new build in werribee

[oasiscdm]

Re: new build in werribee

The shiralite would work but would need to be contained directly against heat and reinforced. I have enough shiralite left over to try this later as a filler between something. I will construct my door in 2 front half and back: half. I am looking at then containing ceramic tape locked into the 2 halves as a sealer around the door that seals against the entry arch side walls. I have noticed that out will end up blackened by soot. If that makes sense. The shiitake would need reinforcing in this type of set up I think.

Aren't blast doors metal?

The insulation I can try is hebel, calsil, shiralite, a combination is also possible.

Looking at SS front, 4" of insulation. Back half SS or ?????? Well isolate the SS from the brick at the front. 2 halves joined by 3 to 4 studs with a sour temp thermometre in the middle.

[david s]

Re: new build in werribee

I tried a 25 mm Hebel panel attached via stainless bolts to a wooden door. It only lasted about four firings before cracking. I know Dave's Hebel door has lasted well, but I think his is much thicker. So far I've found no matter what you use, if you try to make it robust enough it is not insulating enough and the reverse also applies.

Glass slumpers often use Hebel as moulds for their work, but they only last about four firings (generally around 900 C)
I have been experimenting with the use of expanded clay, perlite and foam in varying ratios in conjunction with clay to make suitable panels (fired to 1000C) the main problem is getting the shrinkage rate right and the tendency for clay tiles to warp on drying and firing.

I'd be interested to hear how your Shiralite would perform.

[brissie]

Re: new build in werribee

That could work, although if the Shiralite were fully contained by the stainless you may as well use loose perlite which would be both better insulating and cheaper.

The problem of using stainless at the hot face is that stainless is a pretty good conductor and therefore not a good insulator. If it is thin and it needs to be so that it won't sap too much heat, it is likely to give you sealing problems as stainless has a propensity to warp with heat.

Okay leave SS out of it. almost any commodity metal will do.

If the Shiralite product can withstand the workload
it could be:
wood -- Shiralite -- metal
or
wood -- Shiralite

Can Shiralite handle this? The metal is only for protection and may be disregarded if Shiralite is tough.

For a door it may outlast hebel, and be easy to make. Hebel breaks down with heat, but Shiralite may not at WFO temperatures.

[david s]

Re: new build in werribee

Colin, how strong and abrasion resistant is shiralite?

I am rethinking doors, and the issues with SS and other metals.

If a door was cast with shiralite and perhaps coverd with SS only on the internal face, and external face with wood. Would it work?

Note, if the external strength is good enough, the core could be a better insulator encapsulated in shiralite

also is shiralite safe? carcinogen etc.

Steve.

That could work, although if the Shiralite were fully contained by the stainless you may as well use loose perlite which would be both better insulating and cheaper.

The problem of using stainless at the hot face is that stainless is a pretty good conductor and therefore not a good insulator. If it is thin and it needs to be so that it won't sap too much heat, it is likely to give you sealing problems as stainless has a propensity to warp with heat.

[brissie]

Re: new build in werribee

Colin, how strong and abrasion resistant is shiralite?

I am rethinking doors, and the issues with SS and other metals.

If a door was cast with shiralite and perhaps coverd with SS only on the internal face, and external face with wood. Would it work?

Note, if the external strength is good enough, the core could be a better insulator encapsulated in shiralite

also is shiralite safe? carcinogen etc.

Steve.

[oasiscdm]

Re: new build in werribee

Some one else recently did a door from hebel and wood. Cannot remember who any ideas.

[cobblerdave]

Re: new build in werribee

Gudday Colin
http://www.fornobravo.com/forum/f51/...html#post99622

The Hebel door is not my idea, I got it from this bloke, he warned me as well that even if you call it a temporary door it works and you never get around to building better.

Regards Dave

[oasiscdm]

Re: new build in werribee

Agree.... the radiant heat made it very difficult working the oven. The best figures re heat break were had with no active fire.

The stainless was always [heat wise] in the middle of temp range but closer to hearth with an active fire.

It's interesting I guess I will learn more as I use it more.

