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Thread: Scavengers new furnace build!!!

  1. #131
    Senior Member cactusdreams's Avatar
    Join Date
    Aug 2014
    Canoga Park, CA
    Yikes! That crucible in the 'after' picture looks mighty thin. How long can you keep using that one? Interesting how the slag builds up. Seeing everyone's new vs now furnace pics could be fun.
    People who say it cannot be done should not interrupt those who are doing it.

  2. #132
    Yeah the crucible looks thin, but you can chip off about an inch and it becomes quite serviceable. Only the top part of the rim gets fluxed away (slag being very corrosive). This is why you run your crucibles full. If you only fill the crucible to half you will flux away the middle part and that is when a crucible becomes dangerous.

    That particular crucible has about 20 melts on it, but after shortening it it will have another 10 before it needs to be shortened again. At that point it is okay to retire them. One pour pays for the crucible twice depending on what you pour into the molds.

    I got tired of being told what I can't do...

  3. #133
    Justin Some people just don't understand that melting iron is hard on crucibles and furnaces, your set up shows that things do not last forever. I see that you are still making mufflers, I know I made so many over the years.

  4. #134
    Moderator DavidF's Avatar
    Join Date
    Jan 2012
    Wilmington DE
    Ouch!! Yep, need to figure in the cost of furnace rebuilds and crucibles into the cost of production. !5 months seems like a pretty good service life to me, considering the number of melts you do.
    A calm sea does not make a skilled sailor...

  5. #135
    Thanks Ironsides, I am largely where I am thanks to your advice and videos! The mufflers are a good steady cash flow and I have never been able to catch up (hopefully the crane coming online will change that.)

    David, the crucibles cost 150 plus shipping of about 40. So $190 each. One pour yields between $200 and $300 of castings (finished value after machining), so in the big picture crucibles are a small consumable expense. I can squeeze about 30 melts out of a crucible before it is retired. The furnace cost about $600 to build, so 2 to 3 pours will pay for itself.

    On machining, when the iron is right (no chill) it cost virtually nothing to machine. I bought 2 new double sided triangle shaped inserts over last Christmas (2014) and have only now moved onto the last cutting edge. Most of the edges were broken off by my own misdirection. My NPT taps were bought used on Ebay and some have cut hundreds of holes. Even a dull tap will cut great threads with the power of the new lathe.

    Hardware for the mufflers only runs $2 or $3 dollars. I sell many of my mufflers for $50 to $110 each.

    Oil is cheap to free and the iron is also virtually free. For a few cases of water and a few flats of cokes I have dump truck brake drums delivered. My neighbor drops them over the fence and all I have to do is stack them for future use then break them down with a sledge hammer. I have about 40 brake drums at the moment and each weighs about 80 pounds. My neighbor is about to start changing oil in their fleet again so I will have a few hundred gallons of oil to pick up. With oil prices down, the days of people PAYING for used oil are done. Now they are charging to have it hauled away. I haul it for free!

    Then there is time. Time is hard to calculate, but if you are doing something you enjoy I suppose it does not matter as much. It keeps me out of trouble and in good physical shape. I could be spending the same time and money on a gym membership. I bet I have more endurance than most gym rats. Hell, the ironman competition ain't got nothing on me! I am a real ironman in the literal sense!

    I gross about $60 an hour when I am working on revenue projects with potential for more as I grow. The numbers are there, I just have to get everything working right!

    I got tired of being told what I can't do...

  6. #136
    Senior Member
    Join Date
    Mar 2014
    Charleston, West Virginia USA
    Holy Cow Justin!
    My jaw dropped open seeing the after picture of your furnace. I had no clue that the refractory would vitrify like that. That's some serious heat.

  7. #137
    Boy that was some build. I to have been working on a furnace like the one that SV Seeker has. Have talked with Doug a few times. He has been very helpful. Thanks for all of the information fellows.

  8. #138
    Senior Member 4cylndrfury's Avatar
    Join Date
    Jul 2009
    Cincinnati, Ohio, USA
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    Quote Originally Posted by indiscriminate scavenger View Post

  9. #139
    Join Date
    May 2012
    Justin's furnace sort of begs the question "Can a cover be used on the crucible".

    Morgan does make crucible covers, but I have never seen one used.

    A lot of iron is splatting out of the crucible and onto the furnace walls.

  10. #140
    Scavenger, I'm inspired by your last design to do my first foundry build much the same way but scaled down. Solid and rigid seems to be the best way to go using fire brick only and no ceramic blanket. A few questions: I take it those 2800 bricks were the hard bricks, not the soft ones right? And-- what size masonry blade was required to make the full miter cuts through those bricks? I'll have to buy a larger table saw than my portable Makita which accepts only 7 1/4" blade.

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