Oven on wheels

[cobblerdave]

Gudday Watavidone
Hows progress? Ive been watching your posts for a while now....your in the classic Aust position of not being able to obtain the "proper" recommended forno materials. So your in the position off having to adapt what you can in the best Australia tradition.
I know a few people that have now have great working ovens who would not post thier ovens on the Forum due to the fact that there not built to the proper Forno plans or materials......so please keep up the posts...there are people who are very interested in your progress. not only myself

Regards Dave
PS check out a thread called "Tanzania /Canada" in the "pompeii oven contruction" section. Built an oven in Tanzania from some very interesting materials....

[wotavidone]

Good day Dave.
I have finally made some progress, not much by most people's standards, but good by mine
I've taken a bit of a change in direction. (I apologise to a few people I got a bit short with. I don't take the most well-meant of criticism well, some days, but I am capable of taking it on board eventually.)

So here's where I'm at:

Decided the base under the floor will be scoria concrete. According to an academic paper I read, a sand cement and scoria concrete, i.e. normal concrete with the large aggregate replaced by scoria, has a W/m/K of 0.252. Not as good as vermiculite, but I've always worried about the structural integrity of vermiculite, because in my frame it had to be more than just an insulating layer with a resistance to compression. The floor of the frame is just roofing sheets over steel purlins, so the concrete floor needs some tensile strength as well.

Having made the decision to use the scoria crete, I reviewed my stand in light of the heavier floor. With scoriacrete density of around 1.6-1.8, my 90 litres of floor was going to weigh in at maybe 150 kg.
This weight would mean the finished oven would now be heavier than the screwed joints and castors were designed for.
This lead to two further decisions.
1) Welded joints (left the screws in though)
2) Fixed location, no castors, this baby is staying right here when we move.

So I bought myself one of the best tools I've ever invested in. I got on Ebay and spent $40 (with an OZ supplier, I might add) and got me a mickey mouse auto darkening welding helmet. It is simply amazing how much better I can weld when I can see what I'm doing.
The frame is now welded and I'm very happy with the outcome. Never thought I'd see the day I'd lay welds for the sheer enjoyment of it.
Poured the scoriacrete floor yesterday, with some galvanised mesh for reo.

I was a little sceptical about the scoriacrete, but when the guy (Italian descent, I think) at the gravel yard heard I wanted it to make an insulating concrete base for my pizza oven, the price became very reasonable, so I figured I'd give it a whirl. The cement, sand and scoria for this base cost me about $32. The scoria I got was quite large, as far as concrete aggregates go, probably 1 inch chunks, but I think that's actually a good thing.
I thought all the air pockets would fill with cement paste, but as the attached photos show, they didn't.

Next step is to put it in its permanent position while I can still lift it, and take the wheels off. Might put them on my Dalek.

[wotavidone]

A little clip of my previous project. That one took two years to do as well. Seems like life is so full of things you have to do, that the things you do just because you want to, get left till last.

Dexter the Dalek goes to the Chrissy Pageant - YouTube

[wotavidone]

Drew out a 30 inch/760mm pompeii oven on a piece of particle board last night.
I am referring a lot to the published dimensions of the FB ovens.
So I'm thinking 16 inch by 10 inch rectangular opening.
Started stacking bricks to see what the oven will look like.
I was always intending for my oven to have a square mouth, about a brick deep. i.e. 9 inches deep.
I intended to use a lintel, rather than do a curved arch.
The design of this is testing me. I have several options.
I can get an off-cut of 6 mm 316 stainless steel plate from a mate, and just lay it across the top of the side walls of the opening, with a 6 inch hole cut for my flue.
Or I have a few options with mild steel angle iron.
The thing is, I also want to use this plate as a lintel to support the front edge of the dome.
Does anyone who used a rectangular opening rather than an arch on a small oven have some close-ups of how they did it?
Also, is there a general consensus on which material is best for use against open flames - stainless or mild steel?
Which one would expand/contract the least, thus putting the least strain on bricks and mortar?
So many questions, and I still haven't finished painting the house. My employment seems to be impacting my lifestyle too much

[wotavidone]

