Steel Dome Oven

[Wiley]

Re: Steel Dome Oven

Wayne,
I think broken up pieces of firebrick would be comparable to the crushed basalt. Rado uses it in his homemade concrete mix if I remember right. The advantage I found in using straight 1/4 minus crushed basalt was that all I had to add was the cement. The proportion of fines to coarse was such that the finished material created was dense and worked easily. I will look into this "Devil's Putty", it sounds interesting.

As for making a mold for creating the separate and expandable heatsink on the outside of the dome: Although the domes look very symetrical I suspect they are not perfect spheres/hemispheres and placing a section anywhere other than where it was cast would most likely not allow as close a fit as a section cast over the area where it will reside. Don't know if that is clear. If there was a slight dent the piece cast over the dent would accommodate the dent and fit well, however, the piece wouldn't fit as well elsewhere on the dome.

Anyway, I found casting shaping the concrete a fairly easy process save that one had to work fairly fast. At the end of each section I was forming I placed a folded up piece of aluminum foil to form a parting surface so that the next section could closely join the previous yet be separate for expansion purposes. That the sections weren't perfect geometric shapes was less of an issue although I tried my best to keep them as uniform in size and shape as I could.

[waynebergman]

Re: Steel Dome Oven

Hi Wiley....thanks again for your help. Good point on the fitment of castable pieces to the dome. Thought I would send you the info on the Moldit-x. The link below gives the specs on it. The link is from a site I am not familiar with but found it on a web search. I had bought this mortar from Fairey & Co in BC Canada. Not sure who else sells it but sold in small quantites its bagged and labeled labeled Devil's Puddy, it is super expensive. These are like one pound bags for about 6 dollars or something. I found out the Moldit-x was the same thing as the devils putty but way cheaper in the 55 lb bags. Not sure how the prices are in the states on this product but up here the Moldit-x will be about 40% cheaper than the fondu.
http://www.maxrefractory.ca/images/p...11/molditX.jpg

[propane man]

Re: Steel Dome Oven

Very interesting post. I have been thinking about making a WFO out of the head of an lp tank as well. I have a few ideas and your project seems to have turned out quite well. I have only been contemplating this for a few days and figured someone else must have done this by now. I googled it up and found your post, nice work.
I have pretty good access to old tanks & have a few projects in mind, I will post more details later, I will probably need some advice as things progress.

[heliman]

Re: Steel Dome Oven

This is an amazing build - seems like there are some "ready made" WFOs lurking in the local scrap yard...

One question though - would rust not be a problem given the high temps and moisture involved?? (apologies if this has been asked already).

Rossco

[Wiley]

Re: Steel Dome Oven

Hi Rossco,
Save for the incident I mentioned in post 149 regarding speckling when I sprayed water straight against the steel dome at temperature to create steam, I have not had issues or problems with regards to rust.

All that being said I have also stuck with red /brown/rust colors; anyone who has seen a wood boat that was fastened with steel fasteners knows the familiar rust staining. It doesn't take much in the way of iron particles to cause noticable staining. I chose to embrace the color scheme rather than fight it ("it" being the inevitable rust staining). I would certainly not suggest or encourage anyone to build a steel dome WFO with a hope of having a light colored or white entrance area. The rest of the dome it shouldn't matter. And on the other side, there are alot of steel boat owners who manage to maintain a white colored hull. All depends on the amount of work one wants to make for themselves.

As for major degradation or deterioration, we burn our paper trash in a open ended 55 gallon steel barrel. Like the familiar soda cans oven the years these steel drums have also undergone a thinning of wall thickness. Even so without any care and with both sides exposed to the elements we get over four years of use before the barrels need replacing. Given the thickness and that only one side is exposed to the rigors of the fire...exposure I expect my 5/16 inch thick dome to easily outlast me and most likely my children. But so far I have not had any incidence of "rust in my pizza".

Aside: We have grave sites on island and expect (and hope) that this is our "last stand". So unlike some statistical average homeowner who moves every seven years or some such nonsense.... we are here and here we happily be :-)

Bests,

Wiley

[heliman]

Re: Steel Dome Oven

Hi Wiley - thanks for clarifying that for me.

Good idea to go with nature - the redish colour makes it nice and earthy which I guess is the message which WFOs in general are trying to send out.

