000080

Brick:
.0000030

Slate:
.0000058

Sandstone:
.0000065

Pine:
.0000028

What do we learn from this? If mortar expands more than twice as much as the bricks it holds together it's no wonder that masonry walls fall apart. On the other hand, there's still a bunch standing from the time of the Romans.

My guess is that freezing water in wet masonry is the cause of most masonry failure.

[tdibratt]

I can speak to Paul's vane idea as well. I used it and had about 6-8 of them. It worked great. Since I did not have the entire hearth covered I was able to rotate the vanes silightly left or right as I set my bricks and used my fingers to smooth out any mortar that may have entered into the underside of the dome. When I was done, there wasn't much cleaning or pointing to do.

Regards

[Marcel]

#21

(M) David wrote:

(D) "What do we learn from this? If mortar expands more than twice as much as the bricks it holds together it's no wonder that masonry walls fall apart. On the other hand, there's still a bunch standing from the time of the Romans.

(D) My guess is that freezing water in wet masonry is the cause of most masonry failure."

================================================== ====

(M) What else we learn from this is the importance of using mortar with the closest coefficient of expansion to that of the material it bonds, i.e., refractory mortar.

(M) I suspect that in the time of the Romans there were no firebricks with precise % of Alumina and Silica. I also suspect that even their "normal" non heated masonry walls were made of brick that was probably more porous and consequently less strong than the bricks of today.

(M) I agree with David's guess that freezing water in wet masonry is the cause of most masonry failure but to support our guess we'd have to try to eliminate the material variables and then compare the failure rates of masonry used in equatorial South America with that in frost zones. This would have to exclude "dry fit" masonry, of course. It would probably be a very unreliable study since the materials are so different as well as the ages of the masonry work. Enough!

[paulages]

what's the expansion rate of a pot of lentils? and marcel, i don't know if we're close enough yet to be concetenated.

[Marcel]

#22

(M) Paul wrought:

(P) "what's the expansion rate of a pot of lentils?"

(M) What's the expansion rate of pot?

(M) "Collapse of the Forum"

Chow,

Marcel

[paulages]

lentils really expand your mind, man...

and now back to the scheduled program.

[Robert Musa]

Originally Posted by dmun

What do we learn from this? If mortar expands more than twice as much as the bricks it holds together it's no wonder that masonry walls fall apart. On the other hand, there's still a bunch standing from the time of the Romans.

My guess is that freezing water in wet masonry is the cause of most masonry failure.

imho, the mortar really doesn't contribute much to holding the oven together. gravity, on the other hand, doesn't change with the temps we are talking about. from a practical standpoint i think we are really talking about bricks slipping into the oven (they'll never slip outward).

the downward and lateral pressure of the bricks above and adjacent, in most cases will be sufficient (barring volcano or earthquake) to hold the brick in place. i think its interesting that if for one reason or another a brick is no longer subject to the downward and lateral pressures of its neighbor bricks, because of shifting bricks or crumbling of mortar then, at that point, the brick is no longer contributing to the overall structural stability of the dome. or to put it another way, the bricks with the greatest likelihood of slipping into the chamber are those bricks which are contributing least to the structural stability of the dome. i take comfort in this thought.

as i was placing the top courses of bricks on my oven, it was fairly clear as to which bricks were going to be potential problem children. they'll try to slip in as you lay them. those bricks, i cut into a squat pie shape to eliminate any chance of slipping in.

[arevalo53anos]

Friends/Marcel:

Luckily, you are in a great group, which use your birth language (or, at least the one that you are habituate to).
The other countries members have his “charming”, but his headache too… 8>}
My birth language is Spanish, living in a Portuguese language city and my work forces me to understand French, Italian and English, of course.
Let´s your imagination flight and think in translate BTW, IMHO, AKA or simply bro (from brother). And ours is Latin root, not Germanic one, auch! Thanks God we have Sony and WB by here. Or then, VPN (that in Italian language means Vera Pizza Napoletana!!!)
Ok, sorry because I use an old/not normally used word, I just try to be as clear as possible (and the opposite was obtained) (Murphy, perhaps?).
And even you do not catch the dog joke!!! I tried to say that the Styrofoam is too easy to work as it is to break. You could remove it from the dome using your fingers (or your dog fore-foots). By static charges, the dog will look as a snow ball! Lol
The VPN style is a kind of pizza (and pizza certificate too) that do not permit other thing that flour, water and yeast in his dough, is cooked in high temperature ovens and has little topping. (You could google)
I hope this message do not carry concatenated problems at this time.

Luis