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Thread: Building my first furnace

  1. #1

    Building my first furnace

    It begins! Analysis paralysis overcome! (well...it's an ongoing battle) This thread will be mostly for my reference, and to keep J. Vibert at bay, but if you have any suggestions/thoughts, please feel free to post!

    Purpose: I would like to melt aluminum to make replacement parts for some old equipment, plus toys, plus designs/sculptures, plus etc. This is something I've wanted to do for a very long time. One day it'd be cool to do bronze, but that's probably not with this furnace.

    Precursory notes
    • Crucible is A10-sized, so the furnace will be built around that dimension
    • Heat is provided by propane & a GypsyTinkerer-provided Mako burner - dimensions will follow propane heatsource best practices
    • I would like this furnace to last, don't have a lot of garage time these days
    • I would like to learn a variety of metalworking skills, foundry work is part of it


    Dimensions
    • Hotface, 0.5" thick, 100% 3000F refractory cement
    • Insulatory layer, 2-3" thick, mix of refractory cement and foam pellets (from packaging I need to shave down)
    • Outer skin, probably sheet metal of some kind, if I can find some
    • Cart, welded steel, incorporated lid-lifting mechanism of some kind that I have no idea about and/or how to make it


    Building the forms - Hotface
    This has been a serious mental roadblock for me, took prayer and my wife's encouragement to get me to today.

    Started with a 5-gallon pail and cut it to the height I needed. Found an old sieve that had the magical inner diameter of 10" and cut it in half.
    furnace_build1.jpg
    furnace_build2.jpg

    Thennnnn...cut it in quarters and trimmed to get some more thickness at the bottom end. I believe this could be called 'drift stitching'. Or just zip ties.
    furnace_build3.jpg

    Building the forms - Insulation
    I KNEW keeping that old pool filter would pay off!! Haha. This above-ground pool filter has been in my attic after being rescued from someone's garbage a few years ago. Always intended to use it in conjunction with our rain tank, but babies. Now it has the magical outer diameter size I'm looking for and will form the outside of the insulatory layer.
    furnace_build4.jpg
    furnace_build5.jpg

    Crucible lifter/pourer
    This was actually the second thing I started working on. Also decided to do one more addition to this - a sliding collar that locks the tongs in place. Inspiration from here and from myfordboy's crucible lifter. Myfordboy inspired a lot of my interest in foundry work, actually.

    All of the metal in this is recycled. The obviously pipe part is old gas pipe, the other handle piece is two inner tierods welded together, heated/bent into shape. The rest is scrap I purchased from a friend's trailer fabrication shop. Oh, the handle is an old swaybar link, and the rubber from top part caught on fire from the weld heat. It was stinky and most likely carcinogenic.

    crucible_lifter1.jpg
    crucible_lifter2.JPG
    crucible_lifter3.JPG
    crucible_lifter4.JPG

    Ingot mould
    This was the first thing I worked on after the inspiration hit. I am pretty new to MIG welding, if you weren't sure. (120V, at that) Backup plan: I have a muffin tin if this really doesn't work out. It needs some serious bevelling/cleanup, and I'll probably just keep adding weld material to form soft edges.

    ingot_mould.jpg

    Next steps...
    • Figure out how to work the tuyere into the forms
    • Finish the hotface concrete forms & pour! Thinking I'll use a phone technician's drillbit to stir/vibrate the mix (it's ~18" long)
    • Start shaving down that foam
    • Re-research the foam:refractory ratio for the insulator layer

  2. #2
    This took a bit of a backseat due to baby#3. Also I wasn't really happy w. the forms.

    So yesterday I cut up the 50-gallon drum I bought 3 years ago! Then during cleaning promptly sliced my hand up on the freshly cut edges - a cheap lesson on rushing shop time!! Managed to get away without stitches.

    Today, back at it, going to get the drum cleaned up (edges and degreasing), and get the exhaust/tuyere holes cut. If I get those done, will start on the interior forms. Pics later!

  3. #3
    Senior Member caster's Avatar
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    Progress is always good! I stopped at two, I didn't have a third hand. Congratulations. I know I need to wear gloves when working with sheet metal but I don't always do. Glad you don't need stitches. The lifter looks pretty beefy make sure that you have enough clearance to easily manipulate the crucible with those lifters.

    Good luck,

    Caster

  4. #4
    Senior Member Toolshed's Avatar
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    Yeah, being the guy who spends too much time in the ER for.... lets see....
    Bandsaw cutting halfway through the tip of a finger
    Tablesaw taking off 1/4" of a tumbtip

    I'm happy to hear you got away without going there....

    I wish you luck on the "restart" here....take it easy and wind this thing up. ;-)
    "If you work with your hands, youíre a laborer.
    If you work with your hands and your mind, youíre a craftsman.
    If you work with your hands and your mind and your heart, youíre an artist."

    Saint Francis of Assisi

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  5. #5
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    Congrats at getting back at it Chris. My ever continuing efforts to learn how to make stuff with molten metal has taken a back seat to life. Life happens as they say...

    Looking forward to the pics.

  6. #6
    All good!
    furnace6.jpg

    The basics of a cart are taking shape...an old floor jack that I kept for some reason is disassembled, a new middle section welded up and attached. The exhaust hole cut in the lid as well. Plus I think I have an idea what the lifter mechanism will be.

    Some pictures in an order.
    furnace1.jpg
    furnace2.JPG
    furnace3.JPG
    furnace4.jpg
    furnace5.jpg
    furnace7.JPG
    furnace8.JPG
    furnace9.jpg

    Don't rush yer shop time!!!
    furnace10.JPG
    Last edited by chris.trotter; 10-23-2015 at 12:03 PM.

  7. #7
    Senior Member
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    I can't view any of your pics Chris

  8. #8
    same, shows invalid attachments.

  9. #9
    Try that...guess the attachments are per-session, not 'upload once'. My bad!

  10. #10
    Senior Member
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    Congrats on your progress, and on #3 Chris. It looks like you're making the most of your available shop time. I like your use of the cannibalized floor jack. I tend to overdo so take it for what it's worth: if you have a couple of extra lengths of that angle iron I would weld uprights from the unsupported corners of the frame to the jack sides. Your furnace will be heavy and the extra support will add rigidity as well as taking some of the load off your existing welds.
    Keep up the good work!

    Pete

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