Kang

Kang's Kreations - Molten Metal Madness

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Never really checked out this section much before, but it seems like a good place to put some pictures of the stuff I've been working on over the past few years. I'll start with the very beginning of my molten metal obsession which began 3 years ago during the 13th annual "Boys' Camping Weekend". Every year we try to have some sort of unusual and memorable activity planned. That year, it was seeing if we could get aluminum to melt in our campfire. Someone brought a crucible from the internet. Someone else brought a novelty ice cube tray. Yet another guy somehow got totally hooked on this molten metal stuff, and that someone would be me. Aaaand yet another someone brought his video camera AKA phone:

 

https://vimeo.com/75917079

 

So that was it for me, I dove in headfirst and haven't really surfaced since, from the strange world of backyard metal casting.

 

So, you see those ugly little skullules in the video? Pretty cool, but definitely hideous and not as intended, right?

 

I just got back from Boys' Camping Weekend #16. Oh, how far I have come in 3 years! I brought a homemade bronze axe with me this year, so I could field-test it right back where it all started, by using it to cut wood to feed the very same fire that was responsible for its creation.

 

First some background on the bronze axe though. I was inspired to make it by George R. R. Martin's world of Westeros, where in ancient times the First Men crossed the Narrow Sea wielding bronze weapons to make war on the Children of the Forest. I don't know much about axes, but I did some googling to come up with a cool looking shape that would be believable as a battle axe yet still useful for chopping wood, which I am more likely to find myself doing. Then I made a wooden pattern to use in making the sand mold needed to cast it. Here are the two halves of the "split pattern" - each part goes in one half of the mold to form the mold cavity, then they patten is drawn out of the mold, the mold is closed, and metal gets poured in:

 

image.jpg1_zpsjesuytxp.jpg

 

Here is the mold just after I poured in the bronze:

 

IMG_20160910_150008547_zpsxtams40c.jpg

(See? The mold is literally a 'sandbox', so I know I'm in the right section...)

 

Here is the raw casting just after I shook out the mold. This side of the casting was in the cope, which is what we call the top half of the mold though I am not sure why. You can see the gating and 2 risers and the sprue here as well as the axe blade. Note the shrinkage on top of those risers. That is their function, to feed their own molten metal into the cast part, to compensate for the shrink that would otherwise occur on the casting itself. They will be remelted when I pour my next bronze casting:

 

IMG_20160910_160821904_zpssvgywap1.jpg

 

Drag (bottom half of the mold) side. You can see the remains of the hardened sand core I had to insert into the mold to create the hollow "eye" where a handle wiould later be fitted. I used sodium silicate (AKA waterglass) based woodstove gasket cement to bind the core, then catalyzed the hardening reaction by baking it in my oven on low for 15 minutes. The core was made in a small plaster mold I made from the core prints on the pattern before they got attached to it, which is visible above. Note, there is a visible screwdriver shaft-thick vent through the core in this pic, to allow gases to escape the mold

 

IMG_20160910_160913291_zpsw1dkcauu.jpg

 

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Here is a big ingot I poured with the leftover bronze, to be remelted next time along with the risers, sprue, and gating from this casting.

 

IMG_20160910_145951855_zpsnljj5tjg.jpg

 

And here is it pretty much finished up. I put a sledge hammer handle from the hardware store on it because otherwise it would not have been ready for this year's camping weekend, but I did come home with a nice piece of hickory from our campsite that I'll use to make a new handle, now that I have had a chance to field-test the axe. I also ground off the flashing around the parting line and sanded the blade a little shinier than how it came out of the sand. There is a lot more sanding to do before it has a golden mirror-finish, but in terms of usefulness, it is all finshed up here in this pic. The edges were hardened by hammering on them. Bronze does not need to be heated up like steel for this sort of forging, and most bronzes are not hardened by heat treatment.

 

IMG_20160911_221512743_zps33vqgivk.jpg

 

Now. So far I have been discussing this like I used traditional bronze-age bronze - alloys of copper and tin. But the fact is, nowadays "bronze" refers to many different alloys of copper. The alloy I chose for making blades is aluminum bronze, AKA alloy C95400 (which in fact CAN be hardened by heat treatment, though I am not equipped for that). The aluminum bronzes are the toughest of the copper alloys, so they should make the most durable bronze blades, which should be able to hold their edges. Here's where the campsite field test comes in...

