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  • Wiley
    started a topic Steel Dome Oven

    Steel Dome Oven

    This is what I am doing in the way of constructing a somewhat different WFO. It will still have a brick hearth and the actual design is not unusual, only the materials of it's construction are different. I'm going to try and stick to using commonly available recycled materials because (to me at least) going into detail about a project using truly unique one-of-a-kind materials, while perhaps interesting, is of limited use to others who might be so inclined to follow and build one of their own. That's providing, of course, that this works, which I believe it will or I would not be spending my time, money and energy on the project.

    I'll try to add lots of photos. Suggestions as well as comments are welcomed.

    First off this oven will be using one half of a condemed spherical propane tank. Tanks are condemed for various reasons, a common one being the serial number and spec plate has become separated from the tank. Once separated a tank is condemed and cannot be reused for propane. I got this one from our local scrap metal recycler. In point of fact, I got two, one a half tank with a diameter of 40" and a full sphere with a diameter of 48". The 40 inch one is what I'll be using in big part because it is aready cut in half and because the size is better for my use. The thickness of tank is approximately 5/16 inches.

    This dome will serve as the interior surface of the oven. Refractory material will be exterior to this surface, with insulation outside of that, just like a typical WFO. These tanks were constructed of two hemispheres welded together. Where the weld is made there is a backing plate, in this case a backing ring. This backing ring aided in the welding because it allowed for higher amperages to be used in joining the halves resulting in a better weld (since it could only be welded from one side). The sphere was cut in two on one side of that backing ring and as a consequence when cut, the two halves were not equal. The half I have has the backing ring so that it is slightly larger than a true hemisphere. See photo of backing ring. The addition of the backing ring makes the interior height of the dome 20.75 inches.

    This is all boring but the reason I included it will make more sense in a bit (hopefully).

    So that will be the interior of the dome itself, a steel dome. But what happens where the interior makes the transition to the entrance/doorway and the entrance itself? My answer is one half of a steel "split rim" off a truck. This one came gratis from our local Les Schwab tire dealer. It was the biggest I could find with an interior diameter of 22.5 inches. That makes for a radius of 11.25 inches. This radius would be the height of the doorway/entrance to the oven. Split rims are thicker than conventional "clincher" rims, and this one is approximately 1/4 inch thick.

    Now according to Alan Scott and others, in a correctly proportioned WFO the height of the doorway should be 63% of the height of the interior of the dome. So how far off are we with these two pieces? The height of dome (20.75 inches) minus the thickness of a standard firebrick (2.50 inches) creates an interior height of 18.25 inches. 63% of 18.25 inches is 11.497 (basically 11.5 inches). Height of split rim entrance 11.25. So matching the half split ring with the half dome is within 1/4 inches of being correct.

    So it seems a straight forward matter of welding a piece of 1/4 inch steel plate to the bottom edge of the split rim (which will make the height of entrance to height of dome proportion correct); then welding the rim to the dome; cutting out the entrance/doorway and back welding the join. Then fitting, welding and cutting a suitable transition piece for the chimney. Followed by setting the whole assembly on a suitable raised base and covering with refractory and insulation etc. and finishing in a more conventional way with a layer of stucco.

    For refractory I'm planning on using "traprock" or basalt (which is available locally) with LaFarge "Fondu" as cement. Per suggestions on this forum I am now expecting to use about 3 1/2" thickness of refractory. Insulation will be first a blanket of Frax (kaowool) and then a couple of inches of vermiculite and Portland cement.

    Thoughts or suggestions anyone? I'm looking for ideas on the transition piece to the chimney, thanks.

    Bests,
    Wiley

  • buckeyebreadman
    replied
    Re: Steel Dome Oven

    If there's a slower build I don't want to know about it.
    I actually opted for 2" of insulation board on top of 4" of vermicrete.
    I'll now add a layer just like Wiley did. The thinner Firebrick and the usual thicker ones (2 1/4"?) Going on Three years and that's where I sit. Should get the dome on this spring. I'll update then.
    The soapstone was just too expensive.

    Leave a comment:


  • nmich_mason
    replied
    Re: Steel Dome Oven

    How did it turn out?

    Leave a comment:


  • Wiley
    replied
    Re: Steel Dome Oven

    Buckeyebreadman,
    Using a layer of soapstone where I used a thin layer of firebricks should work fine. The thinner layer of firebricks was to provide a stronger more wear resistant surface for the steel dome to sit upon rather than simply sitting the dome upon soft vermicrete. I was concerned as the steel dome expands and contracts with each firing that it would slowly wear into it. This could potentially cause all sorts of problems with intimate contact (think heat transfer) from the steel dome to the refractory heat reservoir overlaying it.

