A&M's 42inch Pompeii

[waynespizzaworld]

Thought I would start this post to document the build of an oven that is currently a work in progress. A friend and I are hoping to have this oven built for the start of May for a customer that has taken a liking to my first oven built in 2007. I will be posting a step by step series of photos on the building of this oven on as picasa album with hi res photos....... https://picasaweb.google.com/waynebe...42PompeiiOven# I like the picasa album format as you can easily scroll through the series of pictures quickly without jumping around from post to post.

I would also like to use this Forno Bravo site for posting some photos of interest along the way that may be of interest to fellow builders and also be used by myself to have others help me with questions and concerns I may have along the way.

This FB site was a huge help for my first build and I would not have been able to make the oven that I did with out the help of this site and its members.

Thanks in advance for the help any members will offer me on this next build and I hope the photos I post and issues I bring up will serve to also help others in there quest to make there own oven.

Wayne

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Well I guess I am ready for my first question. The third picture on the attachments from first post is a model we made for the customer to approve. Any feel on how the cupola on top will smoke up and handle venting duties. I will fabricate the main part of the cupola out of 3/8" aluminum. The roof of the cupola will be 3/4 " plywood & epoxy coated for strength and water proofing. The inside of the plywood roof will be lined with thin gauged metal and wrapped up the end grain of plywood for shielding wood from the heat. I may paint the Aluminum a flat black as I think its going to smoke up and discolor anyways. We may put a little vent on top of the cupola kind of a cupola on a cupola for the smoke to exit the top side of the first cupola. Upper cupola may be 6 inches in height and made of copper. The upper cupola I am talking about here is not shown in the model above. Hope this all makes sense. I have been looking for a design that has been built like the one I am showing here but I do not see one so I have to ask if anyone can see any problems with this concept.

[Tman1]

Re: A&M's 42inch Pompeii

Nice floor protector!! I like how you've angled the cut to the back to make it smaller.. remember to make sure there isn't any bits of mortar on the inside of the dome so it can flip up. The only thing I could think of to make that less of a problem is to run the angles the other way (smaller to bigger from the opening) and use hinge pins that you could pull out at finish. Then it would just be 3 separate pieces to extract.

Gorgeous working location. I've got a buddy with a cabin in the middle of nowhere, and he says it doesn't seem like work when its so beautiful around him.

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Thought I would run an idea by folks for the install on my floor of the dome and vent area. I realize most like to lay the fire bricks on a bed of fireclay and sand to level things out and have the ability to remove damaged bricks down the road. On my last oven I mortared the floor in place with super 3000 and set my dome right on top of that. I just did not like the idea of the bricks all floating on the loose mix with no mortar. I realize they should stay somewhat where they were set but I just prefer the mortar in place if I can. I have an idea I want to try on this oven so I can still address the need to remove the bricks down the road if needed and also mortar them in place. The idea I have would only work if you are using something like the FB board under the cook floor for insulation rather that the Vermiculite option.

What I have done is set a brick on a test piece of insulation with my mortar and let it somewhat cure out in the garage. When I tore the brick off of and away from the FB board I was pleased to see it only took about 1/16 th of an inch of insulation away with the mortar and brick. So, what I got to thinking may work is butter up my floor bricks stopping short of the outer edges so when putting the floor down and leveling I can make sure no mortar squishes out past the brick edges and over into the next brick beside it. Also of course no mortar would be touching any of the sides of any of the floor bricks only the bottoms. This will then in theory let me pull out one brick at a time down the road. It should come out with the mortar still stuck to the brick and only a little bit of the FB board stuck to the mortar. Then I would set the new brick in place with some fresh mortar and all is well.

For pulling out the old brick when the time comes I would bond with more mortar a couple of handles to the top of the brick to be removed with bit more brick to hang on to and pull out the bad brick with. Of course the bricks right under the load of the dome walls will not be able to be removed but they are not bricks that really have food on them anyways they are more often than not covered with fire or coals.

Any thoughts on this one?

[azatty]

Re: A&M's 42inch Pompeii

Concerning mortaring the floor bricks, you get thermal expansion and contraction anyway, so the bricks will likely float anyway. And when you add water to the fireclay and sand mix it becomes a mortar. I found that it keeps the hearth bricks in place well enough.

As for the bricks on the edges of the dome, why not just cut the hearth bricks to fit inside the dome? Then you can remove any brick you need.

When it comes time to remove the brick, how about setting a tapcon screw or Redhead in it and pulling out the brick? You can even rig a lifter from angle iron and wood blocks and a rachet if you need more force to pull the brick.

[dmun]

Re: A&M's 42inch Pompeii

Experience has shown that you really don't need to mortar down the floor bricks. They aren't going anywhere. As the riggers say, gravity always wins.