 

Our usual campsite is surrounded by a forst of hickory and oak and maple (and the lake), so basically a lot of hardwood. We prefer to burn the fallen hickory logs, because the smoke smells nice, but mostly because one of those hickory logs burns hot (hot enough to melt aluminum, see video clip above) and burns all night long. I knew I wanted to use a big dry super hard thigh-thick hickory log to test the edges on my super hard (for a bronze) axe, so that is exactly what I did when we found on that size leaning dead against a couple other trees (rather than green and growing or rotting on the ground).

 

IMG_20160916_195045131_zpsqr47ipka.jpg

 

IMG_20160917_130812361_zpsarn3viqw.jpg

 

I'm not saying it was easy going, or even easier than using our camp saw... But the camp saw is also easier than using a store-bought forged steel axe, and what really matters here is that the First Men bronze axe works, and it held its edges! Both blades were used, and both came through it completely undamaged; the edges are as straight and sharp as when we began chopping ("we" because we took turns), no visible shiny spots or bumps or nicks can be seen or felt.

 

I call that a 100% success, and I call this the greatest thing I have made in my backyard foundry so far, by far.

 

Here are a few gratuitous fire shots of the burning test log keeping our campfire burning hot all night long:

 

IMG_20160917_144752937_zpsha3w6aeg.jpg

 

IMG_20160917_244229830_zpswn7oysf0.jpg

 

So that is my latest creation. I have posted my cast aluminum weirwood tree here somewhere before and I think my little rabbit-robots. I'll try to link those here if I can find those older posts. Otherwise, let me know if you guys want to see more and I can dig up some more pix of my castings. Spoiler warning: mostly it is a lot of aluminum skulls. Or you could try googling "Ghost Vines Band". It's not my band, it's one of my camping buddies, and I just learned he's wearing one of my skull belt buckles in one of their promo pix which I had no trouble finding. But I also have pictures of all the foundry equipment I've built over the last 3 years, everything from my oil-fired melting furnace (Balerion the Black Dread) to Big Bucket Mull the sand mixing machine to my cast aluminum sand rammer (King Robert's Rammer) to Lightbringer, my homemade waste oil burner, and on and on. So it's not ALL metal skulls

 

Not bad for some crazy Canadian computer programmer tinkering in his shed for kicks, eh? I even got an "order" for another bronze axe from one of the guys I camp with, which is a huge step for me. This has always been just a hobby, but this opportunity will allow me to try and make an even better axe without having to pay for the bronze myself. Who knows, maybe someday I'll be able to make my casting hobby start paying its own way in the world instead of costing me money...

 

Kang

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This is a WICKED COOL post!  Thanks for showing this process.

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Thanks! It is a really fun hobby but not one to be taken up without doing your homework first, there are some dangers involved, obviously...

 

I just got permission to share that band photo I mentioned. Not my photography, but it is my skull shaped belt buckle. Wearing one like it right now...

 

IMG_7684_zpsaftalcq4.jpg

 

Mine is similar, but they are each unique and a little different since a new pattern had to be carved off a Halloween styrofoam skull decoration for each one I've made. Lost foam casting is great for one-offs, but sand casting is a better way to make more than one of something due to the reusable patterns.

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Close up of another angle on the belt buckle skulls in a few stages of construction...

 

image_zpspxinzoy9.jpeg

 

image_zpswskc2duo.jpeg

 

IMG_0439_zps71f8252f.jpg

 

Kang

Edited by Kang
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In case nobody noticed, I edited in some WiP pix for the skull belt buckles in the previous post. Hope you like them or at least find some inspiration there...

Here's how I made King Robert's Rammer, yet another component of my foundry that is named after characters or arifacts from A Song of Ice and Fire.

This was the first time I used a "real" crucible. It is possible to use a welded steel pipe crucible for casting aluminum if you are not too concerned about alloy purity and you have thick enough steel that you aren't worried about it deteriorating within one melt, and that is what I have been doing up until this casting. I had been given a #12 Silicon Carbide bonded crucible as a Christmas gift.

image.jpg1_zpswgx2jaio.jpg

I had been saving it for bronze casting, but since by this time I had already decided on using aluminum bronze, I figured using it for aluminum just this once would not contaminate it too badly. Real crucibles need tempering before they get used. In the case of SiC crucibles, this is to set the glaze properly. So the night before I cast the rammer, I had to light up the furnace and bring the crucible up to red heat, then allow it to cool before using it for melting.

