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Post by SentencedToBurn on May 30, 2016 3:35:57 GMT
Hi there First off, I hope I'm not intruding since this is a UK forum, this seems to be the only active and sizeable forum I could find on the subject. I have seen a few people from other parts of the world register so figured why not. Plus we still have the Union Jack on our flag (I voted to keep it!) I'm guessing this is probably one of the weirder builds, I went through a bunch of the existing builds but couldnt find anything similar. Worst case if this turns to be a fail, I'll learn something new. Anyway, here are some goals I've set for myself with this build: - It has to be mobile (or at least movable in case we ever move house, I want to be able to take it with me) - I'd like to make it different, try something new but still leverage enough experience that others have shared on this forum to make sure it actually works - It has to resonate with my love for metal (music, not material, although I like the material too) After having a good think about it I came up with the following concept: - The bottom section is made out of steel frame, which will allow the whole structure to be move if needed (like your workshop machinery). The frame will be covered with timber, treated, etc. - The top part is all brick except for the doors (which are decorative, but can be closed if necessary, the idea is they'll stay open while the oven is in operation) - The top part is made to resemble a gothic castle, I've been collecting various images of castles of "notre dame" style and attempting to take note of their most prominent features I can't be bothered 3D-sketching this, so here is my "awesome" sketch of what I'm attempting to build. Here is the frame I've welded up on the weekend: its 1500mm across, 650mm high and 780mm deep. Im using 1" box section with 2.5mm walls. I spaced the bars at the top to make sure the bricks joins are placed on top of the metal bars. I'll have to work out the best way to cement the bricks to steel. All sides and the bottom part of this frame will be covered in wood, treated, etc, so it'll give me a nice firewood storage area. The doors are 650mm high, there are two openings so that's 4 half-door sections. They are 3mm thick, the hinges will need to be quite solid so I'm making them out of 10mm rod / 11mm id / 14mm od tube. My next steps are to seal the entire frame with heat resistent primer (mostly to ensure the top part where the bricks will be sitting on the frame doesn't burn the paint off). Then I'll be able to start laying the bricks out on the top which will be the base of the oven. Before then I need to go through this site and record the types of cement I can use (or make) to ensure it's heat resistent, etc, so will definitely do my homework before doing anything with bricks.
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Post by oblertone on May 30, 2016 8:59:55 GMT
Welcome to the forum; no two builds are the same which is part of the fun in watching someone else's creation take shape, yours will certainly be different. I built a mobile oven (see thread below) but it takes four strong blokes to move it even on a level surface. The point I'm making is that it is very heavy (500kgs +) and I'm not sure your frame is robust enough as it stands, I'd hate to see it buckle.
You also need to plan for underfloor insulation beneath whatever hearth bricks you use; there are board materials available but I'm not sure what would be available to you in NZ.
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Post by downunderdave on May 30, 2016 9:12:49 GMT
The usual way to design an oven is to decide on the internal dimensions, then decide on wall thickness, insulation thickness and outer render or enclosure thickness. Then you can calculate the weight of the materials required and build a stand to suit. As you have already built the stand you will need to work backwards to get the interior dimensions. Looking at your stand, to me it looks inadequate , I'd suggest you add some substantial diagonal bracing. Regarding making it mobile, remember that you are really moving a pile of bricks and the fire and expansion and contraction tends to weaken the mortar bonds between the bricks. Brick ovens do not like to be moved, this is the reason almost all mobile ovens choose cast or modular ovens. Regarding the oven floor, you need to insulate under the oven floor bricks so heat is not lost via conduction. This means your stand will not be affected by heat if properly insulated. Normally a concrete supporting slab on top of the stand is used with the insulation sitting on that and then the oven floor bricks. This all adds to the weight of course. To learn more try community fornobravo .com
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Post by SentencedToBurn on May 30, 2016 9:54:58 GMT
Hey thanks for the suggestions guys.
