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Post by talltuk on Sept 15, 2015 13:08:56 GMT -8
Ok so I have managed to get a week to finally start work on my little 125mm/5" batch box for my garden.
I figure that, seeing as I really want to build these as part of my business, I should try to go as user friendly and tech forward as possible. Therefore I reckon the Walker tube for secondary air seems to be the best option.
Do we have any hard dimensions to work from yet and do you think I could get away with using a bent copper tube as I have tons lying about and the tools to, mostly, work it.
Steel I would have to get fabricated though I also need a door which might have to be made as well, so not the end of the world.
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Post by talltuk on Sept 20, 2015 12:30:27 GMT -8
Nobody?
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Post by talltuk on Sept 26, 2015 13:28:51 GMT -8
Ok so after reading through what Mat has posted it seems 9% of system size is what we are looking for. So 130mm/5" system would need 1540mm2 csa for secondary. Therefore 40mm id square mild steel tube for horizontal and 40mm id circular tube for vertical. Sound about right?
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Post by talltuk on Sept 26, 2015 13:53:50 GMT -8
Just don't know how large to make the slit.
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Post by mkrepel on Oct 3, 2015 16:12:24 GMT -8
From what I read, it doesn't really matter. I think Matt used a 1/4" slot that was about 3" long. The air came out mostly near the bottom of the slit. That's just a guess though. He would have to weigh in to get the actual dimensions.
I would be a little concerned that the copper won't hold up to the heat. If you start getting around 1000C, you will get localized melting. You will get serious oxidation well before that. Steel melts at about 300C higher than copper. I believe copper will be much less durable than steel in this application, and I think Matt has burned out at least one of his steel rigs. Copper might be okay to test the concept, but for long-term use, you will want something more durable.
I'm not the expert, but those are my thoughts. I would consider some high temp-rated stainless for the longest durability.
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Post by talltuk on Oct 3, 2015 23:52:06 GMT -8
Yeah I was gonna use copper as I had some but just found out my mate has a nice little metal shop set up so we can fab the door and steel tube there. Yay! I was most interested to find out what Matt's experiences had been since his last posts but he doesn't seem to be around at the mo. Especially az I am going for 130mm rather than his 150mm batch
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Post by mkrepel on Oct 4, 2015 7:38:30 GMT -8
Hmmm... Sounds like another experiment. Are you planning to keep the firebox the same size?
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Post by talltuk on Oct 4, 2015 11:16:42 GMT -8
It will be sized according to peter vdb's spreadsheet for 125mm riser so smaller than Matt's
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Post by matthewwalker on Oct 18, 2015 9:37:13 GMT -8
Hey Talltuk, Peter let me know you were looking for measurements. It's all on this page on my Walker Stoves website.If you need more info, I'm happy to give you details, although I may continue to be slow to respond here. Good luck man, I'm loving the set up still.
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Post by talltuk on Oct 23, 2015 12:47:57 GMT -8
Thanks matt. I had already read up on that page. Just wondering if you had experimented with slit size as I am going an inch smaller.
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Post by philippeelskens on Feb 17, 2016 6:54:35 GMT -8
I have a question about the Walker dimensions when scaling down the system, when going from 6" to 5" riser diameter: Do I scale down the primary inlet 2 sq inches x 5/6 = 1.67 sq inches OR ((square root 2) x 5/6) ^2 = 1.46 sq inches
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docbb
Junior Member
Back from ZA
Posts: 92
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Post by docbb on Feb 17, 2016 7:37:45 GMT -8
I have a question about the Walker dimensions when scaling down the system, when going from 6" to 5" riser diameter: Do I scale down the primary inlet 2 sq inches x 5/6 = 1.67 sq inches OR ((square root 2) x 5/6) ^2 = 1.46 sq inches linear dimensions will be proportionnaly reduced 5/6 ,surfaces in square proportion and volume cubic proportion yes
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stoker
Junior Member
Posts: 61
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Post by stoker on Feb 18, 2016 9:20:17 GMT -8
But the 1.46 number should be 50/36 = 1.38888888...
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Post by philippeelskens on Feb 18, 2016 11:41:54 GMT -8
But the 1.46 number should be 50/36 = 1.38888888... Yes, that's correct! Not sure where I got that 1.46 from... Thanks!
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