Any date firmed up for the big launching of the oven? I take it that there wouldn't be much "curing" involved with a metal oven.

Rossco

[Wiley]

Re: Steel Dome Oven

Hi Rossco,
Sorry I don't understand. I have been cooking for over a year in the WFO. My patio and well, my home is constantly being reinvented. Spaces change as uses and needs change. Still working on the patio, and lots other reinvented spaces around here.

Bests,
Wiley

[heliman]

Re: Steel Dome Oven

Oh sorry Wiley my apologies... I was directed to your post from another thread that focussed on your build so I think I may have confused the progress of the other WFO project with yours.

Rossco

[firebug]

Re: Steel Dome Oven

Hey Wiley

Well what a journey and I'm not even close to done,the trailer is done with the oven stand built on to it. I have two questions ,if you would be so kind.

1.My oven will be big about 55 inches inside(wide) by 70 inches inside(long) my sides will be about 12 inches tall then arch up to the center of the vault another 14 inches.total height 26 inches.is this formula correct? I know the door height should be 63%of overall oven height but I'm not sure about the rest.

2.what would be a good way to add heat sink over my steel vault,I was going to use sand but thats not an option for me anymore,what would be typical cost wize in doing this?

Thank you for all your help.

[Wiley]

Re: Steel Dome Oven

Firebug, Last I heard you thinking of using 1/2 inch steel plate, is this what you ended up with? What I visualize from your description is a shape more in keeping with a barrel dome WFO. Almost All Scott design shape. Regardless of shape the usual ratio of height of the interior to the height of the door is usually stated to be 63% for optimum gas flow. So I would think if you designed your door in keeping with that you would have a good chance of success. I have not seen any ratios relative to length of WFO to width relative to height. One would think there would be some point at which the WFO would be too long (length) to draw intake gasses across the hearth and flow them out across the top of the oven smoothly, However, I do not know if anyone has conducted empirical tests to determine if such a point exists and if so the ratios between the length and width and height of door. Same of course would be true for an WFO too wide, at some point it wouldn't work, but just where that point is I haven't a clue.

As for a thermal mass to be added to the exterior of your structure: My personal experience was using crushed 1/4 inch minus basalt with calcium aluminate cement. This is nice stuff to work with, handles easily and packs well. This so far has worked well for me or at least without problems. The cement is fairly expensive and the size of your WFO is large. So in the interests of keeping expenses to a minimum I would think that you might consider using something more on the lines of the "Home Brew" refractory mortar mix save that I would use crushed 1/4 minus basalt in lieu of the sand in the mix. From your signature you are located in Portland here in the Pacific Northwest. As you are near "The Gorge" you should be able to find somebody who produces crushed basalt in your area. Have you called local quarries? It's a common material here that is used to cover paths and infill between flagstones. It is inexpensive. A cubic yard in my trailer cost all of $13.00(home built trailer with steel deck and designed to carry a solid yard of rock or sand or whatever). If you cannot find that see if you can find somone who carries firebrick and see if you can cut a deal for broken seconds and crush them. (A couple of hours with a sledge hammer will probably end up with your re-vitalizing a quarry search for ready crushed rock...I know it would for me :-)

Regardless of what you end up using some accommodation for the expansion and contraction will need to be included in the design. If it were mine I think I would consider welding a large quanity of bolts on the outside of the steel (threaded end toward WFO and head away from WFO). These would be spaced out such that they provided a gross mechanical attachment between the refractory heatsink and the steel liner. Like I did with my WFO I would cover the steel with a slip surface of aluminum foil. I would then design my sections such that each contained at least two welded bolts (two so that no piece can rotate and "jam") and the joins between the sections having a piece of foil as a predetermined separation/break point.

As to the size of the bolts and the thickness of the heatsink, if you are using the 1/2 inch plate you probably would be fine with a heatsink of around 2 inches perhaps 3 or more if you are thinking multiple bakes on one firing for bread. The bolts themselves would be something inexpensive think along the lines of 1/4 inch x 1 1/2 inch if going for 2 inch refractory thickness and 2 inch bolts if three etc. You are breaking new ground here in your design so what the proper thickness for your intended need is will be determined after you build the WFO (by the results of your WFO!). And get "black bolts" they're cheaper and don't have any zinc wash to cause nasty fumes when welding them on. Not rocket science welding them on, mark positions with soapstone, a touch with a grinder at each spot to get thru the mill scale, hold bolt in position with left hand, stinger in right, bzzz and on to the next bolt.. Mix the basalt concrete so that it is "packable" without slumping, you may want some simple forms when doing the vertical sides and ends but when you start across the curved sections I would think forms would not be needed.

