My 90cm x 125cm bake area oven build

[matthewcove]

Had a go at doing a bread bake in the unfinished oven last night. Conclusion, need a proper door and lots more insulation.

Made a record of the bake and firing in a blog post here



My regular bake looks much better when baked in a real wood fired oven



Matthew

[firebeard]

What kind of door are you going to use? Have you seen the counter balanced pivoted doors that lay flat when you push it with the peel?

Joe

[matthewcove]

I have seen those, but i think that I would need a second more insulated door for when the oven is sealed up equilibrating as a fold down door would have to be quite thin. I think some designs have the fold down door that us used during loading and unloading and then a second insulating plug that is put in place when you know the door will remain shut for a longer time?

Another thought, should I plug up my ash slot during baking and how would I do that?

Matthew

[matthewcove]

A week away for work again has kept me away from the oven, although I did keep up with the forum and thinking about the next steps. There is one area of the oven design I would like to improve, the transition between arch and the back wall opposite the oven door. The end wall just stands there, not bonded to the dome, just mortared together. I was assuming that this area would crack and it has. Often oven had a poured concrete jacket over this area, but as I only have brickwork I need an alternative solution. I have seen on a few posts people discussing a break between the dome and the external arch of the Pompaii builds. I my current best plan is to leave a small gap there and fill this with a ciramic roap or compressible gasket material, such as this link. I wanted to hear the forums experience with this, get some ideas etc.

Thanks

Matthew

[matthewcove]

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 pos here



Thanks

Matthew

[cannyfradock]

Mathew

Love those pictures...

A lot of what you are building are out of my knowledge range as I haven't yet attempted a vault build. I'm not sure what to suggest on the rear wall. If it were me I would have tried to tie in the rear wall with the end arch using 5mm carbon fibre rods. These are used by some modular oven manufacturers in place of re-bar. It looks as if you are a little tight on space at the rear of your oven, but you may be able to bend some (12") strips of ex-met over the joint and cover with a layer of refractory concrete, incorperating it in your thermal layers?

I have only ever seen 1 ash hole in operation. This had a sprung/hinged metal plate over the hole. It would allow the ash to be emptied via the hole but the plate would always spring back to close the gap. I'm not sure of the mechanics of this plate. This is used by a excellent baker....Rick Mair who bakes roughly 600 sourdough loaves a week using his Allan Scott designed 7' x 5' Vault oven.....



Terry

[matthewcove]

Hi Terry,

The carbon fibre reinforcing idea sounds interesting. I had not thought of using carbon as a reinforcing material, I'm sure it can deal with the temperatures, but I will have to look up its coefficient of expansion to see if it is similar to any refractory concrete. So far I have not seen anyone with an ideal solution, there are definitely drawbacks to the Allan Scott approach to using a concrete jacket, but this would give me far to much mass. The turtle rock approach seems to be just mortar, it looks like they probably allow cracking and then deal with the containment of gasses using foil faced insulation. dont know if you have seen their stuff, but I got much of my inspiration from the pictures on their site, here you will see more than a few similarities between their mobile oven and my little project. Their bigger ovens are amazing and they have contracted replaced a few Alan Scott ovens that have failed, but at 40K for a largish oven...

The ash slot is something that I have not thought about yet. I would like to have some way of closing it off, I would like to be able to use it as an air intake for final stages of firing, when the fir is small and the doors are closed. I'm planning a 3 door system there the centre door is opened for firing, got myself the hinges today, going to have to start welding this week I think. Not done much as we have been putting a proper roof on the bakery this week, will put some pics up tomorrow when finished.

Great picture. I would love to see it in action and ask an annoying number of questions

Matthew

[firebeard]

Hi Matthew,

I was thinking about the back wall of your oven, the main think I would be looking to do is stop dust and insulation falling into the oven chamber. It is hard to tell from the pictures, if your gasket material is tightly packed and springy enough to allow for the repeated movement then you should be ok as you are. One idea I was thinking about is to bend a 6 inch wide strip of thin sheet metal to put over the top of the joint. Otherwise you could cover the top of the joint with a few layers of the thickest aluminium foil you can find.

Joe

[matthewcove]

Hi Joe,

This is a good point. The perlite is insulation is going to be dusty. I bought a big roll of high temperature alu tape last night and was planning to envolope the oven in aluminium foil before using the perlite, but your idea of sheet mettle is a good one. I just remembered I have some 0.2 mm thick sheet aluminium left over from a heat exchanger project I have been working on, i think I will experiment with covering that area with it first. Do you have an figures or experience for how hot the exterior of the roof of the dome could get, if I remember correct Alu mealts at around 630 C. I'm prety sure it wont get that hot, but I've never removed the insulation to take a reading.

Matthew

[firebeard]

Hi Matthew,

The aluminium should be OK. The exterior of the roof where it meets the rear wall is going to be the coolest part of the roof.

What kind of heat exchanger have you been making?

Joe

[matthewcove]

Hi Joe,

It is a contra flow air-air heat exchanger for the forced air ventilation in our house.

Matthew

[matthewcove]

expansion joint news. Few hours of curing fires and no sign of smoke from that end so it working better than the gap on its own. oh and the bakery has a roof!



Matthew

[matthewcove]

started making the exterior of the oven this evening. Got some of the panels cut and have tack welded the door together. Still needs lots of work before it will look and work ok, but its good to have started.





Matthew

[kipper]

how I wish I could weld.I made my door from oak and its already started to warp and disintegrate after a handful of firings.back to the drawing board on that when time/weather permits.

your oven front on the other hand looks like a job well done.and may I ask what insulation is that on the door itself?

[matthewcove]

I can't say that I can weld ether, I only have a few hours under the belt and a very cheep stick welder. I watch a few youtube videos and now I love welding. The insulation is high temperature foil faced rockwool. I will also encapsulate that in some 0.2mm aluminium to keep the fluff away from the dough

Matthew