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Old 09-03-2009, 02:01 AM
Doug Harroun
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Furnace build thread

So if it's all right with everyone I'm going to document my furnace build here. Feel free to comment, add notes, etc... this is a work in progress.

I'm building a freestanding pot furnace essentially as depicted in Glassnotes as the Penland Pot Furnace.

Years ago I obtained a Dyson pot 18" OD, I am going to keep it as my standby pot and order one to build around. Probably the 19" EC, unless otherwise guided.

Furnace dimensions, approx: 50" tall, 50" OD, 24" ID.


Wall will be 3" Kast-o-lite 30: 2.945 cu ft. Surround that with 10" of frax, and some sheet metal.

Crown will be ...dunno what yet. Phlocast, Mizzou? ~2 cu ft. With similar frax over lay and a very artistic metal shell.

base will be Kast-o-lite, IFB and hard brick....

Cast various parts from what I have left....

Need advice on burner heads.

will add more as needed, including pics if they'er allowed

-Doug
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Old 09-03-2009, 06:38 AM
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I would recommend the 19 inch pot from High Temp in Portland. It's a better pot for less money and you don't have to wait for it.

Don't ask them about horseshoes either. They know nothing about them.
Put the ten inches of frax on the crown and eight around the outside. More is simply unnecessary. I would suggest recuperating it. Wake up Hugh! If you do recuperate, the burner needs special consideration and Hugh does sell them I think. I've seen them work and they do it well.
Phlocat will work fine as a crown. Morco 95 would be better but it's hard to get.
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Old 09-03-2009, 08:48 AM
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i agree with Pete, recuperate. my furnace is a lot like my v-10 F-250 and that's getting old
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Old 09-03-2009, 10:31 AM
Eben Horton Eben Horton is online now
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Quote:
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i agree with Pete, recuperate. my furnace is a lot like my v-10 F-250 and that's getting old
same here...
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Old 09-03-2009, 11:37 AM
Doug Harroun
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Recuperation will be part of the furnace as well. I'm not entirely sure which scheme I want to go with yet. I can fabricate stainless steel parts pretty easily, but the designs that seem to work well are cast refractory, correct?
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Old 09-03-2009, 11:45 AM
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Both. Get together with Hugh. Pay him. You won't regret it.
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Old 09-04-2009, 09:15 PM
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Quote:
Originally Posted by Doug Harroun View Post
Recuperation will be part of the furnace as well. I'm not entirely sure which scheme I want to go with yet. I can fabricate stainless steel parts pretty easily, but the designs that seem to work well are cast refractory, correct?
Yeah, Doug...if you recuperate you will need a completely different burner setup. Its a surface mix burner as opposed to a premix burner.

Charlie Correll also builds and sells them as complete units: the recuperator and the burner.

http://www.correllglassstudio.com/recupburner.htm

http://www.correllglassstudio.com/recuppaper.htm
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Old 09-04-2009, 12:29 AM
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Quote:
Originally Posted by Doug Harroun View Post

Furnace dimensions, approx: 50" tall, 50" OD, 24" ID.


Wall will be 3" Kast-o-lite 30: 2.945 cu ft. Surround that with 10" of frax, and some sheet metal.

Crown will be ...dunno what yet. Phlocast, Mizzou? ~2 cu ft. With similar frax over lay and a very artistic metal shell.

base will be Kast-o-lite, IFB and hard brick....

Cast various parts from what I have left....

Need advice on burner heads.

will add more as needed, including pics if they'er allowed

-Doug
Welcome to the board! It's think it's great your documenting your build. I always learn a little more with everyone.

Kast-o-lite 30 make sure there are several varieties.

You need to think about your floor. It will see glass and kast-o-lite won't hold it back. Some use mizzou or a ramable clay I used a few inches of mizzou over 2800 brick on our last build (only because they are salvage). Don't forget to cast a drain port this to will need to be resistant to glass attack. You also want to angle your base towards the drain. I placed mine on the back of the furnace with a fiber plug. I do think most have the cleanout in the front.

