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Thread: Smaller Gingery-esq. foundry for beginner

  1. #1
    Senior Member r4z0r7o3's Avatar
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    Gingery-inspired split-body crucible foundry furance

    Update: It's no-longer "smaller" but still Gingery-inspired
    Another Update: Removed "Beginner" from title. I'm less of a beginner now, but don't recommend you attempt this project unless you're insane enough to read this entire thread
    It's finished: Jump past 346 posts, right to the end.


    Hey y'all,

    Brand-new back-yard forger, just finished Gingery's "Gas Fired Crucible Furnace" and was inspired by the body-lifting design. I'd like to start with charcoal + blower w/ #6-size "crucible" (iron pipe). However, I'd like the capability to eventually upgrade to a proper #8B graphite crucible and propane or used-oil fuel. My design is below w/ annotations (open up and ZOOM in):



    Before I get into building:

    • I left about 1.5-in gap all around for a #6 crucible (so 1-in for #8). Will that be big enough for charcoal firing the #6 size if it's raised up on a tall plinth block?
    • Also, will a 3/4" inner refractory wall (backed by 2" kaowool or similar), stand up to direct burning propane/oil/charcoal contact?
    • I'm right next to a refractory distributor for Vesuvius, Harbison Walker, and Thermal Ceramics. They happen to have "Cercast 2900" in stock @ $47.25 for a 55#, would that work for this design? (sorry I can't find datasheet)


    Thanks in advance,
    -Chris
    Last edited by r4z0r7o3; 02-01-2018 at 03:22 PM.
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  2. #2
    Senior Member caster's Avatar
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    Welcome aboard,

    I too was inspired by Gingery

    20150611_113715.jpg

    I had difficulties with the bearings riding up the side angle irons, I kept breaking the bearings (door rollers). I modified the design to incorporate a come-along lift mechanism, works well. I am glad you are starting with commercial refractory, I used diy refractory and had to reface a year later with commercial refractory. Aluminum melts at 1,200F, brass at 2,000F any castable refractory rated at 3,000F will work fine. I would suggest that you size your furnace based on your future needs for molten metal. If you think you need 2-4 lbs of aluminum today maybe you will need 10-15 in the not so distant future. I think 10" bore is good, it will give you plenty of room to grow. If you plan on using oil its good to have ~2" of clearance between the crucible and furnace wall. As to the hot face, usually its 1". Think about having to ram the refractory between two walls 3/4" apart, its doable but its easier to ram and remove voids / bubbles at 1". The refractory will need to cure, read the instructions, then it will be as hard as a rock and withstand anything your burner will throw at it. 2" of Kaowool is good, it will keep the outside of the furnace cool but more importantly it will keep the heat in the furnace.

    Good luck,

    Caster

    EDIT: If you plan on using a burner its best to build the tuyere as well. retrofitting a tuyere will not be easy.

  3. #3
    Senior Member r4z0r7o3's Avatar
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    Thanks. Based on my reading, it seems nearly everyone ends up building a larger foundry later Your point is sound, and it's cheaper to add in an extra inch here and there in CAD than after it's built.

    My intent is to traverse the road paved by Gingery, so the lathe will come next, once I have enough aluminium ingots and experience.

    I was wondering about the lifting mechanism, seemed a bit flimsy to rely on those angle iron's remaining angular. Ahh okay, I see what ya did there, good idea and safer too.

    For the frame, I'll need a mig-welder, and any excuse for a new tool is a worthy-cause in my book

    Should I be worried about casting the carriage-bolt heads into the lid's refractory causing stress-cracking as it dries or cures? Probably I should just go the tried-and-true way with woven-wire, what kind did you use?

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    Senior Member Tobho Mott's Avatar
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    I'd lose the steel between the hot face and insulation from the diagram. Otherwise, what Caster said, looks good.

    Good luck, post pictures!

    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.

