Oven on wheels

[wotavidone]

Re: Oven on wheels

Hi Wotavidone,
Hairline cracks occur in wood fired ovens from time to time, but these hairline cracks never become large enough to become a problem. Cracks simply happen with brick ovens on occasion because of the expansion and contraction of the dome and the individual bricks. It's essentially part of nature.

What is important is that these hairline cracks do not impact how well the oven cooks or how long the oven will last.

The homeowner can continue using the oven, not worry about the crack and let us know if it gets bigger (again, something that has never happened). Here is the text in Italian, from the Artisan who makes the oven, and in our translation.

"Come tutti i forni tradizionale anche "il Forno del Nonno (Artigiano)" subisce durante il funzionamento una normale dilatazione termica che si presenta sotto forma di una piccolo crepatura in corrispondenza della cupola.

Tuttavia questo fenomeno naturale non deve preoccupare poich? non altera e non limita le caratteristiche del forno che potrete tranquillamente usare come vostra consuetudine."

As with all traditional ovens (brick), including the Artigiano, that undergo thermal expansion during operation, there is the chance that small cracks can form in the dome.

This phenomenon is normal in every way, and you do not have to worry, because these small cracks do not alter or limit the characteristics of the oven, and you can happily continue to use the oven as you would otherwise.

Thanks, mate.
I'm not too concerned. I recognize that something has to give when things expand and contract a lot. I'm used to looking at furnace and kiln re-lines that cost hundreds of thousands of dollars, and still drop bricks and chunks of refractory out of the liners the first time we fire them up. That's with embedded thermo-couples, rigorously monitored curing schedules, the lot, and we bring them to temperature and keep them there, not go up and down like a wood oven does.
So, I'm more amazed how well homebuilt brick ovens hold together, rather than alarmed at minor cracking.

[wotavidone]

Re: Oven on wheels

Being an Aussie country bumpkin, I naturally own a whole shed full of junk that "might come in handy one day."
I keep promising myself I'll take it all down the scrap yard and get some money for it and some room to park the motorcycles and cars. Of course, I never do, coz it'll come in handy one day.
So yesterday I was poking around in the shed, when I came across this old, well used hub cap off a 1976 Holden.
Three strips of stainless steel, a few of monel rivets later, I have a chrome plated rain-cap on my oven flue.

[wotavidone]

Re: Oven on wheels

Another try.

[cobblerdave]

Re: Oven on wheels

Gudday
Very "kings wood"
Regards dave

[UtahBeehiver]

Re: Oven on wheels

Great recycle use.

[wotavidone]

Re: Oven on wheels

The other night the missus "suggested" a BBQ for dinner would be welcome.
So I fired the oven, and made a rack for the sausages and chops form a couple of old refrigerator shelves.
I did the chops and snags on the rack.
Something I didn't realise, when you cook your meat on an elevated rack in a fully heated oven, the top and bottom cook at the same time, and you don't have to turn the meat over.
Did a tray of capsicum, zucchini, onion and carrots tossed in garlic, oil, salt and pepper, and a tray of roast spuds.
It all cooked really quickly.
Pretty happy with the outcome. We'd just started serving it up when I remembered to photograph it.

[nu_brew]

Re: Oven on wheels

Thanks for the detailed thread.

Some great ideas and trouble shooting in here.

[WJW]

Re: Oven on wheels

Be careful cooking on refrigerator racks. I have no idea if it's true, but I was always taught in Boy Scouts that such racks are typcally galvanized...and cooking on galvanized surfaces was a big no-no.

Bill

[wotavidone]

Re: Oven on wheels

No worries, these are chrome plated steel. Had a moment's concern about hexavalent chrome and decided life is too short to stress about it.
I reckon if we are not worried about chromium in the bricks, no need to worry about chromium on the rack.
According to my research, you need welding temperatures to generate hexavalent chrome from chromium metal.

Having said that, I just went and looked at the rack I heated in the oven - the plating is flaking off, differences in thermal expansion rates?
Thinking about it these were kinda rusty looking. It was an old fridge, so maybe it was nickel plate.
I figure I'll hit it with the wire wheel, or just re-heat it in the oven until I burn it all off.

