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Post by Karl L on Jan 27, 2023 6:59:18 GMT -8
I quite like the 45 degree 'diagonal fold' shelf idea. It's good you've maintained the same surface area to volume ratio. I would extend the top chamber and shelf back level with the rear of the stove though, that would avoid any more bends while maximizing the use of the space and remove the path of least resistance on the right hand corner. Thanks Trev. I'm not sure I understand you about extending the top chamber back. Do you mean move the back wall of the top chamber towards the back of the stove, and move the diagonal edge of the triangular shelf back too? (I think I understand what you mean by the path of least resistance: that bit where you can look straight down past the triangular shelf and the afterburner shelf, and into the front of the afterburner.) Is it a 125mm or 115mm system size, you seem to have mentioned both? I have a 115mm system here currently, and was planning to build a 125mm system. But now I am wondering if a 125mm will be larger than I really need, just to heat a large-ish room. The 115mm core, being slightly smaller, seems to fit better with the other elements of the design. It's very hard to know, but I guess this new stove will harvest and store more heat than the old one because it has a higher ISA (allowed by a bypass and better flue) and more mass. In which case it may not be necesary to build a 125mm system. |
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Post by Vortex on Jan 27, 2023 10:32:04 GMT -8
I'm not sure I understand you about extending the top chamber back. Do you mean move the back wall of the top chamber towards the back of the stove, and move the diagonal edge of the triangular shelf back too? (I think I understand what you mean by the path of least resistance: that bit where you can look straight down past the triangular shelf and the afterburner shelf, and into the front of the afterburner.) Yes that's exactly what I meant. How many fires a day are you presently lighting? It's possible you could light less often with the larger system size. It's also easier to scale down the core of a 125mm system than to try and scale up a whole 115mm system and core. |
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Post by Karl L on Jan 27, 2023 12:33:52 GMT -8
How many fires a day are you presently lighting? It's possible you could light less often with the larger system size. It's also easier to scale down the core of a 125mm system than to try and scale up a whole 115mm system and core. The number of fires depends a lot on how cold it is. On average: 2 fires a day.
But one thing I forgot to mention is that my current stove is a quick conversion from a 125mm DSR2, using the DSR2 firebox. This is narrower and taller than a proper 115mm Vortex firebox. I haven't figured out a way to get a steady and reliable burn with this firebox loaded to the top.
So, using a proper 115mm firebox I think I will be able load in 50% more wood. But I'll think about your comment about it being easier to scale down than up - thanks.
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Post by Karl L on Feb 3, 2023 4:06:38 GMT -8
The heater bricks arrived today, 75 of them, from a reclamation company. They said the bricks were all the same, but they've delivered two different sizes. photosI think I can design around that, and it might be better to design it to cope with slight diffences in available bricks if any need replacing. But I did buy some extra to allow for breakages and replacements. The heavier bricks weigh around 8kg each, the lighter around 7.6kg. So 60 of them in a stove will be ~480kg! |
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Post by Vortex on Feb 3, 2023 5:13:56 GMT -8
I got a mix of them as well. Delivery man couldn't believe how heavy the pallet was when it looked like there wasn't much on it. I used the ones with the recess so the gap was facing downwards. The ones without the recess were a bit shorter in height so worked well for me in front of the bypass flap. vftshop.com/images/others/Stove/newbuild4.jpg |
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Post by martyn on Feb 3, 2023 7:06:23 GMT -8
Karl, if they have been kept outside then they will probably loose 40% of that once dried out, if fact you will want to get them as dry as possible before using them.
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Post by Karl L on Feb 3, 2023 7:25:08 GMT -8
Karl, if they have been kept outside then they will probably loose 40% of that once dried out, if fact you will want to get them as dry as possible before using them. Thanks for the tip Martyn, I was thinking the same thing about making sure they were dry before heating them up a lot. But I don't think it's possible for them to lose that much weight. If they were made from 100% water they would weigh 2kg each, so max possible loss would be 25%. |
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Post by martyn on Feb 3, 2023 8:48:07 GMT -8
Ok sorry I will obviously have to be careful to be more accurate!
In reality it is difficult to quote exact figures due the make up of individual bricks but a standard fire brick can absorb 10-12% of water in the space of minutes.
I dont know what the maximin % would be after a few years outside but soaking a fire brick in a bucket of water for 30minutes with give around 10%
That water can cause a lot of issues when trying to start up a new stove so it is always best to use as dry a brick as possible.
The one benefit of a wet brick is they make less dust when cutting with a dry saw.
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Post by Vortex on Feb 3, 2023 9:28:18 GMT -8
The ones I got are around 7.5Kg each when completely dry.
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Post by Karl L on Feb 5, 2023 8:50:43 GMT -8
Trev (or anyone),
Do you have any idea how magnetite bricks might cope with being laid horizontally to form the roof of the top chamber? I was thinking I might put one or two layers in that position, but they will likely get very hot -- glowing red? -- and so undergo extreme thermal cycling hundreds of times over the life of the stove. Especially if I put some insulation over the top of them, as I want the heat they hold to slowly distribute within the stove, not be radiated quickly from the hot spots.
I am not worred about these bricks in the other parts of the stove as they will be in compression. But laid-flat bricks will have to hold up their own weight (as beams) so the material will be in a small amount of tension. I wouldn't want them to fall into the gas path or damage the afterburner if they failed. |
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Post by Vortex on Feb 5, 2023 9:21:54 GMT -8
I used some magnetite bricks horizontally on a bench 7 years ago that are still going OK, but I've never used them anywhere that hot though. If it was me I'd use them for the bell top but cast a slab for the top chamber.
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Post by Karl L on Mar 15, 2023 3:36:51 GMT -8
I tried a piece of my 1000*C rated 1" calcium silicate board as a firebox roof last night, it buckled and cracked up within the first 5 minutes. Hi Trev, I bought some calcium silicate board to try to get a feel for it. I plan to use it behind the cast refractory, as you do. But I was also wondering if it's possible to use it in contact with hot gasses at all? Do you have a sense of why it failed in your firebox? Do you think it would fail if situated just after the top chamber exit, in direct contact with the hot gasses at that point? Thanks, Karl |
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Post by Vortex on Mar 15, 2023 6:18:18 GMT -8
After that initial experiment I avoided using it anywhere it would be in contact with flame or hot gases. I think it was differential expansion that caused it to contort and crack up. Used after the top chamber it would probably be OK for a while but gradually become brittle and crumbly, I'd use vermiculite board there instead.
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Post by martyn on Mar 15, 2023 7:38:15 GMT -8
I used to use calcium silicate board under the fire brick floor of my pizza ovens but changed over to ceramic fibre board when it became more readily available.
The back side of a pizza oven floor brick, will get to 400c but more normally 300c and the calcium silicate board is fine for that.
I cant say I have any experience using it other than under bricks but I have read that it is not good in any form of exposed flame path.
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Post by Karl L on Mar 16, 2023 2:42:30 GMT -8
How important is it that the bypass is capable of opening to full system CSA?
I've remember someone suggesting that 50% system CSA is sufficient, and maybe safer if it's accidentally left open.
One thing suggesting that 50% system size might be OK is that the port is 50% system CSA -- but it would be good to know what works in practise.
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