    Soapstone is also known as talc and when ground to a fine powder is talcum powder. In this case I would expect the soapstone (although softer than a firebrick) would act as a self lubricating surface. It should work very well.

    Bests,
    Wiley

    Leave a comment:


  • buckeyebreadman
    replied
    Re: Steel Dome Oven

    Wiley, I hope you're still up on this page. I'm all the way up to the insulating layer (only two years in the making here) and was wondering.....you have, in post #41 a thinner layer of firebrick and then the oven floor on top of that. For the purpose of keeping the floor level, would a layer of soapstone suffice for that thinner firebrick layer? I'm not sure my vermiculite insulating layer is perfectly level....

    Leave a comment:


  • Wiley
    replied
    Re: Steel Dome Oven

    Ellisco1,

    Due to a computer virus several years back I lost a great many of the photos I took during construction. A good reason to back up important files which actually I did, however, I have miss-placed the dvd with the backed up photos. So it is as if they were same as lost except that there is a hope that someday the disc will turn up :-|

    However, in answering your question, if one looks closely at this photo:
    http://www.fornobravo.com/forum/atta...-side-view.jpg
    On the insulation layer about one foot up from the bottom, one can see the indent of a line that originally ran all the way around the WFO. This was from a piece of kevlar measuring tape I re-purposed.* Now there are many ways to cover a dome with insulation. Since my kaowool was about 4 ft wide, the method I selected was to wrap the insulation around the dome so that it was standing on edge forming a sort of cylinder. The Kevlar tape held it against the dome and allowed the cylinder to stand upright while I cut slits down from the top. These slits allowed me to fold the insulation down onto the dome and allowed the extra material to lie over the adjacent piece. Extra pieces were laid on and over the top and held the whole insulation fold-up/layup together. There are two layers done this way and the folds are laid out so the overall thickness of insulation is fairly uniform and increases as one measures up the outside of the dome.

    I originally planned on leaving the kevlar tape in place until I placed the birdcage and started filling the loose vermiculite. At that point I had planned to cut the tape and tuck it in and forget about it, (and it is in place around the inner layer). However, in placing the birdcage it became necessary to release the kevlar tape around the outer layer. When I released it I found that the insulation had assumed the desired shape and had no inclination to either slide off or fall away from the dome. The top was held by the pieces laid across which kept it from sliding. And it would appear that in the time between placing the insulation and the birdcage the insulation had formed to the dome and stuck/adhered a bit to the inner layer of insulation. Since it was holding I saw no need to replace it and so didn't. Once the space between the insulation and the birdcage was filled with loose vermiculite, it held the insulation in place and in contact with the refractory (or at least the outer shell never has gotten hot so one would assume it still is holding it in place).

    Kelvar tape is not that uncommon, it's also used as pull rope to pull wire thru conduit. But as it turned out I really don't think it is needed in the method I used. One would still need to hold the layer during assembly but that could be done with wire and after the second layer is placed and allowed to settle in you could carefully cut one end and pull out the inner wire. The outer wire could be left or removed.

    Hope this helps,

    Wiley


    *It was originally a measuring tape that had been damaged in it's first few feet, someone had balled the whole mess up and tossed it. I found it along side the road on one of my walks. I knew what it was and that kevlar is quite heat resistant (check the material used in a OveGlove and you will see it's made in part of kevlar) and being a scrounge at heart, I gladly picked it up. Once you see it it is easy to identify, sort of golden color, very strong and heat resistant.

    Leave a comment:


  • Ellisco1
    replied
    Re: Steel Dome Oven

    Wiley,
    Your build thread is an inspiration and I am starting on my own. One question , how did you get the Kaowool to stay in place while you were working on the cage? I was thinking of sticking some wires into the wet mortar then punching those through the insulation and bending them over but then I have never done this before.

    Leave a comment:


  • waynespizzaworld
    replied
    Re: Steel Dome Oven

    Thanks Wiley, good to know. I am a recycle yard shopper myself. Sounds like a good deal on the tires, way to go. The recycle yard I frequent rarely has any steel, they seem to mostly have aluminum. Looks like you found the components for your build at a good time. Love your oven by the way, very clever.

    The photo attached is my from my last visit to the recycle yard. The guy that sold me this real, figures it is a Data real of some kind. I ran a shaft through it mounted to a 10 inch stand with a wheel bearing in between for some nice spinning action and faced the center hub with some copper. I use it as a giant Lazy Susan for pizza toppings. 4 bigger bowls and 4 smaller to hold grilled veggies, cheese, flour, corn meal etc. Works real nice and I only paid 10 dollars for it. Feels good to get a bargain and then have some fun turning it into something else! When its not dispensing food I just hang it on the wall as decor.

