28" homebrew cast oven in walled enclosure Belgium

[david s]

This is my solution. 95 x 95 x 295 x 0.90 mm

[Kris S]

Yep, that's the kind of design I have in mind.
Gonna take a bit of time to drill ~30 holes.

[david s]

Yep, that's the kind of design I have in mind.
Gonna take a bit of time to drill ~30 holes.

My first one had no holes as it was a prototype, but as I was getting them laser cut I decided to add the holes to allow some heat through and some air in. It’s the same principle as a kiln bag wall to protect wares from direct flame impingement.

[Kris S]

I also want to try my hand at making an andiron like this.

Can I Just bend a few pieces of rebar and weld them together? Would that hold up for a couple of years?

[JRPizza]

It should hold up OK. I made a fireplace grate out of rebar that has survived several seasons. I was going to build a log holder like you are showing, but the Pompeii designed ovens draw so well (at least mine does) that I can't justify the space it would take up when I was not firing the oven.

[Kris S]

It’s more a case of just wanting to try and see if it makes a big difference. I’m not having any draw issues either, (no smoke ever escapes through the oven mouth, except for 5 minutes when igniting the fire) but I think it may help prevent small logs rolling off the fire and into my pizza!

I might make a smaller version, as my internal diameter is only 28” – 70 cm.

Rebar should do, okay – Thanks!

[Kris S]

The heat deflector works like a charm no more fire rolling onto pizzas, and less quick burning of the crust as well !



I also wanted to get more insight in my fuel consumption, so I weighed all my firewood before and after use on 2 occasions: I use 10kg of oak for 12 pizzas, and 9kg for 10 pizzas.
This includes starting the fire and getting the oven up to temp obviously.

I have no idea if that's much or little. anyone else ever try to do this?

[david s]

I also use one of these, it is particularly useful for small ovens and maximises oven floor space and reduces burning the pizza edge that’s too close to the fire. For years I used a prototype made from 0.5mm stainless, but it did warp badly from the heat, so I had a bunch laser cut using 0.9mm stainless with holes in the front face to allow some heat through.

[Kris S]

Dear David, i used the pictures of your heat deflector at the top of this page as inspiration to make mine.
The SS is at least 1mm thick.

[david s]

I have a couple of finger sized sticks preheating on either side of the entry so when thrown in behind the flame deflector they burst into flame almost immediately. This makes it easy to keep the fire going continuously.

[AJH]

I also wanted to get more insight in my fuel consumption, so I weighed all my firewood before and after use on 2 occasions: I use 10kg of oak for 12 pizzas, and 9kg for 10 pizzas.
This includes starting the fire and getting the oven up to temp obviously.

I can see myself doing this after I get my oven built =) At least enough to get a sense of how much wood it takes to heat up and keep making pizza's for a few hours...

[MarvinG]

Hi there!

What a great thread and build! Some might remeber, I built two dome ovens (on the picutres) and run now a small pizza place in tbilisi.
I am about to build an oven on a key truck.

Is the assumption correct that the oven will be better/more durable on the ride to cast 1 piece in situ with ball/sand instead of building a brick oven?
I know that a cast with 3 pieces is probably best, but that is not yet reachable with the time available.
So, is it not possible to use some more reinforcements? What I was therefore wondering is, if one cannot reinforce the homebrew with glass fibre strips.
or would it be smarter to use a thin refractory cement base and then homebrew on top?
or could you even soak a thin theramic fibrewool planket? just for strength of course.
What do you think?

[david s]

Some manufacturers make one piece cast domes specifically for mobile application. The problem is that any large cast section is prone to cracking com uneven thermal expansion. My first mobile oven built in 2007 was a one piece dome sitting on a one piece cast floor, both castings were of proprietary castable refractory. I lasted around 8 years. The floor started spalling and the dome developed a vertical crack at the back, right opposite the oven mouth. You could fit a plying card in the crack, but it never got any more severe and did not affect the oven’s performance. I have seen similar cracks in two other one piece cast ovens in exactly the same location. I’m actually now on my third mobile oven. There have been reports of brick mobiles rattling to bits very quickly, so don’t go down that route. A 3 piece cast is probably a good compromise and what I now have. All mobiles don’t like being moved. Make sure you fit shocks on the trailer and always avoid unsealed roads. Regarding the floor, it is best to stick to fire brick because the floor takes a real beating and subject to a lot of uneven thermal expansion as well as extremely rapid temperature rise.

[MarvinG]

Thanks for this input David! Highly appreciated as always.

Yes, the oven (with a similar bottom construction as done before) will probably sit on (lying) old tires which are placed on the pickup. To constantly shock absorb.
The floor will be bricks, sitting on cermaic boad.
So if I got you right - you recommend not to use homebrew - but use refractory cement instead, right? (cause its nearly impossible to buy this here) I'd have to go over the boarder - which is ok, but take some time.
And yeah, I read most of your threads of course where you explain plenty of details! :-)

Does anyone have experience with this fibreglas to make things stronger? I was thinking of doing this:



with this material. either Glass fibres or Carbon fibres.

[david s]

Because I manufacture I use a proprietary castable refractory, but I believe the extra durability it might give is not really worth it as the material is really expensive and contains ingredients that are designed for much higher temperatures, in excess of the temperature range to which we fire. The homebrew is almost as good as the far more expensive products. All reports on the homebrew longevity say it holds up very well. So cheap and easy to rebuild anyway. The vulnerable temperature range when thermal expansion of most materials peaks, is from 500C-650c should be avoided to prevent damage. Quartz (silica) does undergo significant and sudden thermal expansion in the 571-576C range and as all sand is primarily silica this is either a reason not to use sand as an aggregate or alternatively avoid the higher temperatures. So never fire an oven as hot as you can just to see how high you can get it. Only go as hot as you need.But this advice also applies to all ovens as a variety of different materials are used and the different rates of expansion can be incompatible. See attached graphs as an example of this. Mineral composition.docx

Interesting about your tyre solution to mount the oven on. I have been using that system for years when freighting oven kit parts. I place a motorbike tyre on a pallet, then assemble oven components on top. I’ve never had any breakages in transit.

On using fibreglass, you must get the AR (alkaline resistant) ones. They are coated in zirconium which is expensive, but the coating prevents chemical attack from the cement. They are widely used by the concrete countertop manufacturers so search there to find them. Glass doesn’t melt until sround 900C so fibreglass fibres are suitable for our temperature range as long as they are the AR type.
The other type of fibres that are probably more important to add are the very fine polypropylene fibres that melt at 160C leaving behind a network of fine pipes through which moisture can escape. This provides a measure of protection from steam spalling whe the oven is completed and firings begin


I love your photos, post more please.