The reverse build.

[brickie in oz]

Re: The reverse build.

provides space for thermal expansion of the inner parts of the oven which avoids pressure on the outer arch.

I had provided for expansion all around on the last oven, Ive seen what can happen to brickwork from the effects of the sun never mind a furnace..

Its not my work btw.

[david s]

Re: The reverse build.

Yeah, I use only 10mm vermicrete, but it is way better than direct contact.Apart from reducing heat conduction=heat loss, it also provides space for thermal expansion of the inner parts of the oven which avoids pressure on the outer arch.

[brickie in oz]

Re: The reverse build.

Ive already thought of doing that, is ceramic blanket good sandwiched in between?

[Lburou]

Re: The reverse build.

Include a thermal break between the inner and outer arch if you want to improve heat retention.

David, would you mind defining a 'thermal break'?

I'm thinking about inserting about 5 or 6 insulated firebricks from right to left on the oven landing just outside the first oven arch....Is that what you mean?

[david s]

Re: The reverse build.

Include a thermal break between the inner and outer arch if you want to improve heat retention.

[brickie in oz]

Re: The reverse build.

OK Ill do a straight forward barrel then with no doming down, much easier.

[Lburou]

Re: The reverse build.

Brickie, there is nothing like a clean start, knowing what you know NOW.

[stoveup]

Re: The reverse build.

Depressing pictures - until you get to the last one of that beautiful, clean base ready for a new WFO!

I do not understand the "doming down" at the front of the AS designs either. My past experience has been with building and using high-fire ceramic kilns, both gas and wood fired. Larger pottery kilns are usually rectangular inside and heat quite evenly throughout - even in the corners. The downdraft design of these kilns functions in a similar manner to the low opening height of the Pompeii WFOs which is a critical design component for efficient heat retention.

I believe that a vertical front on a barrel arch (maintaining the height of the arch right up to the flue structure) should be every bit as efficient as the dome-down variety and much easier to build. Probably improved structural soundness, too.

Keep in mind that I am a newbie to the WFO world and am still learning about these things. Can't wait to have my own WFO!

[Tscarborough]

Re: The reverse build.

It just seems to be an unnecessary complication. Coming in square seems to work just fine and the air current forms a roll in that space anyway, so it may be counter-productive.

[C5dad]

Re: The reverse build.

If you are looking for the efficiency of a pompeii, the inner arch should be around 410 (650*0.63) for the heated volume capacity.

As for the AS ovens, I always wondered about that as well - it really does not make sense.

CW

[brickie in oz]

Re: The reverse build.

That is one of the features of the Alan Scott design I am not comfortable with.

Hmmm?
I had thought that the doming down would help fire the oven better and keep some more heat in the oven.

I could be wrong, whats your thoughts?

I have seen the Alan Scott builds and they disgust me, they dont even bond the arch dome in? Why wouldnt you bond the arches in?

[Tscarborough]

Re: The reverse build.

'Verra nice! Do you think that doming the front is worth the extra effort (obviously you do)?

That is one of the features of the Alan Scott design I am not comfortable with. It may be marginally more effective, but the added complexity is significant for the return in efficiency.

Not so much for you, but for ordinary non-mason builders.

[brickie in oz]

Re: The reverse build.

Are you gong back with brick or more castable?

Im going to build it with clay pavers in a barrellish shape.
The oven roof will be a low arch front to back with round tapering front and rear.
The roof will only rise 300mm from the side walls that will be 340mm, all measurements are 'ish

Heres a rough side elevation, the oven will be just over 1M long and 700mm wide x 650 high internally.

[Tscarborough]

Re: The reverse build.

Are you gong back with brick or more castable?

[brickie in oz]

Re: The reverse build.

The cast oven cracked like an Easter egg when I hit it with the large persuader.

The old oven base ready for a make over. Sounds Like a TV show title.

I was really surprised at how much moisture there was in the vermiculite at the rear of the oven.
The oven has a roof over it plus a concrete cap painted with vinyl paint, I would have thought it was water proof? (The oven was 2 years old so was properly cured.)