|
Post by kearnsjoseph on Jul 18, 2012 13:31:55 GMT
I am hoping to start my build soon. I have some recycled firebricks. They have a very slight taper, from 3 1/4 inches to 3 1/2 inches over the length of the 7 7/8 brick. They are also 4 1/2 deep.
These bricks were from an old smokestack. If I put them together they way arranged in a smokestack, they make little of a dome, and really just a slightly curved surface, 7 7/8 inches thick. I want it thick for bread.
I am trying to decide on the best arrangement without cutting bricks. I can stap them together with iron and rods, and then take that very slight curved surface on some straight walls, which would form a box-shape oven.
Or, I could arrange them in a semi-circular arch. This would be easier to construct. But the gaps I would probably have to full with castable refractory. With that gap, I do not think I could use mortar, since that wide a gap may be too wide. On the inside of the oven there would be little gap, and on the outer surface of the brick the gap would be about 1 1/2 to 2 inches.
I just wanted to see if anyone might have any recommendations. Thanks.
|
|
|
Post by bookemdanno on Jul 18, 2012 16:17:28 GMT
Welcome!
Personally, i'd use that perfect taper by cutting those babies in half with a bolster and building a Pompeii dome! I'm not sure that a full 8" thick wall has been done before. Someone with more firebrick knowledge will be with you soon, i'm sure!
re:the thicker joint question for a full 8" wall thickness. You could use a refactory mortar or homebrew with soft sand to bed the thinner part of the joints and then pack the remaining thicker section with a sharp sand modified Homebrew? The Sharp sand mortar will be better able to withstand the thicker application.
|
|
|
Post by tonyb on Jul 19, 2012 7:15:31 GMT
These bricks sound ideal. The taper will make the dome mechanically very strong. Thickness wise, this is a lot of thermal mass, and when you say you want it for bread, are we talking domestic or commercial bread production? If its the former, full bricks will take a lot of heating to soak the bricks, to get good performance. I've no experience of howa 8" wfo would perform. Hopefully others will comment.
|
|
|
Post by cannyfradock on Jul 19, 2012 18:09:01 GMT
Hello Joseph.....welcome to the forum.
As Danno mentioned......the perfect bricks for a Pompeii build, but even then you would have to machine cut them in half and use the larger half ...with the machine cut on the inside for the lower coarses and the smaller half with the natural smaller end on the inside for the upper coarses.
If you want your oven to be mainly used for bread (it can of coarse be used for pizza, meat, casseroles etc) then a square or oblong hearth....or semi-circular arch as you say (Barrel/Vault oven) would be favourite.....as Tony mentioned...if you laid them soldier fashion, 8" of fire brick will take a lot of wood to absorb enough heat. Even the Alan Scott commercial ovens are 1 skin of fire-brick on edge(4 1/2") followed by a layer of refractory concrete....then vermiculite insulation.
Normally a slight taper would be an advantage, but as a Barrel/Vault oven would suit your needs the taper is a bit of a disadvantage. If you have enough of these bricks for a full build(and I wanted to build a Vault oven) I may be tempted to lay the arched bricks of each vault section "alternatively" ....on edge (4 1/2") it may look a bit wierd but the underside of each arch should still show parallel lines....and the natural form of an arch will ensure the strength won't be compromised.
If you are thinking of multiple batches of bread you can then cover the arch with refractory concrete....then insulation.......or for domestic purposes cover the arch with thermal blanket, then vermiculite concrete (vermiculite, cement and water).....or if you house the oven then loose vermiculite is usually used.
Whichever route you choose the perps and joints of the outside of the dome/vault will be quite wide. For this, we tend to go for a "homebrew" mix of 3:1:1:1 sharp sand, hydrated lime, powdered fire-clay and cement.
These are only MY thoughts on a new conundrum.
Hope you get a bit more feedback on your post.
Terry
|
|
|
Post by pete123 on Jul 19, 2012 22:11:15 GMT
Hi terry.
Is it sharp sand or building sand for the classic home-brew recipe? I used building sand (no grit).
