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Post by foxtatic on Oct 24, 2022 10:28:50 GMT -8
Hey peterberg, I am slowly getting closer to starting a DSR3 build. The first obstacle was finding a vacuum formed ceramic fiber tube. Our US suppliers do not like small orders, and the "5 minute riser" option seemed like it was a bad choice that would be prone to collapse in the horizontal position no matter how you treat the ceramic fiber blanket. Finally found a supplier for a vacuum formed tube ($225 from Danser Inc for a 6” ID x 8” OD x 14” L, 2300F rating if anybody else is looking.) My question to you is about firebox length: Can I extend just the firebox by two inches? I show current depth on a 6"/150mm system firebox at 18" including the air frame. All my firewood is already cut to 18" so I need a bit more wiggle room. My DSR2 has the extended firebox AND matching extended top box. I assume the DSR3 top box needs to stay exactly the original size and shape, since the precise negative space is what makes everything run well. Extending just the firebox does make a bit of an awkward overall core shape with longer bottom box, but I can live with that. I know you haven't tested this factor yet and may result in a slightly more dirty burn. Still, I wanted your guess on if it was worth experimenting with this change or not. |
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Post by peterberg on Oct 24, 2022 11:02:03 GMT -8
Hard to be sure. Total depth at the moment is 18", the tube is 14" long. So distance from tube to front would be a bit cramped. Just keep the space around the tube at the same value. Which is, if I remember correctly, 160% of the tube's inner cross section area. My tube happens to be much thinner walled so changing the tube's thickness asks for recalculation of the space around the tube.
My guess is you could extend the depth of the firebox and top box alike. The distance from the tube to the front isn't that critical in the sense a couple of inches more in that spot won't be critical.
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Post by foxtatic on Oct 25, 2022 5:17:55 GMT -8
My tube happens to be much thinner walled so changing the tube's thickness asks for recalculation of the space around the tube. Ok excellent, I think I get: The CSA of the top box must be 160% of tube inner CSA, so I must deduct the total outer diameter of the thick tube CSA because it is occupying space where gas needs to expand. (6” tube inner CSA= 28.27) X 160% = 45.23 square inches of negative space needed in top box CSA Top box dimensions (slightly increased): 12” X 8” = 96” top box CSA Total tube CSA: 8” outer diameter = 50.27” 96 minus 50.27 = 45.73 square inches of negative space available. 45.23 and 45.75 are close enough I believe. |
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Post by peterberg on Oct 25, 2022 9:47:31 GMT -8
Excellent!
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Post by Orange on Oct 26, 2022 1:03:01 GMT -8
The first obstacle was finding a vacuum formed ceramic fiber tube. Our US suppliers do not like small orders, and the "5 minute riser" option seemed like it was a bad choice that would be prone to collapse in the horizontal position no matter how you treat the ceramic fiber blanket. Finally found a supplier for a vacuum formed tube ($225 from Danser Inc for a 6” ID x 8” OD x 14” L, 2300F rating if anybody else is looking.) why would you want ceramic fibre when stove works well with standard refractory tube?
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Post by foxtatic on Oct 26, 2022 8:24:34 GMT -8
The first obstacle was finding a vacuum formed ceramic fiber tube. Our US suppliers do not like small orders, and the "5 minute riser" option seemed like it was a bad choice that would be prone to collapse in the horizontal position no matter how you treat the ceramic fiber blanket. Finally found a supplier for a vacuum formed tube ($225 from Danser Inc for a 6” ID x 8” OD x 14” L, 2300F rating if anybody else is looking.) why would you want ceramic fibre when stove works well with standard refractory tube?
