by matt walker » Sun Mar 23, 2014 4:11 pm
Dang it man, sorry to hear about the thumb! The box looks about like most of my found clay experiments. I actually think yours is holding up pretty well, I can still see most of the shape, it's not just powder. That's good. If you did the same thing and packed cob all around it, it might have made it a month or so. One thing about the batch box, they take a much more structural core mix than the J tube. The big roof span there is always a weak spot, even with real castable refractory they are very hard to keep together.
As for performance, I'd say for your next one do it strictly to the numbers, with the port going into the center of the riser for the typical mixing double vortex there. That way at least you will have a baseline for your continued experimenting. It's a pretty finicky thing, and the difference between almost working and then full lift off with a roaring riser is really not subtle but can be brought about(or prevented) by very small changes.