Pete
|
|
|
Post by kearnsjoseph on Jul 21, 2012 1:16:06 GMT
I guess I'll think on it some more. Thanks.
|
|
|
Post by faz on Jul 21, 2012 5:40:12 GMT
I used building sand for normal work in my homebrew, but switch to sharp sand when I knew that I would have a big lump of homebrew, so that it would help avoid cracking.
|
|
|
Post by turkey on Jul 21, 2012 20:31:24 GMT
I used builders sand and had some cracking, sharp would be my advice unless you find it to stiff to use. My cracks where not fatal so its not the end of the world to use if you have to/ have it. My sand was from wickes (as all sand differs slightly)
with your bricks, if stacked using their camber what is the diameter of the arch they form? Could make a very nice barrel oven, if you want to bake bread then you could look to do an Alan Scott or hybrid in that ilk, he adds cement as additional thermal mass over the 4.5 inch fireproof roof?
|
|
|
Post by cannyfradock on Jul 22, 2012 9:06:29 GMT
Sometimes normal builders sand is not always "normal"...depending on what part of the country you live....and where the sand comes from. In S.Wales our normal builders sand comes from the sea. In other parts of the country the sand comes from a quarry.
Wicks building sand is very fine so to avoid cracking I would push the ratio of the homebrew to 5/6:1:1:1. Wicks sharp sand has a lot of grit and crushed shell in it....this would be better mixed in a ratio of 3:1:1:1.....but as it's coarse, you must make sure that the inner most perp of the bricks are well filled.
Most other builders sand sold in the builders merchants in our area is washed dredged sand....the grains are not so fine, but all uniform. This is the sand I use at a ratio of 4:1:1:1.
Terry
|
|
|
Post by cannyfradock on Jul 22, 2012 9:23:47 GMT
Turkey/Joseph
I think Josephs bricks are 8 inches long. I took a long time responding to Joseph's first post as I didn't want to sound negative or confusing......unfortunately it sounded just that.
On reflection, if an Alann Scott oven uses 4 1/2 inches of fire-brick, then 4" of refractory concrete...an 8" fire-brick should give similar results???.........it would take perhaps just over double the amount of bricks used on a normal vault build.
Terry
|
|
|
Post by kearnsjoseph on Sept 6, 2012 1:20:51 GMT
I cut the tapered bricks in half, and used both halves in making the dome. Tried to cut shew bricks out but only fair alignment. Beddedskew bricks in angle ironwith refractory castable, hooked angle iron together with 3/4 inch rods. Attachments:
|
|
|
Post by kearnsjoseph on Sept 6, 2012 1:29:59 GMT
I tried staggering bricks, but the came out paired in the middle. layers from bottom are slab (near failure of form, hence bowing down) INSULATING FIREBRICK 2.5 INCHES OF CONCRETE ONE BAG OF REFRACTORY ON TOP of concrete firebrick. On top of dome is a thin layer of castable to fill cracks. might put some more concrete on top to add mass. Floor is about 6 inches, dome only about 4. still have to close back, and front and work on chimney. Attachments:
|
|
|
Post by turkey on Sept 6, 2012 9:12:00 GMT
looking very good, with the mass on top I would have thought you want more on top then below as in general you want more heat from the top (for pizza certainly, but also for bread). with the central line most builds are all lined up anyhow for barrel vaults, the refractory on top will make that even more solid, that is not going anywhere Do you have plans for a render finish or to built it into an enclosure? PS welcome aboard, we don't have to many US members so its great to see you here
|
|
|
Post by cannyfradock on Sept 6, 2012 13:55:06 GMT
Joseph
Great to see you have built the bulk of your oven and got around the taper in the bricks.
Before you close the back/front it may be a good idea to fill any of the larger holes on the internal brickwork. This can be done by hand with the homwbrew mix or with the use of a mastic/skeleton gun and a tube of fireclay/cement. any excess can be wiped off with a damp sponge.
I haven't built a Vault oven before and the method of created the vent in the vault entrance transition sometimes vary. Try to do as much research as you can on this stage of the build by looking at as many Vault builds on our...and other forums as you can
If in doubt.....shout out.
Terry
|
|
|
Post by kearnsjoseph on Sept 6, 2012 22:41:27 GMT
The roof mass is low. But I will probably run it a few times to see where it may leak, and can ad mass before I cover it.
Pat Manley in the US recommends a 10-20% thicker floor than roof. I think this is on the theory that wet cold dough goes on the floor and soaks up the heat. May not be an issue for pizza, but maybe bread.
I want to put steel studs around it, then cement board, and fill the void with insulation. If I attach studs to the outside of the slab, I might be able to get nearly 6 inches of insulation on the walls. I would like a fireproof roof, to make the whole thing fireproof, but my wife would not like corrugated roofing.
At first, I might not have a chimney. May only have a semicircular igloo type opening. Maybe later put a semi circular transition chimney on top of that - a semicircle outside a semicircle. It might allow some movement and a thermal break. But first the oven opening.
|
|