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Thread: Planning stages for a new furnace

  1. #11
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    For crucible sizing I have been using this info from this data sheet on the Super Salamanders, I have found it very useful:
    http://www.allamericansupply.net/pdf...ANDERSUPER.pdf

    If I spent half a year building forms ... it would never get done.
    Burner will probably be one of the two commercially available waste oil siphon burners, just for ease and to reduce the dinking around (hopefully). The plan is to keep my eyes out for some tube or pipe, for the tuyere, at the scrap yard this weekend.

    Looking at MyfordBoy's blog yesterday, he has the dimensions for his furnace on there (I had not looked at the drawing before, I was not expecting it to be in inches :-) ). My measurements above are very close to his.

    OK so based on everyone's input, it looks like I have done enough base homework and am at least headed down a track to success. More questions and probably pics to follow.

  2. #12
    Hey Ed. Seriously give it some thought if you are going to have a drain hole or not. I cast one into mine for that possible crucible failure. But somehow, I end up with flames after a long run coming out that hole. I've stuffed it with aluminum foil and placed the plinth on top of it, but that eventually melts out. Then I end up with flames shooting out the bottom. Why it's doing this I have no idea. But I don't think I'd waste the time and effort doing another hole on the next build. :-/
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  3. #13
    Senior Member cactusdreams's Avatar
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    Quote Originally Posted by Mister ED View Post
    ...probably pics to follow.
    No probably allowed. Must have pics. Re. forms, I only had 2 rings to hold the inner tube open at the top and bottom. And a circle to cast the base, plus some long hose clamps and roof flashing. Seems most the people who use the cardboard tubes have sticking issues so be sure to deal with that. Cover it with plastic tarp or use smooth shiny plastic like myfordboy. The flashing sticks a little but not bad but I covered it anyway. Having your burner early in the game is good advice for laying things out and fitting. Some decent Salamander prices here. https://jetsinc.com/brands/Salamander.html
    People who say it cannot be done should not interrupt those who are doing it.

  4. #14
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    Quote Originally Posted by jagboy69 View Post
    Seriously give it some thought if you are going to have a drain hole or not.
    Awe nuts, this is way too much thinking just to build fire!!
    I was thinking to put a drain under the plinth, with cross channels to each side. Is that what you have jagboy? It almost sounds like it. Maybe I will forgo that, just makes things a bit easier.

  5. #15
    Senior Member caster's Avatar
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    HI Ed,

    Ditto with jagboy. When you pressurize the furnace (use a blower) hot exhaust and flames will go out of every hole in the furnace. I did a stupid thing and used urethane casters, they melted. I closed the drain and changed to metal casters. If you don't have a drain and your crucible breaks most likely you will get molten metal exiting via the tuyere/burner. Its unusual for a salamander to break, they do age and eventually need replacement, but you should at least give it some thought if it does.

    Good luck with the build,

    Caster

  6. #16
    Mister Ed. You described EXACTLY what I have on the floor of my furnace. I think the trick with tuyere placement is to have the bottom edge of it ABOVE the floor level. Say maybe half an inch or 3/4". I personally am about to Plug my drain hole with refractory cement. However, I will not be buying a bag of mizzou just to plug this stupid hole. Next melt I run, I'll tampon that sucker with some kaowool. In hindsight, for my oil burner, 3 1/2" wasnt a big enough exhaust hole at the top. Next time it's 4 or 5" as I can always close it down with a spare block of refractory laying around. Live and learn from others goof ups. It's CHEAPER!
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  7. #17
    Senior Member cactusdreams's Avatar
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    Here's my experience on drain holes. Put a 3/4" hole to the side of my flat floor which feeds directly into a 1" pipe that passes through the shell. It got put to the test twice, once from way too much degasser in a too full crucible which bubbled out about half its contents and once from good 'ol clumsy spilling. Clogged the drain both times. Had to use an acetylene torch to clear it out. In hindsight I could have poked it out at the time while it was still soft. Have since bored the hole in the floor to 1" and covered the bottom of the pipe with 2 layers of heavy duty Al foil and a wire clip to hold it or else some serious fire shoots out the bottom. Worked great on an intentional test spill. On higher temp metals I use 2 layers of heavy copper foil as the Al foil melts.
    People who say it cannot be done should not interrupt those who are doing it.

  8. #18
    Senior Member Tobho Mott's Avatar
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    A drain hole that is too small will clog rather than draining, and possibly lock a big furnace-bottom shaped ingot in place mechanically. This almost happened to me with my Gingery charcoal furnace due to way too much blower air torching a hole in my steel crucible; the pic below clearly shows the reason I went with a bigger (1.5") drain hole in the bottom of my oil furnace. Yes, fire shoots out of it when the furnace is running. No, stuffing a ball of aluminum foil in there does not stop the flames for long enough to melt a pot of aluminum. So I think of it as an automatic emergency muffin-ingot pan preheater in case of spills/failure. I don't know if that loss of flame is enough to keep me from melting iron (never tried it), but taking aluminum bronze up to pouring temps has been no problem, and the oil I've been using was free, so I am happy with that.



    If it had gone a cm or two farther up the tuyere, that creepy looking aluminum "tongue" would have been too long for the thing to be able to wiggle out of the tuyere, as the other end of it would have hit the far wall before it could pull out! I guess just enough of it dripped out in my case, otherwise I would have been looking at a pretty much complete furnace rebuild...

    I would not build without a drain, at least not if I ever planned to use steel crucibles. I don't anymore (much), but I also included a drain to keep the option of trying to melt larger chunks of metal directly.

    Which I have not tried.

    ...Yet.

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  9. #19
    Stuffing the hole with copper is a good idea, but i might try kaowool next melt.
    Visit me: WWW.HandcraftedLanterns.com
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  10. #20
    Senior Member cactusdreams's Avatar
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    I didn't describe it very well. In the beginning I stuffed a small, loose ball of Al foil up the drain pipe but that's what clogged up. Now I wrap it flat over the outer end, double layer. Same for Cu foil. I'd be curious to hear others' drain stories; what worked and what didn't when the damn broke.
    People who say it cannot be done should not interrupt those who are doing it.

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