New 36inch castable build in Brisbane

[david s]

Re: New 36inch castable build in Brisbane

I have a question.

How hot does the flue assembly get towards the front and up say 200 mm?

The reason is I would like to put some light into the oven, for lighting the fire at night etc. I have read that it can be quite dark, and need a touch. I was thinking of using light - pipe, technology to relocate the light source away from heat. I would think heat resistant items, like either glass fibre bundles or silicone rubber tube, may work. Its just an idea I am tossing around. It may be easier to just use a touch.

Generally the entry stays black,ie the soot doesn't burn off there, so it's below about 300 C. If you have a fire going in the oven you don't need a light.

[david s]

Re: New 36inch castable build in Brisbane

All sound s good. I use vermicrete for the heatbreak gap too. I use 5:1 so it's got a bit more strength and holds together better than a lean mix. I use around a 10mm gap If you stuff some tissues in the gap at the top from underneath it will prevent the stuff from falling through until it has set. Get a thin stick and just compress the stuff in until it's full.

Brissie,
Just had a second thought since you were asking about temp in the entry.
My heartbreak is actually between the flue gallery and the outer decorative arch. In that position vermicrete holds up ok , however if you put it between the dome and the flue gallery it is considerably hotter there. If it were me doing a vermicrete mix there I'd use some castable with the aggregate sieved out of it to mix with the vermiculite rather than using a Portland cement mix.
Dave

[brissie]

Re: New 36inch castable build in Brisbane

Mikku,

I am just a guy that has used a lot of information from this great site. It's the people who support the forum, and answer questions, and been around a long time that have made this site what it is.

It don't matter how fast you can make an oven. As long as you have fun. And I am having fun, and don't mind sharing the build. I hope people like it. I think its all about sharing, not enough of this these days.

Me - I am the guy in the middle, flanked by my son and neighbour. Who may be looking at building an oven also.

[brissie]

Re: New 36inch castable build in Brisbane

Brissie,
Just had a second thought since you were asking about temp in the entry.
My heartbreak is actually between the flue gallery and the outer decorative arch. In that position vermicrete holds up ok , however if you put it between the dome and the flue gallery it is considerably hotter there. If it were me doing a vermicrete mix there I'd use some castable with the aggregate sieved out of it to mix with the vermiculite rather than using a Portland cement mix.
Dave

I have noticed that some people have inserted a heat break between the dome and flue gallery. So that they can maintain temperature without the "wick" effect sucking heat out of the dome. The whole flue structure is a heat sink, even if the door is on the oven.

Having said that, the flue is going to get hot with the fire going. Do you think its feasible to put two heat breaks in? One at the door, and one at the outer decorative arch. Strength may be an issue...

[stonecutter]

Re: New 36inch castable build in Brisbane

I have noticed that some people have inserted a heat break between the dome and flue gallery. So that they can maintain temperature without the "wick" effect sucking heat out of the dome. The whole flue structure is a heat sink, even if the door is on the oven.

Having said that, the flue is going to get hot with the fire going. Do you think its feasible to put two heat breaks in? One at the door, and one at the outer decorative arch. Strength may be an issue...

I have two breaks, the vent area is independent of the oven and the outer arch. The vent arch does not need to be tied into either of the latter sections, it does not strengthen the arch, because it is self supporting.

Correct that if you have a direct connection between the vent arch and the oven wall it will draw heat, and a break will help slow that action down...I doubt that a 1/2"-1" break will stop conductivity completely though. Loss of heat without a break between the oven and vent might not be measurable but it certainly won't hurt anything by doing it. The greatest benefit to a break (IMO) is between the outer arch and the vent walls, because almost all finish material does not have refractory qualities.

As far as the vent being a heat sink, my view is that as soon as the heat that is radiated by the fire and stored in the masonry of the oven passes through the oven opening, it doesn't matter if it is absorbed the vent or the flue...it is lost to the oven anyway.

[brissie]

Re: New 36inch castable build in Brisbane

I have two breaks, the vent area is independent of the oven and the outer arch. The vent arch does not need to be tied into either of the latter sections, it does not strengthen the arch, because it is self supporting.

