Oven on wheels

[david s]

Re: Oven on wheels

Any unfired clay in the brew will lead to shrinkage problems if the proportion is high.

[wotavidone]

Re: Oven on wheels

I've narrowed my choises down to 2. I have 30kg of commercial terracotta, or my home processed local whitish clay. It fires to a nice pale red. The bits I manage to get redhot in a gas flame don't melt, so I think it is very good for heat resistance.
However, as Davids points out, shrinkage could be an issue. I reckon the next step is a couple of test batches of homebrew mortar.
Other than tha progress is nil, unless you count the brand new length of chimney flue I bought at an auction yesterday for $5.
Nearly finished painting the house........

[david s]

Re: Oven on wheels

If you are using a sand form the shrinkage problem can be overcome by removing the sand carefully after about 3 hours after completing the dome. That way any shrinkage can take place without stressing the material. This is also the best way to avoid shrinkage cracking if building a cob oven.
Re the chimney you got, is it stainless steel? if not don't bother using it, you will only have to replace it with stainless down the track. Secondly for your sized oven you will need at least a 6" diam flue.

[wotavidone]

Re: Oven on wheels

Got a bit of progress done. Made my frame. Decided to go with TEKS. Worked well. Haven't got the cross bracing in yet, nor have I laid in the sheet steel on which i plan to cast the vermicrete. However, I thought I'd post a couple of photos to show how far I've got. Tempted to leave out the cross bracing, because I intend to give it an aussie look by cladding it in corrugated iron. As any one who has ever built a shed will tell you, the cladding is what adds the rigidity to the frame.
Castors are rated at 100kg each. Should be enough, but when I settle on a final location, I'll probably take them off. Main uprights, and the longitutdinal brace under the tray rack are 2 inch square tube. The rest is 1 inch by 1.5 inch tube. Teks are 12 and 14 guage. The tray will give me a layer of vermicrete 3 inches thick. Not ideal, but neither is the rest of this budget build.

[brickie in oz]

Re: Oven on wheels

Castors are rated at 100kg each.

Maybe so, but how will it wheel?
They might be good for a tea trolley but an oven may require a bigger dia wheel to be able to move it.

[david s]

Re: Oven on wheels

Maybe so, but how will it wheel?
They might be good for a tea trolley but an oven may require a bigger dia wheel to be able to move it.

For my mobile oven I used four 3" wheels. I replaced them with six 4" wheels because I wanted to spread the load and raise it a little. The difference in the way it wheeled was enormous. The tiniest bump with small wheels and a heavy load is extreme.

[brickie in oz]

Re: Oven on wheels

The tiniest bump with small wheels and a heavy load is extreme.

Game set and match......

[wotavidone]

Re: Oven on wheels

These wheels are 5 inch diameter, and I intend to run them on the concrete of my carport. Should be OK, though once I find the ideal spot, I may take them off.

[shuboyje]

Re: Oven on wheels

I think focusing on size alone is a road for disaster. I have a 42" oven on a welded stand and wheels. In my search for the proper casters I went by load rating and found many of the large wheels had a load rating far to low for an oven. The only ones that didn't cost nearly $100 a wheel. The wheels I settled on where top quality industrial casters that are 4", but most importantly where rated for the load that will be on them. I can roll my oven around alone one them.

[wotavidone]

Re: Oven on wheels

Thanks shuboyje. What I did was weigh the bricks I intend to use, add a bit for the mortar and other bits and pieces and go from there. I also took a look at the stand FB supply for their Primavera 60. Since my oven won't be much bigger than that, I reckon it'll all work. In anycase, I've set it so that I will be able to remove them easily if they look over-stressed.

[nissanneill]

Re: Oven on wheels

Your frame looks rather fragile with just the teks holding it together though!
I would most certainly weld it together, preferably mig as the tubing seems thin, probably 16g? I would also 'perimeter weld' each join.
If you start pushing it around, and with your oven weight on board, the tyres will develop flat spots, you will stretch the bracing and the lot could collapse before your eyes!

Cheers.

