Moveable 26" Build Thread

[di11on]

Hi folks,

So I've eventually got started.

My principal design challenge is that I live in rented accommodation... so I may need to move one day and would like some chance of taking my oven with me. At the very least, I don't want to make too many permanent changes to the property that would be difficult to reverse.

My first ideas were to make something portable like here but I quickly realised that putting something on wheels placed too many limitations on the design, increased the cost and were of limited use - if it worked at all, it would only allow me to move it about on a flat surface. As cobblerdave pointed out, the key is in the subtle difference between portable and moveable, so I began focussing on how to have some chance of moving the thing with a forklift should I need to move one day. I have seen some designs on a pallet - but I wanted something a little more elegant.

In the end, I noticed that the stones of our garden bench weren't mortared together - so this has become the basis of the design.

I made a very sturdy "pallet" to go on top of these stones using 9cm beams for garden decking. Although I intend covering the thing, the treated wood should give me a few years. Across 4 9cm beams I have placed 3cm treated planks and on top of those, 4x50cm paving stones to provide some separation between the wood and the vermicrete layer that will go on top.

So here's my "moveable" "slab":

[Greenman]

Re: Moveable 26" Build Thread

Looks like a viable solution. Definitely a step up from the standard pallet. Some kind of banding to hold the base together, stainless straps or the like would aid the 'moveability' of the thing. Hope it works for you.

[di11on]

Re: Moveable 26" Build Thread

Ok, so I have 10cm of vermicrete down.

What do you put between the vermicrete and the oven floor bricks?

Incidentally, I have 5cm (2") thick refractory bricks. From here they seem to suggest that 6cm (2.5") is optimal. I presume I'm close enough?

[hubert_s]

Re: Moveable 26" Build Thread

The pdf instructions say to use a 1:1 fireclay and sand mixture for leveling the floor.

I would not worry too much about the floor thickness. There are commercial ovens with thinner floors.

[di11on]

Re: Moveable 26" Build Thread

Thanks hubert.

While waiting for the vermicrete to set, I've started cutting bricks. I wanted to try with a hammer and chisel as others have done before I buy any more tools... perhaps an angle grinder with diamond blade as others have suggested.

I've been reasonably successful on my first two test cuts with hammer and chisel. These cuts were almost straight along the shorter brick dimension, so relatively straightforward. However, some bricks will need to be cut in half longitudinally, along the longer dimension, and I don't think you'd get away with a straight line either - is this possible with a hammer and chisel?

[david s]

Re: Moveable 26" Build Thread

Buy or borrow a 5" angle grinder and fit it with a decent diamond blade. Don't try a 4" grinder the blade will not cut deep enough.Make sure you use a decent respirator, the brick dust it creates is dangerous to inhale.

[hubert_s]

Re: Moveable 26" Build Thread

An angle grinder is definitely a good tool to have. I only used a grinding disc, so I can't say how well the cut-off wheels work at making precision cuts. Maybe you could get a masonry blade for a circular saw if you have one. Or just go by Maslow's old adage: If the only tool you have is a hammer, every problem tends to look like a nail...

Why do you have to split bricks the long way?

[stonecutter]

Re: Moveable 26" Build Thread

Thanks hubert.

While waiting for the vermicrete to set, I've started cutting bricks. I wanted to try with a hammer and chisel as others have done before I buy any more tools... perhaps an angle grinder with diamond blade as others have suggested.

I've been reasonably successful on my first two test cuts with hammer and chisel. These cuts were almost straight along the shorter brick dimension, so relatively straightforward. However, some bricks will need to be cut in half longitudinally, along the longer dimension, and I don't think you'd get away with a straight line either - is this possible with a hammer and chisel?

You won't be able to split firebrick along its length and get two good pieces by chiseling. Look for splits,which should be 3cm thick. If you're going to cut them, a segmental is more aggressive than a continuous rim, but both will work. Use the blade on an angle grinder, not a circular saw because unless you make a jig to hold the brick, it will be dangerous to cut one handed.

[di11on]

Re: Moveable 26" Build Thread

The pdf instructions say to use a 1:1 fireclay and sand mixture for leveling the floor.

I would not worry too much about the floor thickness. There are commercial ovens with thinner floors.

Do you add water to this mixture? Do I really have to wait 7 days for the vermicrete layer to cure before I can lay my floor? :-)

[hubert_s]

Re: Moveable 26" Build Thread

I did not add any water, but there was some moisture in the sand. I used a notched trowel to spread the sand. I am not sure about vermicrete, I used insulation board and used the fireclay/sand mixture to level the boards and then put the bricks on without any further leveling.

[cobblerdave]

Re: Moveable 26" Build Thread

Do you add water to this mixture? Do I really have to wait 7 days for the vermicrete layer to cure before I can lay my floor? :-)

G'day
I would leave it as long as I could. There's are lot of moisture trapped in there. Packing a hearth floor on top will not help it dry, and it will still be when you try to cure the oven
Regards dave

[di11on]

Re: Moveable 26" Build Thread

Thanks Hubert

[di11on]

Re: Moveable 26" Build Thread

Ok, so Vermi layer poured - bricks cut and bottom facade laid.

For the brick cutting, I got a 115mm (4.5") angle grinder. My firebricks were only 5cm thick so the small angle grinder was fine, although I did have to cut the whole way around.

Some thoughts about cutting firebrick with an angle grinder
- It works pretty well in my opinion.
- Soaking the bricks overnight reduces the dust a lot and results in a smoother cut
- You really need to wear a full face mask... I was wearing safety goggles that were closed around the sides and got stuff in my hair and forehead...
- I forgot to show the dust mask in the photo - you really need to use one.

I'm not good at waiting. I want to lay my floor but the internet says I have to wait :-)

[di11on]

Re: Moveable 26" Build Thread

Hi folks,

Update on my build...

While it felt right, I didn't actually realise the advantages of casting in sections until now... they are:

1. With refractory cements/ciment fondu, you have limited working time, so it helps to do a fraction at a time
2. It's an awful lot easier to mix smaller amounts. I found that with my 65 liter bucket, the optimal amount to mix was around 18-20 liters. Mixing 30 liters was 4 times the work.
3. Because the cast sections weigh around 25-30kg, you can cast the dome while waiting for your vermicrete layer to dry (although it was more difficult than I imagined reassembling the jig-saw after taking it apart - even though it only had 4 pieces :-)
4. You can dry the cast sections inside out in the sun
5. You can cure before mortaring the sections, allowing the water/steam to escape easily thus reducing the risk of cracks during curing
6. When the oven is cast, you have expansion joints (this was the main reason I went this route.

Edit: Forgot to ask.. anyone know who the spotted quality control inspector is? :-)

[di11on]

Re: Moveable 26" Build Thread

More pictures...

Some thoughts so far...

- Even though casting in sections and using iced water.... it was still sometimes a challenge to get the work done before the castable concrete became unworkable.

- I chose to do the casting on the ground while waiting for the vermicrete layer to dry. It was more difficult than I though reassembling the floor and dome on the vermi layer afterwards.

All in all.. happy with results so far but only time will tell.