I have a number of reasons. Sourcing- I failed to find anyone in the US selling them. We only do the terra cotta clay chimney liners here it seems. Making one- I could make molds and create a cast refractory myself but hesitated to go that route due to lack of experience and what I hear is a dicey curing process. Material- An insulated material is a better choice in general for this part of the stove, and I want the quickest start possible to minimize smoke in the house. Alterations- If I did find them I would still have a difficult time altering it with the expansion cuts and port cutout. The ceramic riser sleeve will cut easily and flattening the bottom will make it sit in place on its own without the additional support a rigid tube will need. Cost- Most of the US suppliers I've talked to about specialty materials like this will completely ignore requests for single piece small orders. Any ceramics I've found that are even close to the refractory material were super expensive, even before weighty shipping cost. But the way you say "standard refractory tube" makes me think (hope) I'm missing something obvious, so I welcome your greater experience if you believe I am over thinking this. |
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Post by foxtatic on Nov 1, 2022 5:43:18 GMT -8
- Some notes from a couple of US based enthusiasts- April over at Permies (and also myself) are interested in building a DSR3. She was kind enough to ask all the right questions of peterberg and put together this brilliant spreadsheet that calculates values for DSR3 dimensions. It is 'read only' so you will need to copy it over to your own Google sheet to use it. docs.google.com/spreadsheets/d/1NtSG8JYFwjceHdosV2u81YJz48gw78qr8_DaigujjMo/edit?usp=sharing*You could try copying it over to your own preferred spreadsheet program, but I have found that sometimes this does not translate well outside the program where it was made.* Some of the things this will help you calculate are the port- 50% system size, the top exit port-100%, and CSA of top box-185% of system size. One tricky component to this build is the afterburner tube. If you cannot find the same style of high heat ceramic chimney liner tube like Peter found for his, you will need to find a vacuum formed ceramic fiber tube. Somewhat hard to find in the US. April has talked to various manufacturers about this and determined that the "5 minute riser" style tube is NOT a viable option because the way this tube is in the horizontal position. Building the tube from ceramic blanket is too risky because the lack of rigidity risks collapse, even with the various coating products available. The manufacturers of the blanket and coating all say "don't try it" but some forum builders have suggested it's still possible if you affix the blanket to a round form and pin it to the form with heat resistant wire and use rigidizing and zircon coating products. But general consensus is that something with rigidity already built in seems essential. To that end, April is working on making her own octagonal afterburner out of CFB cuts. You can follow along with that thread here: permies.com/t/40/192518/Planning-DSR-Build-Cooktop-Questions#1609097 I am trying the vacuum formed tube route like skywalker did in the big 200mm system build he did. Note that cutting the tube flat on one side to make it sit properly in the top box has an effect on the negative space left behind in the top box which is something else discussed in the Permies thread above. These seem to be the current state of affairs in the development, subject to change of course. Many thanks to Peter, April, and everyone else who has contributed to this exciting new design! |
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Post by foxtatic on Nov 1, 2022 11:26:01 GMT -8
peterberg, in light of all the difficulty we are having with round afterburner tubes here in the US, I'm now wondering... why round? I hate to question such a foundational thing that makes this design what it is, but I see on page 7 that you got started with round simply because you were looking to insulate the afterburner and had a round item and some ceramic blanket on hand. So many of the batch box designs, the DRS2, and the Vortex all have square afterburners that still make the double rams horn circulation of flame. Do you think a square or perhaps hexagon might work well enough? Granted, square would take up more space and require a larger top box to meet the 185%.
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Post by peterberg on Nov 2, 2022 3:35:31 GMT -8
peterberg , in light of all the difficulty we are having with round afterburner tubes here in the US, I'm now wondering... why round? I hate to question such a foundational thing that makes this design what it is, but I see on page 7 that you got started with round simply because you were looking to insulate the afterburner and had a round item and some ceramic blanket on hand. I've tried a plethora of ways to incorporate a reliable afterburner system inside a confined space. Making the thing much higher could result in a core that would be nearly as high as the straight batchrocket. Whatever I did with the Vortex concept, I couldn't replicate the results Trevor was showing. I tried lots of sizes and so on, to no avail. The main culprit seems to be the tendency to go into thermal runaway, this spoiled most of the results. Conclusion might be that Trevor's core, fuel, materials, heat absorption area and chimney all worked together to keep the heater in check. Remember, this experimentation was done for a commercial endeavour (not for me by the way) so parts such as vermiculite board that need to be changed out regularly were out of the question. I didn't like the ceramic fibre board and vacuumed ceramic fibre tubes because of loose fibres inside a consumer's heater. In all, I needed to use some hard highly heat resistant and inert material. The result of all that meddling is that the ceramic afterburner will get bright cherry red, in and out, every time it's run. With a very short pre-complete combustion fase, I might add. So many of the batch box designs, the DRS2, and the Vortex all have square afterburners that still make the double rams horn circulation of flame. Do you think a square or perhaps hexagon might work well enough? Granted, square would take up more space and require a larger top box to meet the 185%. The DSR2 is doing things somewhat differently, not much of a double ram's horn in there. An octagon might work quite well for a DSR3 due to the close approximation of a circle. At some point I tried a square one with chamfered lower edges and it worked up to a point. At the time, the larger back fold wasn't in play yet due to the mentioned space constraints, I have to add. Nothing that'll keep you from trying the same concept with a square afterburner tube and a wider back fold above and even around it. It would simplify the design greatly. It's a bit beyond what I can accomplish without buying new materials, preparing new barrels and welding new doors and so on. |