Regarding the stand, I take your point, although I used this same grade box section to make car ramps, and a few other relatively heavy duty things, I might run a couple of bars along the bottom and then run vertical supports up from the middle of it. I worked out the total weight of all bricks and everything else will probably be about 500-600kgs, and on the weekend I had 4 of us stand on it and jump a bit, there was no visible bend (the 4 of us weigh about 300kgs all up). But its easy enough to add extra supports so I will do that for sure, this way I can think about the concrete support slab too and other insulation as you guys have suggested.
I'll have a good think about the dimentions, I definitely didnt take the multi-layered walls into account, although given that my "usable" surface is about 1500x750mm there is still quite a bit of room to play with.
Will post a few more pics once i've added the extra supports, and meanwhile I'll read up on insulation to see what's the best way in my case.
Thanks again for your advice!
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Post by downunderdave on May 30, 2016 11:57:00 GMT
You might want to rethink the stand. With only 750mm width on your stand, let's say you build a dome using half bricks (110 mm), a couple of layers of blanket (50 mm) topped with 25 mm vermicrete and a 25 mm outer shell, that adds up to 220 mm each side leaving you only 310 mm wide for your ovens internal width. Hardly room for a pizza, let alone a fire as well. You could cantilever the supporting slab over the sides of the stand in an effort to gain more width, although this will add significant extra weight which your design brief precludes. You could also cast the inner oven (typically 50 mm) to reduce wall thickness and also weight. My own ovens are 540 mm internal width sitting on a 910 x 910 mm supporting slab, and I think they're about the smallest around.
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myke
valid member
2 boxes of insulation for sale see my sig
Posts: 60
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Post by myke on May 30, 2016 19:31:51 GMT
I would definatly add some diagnal bracing it will make the stand more rigid. I would also cast the oven as a brick oven will "move" to much (both points were picked up by Downunderdave). Like your Idea and will revisit the thread often to see your updates. Please dont tke constructive critism to heart most are trying to help. If you dont agree just ignore and carry on with the build.
Cheers for sharing Myke
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Post by SentencedToBurn on May 30, 2016 19:50:16 GMT
Thanks guys. I never take constructive criticism personally, always opportunities to learn. And last night I measured up enough steel for diagonal bracing and will add a few vertical ones too.
Width-wise I'll follow downunderdave's advice and see what I can do to reduce the wall thickness. I definitely want at least 450mm width on the inside, which only leaves me with about 125mm for each wall. I can easily widen the structure if needed though. So before I go any further I'll have a look at what materials for insulations and how thin I can make the walls.
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Post by SentencedToBurn on Jun 6, 2016 2:12:23 GMT
I've added 4 diagonal sections to this, I can't see this buckling under 500 or so kilos, I'd expect this to hold at least a ton or more. (thanks again for the advice) Next is to spray it with epoxy-based primer inside and out, and start looking for firebricks and the insulation for the bottom part. Hoping to post the next update in the next few weeks once I get that sorted.
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Post by SentencedToBurn on Jul 3, 2016 5:39:43 GMT
Just got a 2mm sheet to go on top. Will weld it on tomorrow after work, and will then etch primer the whole thing before moving it outside. Afterwards will put down 1" thick layer of refractory cement on top of this steel sheet (same height as the box section thickness). And then the bottom layer of bricks will go on top of that.
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Post by downunderdave on Jul 3, 2016 6:35:19 GMT
Unless it's a special insulating refractory concrete (most are dense and not insulating) you will find that heat stored in your floor will quickly wick away into the more conductive steel leaving you with inadequate heat in the floor bricks. One inch of quality insulation is considered insufficient, two is recommended. Cal sil board is the best for underfloor application, but there are other alternatives. If cost is a factor 4 inches of 5:1 vermicrete is a popular choice. Good job on the diagonal bracing, but it looks like you didn't add any on the long side.