So to sum up" pattern layout for refractory sections, weld on bolts, apply Al foil, apply refractory, insulate, cook pizzas. You can be cooking pizzas before insulating but slow cure the basalt concrete refractory...ie slow fires to drive out the moisture. This will also allow you to observe the expansion and contraction of the ovens surface.

A long post and I hope it has helped,
Wiley

[firebug]

Re: Steel Dome Oven

Hey Wiley,

Everything you said makes perfect sense and pretty much was what i planned on doing,I was going to use 3 inch pieces of rebar instead of bolts.bolts make more sense. do you know of a good recipe for basalt mix, or know where i could find one. what percentage of basalt would be used in mix.then on top of heat sink i assume, i would put kaowool 2 inches thick then 6 inches of perilite or equal. i guess the bolts welded on would also keep things uniform.

Wiley Thanks for all your support, seriously you really are a great help.

[Wiley]

Re: Steel Dome Oven

Firebug, you're certainly welcome for any help I have provided.

I don't have a tested formula for using "Home Brew" refractory mix as the cement. However, one thing I really liked about using the 1/4 minus was that it seemed to have the fines and larger aggregate in a good proportions such that (if memory serves) I simply measured out five containers full of the 1/4 minus and then dry stirred in one measure of the Fondu. I then added the water but Fondu is very sensitive to amount of water so that quanity is less relevant here. The result was a good plastic workable mix. Since the Fondu goes off in a hurry I was using a 1 quart ex-yogurt container and mixing in a wheel barrow and so was doing small batches. I've not worked with the Home Brew so do not know how quickly it goes off.

However, I would think a good place to start tests on samples would be mixing together the cement part of the Home Brew dry and then trying a five parts quarter minus to one cement mix and see how long the working time is and the final strength (alright not final strength but strength after say five days). Originally I used five to one because a typical concrete mix is 3-2-1 with the cement being the one. So the aggregate and sand together added up to the five.

Hope this helps, and please keep us posted on the results of your tests,
Wiley

[firebug]

Re: Steel Dome Oven

Hey Wile

I would like to know how much fondu cost (ballpark) also in the bread builders book they give some recipes for cladding,is this the same thing?

I look forward to your response..thanks again

[Wiley]

Re: Steel Dome Oven

Firebug,
It was almost two years ago that I purchased the Fondu that I used and so I would think that the price has probably gone up (hasn't everything?) but if memory serves it was something like 50 cents a pound for a 50 lb bag, The stuff is put up in smaller bags than the usual 94 lb (one cuft) bag of normal portland cement.

As for the recipes in The Bread Builders book, I read that book almost two years ago when I was thinking on building my WFO. It was a borrowed book from a friend and so I don't have it at hand for reference. Since your WFO (like mine) has a steel liner, the problem of spalling or cracking as detrimental to the functioning of the WFO is lessened. The exact limits of what would or would or not work in our application is open to a great deal of conjecture. I used Fondu (calcium aluminate cement) but perhaps portland cement might work. I don't know, and like I said alot of what we are designing and building is "breaking trail" some ideas will work and some not and all gradations between.

That's why I have gone to some effort to document what I have done and give reasons for what I did. No need for anyone following me to make the same mis-steps I made... no need to "reinvent the wheel" so to speak. I would hope that those following and interested in the idea of a steel dome WFO would explore the medium/design a bit; tweak the idea, advance it and see what works. My WFO works pretty well, there is still more smoke out the front than I would like during fireup. However, I have seen more traditional designs with more soot staining and smoke out the front than I have. And I have yet to encounter or learn of any other WFO that "pants" on fireup. So in that little way so far my WFO seems to be unique. That little anomaly was unexpected; it's alive and it breathes!

Bests,
Wiley

[firebug]

Re: Steel Dome Oven

Hey Wiley,

Quick question ,I'm making my insulating slab this week that over 200 fire bricks will be laying on.what do you think is a good ratio for perilite and Portland cement.3:1,is what i was thinking for strength something that can help support 200 firebricks, what do you you think?


thanks kevin.