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Post by peterberg on Nov 21, 2024 3:11:53 GMT -8
I couldn't get my head around it. Now I see what is going wrong: I did the calculation with the base figure of 125, the width of your brick. While you are calculating from the 165 mm system size.
So there's a discrepancy between our methods, you are absolutely right. I'll redo the core again with a system size of 173 mm, which results in a base figure of 125 mm.
Cannot promise it will be done today, but we'll see.
You might run into trouble with the rest of the system, you'll need a chimney of approx. 180 mm diameter for a core this size.
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Post by peterberg on Nov 21, 2024 10:27:29 GMT -8
OK, I mistakingly had system size at 165 mm, this should be 173 mm in order to have a base figure of 125 mm. I amended the drawing, renamed it and as far as I can see it's correct now. The only details that needed to be changed were the liner and the exhaust port. The drawing is in SketchUp 17 format and is to be found here.Regarding the depth of the port: there haven't been a firm size of that in the course of the past 12 years. That won't be different now, this extra deep port in the Shorty design is something that perhaps could be used in the standard batchrocket. But it doesn't appear as to be very practical, though. I seem to recall depth of the port could be larger than the width of it without repercussions and less deep than the width also. The port in this particular implementation is 13.6% larger as 1B. In my opinion, this is a reasonable tolerance, as far as experience goes. Maybe we could define the tolerance of the port's depth the same as the firebox' depth, being 25% plus and minus. |
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 272
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Post by dvawolk on Nov 25, 2024 4:42:13 GMT -8
Oh, I am glad that we sorted it out. I understand that 173 mm system needs the chimney of 180 mm diameter. Since my chimney is already built - the main flue is 200 mm insulated stainless tube. But chimney input is 160 mm. Do you think this should be a concern? That is 17% difference in CSA - but only for one short length of a tube where the stove will be connected to the chimney. There will be a bypass and the ISA will be 90% of accepted batchbox values... I checked the 173 mm file, well this is much more lovely to cut :-) The height of the port in your .skp is 250 mm instead of 263 mm (2,1 x B). This is -5% difference - can this be added to tolerance? If not, it is not that much of a problem to cut away this extra from the brick in the third row... I do like the tolerance info - below the tolerance is implemented in a sketch with gathered dimensions. Regards, Klemen  |
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Post by peterberg on Nov 25, 2024 9:37:23 GMT -8
Since my chimney is already built - the main flue is 200 mm insulated stainless tube. But chimney input is 160 mm. Do you think this should be a concern? That is 17% difference in CSA - but only for one short length of a tube where the stove will be connected to the chimney. There will be a bypass and the ISA will be 90% of accepted batchbox values... It firmly depends on the length of the 160 mm chimney pipe and whether it is vertical or not. In case it's vertical and, say, 500 mm long, that shouldn't be much of a problem because of the larger diameter chimney behind it. The piece of pipe being a temporary orifice, with the higher gas velocity and pressure drop associated with it. The height of the port in your .skp is 250 mm instead of 263 mm (2,1 x B). This is -5% difference - can this be added to tolerance? If not, it is not that much of a problem to cut away this extra from the brick in the third row... Unless you are planning to dry stack the core, the mortar between the bricks will add up to the height of the port, usually enough to get it closer to the target. Tolerance on the port is about its area, not so much about its width or height. Let's see... it's about the value of 70% chimney csa. If you are unsure about it, make the width of the port just 2 mm wider and combined with the 1 mm mortar of 4 seams you are on 99.66844% of target value. Taking some distance, the port would work all the way down to 50% and up to 80% of chimney csa. The lower the percentage, the more agressive it will run and also easier to get an instable burn, the higher it will be more sluggish. What I mean to say is: there's a sliding scale, and keeping the dimensions of the port within half a mm is not a realistic goal, in my opinion. |
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