    Leave a comment:


  • Wiley
    replied
    Re: Steel Dome Oven

    Hi Wayne,
    I do not know all the sizes these old tanks came in. But right now finding any suitable tank is going to be problematic. The problem seems to be the high price of scrap steel. The man from whom I traded for my tanks used to have several sitting in his yard. The story I got was that he had a contract with some scrap yards in California. Seems they were unwilling to cut them up for fear or liability. So he had a fairly steady stream of tanks which he cut in half and sold for backyard BBQs and such. That was 4 years ago. A few months back I chanced to stop by his yard in search of a set of used tires for my utility trailer. His yard was almost cleared of all the scrap metal, but there was a goodly sized hill of used tires. He told me that the price of scrap was so high it made sense to simply take the wheels off and crush the cars and send them to Seattle. From there they went to Korea or China or ? I got my tires (a nice almost new set of heavy duty tires for travel trailers and the cost was all of $5 each). Seems tires are hard to recycle and cost him money to get rid of.

    I expect the situation to be similar anywhere along the West Coast, but you might try calling scrap metal dealers in Vancouver and see what they can do for you.

    Bests,
    Wiley

    Leave a comment:


  • waynespizzaworld
    replied
    Re: Steel Dome Oven

    Wiley do you know if these old spherical tanks can be found in both a 42" and a 46"? The reason I am asking about this size is I am thinking of using the two sizes of tanks for a two part mold on a castable project. 44" and 48" would also work I guess. Also 40" and 44" in a pinch. The idea is to have a mold that would give me room for a 2" thick cast dome.
    Also would you have any ideas for locating one of these beasts. I am in the Vancouver Canada area but could travel state side to pick up if I could buy two different sized hemispheres to accommodate this project.

    Thanks Wayne

    Leave a comment:


  • Filthymutt
    replied
    Re: Steel Dome Oven

    Wiley, I like your oven. And the steel dome.
    Thought you might appreciate these photos.
    http://http://www.fornobravo.com/forum/members/filthymutt-albums-stainless-arches.html
    Not mine, they are photos from an Australian modular kit maker. I just want to do my Arch and chimney this way

    Leave a comment:


  • buckeyebreadman
    replied
    Re: Steel Dome Oven

    ENZ....could you elaborate a bit more on that?
    what do you mean by having the flu go straight into the overhang with no transition?
    more space between where the smoke leaves the oven and goes into the flu perhaps?

    Leave a comment:


  • enz
    replied
    Re: Steel Dome Oven

    On the matter of the transition into the flu pipe, I would make a nice smooth transition. I built a 40" cast refractory oven in 2006/2007 and had a the flu go straight into the overhang with no transition. It's the one thing I wish that I had done differently. Even though the flu was sized appropriately, it never drew as well as it should have and I think that's why. MTC. YMMV.

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  • buckeyebreadman
    replied
    Re: Steel Dome Oven

    It's actually Durango Marble.........looks a lot like travertine......my mistake.

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  • Wiley
    replied
    Re: Steel Dome Oven

    Buckeyebreadman,
    Questions are not a problem :-) I'll answer as best I can, and if I don't know an answer I will tell you that. You may wish to start your own thread but that is totally up to you.

    Regarding the 8 inch pipe directly connected (as opposed to creating a transition area/volume): You spoke of 9 inches of space at the top of the rim where it joins the dome, however, what is the distance at the bottom where the rim joins the dome at the hearth? The 9 inches of space on the top of the rim with an 8 inch hole would most likely place part of the chimney opening such that a vertical door (stopping when it intersects the dome at the hearth) would not close off the whole chimney. You could get around that by making a door with a extension overhang (like a visor on a ball cap) that would close off the chimney. Insulating that overhand could probably be figured out, but a really tight fit might be more problematic. Otherwise I seen no problems with using the direct connect, the volume of the 8 inch pipe would certainly be a great deal larger than mine (area of 8 inch circle being just over 50 square inches, the exit into transition on my WFO is 27 square inches).

    As for using travertine. Travertine is a calcium based mineral. It can be very beautiful but it is quite soft and quite susceptible to damage by anything acid and also it is easily stained. Dragging cast iron pots, pans and grills etc over the surface would easily leave scratches. Personally I would suggest considering something harder and more durable, but with care I'm sure one can make it work. It would probably have to be sealed more often than something like granite.

    Hope this helps,
    Wiley

    Leave a comment:

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