When I was building my dome, i spent a lot of time standing on my loosely placed firebrick floor. I was frankly alarmed about how the bricks creaked and shifted under my weight, but they never moved significantly, and it's been solid ever since.

There's always talk about replacing floor bricks. Does anyone really ever do this in a home oven?

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Concerning mortaring the floor bricks, you get thermal expansion and contraction anyway, so the bricks will likely float anyway. And when you add water to the fireclay and sand mix it becomes a mortar. I found that it keeps the hearth bricks in place well enough.

As for the bricks on the edges of the dome, why not just cut the hearth bricks to fit inside the dome? Then you can remove any brick you need.

When it comes time to remove the brick, how about setting a tapcon screw or Redhead in it and pulling out the brick? You can even rig a lifter from angle iron and wood blocks and a rachet if you need more force to pull the brick.

Thanks for you help on this one......the brick lifter sounds good.
couple of questions on your comments

1. not sure if I understand what exactly happens when you say thermal expansion and contraction so bricks will float anyways. Do you mean the bricks will tear out and away from the bond to the insulation below?
2. adding water to the fire clay I thought would just change its consistency but its not a mortar that will stick. No Portland no bond was my understanding.
3.the issues of cutting the bricks inside the footprint of the dome in my opinion leaves gaps that are very hard to get looking good. I guess it just seems easier to erect the dome walls on top of the floor and not see any of these spaces.

[azatty]

Re: A&M's 42inch Pompeii

All materials expand when heated, and contract when cooled. Except water, which contracts until it is within a degree or so of freezing, then expands (thats why our oceans don't freeze from the bottom up, incidentally). Your bricks will also expand and contract, and will eventually break the mortar or spall out if set too tightly. I believe it is recommended to leave an expansion joint between the dome and the hearth of 1/8-inch to allow for that sort of movement.

The fireclay and sand mortar sticks, all right. Once it dries, it takes a good whack with a mallet to get the brick loose. It's plenty strong to hold the hearth brick in place until you fire the oven. There isn't Portland cement in the mix, but all you have to do is look at the native american cliff dwellings that have stood for centuries to find proof of clay mortar's strength. But once you break it, it scrapes off much easier than a Portland mix.

After your first few firings, the wood ash will fill the remaining joints and locks everything together. All the opposing forces hold the oven together nicely.

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Thanks Azatty for your help. Point taken on the sand fireclay for its sticking properties. I still don't see why expansion and contraction would cause me any grief on the method I plan to use. My last oven was done this way and no problems or crack except for surface stuff outside around the vent area and its only cosmetic on the very outside.

To me its seems if the dome is built on top of the floor and everything is mortared together it all just grows and shrinks all as one unit. I am sure I have read a good explanation of this somewhere but it is still kind of confusing me. Also if I remember the instructions say the dome around the oven floor is the prefered way but my method that I used last time was accepted as an option. I think for some ovens its recomended. I cant remember reading a good description as to exactly why one is preferred over the other method. I just dont see the dome expanding at a different rate than the floor. Any further explanations are appreciated.............thanks again

[azatty]

Re: A&M's 42inch Pompeii

I think the hearth inside the dome is recommended because the hearth expansion could break the mortar joint between it and the soldier course. But I'm not a mason and have just followed what others have done with reported success. Ultimately it's your choice and if you're comfortable with your design, then build it. From what I can see, the Pompeii is over-engineered to withstand the foibles of non-masons performing DIY work.

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Thanks Azatta...........I am still not getting a clear picture of EXACTLY what would cause a break down and EXACTLY WHERE AND WHY with the method I used last time. Until I get a clear reason for dome outside of floor I will go with what has worked for me on my last oven. This being said I am still open to peoples feelings on the debate and a good explanation on the "EXACTLY comment" above.

[waynespizzaworld]

Re: A&M's 42inch Pompeii

Thanks Doug

A little luck is always nice and from time to time needed.

[dmun]

Re: A&M's 42inch Pompeii

Also if I remember the instructions say the dome around the oven floor is the prefered way but my method that I used last time was accepted as an option.

Both ways work. I built my dome on top of my floor because of less fussing cutting on the edges, and the load of the dome would be more widely distributed.

Again, both ways work. Choose the one you like.

[waynespizzaworld]

Re: A&M's 42inch Pompeii

My buddy Will has made great progress on the rock shear he is making for our stand construction and other rock shearing duties. First pic is of the blades that have just been heat treated and the second pic is of stand that we hope to be testing out tomorrow evening if all goes well.

[dmun]

Re: A&M's 42inch Pompeii

Oh man, keep your hands clear of that blade. Looks like a guillotine.