Share your crack stories

[Laurentius]

Re: Share your crack stories

Interesting, that's what I'm doing with my WFO Can I be so bold as to call mine once completed "The Mini Pantheon" ?? haha Has a ring to it!

Yes K79,

I rings a wee bit louder than "Mini Me"!

[K79]

Re: Share your crack stories

Mick,
The Pantheon in Rome is the largest unreinforced concrete dome in the world. To overcome the problem of weakness at its base they made the walls some 6 metres thick, then as the dome got progressively higher so the walls became progressively thinner.

Interesting, that's what I'm doing with my WFO Can I be so bold as to call mine once completed "The Mini Pantheon" ?? haha Has a ring to it!

[SCChris]

Re: Share your crack stories

For what it's worth, one of the tools I use is a large fish gaff. This tool allows me to gently place the firewood rather than reaching in when things get hot or worse tossing the wood into the oven and onto the fire. I'm confident of the construction of my oven but feel better about placing the firewood exactly where I want it rather than it bouncing off the interior walls.


Chris

[Bacterium]

Re: Share your crack stories

Getting there.....maybe we need more of a Confucius say?

[brickie in oz]

Re: Share your crack stories

.... A WFO crack is like a .......!!

Sad way to end all your efforts for the sake keeping the curing fires small and prolonged.

[Bacterium]

Re: Share your crack stories

This thread is about crack stories!!
So the general experience is whatever the build quality and level of perfection they are generally a reality.......me included. Effectively it becomes a relief point in the oven......for expansion......hopefully in an appropriate place.
Mmmm what's a simple way of saying this?
We have a wood oven mantra...albeit funny yet serious
Insulate....insulate....insulate...

Maybe it's time for a wood oven proverb....... on cracks

A Brickies crack is better than a plumbers crack

Uo oh....maybe someone can help me here
.... A WFO crack is like a .......!!

[stonecutter]

Re: Share your crack stories

I built a 42 so the little bit it buys you is squat...

Yeah, too little to say it makes a difference.

[Les]

Re: Share your crack stories

I'm with you now, and there really is no advantage to starting with a soldier course that I can see.

I believe the thinking of going that route was more room. If you build a small dome it may make sense and help. I built a 42 so the little bit it buys you is squat...

[CoyoteVB]

Re: Share your crack stories

Government backed research, experiments, demonstration and validation projects would only result in regulations, EPA studies, FDA restrictions, special permits, fees and quite possibly the ban of wood fired ovens. That crack is now a signature of my hand built oven.

[Lburou]

Re: Share your crack stories

Speaking in terms of oven construction and the materials used, even how they may react during heating cycles and peak temperatures is interesting, but not important to the fact that your oven will crack. Scores of engineers have built ovens here on fornobravo, they stick to the plans almost without exception. Fits of creative thought are normal in the design phase for all of us. This too will pass, and hopefully you will decide to stick to the plans!

It would take government backed research, experiments, and demonstration and validation projects to construct an oven without cracks. Then, it would probably crack anyway after some use.

The beauty of the pompeii design is that it works as designed! Thousands of us have recorded cracks on this forum, yet the ovens all still work (with two exceptions that I recall where the ovens actually crumbled when they got wet, which were defect in the builder's mortar).

Design the oven as you wish. It will crack. You have about a 99% chance that it will be usable after it cracks.....If you stick to the plans.

[mikku]

Re: Share your crack stories

That is a first--from what I have read on this forum.
Good that I can find a question that right off your head no answer pops out.
Let me know-- the details I described are for huge kilns, refractory maker was AP Green - I think the company has merged with another company but its products are still readily available throughout US .

[david s]

Re: Share your crack stories

How similar are the coefficients for expansion of stainless steel and refractory

I don't know the answer, but it is rather complicated because they vary at different temperatures. Normal steel has almost the same expansion as structural concrete, but then it is not subject to the extreme temperature we use and not at such a high rate of temp rise.The recommended reinforcement for this application is stainless steel needles. I think this is largely because larger sizes will attract more heat because stainless steel is more conductive than the refractory and therefore attracts more heat to itself causing more expansion and resulting stress. With the needles, they are surrounded by more refractory and their heat is more easily dissipated into it resulting in similar temperatures with similar expansion. By the way normal steel is about 3 times more conductive than stainless so is therefore presumably not suitable for that reason, also corrodes more easily especially in the presence of heat. Stainless is about 10 times more conductive than brick (presumably castable refractory too)

[mikku]

Re: Share your crack stories

How similar are the coefficients for expansion of stainless steel and castable refractory? I am thinking they are very similar!

When we did linings of kilns, some areas that were difficult to build or that required special attention for abrasion were either gunned or rammed in place. We used stainless forks (forget the proper name) that were welded to the kiln steel shell. Then the area was built up to proper thickless.

Other areas, like in the pre-heat and cooler areas had same type of forks but then pourable refractory was used.

Ceiling areas had stainless anchors welded to an overhead steel structure that would retain a modified brick that resembled a cone, but square shaped cone if you can imagine that. Then we would form from below up to these bricks and fill from above with another type of castable.

In none of these applications did the castable and stainless anchors interact causing damage to the build.

With those "facts" in mind, do you think that you could use an inner reinforcement net of "stainless steel" similar to concrete mesh to prevent these cracks from ever occurring. Or prevent the cracks from opening that would cause a problem?

[david s]

Re: Share your crack stories

As a completely "unknowledgeable person" on the topic of brick. Here is my opinion why soldier course might be used.

Standing them on edge, with the thin face pointed inwards makes it very easy to make a rounded shape.

If splits are 1/2 thickness brick; then they would produce even a smoother arch.

Cast the normal soldier course area from refractory castable--then wait for it to break wherever it pleases, then blame it on shrinkage!

Good point. Better still design about 3 or four joins in it where you want, making sure you span a brick over the top of each join.

[stonecutter]

Re: Share your crack stories

I have never really understood why a soldier course is recommended.

I re-read your post and it occurred to me that I answered with a Neapolitan dome in mind, not a Pompeii. I'm with you now, and there really is no advantage to starting with a soldier course that I can see.