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Post by Deleted on Apr 30, 2016 10:12:28 GMT -8
1 part- A 1 1/2 to 1 ratio mix of Portland cement to either grog, powdered perlite, powdered vermiculite, diatomaceous earth, or wood ash 2 part- Fireclay 1 part- Sand
You can add 10% lye to common waterglass and still stay within the safety reccomendations by Davidovits. 5% lye may be enough depending on your clay. Remember even Waterglass without lye can damage you. The waterglass will cause a short potlife.
The sand in the mixture will cause segregation in any mixture that is liquid enough to be castable without the use of a strong vibrating table.
Although potassium hydroxide is more expensive it may be cheaper in use as it does not thicken the clay as much and thus less liquid is required.
Grog 200 mesh with 10% lye and 10% lime or cement is much simpler to use, as you need just to add enough water to make it easy castable. No vibrating table required. If you mix it with sand segregation will not happen as easily as grog is much denser than clay.
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Post by stephenson1 on May 1, 2016 3:30:28 GMT -8
Thanks again Karl.
With your last paragraph are you saying a castable recipe could be as simple as 80% sand, 10% lye, and 10% lime?
Or are you saying that some quantity of sand can be added to a mix of 80% grog, 10% lye, 10% lime in order to slow segregation of grog?
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Post by Deleted on May 1, 2016 3:44:20 GMT -8
A castable recipe could be as simple as 80% very fine Grog, 10% lye, and 10% lime. However sand grinded to a few microns would work too. With white grog the result will look like non glare porcelain or stoneware. For a shiny surface add some waterglass and cast it in a polished form. One can add some sand or other coarse aggregate. If you have a heap of old bricks you need just a large hammer some lime, lye and water. See also: Geopolymer For Low-Tech Tinkerer. donkey32.proboards.com/thread/1701/geopolymer-low-tech-tinkererI have updated the "Geopolymer For Low-Tech Tinkerer" with respect to other techniques aside of casting.
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Post by stephenson1 on May 5, 2016 15:41:08 GMT -8
As a matter of fact I do have a heap of old bricks. I also own a hammer. But maybe it would be simpler to build it out of bricks and furnace cement.
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Post by Deleted on May 6, 2016 2:39:42 GMT -8
You would need much less and broken bricks would suffice.
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Post by stephenson1 on Jun 18, 2016 4:14:34 GMT -8
youtu.be/xHdHSXRhVQ8The address above is to a youtube vid of my failed rebuild. So I gave up on the idea of DIY castable in favor of building my barrel with bricks and using diy furnace cement to hold them all together. I used firebrick for the top course and salvaged red clay bricks for the rest. We'll see how well they hold up. Along the way I remembered I have a round, domed, stainless pan that is 22" diameter, 4" tall at the outer wall and domes to an additional 1.5" in the center I hadn't seen detailed dimensions for the rest of the system and assumed that the 18.5" inside diameter of the barrel would be sufficient. I'd built the heater core using the peterburg calculator sized for a 6" I.D. heat riser which I made from 1" kaowool. The riser height is a bit low at 39.5" as measured from the base of the firebox, but all other dimensions were strictly adhered to. I covered over the peter channel because during tests before the barrel was built it seemed to have no effect. When I'd built the barrel, capped it and fired it up it burned really smokey. I stripped some more kaowool down to .5" thick and glued it to the inside of my 6" diameter riser with sodium silicate to approximate a 5" riser. My thought was that by narrowing the riser, I was effectively enlarging my barrel. It helped, but it's still pretty smokey. I put some brick in front of the port to reduce it's overall area, but I'm not sure that helped any. My gap from top of riser to the lowest part of my stainless cap is 2". Any suggestions for how to get this thing clean again without demolishing my barrel?
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Post by peterberg on Jun 18, 2016 7:13:14 GMT -8
Mark, it is hard to say what the problem is, maybe there's more than one. Let's see step by step what could be the possible bottlenecks.
By restricting the riser to 5" the firebox is too large now. I can't see the air inlet clearly but it looks like to be situated opposite the port which is where it should be. This air inlet looks a bit cramped, is it really at least 20% of the riser csa?
The riser isn't smooth at the inside, in the first video it looks quite bumpy.
As far as I can see, the brick barrel (or bell, whatever you prefer) is wide enough. But the riser isn't in the middle so the gases can only escape to one side instead of all around. The top gap as you mentioned is 2", which is combined with that asymmetrical placement way too small. I recommend to make the bell higher, normally the top gap for such a system should be as wide as 1 foot.
You mention the p-channel didn't seem to do anything, is it a steel duct as specified or just an opening in the cover plate of the firebox? Hard to see by the naked eye whether it is doing anything by the way. When during a burn smoke is coming out, 9 out of 10 it isn't properly done.
The opening to the bench isn't visible, how large is that? Also, is the inside of the bench open or is it a chimney pipe folded in a loop?
Best to mention actual dimensions, otherwise nobody would be able to spot a deviation.
My first idea: bring it back to the original specs, free the riser of the additional kaowool and run it without the top of the bell. When it runs nice this way, the core is right, there is a restriction further downstream.
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Post by stephenson1 on Jun 19, 2016 3:19:31 GMT -8
Thanks for those thoughts Peter. Using your last sentence as my starting point, I freed the riser to it's original 6" diameter. It is bumpy inside because the kaowool wrinkles when shaped into a cylinder so I don't know what I'd do about that -short of lining it with a paste of cut kaowool fiber and sodium silicate perhaps- In any case, once I opened it back to 6" it ran perfectly without the barrel top. Rather than raising the barrel straight away, I lowered the riser to 35" which created another 5" of relative barrel height but it was still smokey. I excavated the opening to the bench to make sure that space was as large as it can be and then ran it with the barrel cap in place. It was improved very significantly. Here is a link to a video of the result. youtu.be/GhJtjscrA_kThe p-channel was a hole cut through the top of the cover plate that had a steel tab that dropped down to just below the top of the port at the distance specified. I've since covered it with a layer of refractory clay. My thought now is to raise the barrel by another 8 or 9 inches and raise the heat riser by the same distance. Then I'll be back to the original specification of a 43" tall riser, but with the same 9 inch gap at the top that I have now. I'll post the results when I have them.
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Post by peterberg on Jun 19, 2016 4:50:00 GMT -8
These batch box rockets need a high gas velocity, so any restriction need to be smoothed out. The burn slows down when you put the barrel cap on, right? I'd think it is better to have the riser as it is in the video and rise the barrel by another row of brick. So the top gap would be even larger, something like 1 foot. Then, there's another thing you could do: check the opening to the vertical chimney stack. This could be restricted too, especially when it is situated in a corner. Same recipe as the bench entrance, digging out. And finally: the heater would improve greatly by lengthening of the chimney stack.
All this is to ensure all the restrictions and bottlenecks are eliminated, give the thing as much room to breath as you can.
Oh, and when all that is done and the thing running like mad, it could be smoking again. That is the point where you need to install a proper p-channel.
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