posted 11 years ago
Simpler, yes. Good and quick. Which reminds me of that old sign that says "Good, fast, cheap, choose any two" I downloaded their catalog but couldn't find any prices, which tells me something. Yes, you only need a couple of feet for the riser so it can't be all that much. But, this takes us to the problems discussed in the shippable core thread. In the burn tube, the elbow, and the riser we need specific shapes that have to hold up under extreme conditions and still be insulative. To get good quality, with "off the shelf" speed, it's going to be expensive. Isn't this whole forum is about the slower, cheaper, do it yourself approach.
One big question I have is "just how good does it have to be?". I'm a blacksmith and I've made several forges of the "dragons breath" variety. You just line a container with rock wool and poke a propane torch into it. But, under those conditions rock wool breaks down and emits asbestos sized particles. Not something you want to breath. I've tried lining the forge with ITC-100, and that works fine... till you start working at the forge. The ITC is brittle and if you give it the slightest bump with your iron it flakes off. In the real world you're constantly moving your irons around in the fire and you're going to bump the sides of the forge.
The inside of your core and riser doesn't get bumped, why not (again, other than price) coat it with ITC? ITC used to have an ad where they showed spraying the inside of a cardboard box with ITC-100 then firing pottery in it to 2000 degrees. ITC makes a formula just for coating metal. Why not just form up your J-tube core and riser out of stove pipe and spray the inside with ITC? I think I've seem a thread about that but I haven't read it yet, because I'm remembering ITC prices being in the first born child range.
I suggested to Pyro Man Dan that he search "paper kiln" on U-tube. I think I'd use fiberglass cloth instead of paper but the technique looks like a way to make a more durable inside liner for your riser. Wrap a PVC pipe in newspaper (as a mold release), lay on your slip coated fabric, put a larger metal tube over it and pack the space between with clay-slip/perlite mix for insulation(or use Dan's technique to use straight perlite), then slide the PVC pipe out and let it dry. Seems like it should work. If someone gets around to trying it before I do let me know.
BTW, a friend who is more knowledgeable than I says that firebrick grog has to be made from high fire clay... but it doesn't have to be high fired. Having it fired reduces shrinkage in the bricks you make from it, but there's a point of diminishing returns on shrinkage that occurs in the low fire range. He says to mix your clay slip with sawdust and form bricks, then fire them till the sawdust burns out. He says the firebox in my Kentucky wood gobbler should get plenty hot enough. Once the sawdust is burnt out the bricks are easy to crush down into grog. I haven't tried it yet, but it's on my list.