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  5. #5
    Senior Member caster's Avatar
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    Commercial refractory will not crack when cast. It may once fired but hairline cracks can be ignored. You need support to hold the refractory in the lid, embed all you need in the lid. Run wires across like Gingery shows. Make a decent size vent hole +4". I casted my furnace as solid 3" insulating refractory, no Kaowool. This makes it heavy, heavier than the door rollers could support. I used skate bearing on the lift sled, I doubled them, 8 in total. Make sure you are comfortable with welding, you don't want the frame to break when your pouring. I am a novice welder. Ugly welds are OK, that's what angle grinders are for, but they must penetrate the metal to hold. You may want to add a drain hole as well. You never know when a spill or a crucible may break.

    Caster

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    Senior Member SolarFreak's Avatar
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    Quote Originally Posted by r4z0r7o3 View Post
    it's cheaper to add in an extra inch here and there in CAD than after it's built.
    I love my CAD software (BTW, what are you using?) but it's really easy to over do it... I can spend 30 minutes drawing, and what I've drawn takes 3 yearsand 7 Bazillion dollars to make...

    I agree with what Tobho Mott said - loose the metal. Although, out of curiosity, what was the though process that caused you to include it?

    Gingery got me hooked too...
    When all you have is a foundry, every problem looks like a casting.

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    Senior Member r4z0r7o3's Avatar
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    Question

    Quote Originally Posted by SolarFreak View Post
    I love my CAD software (BTW, what are you using?)
    I'm using VariCAD, made in the Czech-republic. It's a bit funky, buggy, and quirky but the price is fantastic, support is outstanding, and it runs on Linux (which I use exclusively). You can also sometimes (like when there's a debt-crisis) game the USD:EUR exchange-rate :wink: My fav. feature tho is "unbending", basically it will reverse-origami your shit into flat patterns that you can then roll/bend into shape.

    Quote Originally Posted by SolarFreak View Post
    but it's really easy to over do it... I can spend 30 minutes drawing, and what I've drawn takes 3 yearsand 7 Bazillion dollars to make...
    This is true, and I have to make an effort to avoid over-engineering. However, considering how much I'm getting paid for this ($0), I can leverage CAD-time to (hopefully) save in material costs and building time (i.e. some amount of woopsie prevention). Finally, it's much easier to share and discuss electronic designs, which means it can be improved based on community wisdom. To-wit, I plan to re-pay with the cutting plans and build-pix

    Quote Originally Posted by SolarFreak View Post
    I agree with what Tobho Mott said - loose the metal. Although, out of curiosity, what was the though process that caused you to include it?

    Gingery got me hooked too...
    Hrmmm, well w/o the inner-sheet, only the kaowool is left supporting the inner-core of refractory when the mid-section is lifted (see caster's pic above). So I was thinking the inner-sheet does three things:

    1. It provides loose 'anchoring' for the refractory w/o poking holes in it (only dimples from carriage bolt-heads).
    2. It prevents the carriage-bolts from rotating, giving reliable anchors for securing the external lifting-mechanism.
    3. It prevents the bolts from collapsing the outer-sheet by sheer/lever action when the mid-section is raised.


    In any case I will still be needing an inner-form, for the refractory but I suppose I could make it temporary if I embed the bolts into the refractory. The trouble there is, it makes mounting the outer skin onto the bolts much more difficult, I'll need to split the outer skin into sections otherwise it won't slide over them. Meh :S

    Another option is to do the reverse, and embed wing-nuts into the refractory, then screw into them from the outside-in. That would transfer more lifting forces to the refractory by sheer though, which smells dangerous. Also the shrinking/expanding will put the bolts out of alignment WRT the skin, which could lead to warping and worrying-noises as it heats up

    Yet a third idea is to add refractory "flanges" to the top and bottom (so cross-section would look like an ] [ ), and use the bottom one as the anchor-point for the outer skin. This would add to the aesthetics as well (lolz), providing nice clean smooth top/bottom surfaces while allowing for kaowool insulation around the mid-section. OTOH, casting that shape could prove difficult, but maybe there's a way by allowing some of the forms to burn-off during firing. I'll draw it up, lessee whatchall think...

