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Post by peterberg on Sept 29, 2015 1:42:10 GMT -8
As a riser, it would last almost indefinetely. Not sure when used as the tunnel and feed as well. It isn't up to mechanical abrasion but as long as you are very careful it probably survive 3 seasons I would guess.
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adiel
Junior Member
Posts: 119
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Post by adiel on Sept 29, 2015 9:36:48 GMT -8
As a riser, it would last almost indefinetely. Not sure when used as the tunnel and feed as well. It isn't up to mechanical abrasion but as long as you are very careful it probably survive 3 seasons I would guess. mmm. sorry master but - i saw these boards shrink in the tunnel and crack. in a 7" J i'm a little bit afraid using them in the riser. in an 8" J i wouldn't try.
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Post by peterberg on Sept 29, 2015 10:43:26 GMT -8
I think you are right Adiel, but that might be due to the quality you have access to. The highest quality we can buy here is quite good, no warping and shrinking in the riser of my experimental model for several years. On the other hand, the tunnel could be too much for the material, I don't have experience of that.
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Post by surplus6 on Sept 29, 2015 14:07:00 GMT -8
looks like brick fire tunnel, board riser then. Q1. when having the heat riser insulated, then a barrel over it, is there a "best" size air gap between insulation and barrel? the reason being I have to tanks 1 diameter is 375mm and the second is 310mm so would fit inside each other. so I could use one around the riser to have insulation inside, around the board riser, then if the air gap isn't to small have the second one over that like the steel drum idea. Q2 would the metal around the insulation last ok as it won't be in direct contact with the flame?
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Post by surplus6 on Sept 30, 2015 1:42:29 GMT -8
how hot does the outside of a fire brick J tube get? I ask this as it will be on a wooden floor, and need to know what would be best for the under side to protect the floor.
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Post by satamax on Sept 30, 2015 1:46:22 GMT -8
Surplus, there's no real optimum air gap. It can be as large as you want realy. Before you hit maximum ISA of the barrel considered as a bell. There's a minimum air gap thought.
For that you substract the smaller barrel CSA from bigger barrel CSA, and see if the remaining surface area is enough for your heat riser CSA. Barrel gap should never be less than 1.5" (3.81cm) because bellow that barrier, friction losses are too big to be compensated by the draft.
Metal not in contact with the flame should behave fine, till it rusts completely. Which means several years.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Sept 30, 2015 8:01:00 GMT -8
It gets very hot - if you build it directly on the floor there is nowhere for the heat to dissipate. The heat will easily char the wood and start it smouldering! You need an air gap between the wooden floor and the bottom of the bell/stove. I would suggest 4" or 100mm.
Ref the riser - would it be easier & more cost effective to use insulating fire brick rather than vermiculite board?
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Post by surplus6 on Oct 1, 2015 13:01:54 GMT -8
oh well, the bottles/drums I planned on using only have around 1" clearance all round. rethink. air gap underneath sounds doable, I'll weld up a frame work to lift it up. I asked about the boards more for information, as now I know they'll work I can work out prices etc for board V's bricks.
At least when the workshop/shed heater is done, I'll have a better idea what I doing for over the winter/spring when I'll be setting out on an oven building adventure, as my 16yr old daughter has started making breads etc but gets anoyed at the oven being the bottle neck of her production. so I've told her I'll build her one in the back yard.
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Post by satamax on Oct 1, 2015 23:11:45 GMT -8
Surplus, i think you worry too much Your vermiculite board riser is kind of insulated by itself. Some superwool wrapped around, and your good to go. You don't need that second barrel to make a form around the heat riser. Even rockwool would work there, held by chickenwire. And then, you have a nice barrel gap.
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Post by surplus6 on Oct 3, 2015 6:19:12 GMT -8
thanks satamax, I will experiment and see.
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