Neill

[wotavidone]

Re: Oven on wheels

I may have to go somewhere else. Too many negative waves on this forum!
I am reminded of the poor chap who did a magnificent job of his barrel vault in Texas, but considered pulling it down halfway through, based on negative opinions from people on this forum looking at a few photos.
I grant the castors add an unknown element, and I may very well remove them later, but right now they make the construction of the frame in a small space very easy.
I admit it was a toss-up, but I believe the TEKS will be fine. Various metal fabricators recommended TEKS over welding for thin wall tube, as did an American publication on house framing. 16 TEKS have to break to tear one leg out.
The best bit about using TEKS was the accuracy I was able to achieve. Square in every dimension, even after I have piled myself (105 kg - yeah I know, I'm fat) and my son (90 kg - he's just muscle) on it for a test scoot along the carport floor.
I haven't yet added the cross bracing that will ensure there is no flex, but there doesn't seem to be any anyway.
For an alternative point of view, may I suggest a perusal of the webpage below?
Put together with a screw driver and a wrench, and not a cross brace in sight, unless they are relying, as perhaps I might yet, on the external cladding.

Forno Bravo Cucina Pizza Oven Stand

Perhaps I should also add a picture of the tank stand that came with my modular 1000L tank. It held up 1 ton of water, plus tank, for twenty years, on six little steel legs that were are about one inch angle iron.

[david s]

Re: Oven on wheels

Mick,
Please don't take advice people give you as criticism. We want to see you succeed in making an oven that will suit your needs. I always try to qualify any advice with examples from personal experience.
I'm sure you'll be fine, as you are building you can take on board the advice offered, but only you can assess how you think it will perform. You are quite right in stating that it is difficult to judge from looking at photos.

If your wheels are 5" and have a suitable load rating they should be perfectly adequate. When you said castors I envisaged small diam. things.

The last thing you want is to have your enthusiasm killed.
Forge on my son!

Dave

[shuboyje]

Re: Oven on wheels

I certainly hope my post didn't add to the way you are feeling.

My number one concern was the safety of yourself and your family. I personally had a nightmare about my oven collapsing on it's rolling stand scary enough that the next day I beefed it up a bit more. Even a small oven will generate a large amount of force that will cause a shear load on whatever fastening method you use. Many methods are not designed for shear loads, including tek screws. I would know, as a sheet metal worker I use more of them in a week then most people will in their lifetime. That said the way you have them installed the shear load will be spread over 32 teks. Seems like enough to me.

[wotavidone]

Re: Oven on wheels

I certainly hope my post didn't add to the way you are feeling.

No problem mate. Your input is good, and not just because you reckon it'll be OK.
I've been re-reading the construction manual put out by a manufacturer of light steel construction members. It is the manual which gave me the confidence to try using TEKS.
According to the manual, a #12 TEK screw of a nominal diameter of 5.5 mm and installed 17 mm from the end of the connection in the direction of the force has a shear strength of 3.52 kN in 1.6mm steel.
That would be 3520N. Force in N = mass in kg x acceleration in m/s/s
Therefore, mass = force/acceleration.
In a static situation, acceleration due to gravity is 9.8 m/s/s
So, in theory at least, a #12 TEK that is being used in a shear situation to stop a weight sliding down a vertical pole, much like the corner connections on my stand, will break at 3520N / 9.8 = 360 kg.

Pullout strength is a bit over half that.

The same manual puts shear strength of a 4mm fillet weld on 1.6 mm steel at 0.32 kN per mm. So each TEK is equivalent to 10mm of weld, if you weld real good.
That's the theory.
No-one in their right mind would say I only need one Tek per corner, of course. Too many variables - was it over tightened, is the steel very poor quality, are the TEKS cheap and nasty, etc?

However, I believe 8 TEKS per corner will hold reliably. Especially since, once I get it setup, it will only be subjected to static forces. Can't be a massive amount of shock load in throwing the fire wood into the oven, can there?

Anyway, I'm going to stack 250 kg of bricks on there and see what gives, pun intended.
Mick