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Post by tallgrass on Sept 9, 2015 19:49:11 GMT -8
Preparing for my first batchbox bell system. I have used the search function and can't seem to find pre-posted answers on my questions, but please feel free to remove this thread and direct me if there is already such discussion. Is there a disadvantage of stacking the riser out of brick and wrapping in ceramic wool insulation instead of using a round riser cast of insulated refractory? I'm hoping the square or rectangular shape of the riser won't negatively effect the burn. Also, is there a longer term solution that has been tested for the p-channel being made of steel, or a quick way to replace a worn p-channel without disassembling the system entirely? I was wondering if maybe there is a way to disconnect the vertical portion of the p-channel from within the batch-box so that in the case of replacement, one could be slid in and out of place. If this is a pipe dream, is the walker pre-port secondary air tube a good candidate for a replaceable and easy to replace piece? What are the effects of leaving the secondary air intake out? Would one still use a 20% door opening or would it be increased to 25%?
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Post by shilo on Sept 9, 2015 20:18:26 GMT -8
the ideal riser is round, low mass, highly insulate. try to stay not too far from that.
you can make an inox p channel.
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Post by erikweaver on Sept 10, 2015 3:25:13 GMT -8
Preparing for my first batchbox bell system. I have used the search function and can't seem to find pre-posted answers on my questions, but please feel free to remove this thread and direct me if there is already such discussion. Is there a disadvantage of stacking the riser out of brick and wrapping in ceramic wool insulation instead of using a round riser cast of insulated refractory? I'm hoping the square or rectangular shape of the riser won't negatively effect the burn. Also, is there a longer term solution that has been tested for the p-channel being made of steel, or a quick way to replace a worn p-channel without disassembling the system entirely? I was wondering if maybe there is a way to disconnect the vertical portion of the p-channel from within the batch-box so that in the case of replacement, one could be slid in and out of place. If this is a pipe dream, is the walker pre-port secondary air tube a good candidate for a replaceable and easy to replace piece? What are the effects of leaving the secondary air intake out? Would one still use a 20% door opening or would it be increased to 25%? Peterburg has said that cutting the fire brick to form an octagon shaped fire raiser work well. Squares there is a compromise (and I would assume rectangles fall into that same category). So I would at least cut the brick to form an octagon. That's what I'm planning to do. If you can find the lightweight kiln brick, which you can easily cut with a hacksaw, it will be super easy. If you have to use regular fire brick, just get a brick chisel and buy a few extra brick to practice your cuts upon. Or use a masonry cutting wheel on a rotary grinder or cutter. All in all, it shouldn't be all that difficult to form an octagon. Then wrap it with 2 or 3 inches of insulation, like the ceramic wool you mention. It will be fine. An option I am considering for the periodic replacement of the secondary air intake / p-channel is to design the barrel fit so that I simply remove the barrel, and that area is easily exposed. Simply remove it and drop in the new piece. Should be pretty simple. Look at Peterburg's images on his threads where he shows what he has done in his shop. That should give you some ideas.
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Post by insight on Sept 10, 2015 5:29:37 GMT -8
Erik, I've been going over the past threads on P-channel and Matts secondary air channel and after reading this thread want to make sure I'm not confusing the two. I thought the P-channel was the introduction of a 'plate' in the firebox (down from the cieling) to create turbulence and the Walker port was the introduction of secondary air. Please clarify for me if I have this wrong.
Tallgrass I too am attempting to figure out all the refinements you talking about, to start a build. I too was going to use brick, but after reading numerous threads, it seems a moulded refractory is the way to go. Sand (not beach sand, a bagged refined silica), perlite, grog if you have it, and fireclay will make up a good lasting riser. The temps in the riser are very hot so, firebrick, preferably super duty rateed would last for some time in that environment but don't insulate well. Eric is pointing to IFB (Insulated Fire Brick) and it can insulate high temps and is easily manipulated (the shape).
It seems the disadvantage of the shape is lack of efficiency. Peter could prob. tell us what percentage that is, going from square/rectangle to circular.
Has anyone noticed the ash affecting the interior of a risor made with IFB? In wood kilns (built to fire pottery reaching 2300 F to 2400 F and up, ash from wood deposited on IFB can start to break it down once ash melts. Perhaps all the ash in that chamber is tossed out and not allowed to accumulate due to the turbulence of the burn in the chamber(speculation).
Thanks for the thread Tallgrass. Not trying to divert the thread, questions come up as I write/think. I'll try to stay on topic.
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Post by shilo on Sept 10, 2015 6:02:01 GMT -8
"I thought the P-channel was the introduction of a 'plate' in the firebox (down from the cieling) to create turbulence and the Walker port was the introduction of secondary air. Please clarify for me if I have this wrong" this wrong. if we refer only to batchbox, p channel is secondary air from above the box and the Walker port is secondary air from beneath the box
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azor
New Member
,tweaking the build
Posts: 7
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Post by azor on Sept 10, 2015 6:51:52 GMT -8
got it shilo, thanks Yes I was thinking Batch box. I guess the trip wire has to do with the turbulence ?
Does anyone have both P-channel and Walker tube in a batch obx? Is that just too much secondary air?
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Post by shilo on Sept 10, 2015 6:57:49 GMT -8
it's look excellent but no one test it with testo
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Post by ericvw on Sept 10, 2015 13:55:59 GMT -8
azor: Trip wire is used in a J style rocket stove, and yes, for turbulence, sort of.... Breaks up laminar flow in the burn tunnel. Unnecessary in a batch box.
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azor
New Member
,tweaking the build
Posts: 7
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Post by azor on Sept 12, 2015 5:11:20 GMT -8
Thanks for clearifing ,been reading so much, I guess didnt differentiaate between the two.
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Post by mintcake on Oct 2, 2015 10:06:24 GMT -8
Hi, the problem with a square riser is basically that you have extra mass and needless surface area = wasted heat. You want to keep as much heat in the flames a you can, for clean burning, so wasted heat is a very bad thing. The "effective" area of a square riser is a circle that'll just fit in it, so you're making the heat-loss area 8*R instead of 2Pi*R = about 30% worse heat loss. An octagon is a much better approximation to a circle. One option would be to make triangles to turn your square into an octagon, but then you need to work out how to stop them falling over.
Whatever you do, I strongly suggest making a jig to keep your cuts straight and your bricks from moving. Having wrecked my elbow cutting "soft" bricks by hand (carefully not cutting my jig), I highly recommend using a grinder. Oh, and if you have the chance of getting a no-name diamond blade for your grinder at the same price as a pile of abrasive "rock cutting" disks, I'd recommend the diamond blade any day, unless the pile is a foot tall.
Do make sure you're getting real insulating firebricks, if you go that way. I experimented with YTONG 18 months ago and found their claims of it withstanding high temperatures don't mean it'll serve in a heat riser. It's wonderfully insulating, but it shrinks and crumbles. I ended up using a perlite & local clay mix, using a plastic drain pipe for the mould, (2 half circles, with ceramic felt in between, to allow for thermal changes) and there's no sign of trouble after last winter's use.
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