Uk custom cast oven build - Tractors oven will this work?????

[Tractor]

Hi all

welcome to my build..!!!

I've been researching ovens for a while and I've come up with what I think might work best for me.

I plan on mostly using the oven for pizzas with some fresh bread as well

here's what I'm hoping to end up with.




I'd like to cast my oven in place over some foam formers but before I spend the time CNC ing the forms I wanted to discuss with you guys
weather or not you think it'll work.

heres the oven on its own



and a cross section to show the dimensions




Ive tried to stick to the 63% rule here 189mm being 63% of 300mm but have I understood it and got it right?

I've created a very low dome here but is it too low??? my logic is that the top of pizzas will cook better the closer
they are to the heat source.

one other thing I've done is to create a scoop that leads into the chimney flue, im hoping this will prevent smoke from coming out the
front of the oven and making a mess of the front face. you can see this better here along with the above cross section



there's a great deal of other things to discuss here as well I'm sure but I think thats enough for the moment.


I'd be interested in your thoughts guys??? do you think this will work?

I know the pizza oven and in particular the Pompeii oven has been around for 100's of years and there's and argument for if it
isn't broke don't fix it but I'm a big believer in developing and improving


thanks guys
trac

[shuboyje]

Re: Uk custom cast oven build - Tractors oven will this work?????

The oven itself looks ok, but the opening and entry look like they could use some changing to me. In the renderings the outermost arch looks really low, and the entry looks really deep. All these things add up to make an oven that will be hard to build a fire in and hard to work.

At 57% of the oven width I also think the door is too wide. Make it just wide enough of the biggest pizza you plan to bake. If you want to do an 18" new york style pizza make a 19" opening.

At very least I would raise the outermost arch a bit, but my personal preference is to eliminate it all together and use a Neapolitan style with no entry and a cantilevered vent. For pizza this leads to a MUCH more accessible oven.

[david s]

Re: Uk custom cast oven build - Tractors oven will this work?????

I agree about the excessive depth of the entry. Provided you have an adequate flue size you can make the entry really shallow, making it easier to work and no smoke out the front.

[Tractor]

hi guys apologies for the radio silence, its been a very long time but I had good reason and I'm back now.......

I appreciate your replies and your absolutely correct so ive gone back to the drawing board and come up with this this morning.




100cm floor



insulated slab
dome


insulated concrete poured over dome



chimney


alltogether

[Tractor]

Access should be a lot better, would you agree??

I do feel like I'm reinventing the wheel here a little bit however I do want to make it as custom as possible so its important to get the basic oven right first I guess

I should add I now propose the dome height to be 250mm from the floor to the apex and I've made the opening 400mm wide and 157.5mm high,





Q - is 250mm too low for a 1000mm diameter floor? what do you guys recon?





trac

[Johnnyd943]

Love the CNC Idea.. been tossing it around myself. Can't wait to see where this is going !

JD

[Tractor]

stay tuned JD



trac

[SableSprings]

Welcome back Trac!

At your first post you mentioned in addition to pizza that there would possibly be some bread involved. I suspect that Focaccia and then roasts (& turkey) will follow. My suggestion is that you take your current sheet pans and roasters into account when thinking about the width & height of the oven access. I do full sheet pans occasionally and it's really nice to have them fit through my oven opening. In addition, the low profile is great for pizza but may be a problem when doing something like a turkey. Just some things you might want to consider...

I also wondered if you are going to put in a reveal so you can use a fire door to seal up the oven when baking with just stored heat. Looking like it will be a fun & functional pizza oven for sure! I'll certainly be watching your project with interest.

p.s. In posts #4 & #5 above, the top sets of photos are show on my screen only as broken picture/file icons. The lower 3 in post 4 show OK as do the lower 2 in post 5...but no others.

[david s]

I'm sure this design would work, but not so sure you'll get good circulation with the form of the oven being so flat. Even a slight curve on the roof would increase the strength of the dome enormously rather than having a flat one. Your new proposed oven mouth dimensions are almost exactly the same as mine, yet my oven is only 540 mm in diameter and its form is hemispherical. I can just squeeze in a 5kg turkey through my door. I feel you would be better to raise the height of the dome 100mm and also the height of the door in proportion. Also the floor in the entry, especially right up near the oven opening is probably too hot for standard concrete to cope with the heat there, suggest you use fire brick for at least another 100 mm there.

