Tims oven - early days!

[Tim F]

Re: Tims oven - early days!

And a couple more - I swapped the forms around the sides of the arch, poured concrete, let it set, then took the forms off. Then I got the cement board in place, I had to cut a little notch to fit it around the top of the arch. I stuck a strip of duct tape across the joins in the board. Once that was done, I laid a grid of rebar, using the ends of the vertical bars in the stand as spacers. I tied the bar together and now I'm almost ready to put up the forms!

[Tim F]

Re: Tims oven - early days!

I got the forms up and poured the slab on top after work yesterday. It's not the nicest bit of concrete ever poured, but it's level at least!

I tried to stop the forms from bowing by running a rope around the stand and wedging planks along the sides of the form. This wasn't enough, and I ended up with a 2-3mm bulge along the middle of the long sides. I think I'll be able to clean it up with an angle grinder though, and none of the slab will be visible in the end. Any thoughts?

Tomorrow I'm off to get the insulation for under the cooking floor, and I might even be able to start on the dome this weekend! Any thoughts on the easiest (& cheapest) way to make a round form?

[staestc]

Re: Tims oven - early days!

Tim,

The hearth slab looks great, and I would never have even noticed a 2-3mm bow!

One way to do curved forms, or even round forms, is to cut a stip of masonite with a width the depth that you want your pour. Then build a rectangular or square lumber frame, shorter than the width of your masonite. Curve the masonite strip around inside the lumber till you get it like you want it, attach it to the lumber at the points where it touches, the add more bits of lumber in the voids to support the rest of it. Hard to put into words. I will see if I can find one of the pictures I have seen.

Travis

[staestc]

Re: Tims oven - early days!

Tim, here is what I was talking about. This is how Dave did it:



Travis

[Tim F]

Re: Tims oven - early days!

Excellent, thanks for the pic! I will see if I can find some masonite this week.

[staestc]

Re: Tims oven - early days!

Tim, I was thinking a little more about how I might do this. If you have a couple of pieces of plywood around, you could cut them like the attached (sorry, I am not much of a sketchup artist), then run the masonite around the inside.

I would lay one piece down on the hearth slab, determine the highest point with a level, attach the masonite there, the attach the rest of the masonite using a level to make sure you resulting form is dead level. Then just use bits of wood to space the second piece of plywood above the first, and tack it all together.

Just an idea, but it should help prevent any bow in the forms, not that anybody will ever see it anyway!
Travis

[Tim F]

Re: Tims oven - early days!

Good idea actually, but but the time I saw it I'd already got the bits for the first option! I picked up a sheet of the thinnest plywood I could find, and cut it into 10mm strips. I fixed them together with short self tapping wood screws, hopefully they will just screw out once the insulation is set. I decided to pour the insulation in 2 parts, which meant I could use a circle form - much easier and stronger as the force of the insulation pressing outwards should be equal on all parts of the form.

I set up the form tonight and poured the first part of the insulation. To get it placed correctly, I measured and marked out a * on the slab, centered on where I wanted the middle of the dome. Then I marked out the radius of the outer dome along each leg of the star, and put a brick at each point. I made sure the circular form was the right circumference and placed it so that it butted up against each brick. Then I used more bricks to line it to make sure it was held in place.

The insulation I used, 'Coolcast' was interesting to work with. Not too bad but similar to what I imagined verm-crete would be like but finer grained. I managed to get it pretty level, and now it's under a tarp for the night as we're getting a sprinkle of rain.

Off to look at pavers for the floor in the morning!

[staestc]

Re: Tims oven - early days!

The ingenuity to the people on the forum just never ceases to amaze me Looking good Tim. I particularly like the way your arch turned out now that you poured the triangles bits and it has cured. Very nice.

Travis

[Tim F]

Re: Tims oven - early days!

Cheers! I am pretty happy with it too.. it will almost be a shame to cover it up

[Tim F]

Re: Tims oven - early days!

So, time to start thinking about the floor. I picked up some nice bricks today for 55c each - they are 70% firebrick material apparently. They are 50mm thick, and I was thinking of using a double layer. Will this be too much mass? The alternative would be a single layer with a thicker layer of fireclay+lime mortar underneath. I'm not too fussed if it's a *little* more mass than usual as I'd like to be able to do 2 loads of bread if I want to occasionally. Any thoughts?

[Cooter]

Re: Tims oven - on the way

Hi Tim
Started my 36" pompei oven yesterday
Joined as a card holding member today and will be watching your progress with much interest
Cheers
Grant ...Norton Summit S.A.

[Tim F]

Re: Tims oven - early days!

I took off the insulation forms today - the wood screws just unscrewed with no problems. It's very strange stuff, feels kind of rubbery. I think it still has some setting to do. I set up the forms for the landing insulation and poured that - annoyingly I was juuust short, so the landing is a couple of mm lower. I think I'll be able to make up the difference with a light mortar of lime and fireclay.

[staestc]

Re: Tims oven - early days!

Looks very good Tim.

The bricks I picked up yesterday are about 60mm (2.5"). Yours sound a little small, though others here have used similar fire bricks.

I think you would be fine with a single layer even at 50mm. If you really do want the extra mass, you could do your floor with bricks on their side instead of lying down flat, or you could double them as you suggested, or you could pour a layer of refractory concrete (or the fireclay/lime mortar) on top of your insulating layer. I am not sure what the heat capacity is for the fireclay lime mortar though.

I would just lay the floor with the bricks on their sides if you want more mass. I am thinking that 60mm will be thick enough on mine.

Cheers,
Travis

[nissanneill]

Re: Tims oven - early days!

Hi Tim,
as your hearth bricks are 50mm thick and you want to bake multiple batches of bread, I think that you could get away with the single layer, but a better heat retention with a thicker layer of mortar beneath them for thermal mass.
If you want to follow in Russell Jeavons shoes, his oven has two layers of fired clay 50mm pavers and we in Adelaide know how good and successful his oven(s) is/are!
Allow that little extra height on your soldier bricks and a little down the track, if needs be, you can always add a second layer. All yo need to do is maintain your floor level but you would also reduce your arch height if you wait till later.
Play it safe and put a second layer of hearth pavers in now and use a little more wood and a little extra time to heat it up.
Decissions, decissions, life is full of them. Building a WFO only adds to the ones we need to make the correct choice.

Neill

[Frances]

Re: Tims oven - early days!

I think you should lay the hearth bricks on their sides. Because firstly it'll work really well, and secondly it would just look sooo cool! Just immagine, herringbone pattern with thinner shapes... lovely!

You'd be the first person to do it like that, but don't let that put you off... it would work and it would give you some extra mass (specially considering your bricks are a bit smaller). Who knows, you might even start a new fashion.