I used kast-o-lite 30 for my crown and never had a problem. If you want extra strength you can cast a dome shape on the top. I also used it for my door. For a sill I like to use a large clipper brick but there are several castables you can use. .

Burner. I would scrap that idea and go with electric. Seriously you may want to look at gas prices and compare to what you pay a kilowatt hour.
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Old 09-04-2009, 05:18 AM
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Start up costs on electric are high but the convenience is incredible, as is the safety, particularly in a hot town, which Albuquerque is. While I vastly prefer, and would advocate for moly, SiC has the advantage of not needing a transformer. New Mexico has pretty reasonable electric rates, so it would cost a good deal less to run.

Insulate your hood. Mine is six inches thick, all steel and insulation. It's very cool in my shop, almost too cool.
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Old 09-04-2009, 09:46 AM
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The guys at Hi-Temp Refractories in MO. supplied me with their Morocast 60 HS (60% alumina) product as a substitute for Mizzou to replace the 3-4" of floor that had gone to mush from pot leaks over the last 12 years. The old floor was unstable at melting temps but hard as rock at room temp. Had to use a rented electric jack hammer to get the old stuff out.

But I have listened to Pete & others long enough to decide to go Moly for the sake of lower fuel bills among other things. Just my maxon blower running 24/7 consumes $100.0 plus a month in electric charges. Now it'll only run while I'm blowing (glory).
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Old 09-04-2009, 02:01 PM
Lawrence Ruskin Lawrence Ruskin is offline
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Ya know what, it might be a good idea to start a thread for guys that are just starting to build or are doing a total rebuild.

We could offer some precepts to follow, for example if you don't have to be in a city, moving to a spot where building standards are easyier to deal with is a good plan. Nice little backyard studio.

Also figure out how many pounds you use a week and designing your equipment around that.

I way overbuilt my studio when I started, I made a huge glory hole and a 150 pound electromelt. This cost me big bucks over 20 years.
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Old 09-04-2009, 05:12 PM
Doug Harroun
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At first I considered electric elements. Being electrically inclined the wiring and power is a non-issue for me. SiC was out of the question. I know a few people using them and the replacement cost of shot elements would run higher than the cost of gas. Moly elements look better, but the _VERY_ high initial investment was the factor that pushed me back towards gas.

Also, unless you live near a wind farm or hydro plant you power is most likely coal/gas/oil based anyways, why deal with a loss in conversion?

Right now I pay about $0.015-$0.02 per kWh for gas. For electricity it's $0.1085 per kWh.

So I'm still pretty sure I'm building a gas furnace.

...unless someone knows a source for moly elements for less than $100 each.
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Old 09-04-2009, 09:37 PM
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Quote:
Originally Posted by Lawrence Ruskin View Post
Ya know what, it might be a good idea to start a thread for guys that are just starting to build or are doing a total rebuild.

We could offer some precepts to follow, for example if you don't have to be in a city, moving to a spot where building standards are easyier to deal with is a good plan. Nice little backyard studio.
**************************

I think thats a great idea Lawrence. I will take this thread and make it sticky so it's always at the top. as long as it keeps getting added to, I'll leave it there. If it winds up being really good, I'll move it to antiques and classics and stick it there.
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Old 01-21-2011, 02:22 AM
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I really like the idea of a design where the pot and front of the furnace are basically a cart that can lower and roll out for changes. The current design where you have to move the most fragile and critical parts of your furnace (elements, crown) to get to the part you're going to trash (old pot) seems like it could use some re-engineering.
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Old 01-21-2011, 07:38 AM
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Even in a kiln car design. you had better pull the elements. Things get stuck together in a glass furnace and getting them loose takes force. The difficulty in the design in which the crown remains in place is always the same- the span of the crown that is unsupported.
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