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Post by SentencedToBurn on Jul 4, 2016 6:44:09 GMT
Unless it's a special insulating refractory concrete (most are dense and not insulating) you will find that heat stored in your floor will quickly wick away into the more conductive steel leaving you with inadequate heat in the floor bricks. One inch of quality insulation is considered insufficient, two is recommended. Cal sil board is the best for underfloor application, but there are other alternatives. If cost is a factor 4 inches of 5:1 vermicrete is a popular choice. Good job on the diagonal bracing, but it looks like you didn't add any on the long side. Hey thanks for the reply Dave. I have had a look and was thinking of using this insulating concrete here: www.perlite.co.nz/perlite/concrete/ - not sure if you've ever seen anyone use that before? With the diagonal bracing, after I added 4 diagonal braces (2 on sides and 2 inside of the structure that supports it in the middle) we loaded 2 wrecked engine blocks on top (308 and 202) and two gboxes on top of the base. All up (from what I've looked up online anyway) it came to about 700kgs. The frame was fine, but funnily enough one of the bricks that the corner of the base was resting on cracked from all the weight. So I'll have to pay attention to where I actually sit this frame when I'm ready to start pouring concrete etc.
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Post by downunderdave on Jul 4, 2016 8:59:37 GMT
Perlcrete and vermicrete are pretty much interchangeable, I've mixed tons of this stuff. I find a better mix is created if 50% perlite and 50% vermiculite is used as the aggregate. Also a more workable mix is obtained if you throw in a handful of powdered clay for every litre of cement added. The correct amount of water in the mix is essential. If water pools in the bottom of your mix then you've added too much. I find for every 10 parts of dry mix you need 3 parts water. Mix dry ingredients first then add the water. Don't bother using a mixer because it sticks to the paddles and sides, a barrow is better. You need to leave in the sun and wind for a few weeks to allow it to dry. If you build straight over it you will lock in the water and it'll take months to dry properly. Only one inch of perlcrete is still inadequate, you'll end up with a floor that will take longer to get hot enough and will lose its heat too fast.
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Post by SentencedToBurn on Jul 5, 2016 10:08:29 GMT
Perlcrete and vermicrete are pretty much interchangeable, I've mixed tons of this stuff. I find a better mix is created if 50% perlite and 50% vermiculite is used as the aggregate. Also a more workable mix is obtained if you throw in a handful of powdered clay for every litre of cement added. The correct amount of water in the mix is essential. If water pools in the bottom of your mix then you've added too much. I find for every 10 parts of dry mix you need 3 parts water. Mix dry ingredients first then add the water. Don't bother using a mixer because it sticks to the paddles and sides, a barrow is better. You need to leave in the sun and wind for a few weeks to allow it to dry. If you build straight over it you will lock in the water and it'll take months to dry properly. Only one inch of perlcrete is still inadequate, you'll end up with a floor that will take longer to get hot enough and will lose its heat too fast. Awesome thanks. I'll go with two inches then no problem. Will follow your recipe for it too. And can definitely leave it to dry for a few weeks. I'm in no hurry, the idea is to try and finish just before Xmas. Will be nice to use in summer.
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Post by SentencedToBurn on Dec 17, 2016 2:40:57 GMT
Finally, I'm 1 weeks away from my Xmas break. Went out and got the bricks today, and managed to score 30kgs of refractory mortar. Also got a few old terracotta pavers to use on the sides, etc. I'm currently just measuring stuff up to see how everything fits etc. I actually found another lot of bricks to have as a 2nd layer under the current bricks you see me measuring up here. Dont think I'll go with the insulation around the walls at this point since this is only gonna be used for like 2-3 pizzas at a time, definitely don't need it running for ages. Man I can see all the purists leaving this page right now at this point. I just gotta work out how to make the floor of the actual oven smoother, whether the refractory mortar can be used to bind the foundation or not, will look through the rest of the builds on here. Just making some measurements and estimations at this point
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Post by chas on Dec 17, 2016 8:43:21 GMT
Finally, I'm 1 weeks away from my Xmas break. Went out and got the bricks today, and managed to score 30kgs of refractory mortar. Also got a few old terracotta pavers to use on the sides, etc. I just gotta work out how to make the floor of the actual oven smoother, whether the refractory mortar can be used to bind the foundation or not, will look through the rest of the builds on here. Just making some measurements and estimations at this point Just a suggestion: whether you use the bricks or the pavers on the floor consider laying them 'point on' to the door rather than 'square on'. More arseache, but easier to use the peel = smoother floor. Chas
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