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Thread: Build thread - Calcium silicate insulated copy of Myfordboy/J.Vibert furnace.

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    Build thread - Calcium silicate insulated copy of Myfordboy/J.Vibert furnace.

    My first furnace is a little A5 sized, gas fired, one build to Anon's plans. Works great, within its size limitations.

    I have some Calcium Silicate boards and wedges left over from insulating my kitchen and bathroom, and was wondering about their suitablity for insulation of the next furnace? Does anyone have any experience with this stuff as insulation? It is also used for industrial firproofing up to 1000C (1832F). Is is reasonable to expect it to survive behind a thin hotface in an oil fired, iron melting furnance?

    http://tinyurl.com/lhnqpcu
    http://www.youtube.com/watch?v=iSIpnFG8xsw

    I was thinking about cutting the boards into strips and arranging them for about 3 inchs of insulating wall, and then making a Mullite hot face out of plates using Anon's recipe, as that stuff is absolutely impervious to the temps up to iron.

    Is still have some of 1" Kaowool left over. Would it be necessary to insulate the CalSil insulation from direct contact with the hot face?

    Since my hotface cracked badly due to excessively fast firing in the little furnace, I'd prefire these hotface plates in a friends pottery oven. Its probably not hot enough to fully fire mullite, but can get then most of the way there, so they would hopefully survive furnace firing.
    Last edited by DavidF; 03-29-2016 at 08:48 PM.

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    Would it be necessary to insulate the CalSil insulation from direct contact with the hot face?
    The short answer is an emphatic, "Yes!"

    1832 F. is way below the temperatures you will have on the outer surface of your thin hot face. An inch of Kaowool will certainly be a lot better. I would say it depends on how long you plan to operate your furnace at any one session. If you are going to melt iron or bronze for three or four hours then you will need something that can stand up to a lot of heat.

    You really don't want your furnace to melt. I have been there; it's discouraging, and a lot of work to repair.

    Richard
    When I die, Heaven can waitI want to go to McMaster-Carr.

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    Thanks for the feedback.

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    I found an old discarded small hot water cylinder at a recycling pick up point near my house, so it is time to make a new furnace.

    I'll use the outer shell for the furnace casing, and the inner cylinder later for a muller.

    After cutting the shell with the angle grinder, the real PITA was getting the polyurethane foam insulation out to get the cylinder out. Shell ends up about 42cm/16.5" diameter, and 41cm/16" high.

    Following Myfordboy's example, I started by making a wagon for it. I am also going to copy MyfordBoys lid lifting mechanism
    https://www.youtube.com/watch?v=ZbnroanPt4g

    The hot face is be 1650 dense castable which my wife got me for xmas.

    Since my insulation is solid, I will have to cast the refractory into the insulation, rather than the way Myfordboy did it.

    Mark
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    The welded frame and 20mm diameter axles is probably overkill, but I had some used 6204 bearings from the bandsaw gearbox, so I thought I might as well use them in the wheels.
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    I have been kind of stuck, as I need to make a vibrator, but have a spindle problem on my lathe, so can't complete that job.
    http://madmodder.net/index.php/topic...html#msg132682

    I was out doing a casting session with a friend last week, and he lent me his concrete vibrator. Now I can concentrate of getting the hotface made.

    Following Richards advice, I will recycle the Kaowool from my little A5 furnace. I am roughly following Myfordboy's plan, but it will have about an inch of 1650c refractory as a hard face, followed by an inch of 1300 kaowool, then 2 inches of 1000 Calicum silicate.

    Mark
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    Made some progress on the lid yesterda. I welded brace on the sheet metal to spread the lifting hinge loads. (No photo). The hinge mechanism will be Myfordboys design.

    After that installed the CaSi insulation - A 50mm / 2" thick donut. Then the Kaowool from the old furnace lid was cut up and installed. A layer of plastic installed to keep the moisture in the hot face refractory. The Exhaust hole is a simple wood block planed to a rough cylinder, sealed with shellac and paint. A plastic container was cut up to provide some rigid plastic for the OD of the Hot face there. The plastic will burn out. The wood I'll just drill through a few times with a big Forstner drill to get rid of the bulk. The rest can burn out. The hot face will be about 20mm (3/4") thick on the lid, and 30mm/ 1 1/4" in the exhaust.

    Welded in some 6mm rebar to support the lid.

    Hope to cast this tonight.
    Mark
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    Quote Originally Posted by rotarysmp View Post
    The welded frame and 20mm diameter axles is probably overkill, but I had some used 6204 bearings from the bandsaw gearbox, so I thought I might as well use them in the wheels.
    Nah... I did the same. 1" welded square tubing and .75" steel axles that actually ride within oilite bushings. Something to keep in mind is a three point system for the base will stabilize itself on less than perfect terrain. A lot of people make the mistake of using four wheels. Even if you're parking it on a driveway or concrete pad the odds are it will be unstable and rock.


    Quote Originally Posted by rotarysmp View Post
    Following Richards advice, I will recycle the Kaowool from my little A5 furnace. I am roughly following Myfordboy's plan, but it will have about an inch of 1650c refractory as a hard face, followed by an inch of 1300 kaowool, then 2 inches of 1000 Calicum silicate.
    Reduce, reuse, recycle... When I did mine a couple of years ago I did the same with the hot face and kaowool dimensions. Little did I know back then that I'd be following in MyFord's yet to be travelled footsteps years later...lol. In hindsight I wish I had allowed for more insulation. I have no doubt the CS boards you are using will have the same effect as more koawool.

    Quote Originally Posted by rotarysmp View Post
    Welded in some 6mm rebar to support the lid.
    Do you not have any concerns regarding the steel rebar expanding during furnace use and busting up your refractory lid...? This is a well documented "whoops" on the forum. You may want to rethink that approach...

    On a different note... If you're going to use this thread to document the furnace build. You may want to consider renaming it. I honesty only opened it because I was bored and was curious what Calcium Silicate insulation was.

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    a coat of white paint and it could pass for r2d2's brother LOL
    A calm sea does not make a skilled sailor....

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    Thanks for pointing out the problem with Rebar used like that. I hadn't picked up on that problem. Easy enough to chop them back to a little stud on the outer ring, which should be enough to stop the hot face falling out.

    Can I change the title of the thread? If a Moderator reads this, please change it to "Build thread - Caclium silicate insulated copy of Myfordboy/J.Vilbert furnace.

    Mark

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