Post by mintcake on Mar 15, 2014 12:37:34 GMT -8
I re-measured the batchbox I'd made last weekend. Something must have gone wrong with my pencil... no wonder it didn't fire
properly. Today I remade it.. It's now as close to a 5inch batchbox as I could make. Octagonal heat riser, from AAC/ytong with the lower 2/3 having different surface coatings as a trial. Firebox this time was just straight aac/ytong. Will see how it holds up. Cracks filled with 3parts sand, 1part clay. More of same holding the slopes in place in the firebox. But basically there wasn't much more than a few of cups of water in the whole build, so at my kid's request (OK and my impatience too!) I fired it.
Oh, I had about 1.5m of flexible aluminium flue connector as a chimney for the start of the burn. To make the port I'd just raised one segment of the octagon, so I tied the flue to that with some gardening string, with the top tied to a 3m long pole.
It was a bit of a pig to get anything lit, but eventually the kindling caught, with hardly any smoke back, and for a minute or two I had lovely rocket sounds. The wood didn't really want to catch though, so the rocket sound died away and I did get some smoke-back. Tweaking the position of the wood, I must have eventually done something right as it finally flared into life, and there was a nice flame-filled firebox, no backsmoke and no visible smoke form the chimney.
After a while we saw some smoke at the top of the riser, and realised that the the string holding the flue connector had started to smoke. Once it turned black I decided it was time to take that down. Very pretty - I had something like 30cm of
red-hot glowing gas (I hesitate to call them flames, but they obviously had been) coming out of the top of the riser. That lasted a good ten minutes, if not more. No wonder that string had been smoking. I did think of checking for rams-horn patterns, but decided it could wait until I'd be able to keep my eyebrows. Later in the burn I did check, and there they were, curling beautifully left and right at the same time. Lovely sight. About this time we noticed a wet charcoal smell,
before then there hadn't been anything. Complete combustion, I presume!
After all had died down, I removed the upper third of the riser (there was a gale threatening and I didn't want my stove blown over - aac is fragile when its thin.). This was an octagon of AAC with out any surface coats. The joints had been coated with the sand/clay crack filler mix, and I found that the crack-filler clay had changed colour, it's now about half way to a red earthenware-look. So based on www.ceramicartdaily.net/PMI/KilnFiringChart.pdf I'd guess that the top of the riser was getting close to 800C or so. I'm glad I removed the Aluminium when I did.
It'll be interesting to see what's happened to the surface coatings and the AAC in the lower part of the riser.
I will report once there's anything to say.
But... Is that "flame-thrower effect" to be expected? I thought things were normally a little cooler by the top of the riser. If it is normal, then I guess I'm going to need something along the lines of an arch of firebricks for the top of my first bell. Current plans give that bit a triangular footprint... anyone know how to make a triangular arch??
properly. Today I remade it.. It's now as close to a 5inch batchbox as I could make. Octagonal heat riser, from AAC/ytong with the lower 2/3 having different surface coatings as a trial. Firebox this time was just straight aac/ytong. Will see how it holds up. Cracks filled with 3parts sand, 1part clay. More of same holding the slopes in place in the firebox. But basically there wasn't much more than a few of cups of water in the whole build, so at my kid's request (OK and my impatience too!) I fired it.
Oh, I had about 1.5m of flexible aluminium flue connector as a chimney for the start of the burn. To make the port I'd just raised one segment of the octagon, so I tied the flue to that with some gardening string, with the top tied to a 3m long pole.
It was a bit of a pig to get anything lit, but eventually the kindling caught, with hardly any smoke back, and for a minute or two I had lovely rocket sounds. The wood didn't really want to catch though, so the rocket sound died away and I did get some smoke-back. Tweaking the position of the wood, I must have eventually done something right as it finally flared into life, and there was a nice flame-filled firebox, no backsmoke and no visible smoke form the chimney.
After a while we saw some smoke at the top of the riser, and realised that the the string holding the flue connector had started to smoke. Once it turned black I decided it was time to take that down. Very pretty - I had something like 30cm of
red-hot glowing gas (I hesitate to call them flames, but they obviously had been) coming out of the top of the riser. That lasted a good ten minutes, if not more. No wonder that string had been smoking. I did think of checking for rams-horn patterns, but decided it could wait until I'd be able to keep my eyebrows. Later in the burn I did check, and there they were, curling beautifully left and right at the same time. Lovely sight. About this time we noticed a wet charcoal smell,
before then there hadn't been anything. Complete combustion, I presume!
After all had died down, I removed the upper third of the riser (there was a gale threatening and I didn't want my stove blown over - aac is fragile when its thin.). This was an octagon of AAC with out any surface coats. The joints had been coated with the sand/clay crack filler mix, and I found that the crack-filler clay had changed colour, it's now about half way to a red earthenware-look. So based on www.ceramicartdaily.net/PMI/KilnFiringChart.pdf I'd guess that the top of the riser was getting close to 800C or so. I'm glad I removed the Aluminium when I did.
It'll be interesting to see what's happened to the surface coatings and the AAC in the lower part of the riser.
I will report once there's anything to say.
But... Is that "flame-thrower effect" to be expected? I thought things were normally a little cooler by the top of the riser. If it is normal, then I guess I'm going to need something along the lines of an arch of firebricks for the top of my first bell. Current plans give that bit a triangular footprint... anyone know how to make a triangular arch??