[RaymondW]

Re: Oven on wheels

Hi Guys, Do you think its fine to use Corobrik Pavers for a WFO. It's fired at 1500?C and according to them would do just fine for a WFO. They suggested the Constantia paver @ R4.80ea... a far cry from R35ea for normal FireBrick!!

Corobrik |Bricks & Paving - Clay Brick & Paver Supplier - Corobrik

[wotavidone]

Re: Oven on wheels

Sorry, mate, it's an impossible question to answer without seeing them in the flesh.
Bear in mind a paver isn't intended for thermal cycling, but, having said that, people have been successfully building WFO with ordinary bricks for hundreds of years, and a paver is an extra strong, skinny brick.

I can give you some tests and things to consider, and they've already answered a couple:
1) The fact the clay can be fired to 1500C means the clay must be at least a bit refractory.
2) Get a sample. I don't like any paver that has that black iron stone staining and bits of clinker, and there looks to be a little bit of that in one of the constantia pavers in the picture. I prefer pavers that are one uniform colour. I handpicked from a pile if leftovers.
3) Cut one open - look for it to be a uniform colour all the way through. Sometimes pavers look burnt and black on the inside - not heated quite hot enough, or maybe long enough, and these are sintered in the middle, rather than fused. Those sorts of pavers tend to be fragile after they have been heated to WFO temps.
4) If the paver is uniform colour all the way through, heat the paver on a butane stove until it gets to 450-500C, on all surfaces. A cheap 20 dollar Ebay infrared thermometer will do. Then let it cool.
4) If the piece of paver you fully saturated to WFO temp hasn't cracked after it has cooled, give it the drop test. Hold it at shoulder height and drop it onto sharp rocks, or concrete curb or such-like.
If it doesn't break, it has survived being heated to WFO without developing concealed cracks. Should be able to use it. Should also drop the unheated piece - if that one breaks, don't use that type of paver.

After a couple years of use, my oven has no cracked bricks/pavers. Any cracks in mine are where the mortar has let go of the brick.
I have a theory about why, and I would do things a tiny bit different if I build oven number 4.
Pick real smooth pressed ones for the cooking floor.
Hope this advice helps.

[wotavidone]

Re: Oven on wheels

PS, regardless of whether they think their bricks are good enough, I gotta say that the oven they build in their how-to video looks spectacularly awful to me.
I watched it with the sound off because the missus was watching Tvand I get in trouble for making noise, but do my eyes deceive me, or did the guy mix cement and perlite for the cooking floor and inner wall?

[RaymondW]

Re: Oven on wheels

Man, that oven is horrendous!! Thank you for the advice, I quite like the burgundy paver and champagne paver but will get some on tuesday and do your tests.

[wotavidone]

Re: Oven on wheels

Man, that oven is horrendous!! Thank you for the advice, I quite like the burgundy paver and champagne paver but will get some on tuesday and do your tests.

They do look better, wish I could see them in the flesh. Also, I see that some of the pavers are also available as 60mm thick.
That'd be a good thing - gives you some options for floor thickness.
If both the burgundy and champagne pavers are good, you can do some nice things with the colours.
An acquaintance went to a local brick company, told them what he was about and they recommended their darker coloured pavers, as they had been fired higher. I have read that the colour is not just what's in the clay, but is varied somewhat by varying the temperature - might want to check with the suppliers on that.
Also the 60mm ones are only 200 by 98 - this gives you the option of ending up with a dome 3.9 inches thick.
the 230 x 115 pavers we get over here give us the option of 4.5 inches thick, or stand them on edge and end up with the dome being the thickness of the paver.

So, depending which way you orient your pavers and which ones you buy, you have quite a few options for dome and floor thicknesses. Brilliant. R4.80 is about 53c Australian - very cheap bricks, compared to Aussie ones. If you are getting a salary comparable to an Aussie one, that is. (its all relative.)

[RaymondW]

Re: Oven on wheels

I think I will go with half bricks all the way through (for the dome) which would give me 3.9in. I'm pretty sure that would help with excellent heat retention. I must say I quite like the champagne colored brick but the burgundy does "look" harder.

There's two other points that worries me a bit:
1. Dome to arch connection (transition)
2. Building the arch (FB way or interlinking with the courses)

Do you think its better to do a vermiculite "inlay" in the slab before you pack the floor or (depending on the quality and thickness of the brick) just the floor straight on the concrete?