Oven on wheels

[cobblerdave]

Re: Oven on wheels

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]

Re: Oven on wheels

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]

Re: Oven on wheels

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]

Re: Oven on wheels

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]

Re: Oven on wheels

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.

[wotavidone]

Re: Oven on wheels

P.S. did your mate use commercial refractory for his cast, or the homebrew?

[cobblerdave]

Re: Oven on wheels

Gudday
He and his bro both used "ciment fondu" no stainless needles one oven was 75mm (3 in) and Rossco's was 100mm (4 in ) both ovens function well. His bro developed a few cracks and Rossco cut into the wet first layer to leave an even joint to crack along.
I would be making sure you hob around the outside of that "soldier" layer of pavers real well to guard against outward movement....perhaps concider going to 75 mm cast with 25 mm behind the soldier layer?
I know that stainless needles are a bit hard to come by out your way perhaps some stainless Mig welding wire could be used either cut up and plastered to the first coat or built ino a wire cage.

Anyway I'm sure you'll "over engineer" in the best backyard tradition

Regards Dave

[wotavidone]

Re: Oven on wheels

Hmm! I was sorta thinking along the lines of just mortaring the bricks in place and maybe just rendering on an inch of homebrew to increase the thickness. The dome I was intending to aim for 2 -2.5 inches. I was thinking in terms of the one piece cast dome only exerting force in a downward direction, not pushing out like a brick arch. How 'bout good old rusty secondhand barbed wire for reinforcing? I was looking at the little wire rings and special pliers I used for putting the wire netting on the chook yard and thinking maybe putting together a mesh cage with secondhand barb would be quick and easy.
The question, if one puts a belt of wire around the soldier course, is how do you anchor the ends, at the opening. I have seen picks of ovens where there is an angle iron post each side of the opening, with the cable attached by turnbuckle. I always thought that was for monster commercial ovens with massive domes.

[wotavidone]

Re: Oven on wheels

Boxed up to pour a base today. My poor little triton ute has a bobcat bucket of sand and gravel mix sitting there waiting for me to fire up the mixer.
I went to the only hardware shop that was open, and they wanted $10 per 20kg bag of cement. I told them I would wait till tomorrow when the guy who charges $6.95 is open.
Am I the only guy who noticed that, a few years ago when the manufacturers went to 20kg per bag from 40kg, the price didn't go down at all? Pretty much a 100% price rise by stealth.
I don't think we had an ACCC back then, or I might have made a profiteering complaint.

[brickie in oz]

Re: Oven on wheels

I went to the only hardware shop that was open, and they wanted $10 per 20kg bag of cement. I told them I would wait till tomorrow when the guy who charges $6.95 is open.

How many bags do you need?

[david s]

Re: Oven on wheels

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.

Yes just make a small allowance. Part of the problem is that the steel has much higher thermal conductivity than the surrounding refractory materials so it will increase temp and hence expansion at a faster rate.

[cobblerdave]

Re: Oven on wheels

Gudday
My WFO has a soldier course with about 2 in of hombrew behind it!
Would you think that the homebrew mortar with its extra lime would be alkaline enough to protect he steel? That why I think that cast oven on a shoestring has stood up with its metal cage?
I wouldn't think the turnbuckles would be a little over the top... the barb wire sounds like the go. That stuff should never pull out of the mortar with the barbed bits so no need to connect the ends and if the lime protects the steel should make a great re enforcing for a small structure. Glad your playing with it though ....wear gloves thick ones


Regards Dave

[david s]

Re: Oven on wheels

I think the barbed wire idea is a good one. Mud brick houses use it as reinforcing very effectively. Remember though that zinc has a melting point of 419 C from memory so although it shouldn't get that hot outside the the inner brick walls it would be prudent not to fire your oven up too high just to see how hot you can get it.

[wotavidone]

Re: Oven on wheels

David S, That's a damn good point about the rate of expansion. I am ashamed to admit that the thought that the different materials would heat up at different speeds didn't occur to me. Its not just how much they expand, but how quickly, eh?
I take your point, too, about the zinc, which is why I might jump a certain farmers fence and grab the rusty stuff from his old rolled up fence. Relax, its not stealing, he's already said OK.
Brickie, I'm only looking for four or five bags at this stage, but that 30% price differential equals 3 bottles of my favourite cheap plonk. My boss reckons that life is too short to be drinking cheap wine, but he's on $200K+ per annum.
Actually, its all part of my ongoing "Don Chipp" campaign - you know the one, "Keeping the B@$!@%ds Honest"
A while ago I picked up an item that was marked $16 and they tried to charge me $28. Then I bought some steel plates marked 200 * 50 * 3mm, and they measured 185 *45 *2.5 when I got them home. The biggest complaint I have is when they locked my wife in the garden section for over half an hour, then did not even bother to apologise when they finally heard her knocking and let her out. I took note over a six month period and realised I'd never been charged marked price (wouldn't mind if it was under, but it was always over).
Remembering these are the people who advertise that they are the "special order specialists" who didn't bother to ring me back when I asked them if they could get fireclay. The $6.95 a bag guy busts his arse to get what you ask for, just a shame he couldn't get fire bricks at a price I could afford.
I've always said I'd open a Bunnings, assuming you can get a franchise, when I win the lottery.
And when I do, there's one 17 year old girl I'd hire from this mob, (typical chick, working twice as hard as the guys to be thought half as good), the rest I wouldn't touch with a barge pole. There is one young lad who knows his stuff, but I swear if he uses the F-word one more time over the counter at me, I'm gunna jump the aforementioned counter and shove a cake of soap in his gob. Thanks for the opportunity to vent
Say, you'd use more cement and lime than anyone I know over here. Didn't it tick you off when they increased the price by stealth? Or was that only a South Australian phenomenon?
I guess I'm looking at it from a consumers point of view. Over here the builders and hardware merchants are driving the flash cars, the homeowners are driving the 25 year old wrecks, so I get a bit peeeved at what I see as an imbalance.
Anyway, back on topic. My youngest is home from school tomorrow, coz the teachers are having a "student free day". Whatever that is.
He thinks he's sitting in his room playing video games.
Got news, his old man booked a day of annual leave, so he is not gunna be playing video games, he's gunna be learning the finer points of screeding and floating concrete. We shall discuss the hydration reactions of CaO and SiO2, and what happens if you supply too much water. His head shall spin.

[brickie in oz]

Re: Oven on wheels

Seems a shame to waste a whole days building for $15 or $20....