Hi all from Aussie

[robertjusher]

Re: Hi all from Aussie

How's the oven going ?????

[david s]

Re: Hi all from Aussie

It is too late now of course, but some thin wire loops cast into the base of the dome work well to wire in the mesh. Failing this you can probably hold it in with string and snip it off across the entry once the vermicrete has hardened.
Try to let the weather ( sun and wind) dry the vermicrete and leave it for a week(per layer) to dry. Cure the oven before doing the render. Others may do it differently, but this is the way I do it. You don't want steam pressure build up in the insulation layer or it will crack the outer shell.

[Aussie Pete]

Re: Hi all from Aussie

hey David, no i haven't mentioned about a blanket have i,...but yes i am using a blanket as well. I will be placing the blanket on, then some mesh then doing the verm/perl mix.
Couple of questions...

when placing the mesh over the blanket thats on the dome, is there a way to secure the mesh tight to the shape of the dome, so it doesn't kind of spring back. Or will the verm mix push down on the mesh enough to hold tight to the dome. never used verm, so not sure how heavy it is or how it will hold.

Once i have layered all the verm/perl mix down, how long should i wait until i render over the top as a final finishing coat. Should the oven be fully cured & functioning before i lay the top final coat of render on.

cheers all.

[david s]

Re: Hi all from Aussie

Pete,
Just read back through your thread and you've made no mention of blanket. If you are going with vermicrete alone, I wouldn't go any less than 4" it is approx. 1/2 as good an insulator as blanket so you need it thicker to achieve the same insulation value.

[david s]

Re: Hi all from Aussie

Yes, that's how I do it and I leave it for a week for each layer to dry. It's main purpose apart from providing additional insulation is to get a nice even shape. Assuming you have used blanket, there will be folds that create bumps. If you tap the surface with the flat of your trowel you will get a remarkably even surface and judging the form by eye is remarkably accurate. Doing two layers also has the advantage of seeing how the first layer turns out. You will think "this'll never work" but it does, so when you do the second layer you're more experienced and skilled.

[Aussie Pete]

Re: Hi all from Aussie

evening....i suppose i'm ready to put a bit of verm/perl onto the dome now, i am going to use the 50/50 mix with a ratio of 5:5:1:3. "As described by Dave".
is there a recommended thickness to lay this mix, should it be done all in 1 thickness, or maybe 2-3 layers of similar thickness. What would be the ideal thickness, obviously i'm aware the more the better, but theres gotta be a point where it becomes unviable economically & financially. I was thinking 2 layers of an inch thick, layed down over maybe a few weekends. So a total verm/perl thickness of 50mm or 2". "thoughts anyone??". Or should it be more?

[david s]

Re: Hi all from Aussie

".if it works, i'll be a hero (well...in my eyes), and if it doesn't ....i'll be an idiot."

You can be both, I love idiot heroes the best,... Forest Gump, Maxwell Smart, inspector Clouseau, Mr. Magoo... you can add more.

I"m sure it will work so long as you remain enthusiastic.

[Aussie Pete]

Re: Hi all from Aussie

i know Al, thats why i covered the slide with flexible sealant & fire-proof ribbon, plenty of room for expansion. (i think...)
Theres no steel what soever touching any refractory mortar.

[brickie in oz]

Re: Hi all from Aussie

Steel is steel it will expand at a different rate to your refractories.

[Aussie Pete]

Re: Hi all from Aussie

G'day all, its been a while, but have slowly been working on the oven.
Firstly, i have solved my dilemna about the flue/damper. Many have said steel is not the preferred method of making a slide of sorts for a damper.....and i totally agree.
I have tried to solve the idea by making my slide out of 10mm thick stainless steel bar, sandwich on top of each other to form a slide for a plate. I then put fire proof sealant around the slide then wrapped it with fire-proof tape/ribbon, to allow for expansion with the heating cycles. It stuck really good to the steel and the ribbon. I cut out a square bit of the top of the dome, (the flue area) and placed my slide into it, i then surrounded the slide with refractory mortar to secure into place (held really well). I let that cure for a few days, then i made an upside down cone on top of the slide and mortared around that to a make a 6" diameter round hole for the flue to sit into. I made it a little smaller than the flue diameter, (so the actual flue pipe wouldn't fall into the oven). i placed a piece of round steel pipe ( the same size diameter of my flue) and mortared around that, so it would actually make a small ledge for the actual flue to sit on. It worked perfectly. Hope i explained that good enough.
I have added a few pics, let me know what you all think. Will it work???..time will tell.
Its the best i could do with what i had, i really wanted to do the damper out of fire bricks, like brickie had mentioned, but it ment another 2hr trip to the clay bricks yard to source more (and more money). I went with this idea, because i had everything, and i like to be different .
besides....if it works, i'll be a hero (well...in my eyes), and if it doesn't ....i'll be an idiot...either way, i'm ok with.
Its only mortar, i can always cut it out, and do it differently.

[brickie in oz]

Re: Hi all from Aussie

Personally I would prefer not to use any steel and have a sliding refractory piece (kiln shelf) against the refractory surrounding it.

What Dave said.

You could make a captive slide arrangement out of kiln shelving for the damper to slide in.

Have a look at the pic.

[Aussie Pete]

Re: Hi all from Aussie

Al, post number #187 has a picture with a bit of an idea of what i'm thinking.
I'm aware of steel expanding, and honestly its probably not the ideal way to position a damper, but i have all the steel and am getting slots milled out the steel sides for my plate to run inside. I just wish there was a way or an idea that i could use this so that it could work.
i was thinking of maybe wrapping the steel with some kind of thermal material to help with expansion of the steel, honestly its probably not going to matter if it cracks a little, because i will be verm/perl. over the top and all around the flue, so that would cover any imperfections within the damper idea.
theres got to be something i could use, atleast just to help with expansion.Surely it wouldn't grow too much.

[david s]

Re: Hi all from Aussie

Steel will get hotter sooner than the surrounding refractory because it has higher thermal conductivity. This means greater thermal expansion and problems where it is in contact with any refractory. Personally I would prefer not to use any steel and have a sliding refractory piece (kiln shelf) against the refractory surrounding it.

[brickie in oz]

Re: Hi all from Aussie

Pete, do you have a rough drawing of what you are attempting with this, it would help.

I dont think mortaring in steel in an oven is a good idea BTW.

[cobblerdave]

Re: Hi all from Aussie

Gudday
Sorry have no experience with what your doing.... so can only watch at this point....I'm hoping though that "brickie" will come through for you, as he has the experience with dampers....

Regards Dave