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Post by Thomobigands on May 29, 2017 20:37:58 GMT
Hi all,
Second thread tonight is the flue or chimney. I get that it needs to be 6 inch, 1m and fixed to a flat surface with an anchor plate, what I have picked up on though is that there are risks with expansion conflicts where it meets the oven.
I therefore wondered if anyone could offer advice as to how I need to fix the plate to the oven and whether I leave a space between the flue and the oven insulation/render? Concerned that if I do leave a gap, it will surely let rain in?
Any advice welcome.
But thanks to you all on this site, wouldn't have got to where I am without your help!
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Post by chas on May 30, 2017 9:00:41 GMT
Hi all, Second thread tonight is the flue or chimney. I get that it needs to be 6 inch, 1m and fixed to a flat surface with an anchor plate, what I have picked up on though is that there are risks with expansion conflicts where it meets the oven. I therefore wondered if anyone could offer advice as to how I need to fix the plate to the oven and whether I leave a space between the flue and the oven insulation/render? Concerned that if I do leave a gap, it will surely let rain in? Any advice welcome. But thanks to you all on this site, wouldn't have got to where I am without your help! At the risk of confusion, I'd suggest a different approach: 1m tall by all means, but make it detachable - ie form a good solid socket in brickwork that you can slip it into for use. You could make temporary packing with 'asbestos string' if it's too leaky. But that way you can remove it and make your life so much easier when you put a cover over the oven. Chas |
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Post by Thomobigands on May 30, 2017 9:38:09 GMT
Not a bad idea, thanks. I wonder if a fabricator could make me a plate and socket arrangement to just plug a length of purchased flue into?
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Post by oblertone on May 31, 2017 20:12:07 GMT
All twin-wall systems have a register plate (socket) into which the sections twist and lock; No need to have one made, you just need to find a way of securely mounting it on your oven. I de-mount my flue and cover the whole thing in a patio table cover for the winter.
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Post by downunderdave on May 31, 2017 21:32:59 GMT
Hi all, Second thread tonight is the flue or chimney. I get that it needs to be 6 inch, 1m and fixed to a flat surface with an anchor plate, what I have picked up on though is that there are risks with expansion conflicts where it meets the oven. I therefore wondered if anyone could offer advice as to how I need to fix the plate to the oven and whether I leave a space between the flue and the oven insulation/render? Concerned that if I do leave a gap, it will surely let rain in? Any advice welcome. But thanks to you all on this site, wouldn't have got to where I am without your help! At the risk of confusion, I'd suggest a different approach: 1m tall by all means, but make it detachable - ie form a good solid socket in brickwork that you can slip it into for use. You could make temporary packing with 'asbestos string' if it's too leaky. But that way you can remove it and make your life so much easier when you put a cover over the oven. Chas I've built four ovens now with removable flues either because the finished oven needed to be transported or if it's for a mobile oven. I make a stainless sleeve that the flue pipe slides into. The fixed stainless sleeve gets around the problem of abrasion wear on the brick, mortar or refractory.   |
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Post by Thomobigands on Jun 1, 2017 4:31:32 GMT
Thank you both for the replies. What do I actually fix the plate with though? Presumably I can't just cover it in homebrew or the metal will crack it over time? Maybe some sort of premix fireplace mortar over the plate, fixing it to the homebrew on the oven?
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Post by chas on Jun 1, 2017 7:42:01 GMT
Thank you both for the replies. What do I actually fix the plate with though? Presumably I can't just cover it in homebrew or the metal will crack it over time? Maybe some sort of premix fireplace mortar over the plate, fixing it to the homebrew on the oven? Regardless of whether you have a steel-lined socket or use the prorietory plate you 'bury' it in as much brickwork as you think neccessary to keep the thing upright while keeping the look you wish for in your design. Just covering it with any sort of mortar isn't going to give the safe stability you need. I'd suggest a couple of courses minimum - that would be about 6"/150mm of socket. There will, of course, be some sort of ledge to stop the flue dropping through into the oven... Chas |
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Post by Thomobigands on Jun 1, 2017 18:43:39 GMT
Thanks, that makes sense. I'll try and put a couple of brick courses on top of the arch then. Maybe in standard brick to avoid the added weight of firebricks.
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Post by Thomobigands on Jun 27, 2017 9:12:56 GMT
Morning all. I finally finished the dome last night! Will upload some pictures soon as my build thread is non existent!.
Anyway, just the chimney now to overcome. Still liking the idea of a removable chimney to make it easier to cover the oven when not in use but to get the height you need for the draw.
The idea that I have come up with is maybe to buy and cut a 150mm diameter clay drainage pipe and homebrew that in place to the arch with the help of a few surrounding bricks. My 6" flue should then hopefully be just a big bigger to slide over the pipe whenever I want to use the oven. If the metal expands then it has room to do so as it is not fixed in place. Aside from not using the oven in gale force winds, does anyone envisage a problem with what I am proposing? I would be really interested to hear any thoughts on this? The clay pipe would be around 12 inches high. no more.
My thinking is that the clay pipe will not have the same expansion difficulties as the metal pipe. If the clay pipe will withstand the heat?