[Tractor]

hey guys thanks for your advice its much appreciated sable I don't know whats going on with the photos it was a right pain to get them to show I'll have to go back and re read the how to upload photos sticky. I measured my pans and a 400mm opening should be fine. David I revisited the initial shape of the internal and your absolutely right the roof of the oven is far to flat, that's something I missed and out of interest I did just raise it 100mm and it gives a much better shape, I've kept the floor at 1000mm and played with the roof surface to make it as smooth as poss. I have only raised the opening up to 200mm. the oven is 350mm tall in the centre so applying the 63% rule gives an opening height of 220.5mm which I modelled up but it just looked way out of proportion so I've gone with 200mm. I'll do some flow analysis at somepoint to test to make sure the fire will still draw ok I do plan on having a door to retain residual heat so I've modelled in the flange for it to sit up against. heres the revised oven........... a couple of things I should explain..... everything coloured in red I plan to cast in a refractory cement and everything in blue I plan on casting in an insulated cement to help retain heat. Q - the bit I've coloured orange bridges underneath the door and if cast as part of the oven floor will it conduct heat out of the oven when the door is in place? and if so do you guys recon i'll be able to cast that section as part of the insulation slab? I don't want to move the door further out because that will mean its the wrong side of the chimney cheers guys good to catch up trac

[Tractor]

here's a better view of the door Flange

[david s]

"Q - the bit I've coloured orange bridges underneath the door and if cast as part of the oven floor will it conduct heat out of the oven when the door is in place? and if so do you guys recon i'll be able to cast that section as part of the insulation slab? I don't want to move the door further out because that will mean its the wrong side of the chimney"

Firstly, if you cast the oven floor in one piece it will crack. Any large cast sections are vulnerable to this problem and none more so than the floor. It is for this reason that most WFO floors are smaller units (firebricks) and have no mortared joints.

Secondly, if you cast the floor section under the entry using an insulating mix it will not be particularly strong and will be subject to abrasion from moving pots and tools over it continually. There are a couple of solutions I can think of and that is

1 to cover over the area with thin stainless which is durable. Or,
2 use a dense refractory material like firebrick there, but separate it from the oven floor with a thermal break of around 10mm This gap can be filled with blanket and the top cm or so topped with vermicrete to seal in the blanket.

Don't change the position of the door.

[Tractor]

Hi David yes your right. The floor will most likely crack if I leave it as above so what I plan to do is to cast it in five pieces, if you imagine quartering the floor but also having a circular disc in the centre you won't be far off

I was planning on casting it 100mm/4 inches thick but I'm starting to think that's too thick really, firstly because of cracking due to uneven temperatures but also the thicker it is the longer its gunna take to heat up.

Perhaps I'll go for 60mm as a compromise between thermic mass and speed as this won't be an industrial oven I'll have plenty of time to rake the hot embers back over the cooking surface if needed.

Thanks for your suggestion around the entry material I'll look into it.


Also a note to myself here's a good project that uses homemade refractory cement, http://www.fornobravo.com/community/...cost-wfo-build

I'll probably go for the 1-1-1-4 recipe being 1 Portland cement - 1 lime - 1 fire clay and 4 sand purely because these materials are a lot easier for me to source.


Has anyone here had any experience using this recipie? How are you ovens holding up?

Trac

[david s]

4" is very thick for a floor. Generally the floor thickness and dome wall thickness are the same. It depends on how much thermal mass you want your oven to have and the strength of the walls and floor required. Most commercial cast ovens are around 2" thick. Personally I wouldn't be relying on the home brew for a cast floor. While it may be ok for the dome I doubt it would stand the test of time for a floor, but by all means go ahead and prove me wrong, I'd be most interested.Are you planning on using any reinforcing?

[Tractor]

I was thinking of adding plastic needles as well as stainless ones, so the plastic ones burn off and leave voids and the stainless ones stay and help strengthen the whole structure

Trac