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Post by mscantrell on Oct 26, 2014 11:26:33 GMT -8
Good afternoon all, I got myself some firebrick last week (thanks again, Jamie)- heavy firebrick, approx 2"x4"x8". I took a swing at stacking up a 6" batchbox, like so: It did roar a little, and I did get a ram's horn, so that was gratifying. Naturally, with no mortar between the bricks, it smoked everywhere. What came out of the chimney was pretty smokeless, but what didn't got into the riser didn't get burned up. No surprise. So I took it apart and rebuilt it yesterday with mud mortar. Mostly clay, but not carefully screened or anything. Just out of the ground. I looked at the sketchup file for the 6" batchbox with 2"x4"x8" bricks and then went out and put it together from memory. Question: These are heavy firebrick, not insulative firebrick, but I understand an insulative heat riser is highly important. I have a couple sacks of perlite and a tub of castable refractory, so I thought I'd mix them together and build a heat riser. I picture the easiest way being packing the perlite/refractory between the walls of a 6" cardboard tube and an 8" cardboard tube, giving me a 6" cylinder with 1" thick walls. But then I'd need to make a transition between the rectangular base of the riser and the round riser. Is this a good idea?-On the one hand, the round riser would be easy to cast, and without any corners, it would be resilient. Not prone to cracking. -Or on the other hand, I could try to cast a rectangular riser of the same size. That would eliminate any flow trouble at the transition from rectangular to round, but it wouldn't be as easy to make, and corners of casting are where cracks occur.
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Post by Daryl on Oct 27, 2014 3:59:22 GMT -8
You rock
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Post by byronc on Oct 27, 2014 5:21:05 GMT -8
Such a 1" thick wall riser of perlite/fireclay packed between cardboard tubes would be way to fragile, and would not really be enough insulation. Most folks use metal or a small steel barrel for the exterior tube. 16 gallon grease barrels (27x14 inches) are darn near perfect riser "canisters" and used by lots of RMH builders. The grease barrels are sometimes free for the asking from automotive quick lube shops.
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Post by mscantrell on Oct 27, 2014 8:12:48 GMT -8
Such a 1" thick wall riser of perlite/fireclay packed between cardboard tubes would be way to fragile, and would not really be enough insulation. Wow, I hadn't gathered that. So what's a reasonable minimum wall thickness? And what's a good target wall thickness? Thanks!
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Post by pinhead on Oct 27, 2014 8:50:18 GMT -8
On a 6" riser, a lot of people use 11 to 14 inch outside tubes (5-gal buckets, etc).
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Post by mscantrell on Oct 27, 2014 9:18:22 GMT -8
4" walls, yowza! I gotta buy some more perlite.
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Post by jermoll on Oct 27, 2014 10:04:26 GMT -8
I am getting ready to cast an 8" j tube rmh. the feed and burn tunnel will be 8" square, with plywood forms. For the interior riser tube, I am considering a 10" x 48" long (I will have to shorten it) sonotube, which I can get at Menards for $6. A 9" sonotube would more closely match the 8" square surface area, but they are not made in 9". Is my assumption that the 10" size will work ok correct?
For the exterior of the riser I would like to use a 16" sonotube, which costs about $13 for 48" length. That will yield a 3" each side wall thickness. Using Matts 14 parts perlite, 14 parts clay, one gal furnace cement and fiberglass fibers, does it seem to be a workable solution?
The sonotubes just seem to be less screwing around than making round forms, which I have a lot of experience with.
Thanks, I appreciate all the help I get on this site.
Jerry In Minnesota
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Post by satamax on Oct 27, 2014 11:12:30 GMT -8
On a 6" riser, a lot of people use 11 to 14 inch outside tubes (5-gal buckets, etc). Or for eurolanders, 35kg gas bottles are about 39 long and 12 in diameter, with rounded ends
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