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Post by chas on Jun 27, 2017 14:48:30 GMT
Morning all. I finally finished the dome last night! Will upload some pictures soon as my build thread is non existent!. Anyway, just the chimney now to overcome. Still liking the idea of a removable chimney to make it easier to cover the oven when not in use but to get the height you need for the draw. The idea that I have come up with is maybe to buy and cut a 150mm diameter clay drainage pipe and homebrew that in place to the arch with the help of a few surrounding bricks. My 6" flue should then hopefully be just a big bigger to slide over the pipe whenever I want to use the oven. If the metal expands then it has room to do so as it is not fixed in place. Aside from not using the oven in gale force winds, does anyone envisage a problem with what I am proposing? I would be really interested to hear any thoughts on this? The clay pipe would be around 12 inches high. no more. My thinking is that the clay pipe will not have the same expansion difficulties as the metal pipe. If the clay pipe will withstand the heat? Hi, I used a short section of salt-glazed pipe as a stubby chimney and still do, but it cracked top to bottom at the first real heat. It still functions, and this season I plan to use it as a socket to drop a piece of smaller dia steel pipe into. I'd guess yours will go the same way but be similarly functional. Chas |
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Post by Thomobigands on Jun 27, 2017 15:00:11 GMT
Thanks for the heads up, maybe it won't work then. I don't fancy it cracking so easily even if it is going to just be a socket.
The metal pipe I have is tapered at one end so the other option is to cut that section and set that upside down on the oven, plugging the remaining end in as and when.
Maybe I just bite the bullet and buy a fitting plate for the metal pipe and do that.
I can fit some bricks on three sides of the pipe to try and bury it, then will maybe try and seal with a heat resistant sealant.
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Post by downunderdave on Jun 27, 2017 20:54:00 GMT
Hi all, Second thread tonight is the flue or chimney. I get that it needs to be 6 inch, 1m and fixed to a flat surface with an anchor plate, what I have picked up on though is that there are risks with expansion conflicts where it meets the oven. I therefore wondered if anyone could offer advice as to how I need to fix the plate to the oven and whether I leave a space between the flue and the oven insulation/render? Concerned that if I do leave a gap, it will surely let rain in? Any advice welcome. But thanks to you all on this site, wouldn't have got to where I am without your help! If you insulate around it then it should be fine. Uninsulated and it is almost certainly likely to crack. |
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Post by Thomobigands on Jul 4, 2017 5:42:25 GMT
Morning all, Thought I would update this thread for any future readers of the thread. So, my approach to the chimney was this in the end - I took my 1m single walled flue and cut about a third off it with an angle grinder. Then, in one end of the shorter length I cut notches a couple of inches deep, spaced out about a couple of inches. Using a hammer, I then bent these tabs outwards and sat the flue on top of the oven entrance as shown. I fixed it to the bricks using heat resistant sealant/adhesive underneath and all around the tabs, smoothing it out. I then finished the second arch off around the flue and did one extra course of bricks on top. I then filled the gap between the bricks and the flue with vermicrete. I may add another course of bricks and fill with more vermicrete. Either way, I will then cover the exposed vermicrete around the flu with render to protect it from the weather, using the heat proof sealer again where it meets the hot flue. To the remaining length of flue, I have attached the stainless steel connector joint as shown in the photos. This easily slips over the fixed length of flue on the oven, creating a nice tight fit but one that can be removed whenever the oven is not in use or needs covering. Whether it stands the test of time, we'll see but thats my approach to the removable chimney. UPDATE: I have had a few fires in the oven now - some of them pretty big! and the chimney is performing well. When it gets hot, it seals itself at the join and creates an airtight connection. Then, once the oven has completely cooled down it is able to be detached and kept in the shed. I then just top it with a flower pot saucer upturned just to keep the rain out. Having the chimney detachable is great because it makes the oven more of a subtle feature in the garden and when the frost comes along later in the year, I should be able to cover and wrap the oven far easier than if it had a permanent 1m+ chimney on it!      |
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Post by Thomobigands on Sept 1, 2017 9:07:18 GMT
A chimney update for you all. It is working a treat! Have used the oven maybe ten times now.
The chimney goes on before lighting the oven obviously and when it gets hot it seals itself so no smoke at the joint. I have to then let it go completely cold before it will allow me to pop it off and store it in the shed.
A simple terracotta dish then sits over the chimney socket to keep the rain out.
The mortar around the chimney obviously cracks but this doesn't cause a problem. I may eventually fill the cracks with high temp flexible sealant in time.
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Post by chas on Sept 2, 2017 7:05:26 GMT
A chimney update for you all. It is working a treat! Have used the oven maybe ten times now. The chimney goes on before lighting the oven obviously and when it gets hot it seals itself so no smoke at the joint. I have to then let it go completely cold before it will allow me to pop it off and store it in the shed. A simple terracotta dish then sits over the chimney socket to keep the rain out. The mortar around the chimney obviously cracks but this doesn't cause a problem. I may eventually fill the cracks with high temp flexible sealant in time. Well, there you go. At the risk of hijacking your thread but an update from earlier posting, I've been dropping the steel chimney extension into my cracked bit of saltglaze with similarly useful effect. One further mod: using a pair of welding gauntlets, I find it possible to remove the steel at peak burn. Why? Cap the socket and you have the sealed environment needed for baking. Cheers, Chas |
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