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Post by satamax on Feb 24, 2015 13:43:21 GMT -8
Hi ladies and gentlemens.
Well, it occured to me, that a seven incher batch needs about 8m² of bell isa.
I have prety much everything needed to make a seven incher.
I was calculating everything, and, i discovered, that, if you reduce a single bell by 15%, for a double bell, and that again by 15% for a triple bell.
8 x 0.85 = 6.8m²
6.8m² x0.85 = 5.78m²
And last but not least,
5.78 / 1.8676 = 3.09
So three barrel bells in a row are perfect for a seven incher. Or six half barrels.
Ney bad hey?
One thing i can't remember, is the barrel above the heat rised part of that total isa? Or do i add three barrels after the heat riser's barrel?
I will use a concrete or cob mixture for the mass if i go this route. Plenty of it around the barrels.
Thanks a lot.
Max.
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Post by pinhead on Feb 24, 2015 16:05:18 GMT -8
I have a 7-inch batch box running a single barrel over the riser and two half-barrels. It's almost too much heat extraction until it's nice and warmed up... And then the exhaust still never goes above 200°F.
I suppose if you were to fire the contraption daily and keep the mass warm, you could fairly easily get away with that much heat extraction.
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Post by satamax on Feb 24, 2015 22:23:35 GMT -8
Hi Pinhead.
Well, you have mass on the half barrels? Because there, we're talking about something suposed to cope with more than 6m² normaly. And there, you have a total of 3.72m². That seems weird! Do you have a nice chimney above?
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Post by pinhead on Feb 25, 2015 11:04:16 GMT -8
Hi Pinhead. Well, you have mass on the half barrels? Because there, we're talking about something suposed to cope with more than 6m² normaly. And there, you have a total of 3.72m². That seems weird! Do you have a nice chimney above? My chimney is 6 feet of stainless triple-wall pipe inside, going horizontal for about two feet, then up another 4 feet. This gives me a total of 10 feet of triple-wall vertical chimney, the majority of which is mostly inside the building envelope. The half-barrels are covered with cob. They're separated by a dividing wall to create two separate bell chambers. The plenum beneath the barrel is much more open than required. Here's my build thread with pics.. I don't want to hijack your thread... Just trying to explain my experience with a 7" batch box. **NOTE** My batch box features a side riser and S-portal which deviates from Peterberg's original design. It is possible that the side-riser configuration is reducing the output of the stove, though I have no way of quantifying any differences. The total heat output, however, is much more than the 6" standard batch box that I had built before.
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Post by satamax on Feb 25, 2015 21:27:09 GMT -8
Ok Pinhead. Thanks a lot. You say that you have 10ft of chimney. This, imho, is way too low. On the building i've bought, i have about 20' or 24'. And it will be a straight batch rocket. No messing, even if Matt's nummbers are real good. I won't try a s portal either. I need to burn another barrel. And then, i'll experiment a bit.
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Post by pinhead on Feb 27, 2015 7:21:39 GMT -8
Ok Pinhead. Thanks a lot. You say that you have 10ft of chimney. This, imho, is way too low. On the building i've bought, i have about 20' or 24'. And it will be a straight batch rocket. No messing, even if Matt's nummbers are real good. I won't try a s portal either. I need to burn another barrel. And then, i'll experiment a bit. Hmm I'm in a single-story building and the exit of the chimney is above the roofline. Maybe it's closer to 12 feet, but if I were to extend it to 20 to 24 feet I'd have a huge tower sticking up that would probably need guy wires. I really wish I had a 24' chimney though. I do have another 3' section of triple-wall pipe... Maybe I should throw it on top and see if it helps any.
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Post by satamax on Mar 1, 2015 3:27:06 GMT -8
So guys, i'll need your input.
I have the core Inside a barrel, all insulated. Above this one, there's "the barrel" as usual arangement. Heat riser sticking about 30 or 40cm Inside this one. Froùm the bottom of this top barrel, i will run a direct pipe to the barrel tower bell next to it. So two barrels one on top of the other. The top part will act as a real bell, then the gases will go from intake height, above the bottom barrel, to exit into the chimney, about floor level. I Wonder if this bottom barrel will act as a bell, or just a downdraft channel. If it acts as the later, i won't need the 4x CSA. So i could pile up rocks Inside, to make a 20cm space for the gases to go downwards to the flue tube.
Otherwise, if it acts as a bell, i will pile up rocks just on the outside.
Peter, you know bells far better than me. What's your opinion?
Thanks.
Max.
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Post by shilo on Mar 1, 2015 8:08:42 GMT -8
I made a 17cm with 4.5 half-barrels (+ the barrel above the heat riser)+ 1 meter horizontal duct.
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Post by satamax on Mar 1, 2015 8:34:29 GMT -8
Thanks shilo.
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Post by peterberg on Mar 1, 2015 13:17:57 GMT -8
OK, piling rocks inside would be very interesting. That lower barrel is in reality not a bell but it won't fail to influence the top barrel which is. Don't forget you'll need a wider space at the bottom in order to lead the gases to the exhaust. A strong grid kept up by a couple of upright bricks would be alright I think. The rocks could be piled up on that grid then.
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Post by satamax on Mar 1, 2015 15:06:49 GMT -8
Thanks Peter. So, pics are there : www.permies.com/t/44806/rocket-stoves/Cobbling-workshop-heaterThe thing is drafty as fcuk! there's gap on the second top barrel, where i tried to check for draft. The flame of the lighter was sucked up. Even at startup it didn't smoke. And the weather is sub optimal today. Not that cold and damp, raining. I'm just dreaming of adding two more barrels. The second tower, with the bell on top bypasses down. The top tube is sticking may be 20cm inside. Same as the bottom one. Do you think two barrels as a second bell would work? I think i will have to forget about piling rocks inside for the moment. May be outside. I need more heat than experimenting.
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Post by ronyon on Mar 1, 2015 22:16:28 GMT -8
How about running two plunger tubes? One from the riser barrel to just above the bottom of the barrel tower, another from that point,right out of the top of the tower. One or both could be made from chimmeny liners,and should promote bell like behavior.
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Post by satamax on Mar 1, 2015 23:25:15 GMT -8
Ronyon, i'm not sure i quite get what you are saying.
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Post by peterberg on Mar 2, 2015 1:42:41 GMT -8
I'm just dreaming of adding two more barrels. The second tower, with the bell on top bypasses down. The top tube is sticking may be 20cm inside. Same as the bottom one. Do you think two barrels as a second bell would work? I think i will have to forget about piling rocks inside for the moment. May be outside. I need more heat than experimenting. So the lower barrel of the tower is bypassing down. Remarkable. One way to alleviate that is making the inside of the barrel narrower. Piling bricks along the wall for instance, that did the trick in Montana. Or placing a smaller barrel inside, filled with rocks. But that 20 cm pipe sticking inside the barrels, I find that questionably at best. I would try to have those nearly flush with the barrel first. Shortest route to more heat extraction: place another barrel on the tower. When that isn't enough place another one on the riser barrel. No plunger tubes needed. Just guessing.
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Post by satamax on Mar 2, 2015 1:59:11 GMT -8
Peter, i might try the stones tonight! Depends how courageous i feel.
Well, quater past four update! I have the second job getting in the way, so i won't be stuffing stones Inside the stove tonight!
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