Time to build my bread / pizza oven

[Tscarborough]

Re: Time to build my bread / pizza oven

The back wall is going to seperate from the arch; it is simple physics that the arch will expand more than the wall. Mine opens up a good 1/2-5/8" at full saturation. I planned for it by keying the wall into the arch and cutting the wall pretty tight when it is cold (less than 1/4"). By keying, I mean that I notched the wall brick so that they protruded half way into the arch and also had a lip on the outside. I did not mortar the joint or stuff it with anything, it is free to expand and contract and is still fireproof.

[david s]

Re: Time to build my bread / pizza oven

For kilns of this configuration it is recommended that the end walls be constructed to be under the vault rather than outside it, for the reason you mention TS. Would presume an oven is subject to the same problem, but to a lesser degree because the expansion is less as the temperatures and therefore the expansion is around half that of a kiln.

[matthewcove]

Re: Time to build my bread / pizza oven

As is is desirable for my bread baking to have a well sealed oven, able to retain steam, I would like to leave the expansion gap. but fill with compressible material, similar to that which they use of furnace doors. The expansion gap is also a route for smoke to impregnate my insulation with smoke, which i would also like to avoid. I could probably live with the moisture issue, but there have been cases of fires caused by soot build up in the insulation cavity.

Thanks

Matthew

[matthewcove]

Re: Time to build my bread / pizza oven

A little bit more work done on the oven today after not having any time for a couple of weeks. Time to experiment with the expansion gap / gasket at the rear wall/arch.

This may not be the last time I re-visit this bit of the oven design I think and I probably need to find a more substantial gasket material for this approach to work.

I have more details in the blog post here



Matthew

[Tscarborough]

Re: Time to build my bread / pizza oven

The end brick need to be inside the arch, either in full or keyed.

[matthewcove]

Re: Time to build my bread / pizza oven

I have been trying to work out how the turtle rock oven get away without an expansion gap or keying.



It looks like the end wall is mortared to the arch, but I know that does not work on my oven. Maybe it because of the much thicker brickwork on there oven, but I cent see that preventing it breaking along this line. Maybe is does crack and they rely on the foil faced insulation to deal with any escaping hot gasses. Anyway, my oven is meant to be an experiment, to refine a design for a bigger oven. It would not be much of an experiment if I just followed the crowed and just did things the same as everyone else. So I will try this, but expect that it is not the final answer.

Matthew

[david s]

Re: Time to build my bread / pizza oven

With the heavy steel bracing holding the end walls in, you should be fine.

[matthewcove]

Re: Time to build my bread / pizza oven

Unfortunately the bracing only holds the side wall in. The position of the steel bracing is at the level of the soldier bricks, so the top of the rear wall where it meets the arch is 3-4 courses above the level of the steel strapping. With the real wall mortared to the arch, the rear wall failed just above the soldier bricks, but this was expected.

Matthew

[matthewcove]

Re: Time to build my bread / pizza oven

Just did a few simple calculations. The dome along its length at 800 C should expand by approx 0.4 mm and the dome height change due to expansion at the same temperature should be no more than 0.3mm. Anyone know any figures for level of elasticity of refractory mortar / brickwork?

Matthew

[david s]

Re: Time to build my bread / pizza oven

I think you are out by around 10 x. Your barrel arch (not a dome) is likely to expand around 4 mm. It will never reach 800 C maybe 400 C. From memory at 400C the expansion of refractory is around 0.5%

[matthewcove]

Re: Time to build my bread / pizza oven

The manufacturer is quoting 0.2% at 400C. But you correct I have got my arch calcs wrong, this would come in at 1.8mm. Clearly enough to break any ridged coupling.

Matthew

[david s]

Re: Time to build my bread / pizza oven

That is actually pretty low expansion. There is quite a difference depending on composition.
https://www.ideals.illinois.edu/bits...pdf?sequence=3

[matthewcove]

Re: Time to build my bread / pizza oven

Thanks for the link David, useful research material.

Matthew

[matthewcove]

Re: Time to build my bread / pizza oven

Made a start this evening on the exterior of the oven and have also tack welded the door hinges in place. Got a lot more work to do to make it functional and nice, but it is good to have made a start after a few days of not having any time.





Matthew

[matthewcove]

Re: Time to build my bread / pizza oven

Just finished this evenings work on the oven. The first bits of exterior walls are on. Looking forward to insulating and firing the oven this weekend ready for a bake in a couple of days.

Its not much of a looker, unless you like heavy engineering.

All the details as usual in a blog post here.



interested to hear you comments and suggestions

matthew