Must get to the temp door though. Like you Dave hebel and some scrap wood

[cobblerdave]

Re: new build in werribee

Gudday
There's another factor at play here that should be mention is that most of the heat in the entranceway is heat radiating from the fire through the air rather than through the brick.
My oven has no heartbreak. In summer particularly, by the time you have burnt a fire in the dome for a couple of hours the entranceway is roasting hot. It makes it a bit uncomfortable to operate the oven. I have taken to placing just my insulated door in front of the chimney. Not as a blast door as the air is free to flow past the sides unregulated but as a heat shield for the entrance. Never taken any reading of the difference but the entrance I'd definitly cooler. Heat radiates faster though the air than through brick. I recon most of the heat bypasses the heat break through the air.
Heat radiating through the air does some funny things too. I'm ex navy and constantly got to play at the fire ground with some pretty realistic fires. Inside a steel compartment with even a small fire going it gets pretty hot very fast. The heat radiates from the walls making things pretty hot just like inside a WFO .You wear flameproof overalls, boots, elbow length flameproof gloves and a flameproof hood. Everything is covered bar a slit for eyes. It can get so hot the heat will burn your eyelashes off from behind the mask of your breathing equipment. If your silly enought to wear jewelry next to you skin it will attract the radiant heat through you clothes and burn the skin. The girls are in there too, so no underwire bra or metal clips. Underwear and sock elastic doesn't fare to well also, and losses its spring.
The human body, the flameproof overalls and gloves all have an insulating value metal has none. Once those metal atoms start to vibrate it then starts to radiate the heat back by itself. A plastic pen in the pen slot in the from of your overalls will not be at melting point before the metal end has heated up and boiled the ink in it .
Same things happening with the s/steel on the heartbreak its absorbing the radiant heat and once it gets to saturation point it throws the heat back rather than absorbing more like the brick on either side.
Sorry this is not highly scientific but its my practical experience with heat.
Regards dave

[oasiscdm]

Re: new build in werribee

Thanks David and others. For a while there I was quite annoyed with myself. But it all works. Next job more cooking curing tempering and door.

Still not getting floor past 400c

David the metal holding the hebel panel in place does get warmer than the hebel.

Around 70c didn't expect that.

Thinking of now making a sliding draw for tools etc just under the hebel panel. Maybe about 8" high and depth of alcove

[david s]

Re: new build in werribee

Hi guys

I will keep measuring, but the results won't differ. On one test I rested the thermometer on each surface and got the same results, inside hotter than SS hotter than granite. Margins huge. Can't explain it but that is how it was.

Here is your answer. It's the calsil that sits beside the stainless tube that is probably your primary insulation isolating the tube.Your tube is therefore really only being heated on one side only. But it doesn't really matter now because the thing works anyway. Cook away.

http://www.fornobravo.com/forum/51/n...tml#post157630

[oasiscdm]

Re: new build in werribee

Hi guys

I will keep measuring, but the results won't differ. On one test I rested the thermometer on each surface and got the same results, inside hotter than SS hotter than granite. Margins huge. Can't explain it but that is how it was.

[david s]

Re: new build in werribee

I struggle with the idea that different materials in contact with each other can have different temperatures over a sustained period possibly the SS "feels" hotter due to it's better conductivity. The higher conductivity of the SS means that it cannot be a heat break as it will just transfer heat across in an effort to equalise . For a heat break you need high non conduction i.e insulation

The first oven I built had a small rock with"PEACE" etched into it. It was set into the front of the outside of the oven above the outer arch. Being both black and far denser than the surrounding cement/ sand/ lime shell that contained it, it would become much hotter than the outer shell. We used to use it as a test to see if the oven was hot enough for pizza. If you couldn't hold your hand against it, then the oven was ready. Meanwhile the shell that surrounded it was hot, but you could still hold your hand against it. A second example of this is with my mobile oven which is built over a 3" Hebel base. This base sits in a steel cradle which has 40 x 4 mm galv steel bars supporting it underneath. When the oven heats up and the temp climbs the Hebel is just warm, while the steel is noticeably hotter to the touch.

I totally agree that a heat break should be made of an insulating material, but if stainless must be used for purposes of durability then it should be as thin as practicable, preferably only on the exposed surface.

[oasiscdm]

Re: new build in werribee

Hmmmm my IR gun is 50:1. Might pose a small problem.

[Toomulla]

Re: new build in werribee

Yep I can adjust the emisivity on my gun. But to what?

You set the gun to match I.e if you want to read SS set it to 0.1 and if granite 0.9

You also have to match the spot size to the width of the material i.e if the material is 12 mm wide the gun needs tone about 12 times that max away from the material assuming a 12 :1 angle for your gun