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Post by foxtatic on Nov 2, 2022 10:12:48 GMT -8
At some point I tried a square one with chamfered lower edges and it worked up to a point. At the time, the larger back fold wasn't in play yet due to the mentioned space constraints, I have to add. Nothing that'll keep you from trying the same concept with a square afterburner tube and a wider back fold above and even around it. It would simplify the design greatly. It's a bit beyond what I can accomplish without buying new materials, preparing new barrels and welding new doors and so on. Here is the math with a 6” square tube made of 1” thick CFB that results in an 8x8 outer square. To balance the equation I had to make the top box 1.125” taller (rather than wider because of material size constraints.) (6” system CSA= 28.27) X 185% = 52.30 square inches of negative space needed in top box. Total outer diameter of 1" thick CFB square tube: 8" x 8" outer = 64 square inches Top box dimensions 12.75” wide x 9.125” tall =116.34 square inches 116.34” top box minus 64” square tube= 52.3 square inches of negative space available. But the question is: do I still use the 6” circle 28.27 system size of for this math when I’m actually using a 6” square tube? If I have the math right, I’m willing to experiment with this square tube variant. Worst case scenario for me if it didn’t work: I’d simply cut the box back down to the original planned height and buy the round CFB tube to stick in it instead. I wouldn’t blame you if it failed, but I would like your best guess if this will work before I start building. |
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Post by peterberg on Nov 2, 2022 12:10:55 GMT -8
If I have the math right, I’m willing to experiment with this square tube variant. Worst case scenario for me if it didn’t work: I’d simply cut the box back down to the original planned height and buy the round CFB tube to stick in it instead. I wouldn’t blame you if it failed, but I would like your best guess if this will work before I start building. I'm inclined to think you've got the math right. In order to make the square tube the same cross section as the round 6" one, it should be 5.3" square. The difference isn't that large, I would go for the 6" square and see how it goes. There is a chance that the double vortex won't be that pronounced or even be absent at all. But then, the visual double vortex isn't necessarily the sole thing that's the cause of complete combustion. In the last stages of the DSR1 experiments there wasn't a double vortex at all and the thing was running pretty clean. As long as it wasn't kicking into thermal runaway, that is. So, yes, I'd think the 6" square is your best bet. Maybe there will be just a fire fountain but keep an eye on the chimney cap, and sniff at it if possible. Wet charcoal odour is good, laundry reminiscence even better. Best of luck! |
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Post by Solomon on Jan 10, 2023 11:45:42 GMT -8
- Some notes from a couple of US based enthusiasts- April over at Permies (and also myself) are interested in building a DSR3. She was kind enough to ask all the right questions of peterberg and put together this brilliant spreadsheet that calculates values for DSR3 dimensions. It is 'read only' so you will need to copy it over to your own Google sheet to use it. docs.google.com/spreadsheets/d/1NtSG8JYFwjceHdosV2u81YJz48gw78qr8_DaigujjMo/edit?usp=sharing*You could try copying it over to your own preferred spreadsheet program, but I have found that sometimes this does not translate well outside the program where it was made.* Thank you, this is exactly what I was looking for. For anyone who is looking for the CFB riser tube, I sourced some from Zartech in Portland, cost about $250 for a 24 inch piece of 10" OD with 2" walls. Had to order it this way to get 8" ID, which actually ended up being about 7.5" ID. Has anybody measured combustion temps for the DSR3? I have successfully been able to turn my CFB (2300F rated) innards of my J-tube to glass by not paying attention. I do plan on outfitting this core with a set of 4 thermocouples. I need to figure out how to make them replaceable because the last one didn't survive. It was rated about 2450F. Hopefully (and in all honesty) this core can't produce temps like that. It's not good. |
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iau461
Junior Member
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Post by iau461 on Feb 26, 2023 22:52:09 GMT -8
I’m willing to experiment with this square tube variant. Worst case scenario for me if it didn’t work: I’d simply cut the box back down to the original planned height and buy the round CFB tube to stick in it instead. foxtatic - have you been able to do any experimentation? Would be great if a square tube worked. |
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Post by foxtatic on Mar 10, 2023 7:39:23 GMT -8
foxtatic - have you been able to do any experimentation? Would be great if a square tube worked. No. And I genuinely feel bad about it, especially since I have the materials, plans, and want to contribute to the community. But my wife has pretty reasonable demands that I should finish some remodeling projects I started before I go playing with fire again! In my delay, I have been watching Martyn work with vermiculite board and zirconia refractory coatings on his youtube channel and it has been very encouraging to see a similar design succeed with the materials I intend to use: www.youtube.com/@foxfish7115/videos |
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iau461
Junior Member
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Post by iau461 on Mar 12, 2023 5:40:17 GMT -8
foxtatic - have you been able to do any experimentation? Would be great if a square tube worked. No. And I genuinely feel bad about it, especially since I have the materials, plans, and want to contribute to the community. Hey, we're volunteers, don't feel bad about it! Family harmony is important. Thanks for the link to Martyn's videos, fun to watch. I would worry that the vermiculite, even coated, might not hold up well to a decade or three of use, which is what I'm shooting for. But I might experiment with it too, if I go insane and buy a Testo.  |
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