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  #41  
Old 01-27-2014, 01:13 PM
cobblerdave's Avatar
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Default Re: New Build in South Oz

Gudday Mick
I did a bit of head scratching about the gravity defying brickwork. Then it hit me, they are house bricks with reo Steel through the holes! Will it attract heat and warp? I don't know. But with angle iron at least its shape stops it from sagging.
One thing you might want to rethink is that 7 in?chimney in the flat 18? in entry. No smoke chamber to collect and direct the smoke up the chimney. Just a flat surface......just pointing it out
Regards dave
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  #42  
Old 01-27-2014, 01:56 PM
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Default Re: New Build in South Oz

The higher expansion rate of stainless over mild steel explains why it warps so much.
Somewhere else in another thread i took some measurements which showed a stainless sheet in front of the oven mouth considerably hotter than the brickwork around and indeed closer to the fire. This shows that the more conductive material does get hotter and as mild steel is way more conductive than stainless you'd expect the difference to be more marked. I think the fine stainless needles in a castable have a chance to dissipate their heat to the refractory that surrounds them, but a thicker lump of stainless would be more likely to give problems.
I'm not saying it won't work. it'll probably be quite ok, but some members have reported problems when using angle iron as a lintel and without gaps at the ends of the angle iron the expansion creates cracks. I once used a system like yours on a kiln I built years ago, in which i had a lid joined by threaded mild steel rods through holes drilled in firebricks all held together with angle iron and tightened with nuts. worked ok for up to internal stoneware temps.

Last edited by david s; 01-27-2014 at 01:59 PM.
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  #43  
Old 01-27-2014, 02:59 PM
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Default Re: New Build in South Oz

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Originally Posted by cobblerdave View Post
Gudday Mick
I did a bit of head scratching about the gravity defying brickwork. Then it hit me, they are house bricks with reo Steel through the holes! Will it attract heat and warp? I don't know. But with angle iron at least its shape stops it from sagging.
One thing you might want to rethink is that 7 in?chimney in the flat 18? in entry. No smoke chamber to collect and direct the smoke up the chimney. Just a flat surface......just pointing it out
Regards dave
Re: the flat roof, I pointed this out too, but I lost the argument.
It'll be even less efficient due to he wants to make a 45 degree bend straight out of the vent and lead the flue back over the oven. Can't see that draughting as well as a nice tall vertical flue.

Fear not, I have a simple improvement plan for when he finds out a smoke chamber is necessary.

Will the lengths of rod let it sag? Dunno, I doubt it, but we'll soon find out.

It'll be easy to replace if it doesn't work.

The client is always right.

Last edited by wotavidone; 01-27-2014 at 03:18 PM.
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  #44  
Old 01-27-2014, 03:15 PM
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Default Re: New Build in South Oz

Quote:
Originally Posted by david s View Post
The higher expansion rate of stainless over mild steel explains why it warps so much.
Somewhere else in another thread i took some measurements which showed a stainless sheet in front of the oven mouth considerably hotter than the brickwork around and indeed closer to the fire. This shows that the more conductive material does get hotter and as mild steel is way more conductive than stainless you'd expect the difference to be more marked. I think the fine stainless needles in a castable have a chance to dissipate their heat to the refractory that surrounds them, but a thicker lump of stainless would be more likely to give problems.
I'm not saying it won't work. it'll probably be quite ok, but some members have reported problems when using angle iron as a lintel and without gaps at the ends of the angle iron the expansion creates cracks. I once used a system like yours on a kiln I built years ago, in which i had a lid joined by threaded mild steel rods through holes drilled in firebricks all held together with angle iron and tightened with nuts. worked ok for up to internal stoneware temps.
A stainless sheet in front the fire exposed to the radiant heat isn't a valid comparison to any sort of steel encased in masonry.

It's all a matter of which way the energy is flowing. You keep thinking about high conductivity steel transferring heat to the bricks, but when its encased in the masonry, its more about low conductivity material transferring heat to the steel.

Anyway, no angle iron in this set up, therefore no gap left for it to slide when it expands.
My mate used threaded rod, my only concern being the size of it, and reo bar which I don't have a concern with the size.

(My other concern is appearance, but he's happy with the look so who cares? Beauty is in the eye of the beholder, as they say.)

If it worked up to stoneware temp for you, I suppose it'll work for pizza oven entry temps.
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  #45  
Old 01-28-2014, 03:23 AM
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Default Re: New Build in South Oz

I guess if the steel rod is free to move within the holes in the bricks, ie. it's loose and the ends have somewhere to expand to ,then you shouldn't expect problems. I'm interested to hear how it goes.
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  #46  
Old 01-28-2014, 03:28 AM
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Default Re: New Build in South Oz

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Originally Posted by david s View Post
I guess if the steel rod is free to move within the holes in the bricks, ie. it's loose and the ends have somewhere to expand to ,then you shouldn't expect problems. I'm interested to hear how it goes.
Actually, he's got a bit of a cunning plan for the exposed ends. I'll have to post a pic when its done.
By the way, the rods are 650mm long.
So if the roof gets to 400 degrees, which is highly unlikely, the difference between the expansion of brick masonry versus steel is 2 mm.
With a thermal expansion of 13 x 10(-6) m/m K, 650 mm of steel should increase in length by 3.4 mm. 650mm of brick (5.5) by 1.4 mm.
So we are debating about bugger all. Especially since the throat won't get that hot. I imagine we'll be able to put our hands on most parts of the entry without a burn.
I reckon the people who have trouble with lintels have them in the oven proper, where they really do get that hot.