  8. #8
    Senior Member caster's Avatar
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    You will need to consider how the top and bottom sections fit together. I started using an oil burner with a blower, it seems that some of the oil is pushed between the sections and seeps out as smoke. This must have happened with the propane burner as well but the exhaust was clear and was not visible. I am trying to make the seams air (oil) tight. My first approach is to have them mate perfectly flat. If that does not work then I will slope the mating surfaces, I don't think that the oil will travel up hill. Think about this problem and share your solution.

    20150712_112735.jpg

    Caster

    p.s. Linux huh, next your going to say that you are a master of sed, awk and regular expressions too.

  9. #9
    Senior Member r4z0r7o3's Avatar
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    Quote Originally Posted by caster View Post
    You will need to consider how the top and bottom sections fit together.
    Yes, this could be tricky. Though nothing some burn-out forms can't solve (I think). Also, by embedding wing-nuts as anchors, I can attach the skin with bolts from the outside-in. That will leave access to add the Kaowool after curing and re-install the outer skin.

    Quote Originally Posted by caster View Post
    I started using an oil burner with a blower, it seems that some of the oil is pushed between the sections and seeps out as smoke. This must have happened with the propane burner as well but the exhaust was clear and was not visible. I am trying to make the seams air (oil) tight. My first approach is to have them mate perfectly flat. If that does not work then I will slope the mating surfaces, I don't think that the oil will travel up hill. Think about this problem and share your solution.

    20150712_112735.jpg
    Hmmm, okay, good-to-know. So that's from oil/smoke leaking due to back-pressure, between the blower-pipe and (slightly shrunken) refractory opening inside?

    Yes this would be dangerous if it built-up inside the kaowool, that could make a kaboom. I read that those are to be avoided. I'll bet this is a problem also solved by big foundries, boilers, burners...there must be an answer out there...

    Quote Originally Posted by caster View Post
    p.s. Linux huh, next your going to say that you are a master of sed, awk and regular expressions too.
    Oh man, don't get me started, yes I grok those, along with cat and tac among many others. I've held an RHCA for the past 7 years if that means anything.

  10. #10
    Senior Member r4z0r7o3's Avatar
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    Wink More beef, more fat, it's what's for dinner.

    Color Legend:
    • Gray: Sheet Metal
    • Yellow/Green: Kaowool (or similar)
    • Orange/Brown: Refractory
    • Red: Threads




    Updated drawing:
    • Increased blower-hole diameter to 2-in (I read on Lionel page that he thought 3-in was too big)
    • Increased drain & vent hole to 3-in.
    • Added sheet-metal top to protect (somewhat) the lid's Kaowool.
    • Removed inner sheet-metal, it's now on the far-right now as a temporary form.
    • Flipped all the bolts around, moved to the bottom of each section.
    • The square-nuts molded into the refractory are really wing-nuts, (didn't have one in my library).
    • Fixed some diameter calculations, Refractory walls and Kaowool are now really 1-in and 2-in (respectively).
    • Inside diameter is now 8.5-in which will comfortably accommodate a #10 crucible (6-1/4")
    • When closed up, inside height is 15-in, just shy of double a #10 crucible height (plenty of charcoal + plinth room)


    To mold the nuts/bolts into the refractory, I'll first cover the exposed threads with some electrical tape. Inserting bolts/nuts into the form as I ram the refractory up to their level. The flanges will be formed by a combination of a temporary inner sheet-metal secured "round" by two plywood circles (on the outside). I'll further connect the two plywood circles together with some dowling to not distort the form when ramming the top flange. Finally, I'll loosen the bolts a little to allow for the refractory to move/shrink. This way, after fired (in theory) the plywood will all burn off, I'll be able to un-bolt then access and remove the inner sheet-metal form. Then I can install the kaowool, re-install the outer sheet-metal skin and the bolts. The bolts will be covered with vaporized electrical tape, but I think this shouldn't be much trouble to clean (or I'll just replace the bolts).

    Sound / look good?

    If so, I'll get on to the "unbending" and post up plans before starting on the forms.
    Last edited by r4z0r7o3; 02-29-2016 at 02:53 PM.
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

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