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Rebuilding a 28-inch Olympic Torchbearer gas kiln


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#21 Chris D

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Posted 28 October 2012 - 01:35 PM

I moved my meter back near my kiln since I could not put the kiln near the meter.
Marcia




Interesting! We have a gauge that measures inches of water to put in between the valve and the burners so we can keep track of the gas going to the burners. Hopefully this will help us figure out too if we have inadequate gas at the kiln. There's quite a bit of 3/4 inch line between the kiln and the street, so we'll have to see.

#22 Chris D

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Posted 28 October 2012 - 01:57 PM

Got everything mortared up, and strapped the band on it:

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Scraped off most of the excess mortar and then plan to sand off the rest once the mortar has had time to set/dry. At it's thickest, the mortar is maybe 1/16 inch, and I buttered both sides of each joint before mating the brick surfaces. Everything seemed to stick pretty well together, though with such thin joints, it was a challenge to firmly assemble new bricks to the already-built floor. Had to be careful and forceful at the same time. A few notes:

  • I wouldn't try this if I had no previous experience with other sorts of mortar. This is sort of a tricky application, and wouldn't be great for a true beginner.
  • you need to work pretty fast. The mortar sets quickly with contact with air, but takes a good while to set in the center of the joint (we tested this overnight on some scrap)
  • A 28-inch "round" kiln's floor actually has a 34-inch diameter floor. 2 boxes of a dozen K-23 bricks are *just* enough, but you're using scraps from bricks you cut to complete it, so you have to plan very well, or buy a couple of extra bricks.
  • 2 pints of Sairset mortar are *just* enough. We had less just a few tablespoons of mortar left. YMMV.
  • Don't count on the band to "pull everything together" when you're done. The band can be tightened pretty tight, but doesn't come anywhere near tight enough to squeeze the bricks together any tighter than they were when you put them together initially.
Really hoping this works. If it does, we'll have saved some good coin. The floor from Olympic was a couple hundred bucks, and was going to be more than $100 to ship because of its weight, size, and fragility. All told, the bricks cost $66, the mortar cost $7, and the band from Olympic was $30. $100 for a new floor. Not pretending it'll be as good as one put together by pros, but it should be "good enough!"

If it doesn't work, it was only a $100 mistake. I've certainly made worse mistakes! Ha!

#23 Ron B

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Posted 28 October 2012 - 10:15 PM


I moved my meter back near my kiln since I could not put the kiln near the meter.
Marcia




Interesting! We have a gauge that measures inches of water to put in between the valve and the burners so we can keep track of the gas going to the burners. Hopefully this will help us figure out too if we have inadequate gas at the kiln. There's quite a bit of 3/4 inch line between the kiln and the street, so we'll have to see.



#24 Ron B

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Posted 28 October 2012 - 10:25 PM

Make sure that you have a gas meter, and pressure regulator, that is able to provide you with the amount of gas that the kiln needs. Take a look at the regulator and it should give you the orifice size and the spring color. If you have that information, and the manufacture of the regulator, you can call a company that deals with that brand and find out how many BTUs the regulator will provide. You will also need to know what BTUs the burners can provide. If the pressure regulator in its present configuration will not provide you with enough gas the orifices and springs can be changed to what you need to make things work.

#25 Chris D

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Posted 07 November 2012 - 10:35 AM

Well, the floor (so far) was a success. We reamed out the burner orifaces to #28 for gas (turns out they were propane orifaces) and set everything up and gave it a whirl. Worked pretty well! I think we have the fuel/air mix off a good bit, but we were still able to get the kiln to 1,900 degrees in just a couple of hours. Some photos:

The floor, in place, with burner ports cut:

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Detail of burner head and port:

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Low flames on the first firing:

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At full burn, just before we shut it down:

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After cutting off the gas:

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The goal is to get the thing to cone 10. We have a long way to go, and I can tell that the 4-500 degrees above 1,900 we need to get are going to be hard-earned. But I think we can do it. There's certainly no shortage of gas...we got it to 1,900 degrees with the valve barely cracked. Soot around the lid in places where there were heat/flame leaks tells me that the mix was probably starved of air, but that's just a guess.

Very excited at the success so far, but not sure if we need to increase primary air (with the burner venturi shutters), secondary air (with larger burner ports...we cut them pretty small) or both! Time and experimentation will tell.

Looks like the next project for this thing will be to rebuild the lid. After the first firing (probably in a decade) the part of the lid near the hinge was crumbly and falling apart. I can see the whole thing crashing down through the kiln and crushing the floor, so maybe we should replace it sooner rather than later. I really dislike the hinge system that olympic devised for this kiln. Seems built to fail. The lid is pretty heavy, and all that supports it when it's open are a couple of brackets that are attached to thin sheet metal that gets all of it's structural integrity from the K-23 firebrick that it's squeezing. Bad design. Was thinking that it might be good to weld up a frame to go around the kiln and create a "bridge" over the lid with a pulley system so the lid can be lifted with a little winch, kind of like how some raku kilns are designed, but only lifting the lid. Anyone ever see something like that?




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