28" homebrew cast oven in walled enclosure Belgium

[MarvinG]

Great answers - super informative. Thanks so much!

summing up...

- I will try to find the AR resistant fibres. (otherwise buy them online abroad)
- I will take homebrew - use the insitu ball/sand dome way. (its not worth to drive to turkey 500 miles) just for expensive concrete. ;-)
- I'll add the PP fibres
- Sure - the tires are made for this... durable but still flexy.
- I will try not to overdue the heating - however i will def. have 500°plus where the flame hits the ovens. (since I will use gas as well)

Therefore two question I still have:

1. Since sand seems to be the "bad guy" when heated up above 571°. My thought would then be - is there an alternative product instead of sand to avoid this issue? Does it matter which sand we use?
2. When I do the casting - Ill do the dome and I guess the vent separately. I intend to "glue" to dome to the oven floor with a heat resistant "silicone". makes sense, right?

I just had a look to find some pics of my second build. Unfortunately unsuccessful. they must be on an old mobile phone.

For my new project I will def. make a new thread when I get started and share the progress. Now I'm looking tu buy one of these cute things :-)

[david s]

1. I use silica sand because it has sharper grains which should give it better grip in the matrix surrounding it. River sand tends to have much rounder grains. The downside is that silica sand has higher purity, being nearly all silica, but as all sands are pretty much all silica I don’t think it makes too much difference. Perhaps the river sand has impurities that could cause problems. I took my cue from the brick builders who all swore by the homebrew as a mortar, using really thick joints on the outside with apparent problems and years of trial with little error. I therefore could see no reason why the same recipe couldn’t be used as a castable mix.

2.There’s no heat resistant silicone that will withstand the sustained oven temperature that I’m aware of. I use some between the flue pipe and a terracotta weather cap near the base of the flue pipe. It is rated to 371 C (intermittent) certainly not enough for the hot oven interior. You may find something more suitable, but dampening the floor bricks a little before applying the castable against the sand mould is sufficient to get a decent bond.

3.That little HiJet truck will not hold or pull the weight of e 28” oven. My mobile oven is only 21” internal, weighs 250kg and my 2600cc Mazda truck pulls it comfortably but a 3 cylinder700cc certainly wouldn’t.

[MarvinG]

1. I see - I'll go with rather washed sand then. I can have washed (black) or unwashed yellow here.

2. There are silicones out there wich (they say) hold up to 1200 degree celsius. But yeah, mortaring it to the floor makes sense.

3. I think you might be wrong. These things are quite tough. Official payload is 350kg - so that will do. I will not be able to race - but it only needs to move - how fast, not very relevant in my case.
But its a good thought - maybe its smarter to tow - and have a trailer - then I do not need to compromise in weight, especially I want a thick 6cm oven floor.


regarding the AR resistant fibre mesh/strips. I was just thinking: is that not what builders use on the walls - to reinforce concrete plasters - for them not to crack. that's very cheap... :-)

[david s]

The rated payload is overstated and includes the tray body. My Mazda one tonne utility truck is severely down on its springs with 1/2 a m3 of aggregate or sand which weighs around 750kg. 1/4m3 which weighs around 380kg is a comfortable load.

That roll of AR fibreglass mesh could be the answer, but being flat will not conform to a compound curve. You would need to do lots of cutting and ensure it’s embedded . The beauty of random fibres is that you just mix them into the wet mix, then the whole job can be done in one go, rather than two or three coats. It’s a huge time saver.