I know this has been discussed on the forum, but I can’t seem to find it.
I looked on engineering toolbox, for thermal expansion co-efficients. (Dunno what we did before that website came along.)
Anyway it says steel has a co-efficient of 13 * 10-6 m/m K.
I take this to mean for every 1 degree Centigrade that a metre of steel increases in temperature, it will expand 13 * 10-6 m, or 0.013 mm. So if you increased the temperature by 350 degrees, you’d get 4.55 mm of expansion over a metre.
I want to use a lintel about 450 mm long, so I’m looking at 2mm of lengthways expansion if I get my oven up to 350 degrees Centigrade.
I’m thinking for a lintel that is 450mm long, say 6mm thick, I can probably ignore any increase in thickness, but should allow a couple of mm of gap for lengthways expansion.
Same website seems to indicate that masonry will expand by about half as much, give or take a bit.
So I’m thinking there shouldn’t be too much drama with expanding lintels pushing masonry apart, so long as a small allowance is made for lengthways expansion.

[cobblerdave]

Gudday

Have a rectangular entrance (sorry no internal photo avaliable as no flash on the phone camera) As you can see no major cracks and rust is not a major problem ( 18 mth old and mild steel). Did use two lintels and made the tintels a little smaller lenght than the sides so that the could expand at a differnt rate to the brick and also could be tapped out and replaced in the future.
Cutting the bricks to go from a dome to a rectangle entrance was hard with no easy way to figure the angles required. I built on a plywood guide so I basically built the entrance then built the guide up against it Marked the different height of the brick levels on the guide and basically pared the bricks down with a angle grinder till they fitted up to the entrance. It wasn't easy but "do able"...didn't get the dreaded teardrop shape.
Problem I see with your size oven is that the rate of curve inward of the dome will be quite a lot more than for a 42" perhaps you could consider using a longer brick than a 1/2 on the entrance
You'll end up with a lip in the oven itself you get a bit of ash stuck in it but you soon forget about it as you can see it anyway.
Hope something here helps

Regards Dave

[cobblerdave]

Gudday
Found a photo that shows the dome transition from the entrance

Left is the top of the entrance structure and the course of bricks is level with the top of the entrance bricks
Hope this helps

Regards Dave

[wotavidone]

Thanks Dave!
This is exactly what I needed. I'm still intending to cast the top section of my dome, but I seriously wanted to see how other guys have done it. The search function on this site works quite fine, but there is so much info that its difficult to find exactly what you need.
I can see from those two photos how you did it.
I know a scrappy who is quite fond of pizza. I was explaining to him my current sticking points and he took me for a walk around his scrap yard pointing out the options. Steel, stainless, he just happens to have some mild steel rolled to exactly 10 inches high, 16 inches wide that he'll cut off a foot for me, etc. All I can say without getting anyone in trouble is things are looking good. I can just about take any steps I want without spending a lot, all I have to do is decide what I want to take.

[cobblerdave]

Gudday
A friend of mine has made a cast oven and one thing I would pass on to you is there a little more delicate than brick. Definitly use a ring of pavers or brick as your base before you cast the dome so you get a tough level above the hearthbricks that will not get damaged by tools or peels

Regards Dave

[wotavidone]

Dave,
I understand what you are saying, my plan is to lay out my floor, then create a ring of bricks standing upright on top of the floor brick, giving me walls that are 230 mm plus whatever height I get from the mortar. Then mould a dome (upside down saucer) shaped "lid" on top. So the walls will be vertical clay bricks, with a dome of homebrew mortar, or refractory castable if I can score some.
I guess I'm sorta following the Naples style oven that is photographed on page 9 of the pompeii plans, except for not trying to do the low roof from brick. Never know, I might find I actually enjoy laying bricks. Brickie seems to.

I have 2 inch/50 mm pavers without the bevelled edges for the walls. I'm using them coz they look fantastic. They are a rustic looking thing, very light coloured clay. I orginally bought them for the floor, but almost everyone on the forum says that the bevelled edges work better, and I came across some light coloured bevelled edge ones that should work fine for a cooking surface, and they have a much smoother surface.
Anyway, the 2 inch thing is part of why I am not planning to try to make the "lid" from brick. I reckon it'll be great for a quick heat-up for weeknight pizza, and I can back the wall bricks up with a layer homebrew mortar for strength, but I have not convinced myself that 2 inch mating surfaces will ensure a self supporting roof.
Its all on going very slowly - got a kid with a car that won't charge the battery and a blown head gasket after the heater valve fell apart today. Its gunna be a job and a half.