Fireclay and perlite riser, add fire barrier or furnace cement? Oct 8, 2014 14:24:13 GMT -8
Post by PNW Dave on Oct 8, 2014 14:24:13 GMT -8
I definitely think it is a viable option for making a core. I've put my little L-feed test stove through some intentional abuse to see how this mix holds up to physical abrasion. Jamming fuel in against the back wall and scraping it around, I've even kicked the fuel into the feed a few times. It is wearing down, to be sure, but I think that should be expected. I will get a pic of its current condition for you (edit: the second or the third time I lit the stove, it was put out with water. I didn't want that to happen, but it was done. Surely that had a negative effect on the strength). I plan to make a batch of patching material, which will be the same thing except I'll first sift out all the largest perlite particles, and then kick fuel into the feed and see how it holds up.
My mix does seem very durable for its weight, although the heat riser sections have almost half of the furnace cement and water glass mix as the little stove. Of course they won't have to withstand physical abrasion. I will probably weigh the next riser section I make before/after drying.
I've opted to use fire brick for the core for a few reasons. The obvious one, overall durability and resistance to abrasion. Also to allow for trying out various core configurations, I will loose fill and lightly pack my "fire clay coated perlite" (no furnace cement or water glass) into the space between fire brick and clay brick. Then I can just dig out the perlite, reconfigure the fire bricks, and put the perlite back in. I will definitely try inducing a vortex in the riser by having the burn tunnel enter the heat riser off centered.
I didn't burn out the inner form because I reuse it. The outer diameter of the inner form is tapered from 8.25" to 8.75". To taper the cardboard tube, I cut 16 slits with a 1/16" cutoff wheel on an angle grinder then taped around the circumference. 4 cuts almost the full length, 4 cuts a little shorter and 8 cuts even shorter. Then wrapped sheet metal around it and trimmed the edges. I put two screws through the from the inside and cut them off flush with the outer face. So the inner form is constructed, from the outside in, wax paper, sheet metal, tapered sonotube form, another tapered sonotube form made even smaller. This gives pretty good strength to resist ramming the perlite mix, and it's modular so I can easily take it apart if needed. It's just too much work and waste to remake every time.