#11  
Old 06-04-2013, 07:26 PM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Yes, it does help - very much. Thank you Wiley!
I really like your idea and will think about the doubled stainless liner/outer shell concept. I will take some measurements looking at the possible door opening and see what that may look like. My gut is telling me that the smaller liner may be too small as far as the opening is concerned but I will look into it.
Thanks again - I really appreciate the encouragement and interesting view point.

pics: Back yard fire pit - now for my oven...
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  #12  
Old 06-05-2013, 09:46 AM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

OK, I just looked at the 15.5 gallon keg. If I were to raise the cut dome up buy placing fire brick under the bottom walls of the the liner - raising it 4.25", I will have a floor to ceiling height of 14.25". With the 63% door opening rule - I came up with ~ a 9" (8.9775") high door opening (9" x 14"). The total interior will be 25" x 14" not including a domed door opening made of fire brick.
When I cut the stainless liner I can also cut out tabs at the base that can be bent to form over a few bricks to help hold it all in-place.
How does all this sound in terms of size of interior, door opening or anything else I haven't thought of?
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  #13  
Old 06-07-2013, 09:08 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 777
Default Re: steel liner question

Lovibond,
To me having the width of the entrance the same as width of the interior will be unusual. That is not saying it wouldn't work just that I have no experience with a WFO so constructed. Most of the WFOs that I have seen that were built using standard 55 gallon drums have the entrance a bit smaller than the whole width.

There are some compromises that will have to be made: The fire will most probably have to be at the back of the oven. So managing the actual cooking will require close attention...most of us place the fire to one side so we can observe the cooking where the pizza is closest to the fire.

Since the interior of the WFO you are suggesting will be a lot smaller, the luxury of being able to move the pizza to accommodate heat/cooking rates will not exist. Most of us have an areas of the interior of our ovens which are different temperatures so one can move the pizza to adjust rates of cooking.

For a quick one at a time WFO pizza oven I think the concept it will most likely work and probably better than some. At least I would expect it would produce a pizza that looks like wood fired pizza should look. Not like some thing that came out of a toaster oven. IMHO what a WFO pizza should not look like: Green Rocket Oven -

Bests,
Wiley
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  #14  
Old 06-08-2013, 05:32 AM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Great, thanks Wiley,
I can cut the door opening arch making the lowest part 13", leaving a 1/2" on either side of the door... I know, not much, but it may help with the stability having a 90 degree angle at the base in the front. (I just bought a 12" peel so I cant go any smaller - lol)

I may even be able to squeeze (pull) a 15" or 16" width out of the entire base by bending the base wall curve straight (with relief cuts at each corner I imagine) - this would then leave a ~ 1.5" wall on either side of the door opening, at the base.

I just purchased 2 boxes of ceramic blanket - 8#, 24" x 25' rolls and was able to source fire clay, 2 bags (50lbs each) for $22.00.
For the refractory mix - does the type of sand really matter that much - its all pretty much silica anyway....isn't it?

I plan on making my own dense refractory and slapping on a 3" coat over the dome for a heat sink. Many have mentioned to add some type of rope fiber, etc so when that burns away, it leaves a capillary structure for steam to find an escape. If this is the theory - wouldn't it be possible to throw in a cup full of perlite into the mix to allow for similar air pockets/steam egress? I would think at this volume, the perlite would not detract from strength or take away from the heat sink property via insulating the material, with using so little....?

I'm still thinking of your suggestion to use the 55 gallon barrel over the 15 gallon barrel - with the dense refractory, ceramic fiber and perlcrete layers in-between. The outer barrel would protect everything from rain and snow. I was considering slicing a 1" section (length of the barrel) on top to form a ridge vent of sorts to allow moisture to escape, mainly. It would be covered with a 3" or 4" length of curved stainless cut from the waist side of the barrel.

With this ridge vent cut in the top of the outer barrel I could pour in dry perlite over the ceramic blanket to fill the entire remaining space and then cover with the ridge plate? Sound viable?

Is it a good idea to use more insulation under the fire brick or will the 4" perlcrete layer insulate well enough?

Sorry, so many questions....
Thanks again!

Last edited by lovibond69; 06-08-2013 at 05:26 PM.
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  #15  
Old 06-08-2013, 09:56 AM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 777
Default Re: steel liner question

Lovibond,

I like the idea of going slightly narrower (13 inches). That curve at the front corners will add a lot in the way of stiffening the front corners.

I wouldn't try to widen the keg (if I'm understanding what you are suggesting). Stainless has a great propensity to work harden..first bend is fairly easy but after it bends it can increase it's resistance to bending in that spot by as much as 100%. That is why it is hard to straighten...bend a piece 90 degrees and then try to bend it back to straight. It will bend elsewhere making for a "s" shape in cross section. The keg already has shape (thus was work hardened) from when it was formed, personally I would limit my tinkering with it's shape by bending. Note that some alloys are more problematic in this respect than others.

