Tims oven - early days!

[Tim F]

Re: Tims oven - early days!

That would definitely look great wouldn't it! But the bricks are actually wider than twice the depth, so that would give me even more mass. They are 112 wide by 230 long by 50 deep (mm) so 4.5 x 9 x 2 inches (approx). So I could go with a single layer for 2 inches floor depth, a double layer for 4 inches, or on their sides for 4.5 inches.

I'm leaning towards laying the first layer, then the first course of the dome, and then cutting the second layer to fit inside the dome - so it will be 4 inch with the option to remove the second layer if it turns out that I don't like the extra mass.

[egalecki]

Re: Tims oven - early days!

I'm leaning towards laying the first layer, then the first course of the dome, and then cutting the second layer to fit inside the dome - so it will be 4 inch with the option to remove the second layer if it turns out that I don't like the extra mass.

Smart. A removable extra layer! It will change your door opening to height ratio, I'm not sure how bad that would be, really. Give it a thought, anyway. Or maybe just make the opening a little on the short side to start with?

[Frances]

Re: Tims oven - early days!

...or you could do that.

Sounds like a good idea, keeping all your options open.

[Tim F]

Re: Tims oven - early days!

Hey while I'm worrying about it, does anyone have any experience in structural engineering?

The insulation I'm using under my cooking floor has a compressive strength of 0.8 Mpa at the maximum temperature I'll reach - which means it can take 800 kg/m? if I understand correctly. My total insulation has an area of around 1.2m?, so the 300 odd kilo weight of the dome should be no problem. However the weight of the dome won't be spread evenly over the slab, it will be concentrated over an area just over 0.4m?. The 300 kg spread over this area would be equivalent to 712kg/m?, which is quite close to the maximum compressive strength.

Now I think this is slightly less of a problem as the footprint of the dome will already be spread over the outer ring of the cooking floor bricks. But I wonder if it would be a good idea to add a disk of cement fibre board or similar on top of the insulation, to distribute the weight of the dome more evenly?

[Tim F]

Re: Tims oven - early days!

Duh. .8 megapascal is actually more like 80,000 kg/m2! I could have saved myself a week of maths and worrying if I'd double checked the basics. There's a lesson there somewhere.

[staestc]

Re: Tims oven - early days!

Oh, an order of magnitude here, another over there, whatever!
Travis

[staestc]

Re: Tims oven - early days!

Tim,

Are you going to match the curve of the arch you build in your storage door when you build the oven entry? Are you going to even arch the oven entry?

Travis

[Tim F]

Re: Tims oven - early days!

Well all along I was going to make a matching arch but now I've kind of been talked out of it Neil pointed out that if I go a semi-circular arch, it might be harder to get clearance through the door with larger pots etc. Still toying with the final design - now I'm leaning towards a shallower arch supported on piers.

[Frances]

Re: Tims oven - early days!

Oh I don't know, there are a couple of ovens here with semi-circular arches, they seem to work out fine.

I like the idea of matching arches... not that I want to contradict Niel in any way. Or maybe I do .

Get hold of the largest pot you think you are ever likely to use and shape your (semi-circular ) arch to accomodate it, that'd work.

[staestc]

Re: Tims oven - early days!

Another thing to consider is that the outer facade arch does not necessarily have to match the arch you are using for your flue. I love what Christo did with his front arch, allowing installation of lights.

I see no real reason that your outer arch needs to match your flue arches, so long as it look okay. The limiting factor on what size pan will fit in is primarily the actual entrance to the dome where the door seats. Add to that margin an flue tunnel that widens slightly as you get further from the dome, and may have enough margin to make your facade arch more semicircular, without impeading the size pot you can get in. and still make it look good.

Then again, I have seen pictures of ovens with different arches for the storage area and the oven entrance, arches on top but not on bottom, arches of bottom but not on top, no arches at all, and they all look great

Hope that made sense

Cheers,
Travis

[Tim F]

Re: Tims oven - early days!

Thanks for swaying me back to the semi circle I think I'll do some sketches and see how it looks each way. I really like the look of this one though:

http://www.abc.net.au/tv/cookandchef...e_m1639178.jpg

[Frances]

Re: Tims oven - early days!

There you go then... very cool example!

[staestc]

Re: Tims oven - early days!

I finally got to see your example! Work was blocking it for being music, or porn, or video, or some such crap I like the symetry of matching curves, but then I have seen others that don't match that I like too

I can't decide if I want to do two arches that match, two arches that are different, or what ever.

Of course I have a while before I have to make a decision, but making a decision on the base is pretty close!

Travis

[Tim F]

Re: Tims oven - early days!

Yeah it's a tough one... but I think it would be more pleasing to have matching arches but it's definitely down to personal preference on that one.

I feel like I'm starting to get somewhere after today's efforts. I laid out the first level of the floor, marked out a circle, and cut the bricks. It is a little rough in spots but I'll get the actual cooking floor better. I mixed up some brick sand and fire clay and spread it over the insulation, and I just got it all laid out and level before dark - no pic of the finished result until daylight

You can see a darker ring in my second pic - I decided to pour an extra ring of insulation because I was worried about laying the floor right to the edge of the last lot I poured. The extra ring should help to contain the pressure of the dome. It's a mix of 5:1 vermiculite and portland cement, reinforced with fiberglass rope. Might be over-engineering but better safe than sorry!

[staestc]

Re: Tims oven - early days!

Looking good Tim, and better over engineered than under
Travis