Correct that if you have a direct connection between the vent arch and the oven wall it will draw heat, and a break will help slow that action down...I doubt that a 1/2"-1" break will stop conductivity completely though. Loss of heat without a break between the oven and vent might not be measurable but it certainly won't hurt anything by doing it. The greatest benefit to a break (IMO) is between the outer arch and the vent walls, because almost all finish material does not have refractory qualities.

As far as the vent being a heat sink, my view is that as soon as the heat that is radiated by the fire and stored in the masonry of the oven passes through the oven opening, it doesn't matter if it is absorbed the vent or the flue...it is lost to the oven anyway.

Thanks stonecutter,

I checked out your build. Its truly impressive! I don't know you manage to carve granite, its so hard. The look is fantastic. I can see your separation on both sides of the flue gallery, so will try and do this in my build.

Yeah, I don't think my aim is for perfect heat isolation, and I don't know how long heat will be retained for example slow cooking, or bread ... etc. It's just that if you plan for it you can you can reduce design downsides before building it in permanently. Efficiency and heat retention should be considered high on the list.

[stonecutter]

Re: New 36inch castable build in Brisbane

..... It's just that if you plan for it you can you can reduce design downsides before building it in permanently. Efficiency and heat retention should be considered high on the list.

Agreed. Which is why I said it doesn't hurt to add a break, since it has no structural impact or involve any additional planning outside of an inch or so more to the final front dimension.

[mikku]

Re: New 36inch castable build in Brisbane

Mikku,

I am just a guy that has used a lot of information from this great site. It's the people who support the forum, and answer questions, and been around a long time that have made this site what it is.

It don't matter how fast you can make an oven. As long as you have fun. And I am having fun, and don't mind sharing the build. I hope people like it. I think its all about sharing, not enough of this these days.

Me - I am the guy in the middle, flanked by my son and neighbour. Who may be looking at building an oven also.

Brissie,

You have a great attitude and a lot of abilities. It is fun just watching what you are doing. You must have been a pretty good plumber, carpenter and other tradesman along the way. I hope you son is picking up what you have learned during your lifetime.

[david s]

Re: New 36inch castable build in Brisbane

Mikku,
Does this mean that you are now convinced of the economy of the sand mould method?

[mikku]

Re: New 36inch castable build in Brisbane

Mikku,
Does this mean that you are now convinced of the economy of the sand mould method?

David s:
What the heck are you doing up at this ungodly time? Thought that only us nut cases in Japan are running on all cylinders at 4AM (or at least this is when my engine got started).

As for your question, judging by the build in this thread---It is hard to deny the economy of a sand mold method. But it is "all to do" with the craftsmanship put into the preparation! That is true for any style build though.

I might be "hard headed", but there is still a little pliability in what gray matter is left after being bombarded with alcohol molecules on a daily basis!
I call it "anti-freeze"!

[david s]

Re: New 36inch castable build in Brisbane

Mikku,
It's now 6.23 am I've been up for about an hour.
Maybe you should try two alcohol free days a week. It works pretty well.

[mikku]

Re: New 36inch castable build in Brisbane

Mikku,
It's now 6.23 am I've been up for about an hour.
Maybe you should try two alcohol free days a week. It works pretty well.

That is what I call coffee and water, but they are used in moderation!

Caffeine isn't good for your health, and too much water and you can drown. So have to be on the safe side and use in moderation!

So you are an hour ahead of us! Its 5:50 here now and been up since 3:45, hands are sore from using tye wraps to attach pex A tubing to rebar for a little floor heating job.

[david s]

Re: New 36inch castable build in Brisbane

Brissie,
I just reread your thread and was a bit concerned when I read that you said the castable was a "bit spongy". I'm concerned that you may have used insulating castable instead of dense castable. If you used insulating castable it will take much longer to get heat into the oven. The density should be around 2000 kg/m3. Check your specs.on your product.

[brissie]

Re: New 36inch castable build in Brisbane

Brissie,
I just reread your thread and was a bit concerned when I read that you said the castable was a "bit spongy". I'm concerned that you may have used insulating castable instead of dense castable. If you used insulating castable it will take much longer to get heat into the oven. The density should be around 2000 kg/m3. Check your specs.on your product.

Just checked,

Approx Weight Required for Casting ,kg/m3 = 2000
Bulk Density After Drying at 110?C kg/m3 = 2110

It is heavy, not like air filled insulation.

[david s]

Re: New 36inch castable build in Brisbane

Ok, that's correct. Sorry to worry you.