If the throat got that hot, then the carbon would burn off, and I've never yet seen an oven with the soot burnt off in that area.
Still got a heatwave here so there'll be no lighting of my oven to check temperatures for a few weeks yet.

BTW, did you note the expansion coefficient for concrete? At 400 degrees, there would be 0.6 mm difference over a metre of length.
I think I see why the Michelevit's brick oven on a shoestring didn't crack despite all the dire predictions to the contrary.

Last edited by wotavidone; 01-28-2014 at 04:06 AM.
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  #47  
Old 01-28-2014, 03:56 AM
Il Pizzaiolo
 
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Default Re: New Build in South Oz

you talking inside entry or outside entry.

as my inside entry the other day as around 380c

That flue is of concern. Hope he likes lots of smoke in his face as that will happen. Even with the thought I put into my flue gallery I don't get a lot of smoke out front but there is some. With a flat gallery and a flue that wont be straight and travelling reverse direction against the flow of smoke. travel that is a tall ask. Be interested seeing what happens. But you can give people all the great ideas in the world but in the end they just have to see.

Sounds like you are a little frustrated as it appears the collective is out voting you
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Last edited by oasiscdm; 01-28-2014 at 04:03 AM.
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  #48  
Old 01-28-2014, 05:02 AM
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Default Re: New Build in South Oz

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Originally Posted by oasiscdm View Post
you talking inside entry or outside entry.

as my inside entry the other day as around 380c

That flue is of concern. Hope he likes lots of smoke in his face as that will happen. Even with the thought I put into my flue gallery I don't get a lot of smoke out front but there is some. With a flat gallery and a flue that wont be straight and travelling reverse direction against the flow of smoke. travel that is a tall ask. Be interested seeing what happens. But you can give people all the great ideas in the world but in the end they just have to see.

Sounds like you are a little frustrated as it appears the collective is out voting you
Outside entry, my inner arch gets hot enough to burn the carbon off too, but the outer arch gets nowhere near that hot.

I'm not [I]particularly[I] frustrated, except by the way this website logs me off before I finish typing.
If, by collective you mean the guys I'm building this oven with, yes on occasion they can be a little testing. But its all part of the fun.

My mate commented the other day that he didn't think this oven would be as much work as it had been.

I pointed out we made the dome in 8 days, and if it wasn't for the client's penchant for departing from the tried and true, we'd be eating pizza by now.

For example his desire to angle the flue back is based on clearing the edge of his shade sail. I'd relocate the bloody sail.

When he expressed a desire for a square entry with no visible steel showing, I said the only way you could do that is with perforated bricks with reo running through it.
I called it a manufactured lintel, and initially I was keen on it.

The client pounced on the idea like a staffy on a pig's ear, and held on as well too.

My mate reads all these posts during his late night bouts of insomnia. Right now he's probably laughing his head off.

His words were "Let's do that, post it on the forum and see how many people say it'll never work."

I reckon the bricks threaded on reo will work fine, though I wish I'd been there to influence the design and execution a bit.

In the unlikely event that it proves structurally unsound the whole entry is free standing and unconnected to the rest of the oven, so it'll take bugger all to remove it and do it different.

The draughting with the flat roof and the angles in the flue is a different story.
But I do have a contingency plan for that.
And I don't think I've yet mentioned his vision for doors. With adjustable vents for combustion air, the controlled admission thereof.
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  #49  
Old 01-28-2014, 05:05 PM
Il Pizzaiolo
 
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Default Re: New Build in South Oz

Hmmmm. it will work as I said I put a weekend to getting the venting to flow smoothly out of the oven. He wants flat he has got flat. Personally I gave up smoking 12 years ago and don't wish to start again.
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  #50  
Old 01-28-2014, 06:22 PM
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Default Re: New Build in South Oz

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Hmmmm. it will work as I said I put a weekend to getting the venting to flow smoothly out of the oven. He wants flat he has got flat. Personally I gave up smoking 12 years ago and don't wish to start again.
28 years ago I gave up the ciggies.

Funny thing is though, when I anchor on my favourite snapper drop on a dark, dead calm winters night, with the berley stream flowing, the hooks baited and the only sound the lapping of the water on the hull and a dog barking in a farmhouse 2 miles away, and all I have to do is wait for the fish to get interested, I still after all this time, feel like a smoke.
I'd get instantly dizzy and fall over the side, but still I feel like a durrie.
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