Sand is not all the same. Depending upon where it comes from it can be mostly calcium carbonate (coral and shells or limestone) or can be all volcanic or any of a mix. I would look into finding an inexpensive source for blasting sand or if you were fortunate enough to live near a foundry see if they have spent green sand (which is olivine). You want the volcanic sands... usually dark heavy sands (although silica sand can be white colored) or artificial sand such as blasting media.

I do not understand why someone would want to intentionally add something like rope fibers to the refractory...you want it as dense and solid as possible. If I use the logic test of running something to extremes... would you want a solid chuck of basalt or a frothy piece of pumice? Adding the fibers in order to have them burn out and leave steam passageways seems like an exchange of a little saving in curing time for a poorer quality heat sink in the finished product IMHO.

Having a vent is a good idea. I don't know if you need as big a vent as you suggest. In my WFO I left a space around the chimney so it was both high and able to easily be shielded from water intrusion (rain etc).

Pouring loose perlite over the ceramic fiber is similar to what I did when I built my WFO only I used vermiculite. Personally I fine perlite more irritating to my skin so prefer working with vermiculite.

4 inches of perlite cement concrete underneath should be more than enough. This will be a small WFO and I don't think long term holding of heat (overnight for example) for a second day bake will be its long suit.

Hope this helps,
Wiley
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  #16  
Old 06-08-2013, 04:48 PM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Thanks again Wiley,
I was able to get fine white silica sand. I followed your advice and did not add any perlite to the mix. I used the 50:50, fire clay:sand, blend to level the fire bricks and then cut out the form. I didn't end up bending the walls as there was enough space inside. The form felt pretty stiff so I didn't want to mess with it's integrity.

Here is what I have so far...

Any suggestions for that chimney hole on top?

BTW - "lovibond" is a brewing term as I am a brewer (answering the PM I received)
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Last edited by lovibond69; 06-08-2013 at 05:32 PM.
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  #17  
Old 06-08-2013, 07:48 PM
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Default Re: steel liner question

You build is interesting to watch.
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  #18  
Old 06-08-2013, 10:00 PM
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Location: brisbane australia
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Default Re: steel liner question

Gudday
You works looks great .... Real workmanlike.
Regards Adding fibers to the mix . It's an old trick used in oh ovens to encourage excess moisture to exit the oven rather than causing cracking. It makes no difference to the thermal mass of the oven as the very small amount you put in I'd nothing compared to the final thermal mass . What it does it provides really fine capillaries for steam to was escape and not lead to large cracks. 1 ltr of water heated will produce 1600 ltres of steam ... Sobering thought
In you case I would thing you would probably get more cracks from the metal expanding at a larger rate than your mass layer . The result would not be noticeable in your oven as the interior surface is one piece stainless! It's all sealed in and the cracks don't go to the outside!
On the door width. The 63 per cent rule is a rule of oven height to door height not width . The wood fired oven breaths to this ratio. It makes no difference if the entrance is bigger in area because it is wider it will only draw in what air it
needs.
I have a dome oven a friend has a tunnel oven . Both cook a great pizza both cook a mean roast. They are just a bit different to operate . I know my oven best and my mate knows his oven best. I still claim my oven uses less wood but my mate lives on acreage so he just says" wood ... How did you worry about wood !" So I suppose we all just know our ovens best and know what we have to do to operate them best.
Anyway watching your build with interest
Regards dave
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  #19  
Old 06-09-2013, 06:56 PM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Thanks UtahB and CobblerD - I really appreciate the encouragement. I looked at both of your builds and all that comes to mind for both is "Wow"! Excellent skills my friends...

Here is where I am today:
I troweled down a 2" layer of home brew refractory and placed some aluminum mesh over to hold in-place. I plan on skimming another inch or so over the top - which will then be covered in ceramic blanket. I will have enough to cover this in a 3" layer of ceramic. Would this be enough or do you think I should cover the blanket with perlcrete as well?

I cut some more stainless to form the entry arch... I think I will fire brick over the stainless.

Still working on the chimney - I'm pretty sure I have that figured out now and may line the refractory chase way with more stainless. I need to find a suitable stack for the top.

What's the best way to seal this from the weather? I have a large stack of red bricks I was entertaining cladding the oven with. Do I need to do anything to the ceramic blanket or perlcrete before mortaring these over? Do you recommend sealing the bricks?

Feel free to chime in. I enjoy the differing perspectives.

Thanks
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  #20  
Old 06-10-2013, 02:47 AM
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Default Re: steel liner question

Gudday
You have been busy.
3 inchs of ceramic insulation.....overkill...which is good. Covering with a layer of perlite/cement....not sure its required as most use it to cover the lumps and bumps left after trying to make the blanket fit over a dome shape. Being a barrel shape I dont think you will have that problem? I suppose theres onl;y one way to find out.
As for covering the dome with a brick exterier, do it! but of course I bias. I would consider covering the insulation blanket with a layer of render so you have something to mortar the brick too thats solid.
Not to sure that hand hole is going to let through enough smoke as a rough rule of thumb it should be 15 per cent of the area of the oven entrance. Again I a bit bias... go big...the smoke has to go up, you just have got to let it do that.
Regards Dave
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