IMG_1266_zpsewnvc3tb.jpg

Here is the hot crucible being held by the lifting tongs I made. I don't exactly recall why I pulled it from the furnace at this point instead of allowing it to cool slowly inside the furnace. Might have just been for the photo op, my son wanted to take a pic if I recall...:

IMG_1257_zpsirn4dndv.jpg

So that is my crucible. I guess a better pic of the lifting tongs and pouring shank I made are in order here... I got a small (possibly the smallest at 80 Amps max, and it was definitely on sale) fluxcore welding machine not long before so I could make these. I had learned a little bit about how to use it from my friend's brother in law when I was building Balerion (AKA the Black Dread, my big furnace that runs on free waste oil) last year, but I didn't want to show up at his place begging to use his machine again, and in this hobby it is going come in handy now and again anyhow...

Tongs open:

image.jpg1_zps8p9jqbsv.jpg

Tongs closed:

image.jpg2_zpsve8gnvqy.jpg

Pouring shank with crucible holder in place (to keep it from falling out during a pour):

image.jpg1_zpszhz0ramg.jpg


On to actually casting King Robert's Rammer!

Unfinished pattern (still needs paint and a slick coat or two of shellack to help it draw from the mold, see pic of axe pattern above where the finished rammer pattern is also visible):

RammerPattern_zpst2cpsq4o.jpg

Molding equipment: 2-part flask (cope and drag), molding board, a sieve for facing the pattern with fine molding sand, pattern halves, improvised rammer block, forms for sprue and riser, spoon for cutting gating, bucket o'greensand.

IMG_1271_zps8r5korpm.jpg

Half of pattern positioned in the inverted drag on the molding board, parting dust added so the mold halves won't stick together:

IMG_1272_zps2rsr0k43.jpg

Greensand sifted over the pattern-half in the drag through the sieve to provide fine facing sand for a smooth finish:

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Drag rammed up with hard-packed greensand using the improvised rammer, the excess molding sand struck off to leave the surface flat and even with the flask half:

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Drag rolled over so it's top side up:

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Cope added, second half of pattern added, parting dust added:

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Sprue and riser forms added. The sprue is the narrower one:

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Cope rammed up and struck off, riser and sprue forms removed:

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Mold re-opened, gating cut into drag using a spoon:

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Mold just poured (not shown: drawing out the pattern before closing it back up, cutting the top of the sprue into a funnel shape to aid in pouring)

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Leftovers pigged out into ingots (also shown is the blower for providing combustion air into my furnace - a bucket-sized shop vac):

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The shakeout:

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Casting next to pattern, cleaned up a little and ready to ram up a bronze axe mold:

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For this one, my greensand was a little on the dry side after sitting in 5-gallon buckets for a year. apparently those things aren't quite airtight. Afterwards, it was just too dry to use anymore, so I had to build a sand muller to refresh it. I could have done it by hand, but I have never built a machine before, so that sounded like a more fun idea by far! More on the Big Bucket in a future post.

Kang

Edited by Kang
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Building "Big Bucket Mull", my greensand muller:

A friend of mine stored his apartment-sized washer/dryer combo machine in my back shed for a decade when he moved into a house, so I had asked him if I could scavenge it for parts, such as a motor and gearbox. clearly, he said yes, hence the Big Bucket being alive... A muller smashes and smooshes the sand to break up clumps, mix in ingredients and added moisture fully, and ensure that each grain of sand is wearing a thin coat of clay so that molds stay rammed up. At this point Big Bucket Mull is really just a mixer, but since my sand grains already had their clay coating, a mixer was good enough to get my and back into shape. I'll need to finish upgrading it when I want to make some more greensand (though I bought the sand I have now), at which point the big heavy barbell weight wheels will hopefully actually roll over the sand to provide the mulling action. This means lowering the hanging assembly, which means trimming off the bottom of the plows ans scrapers so they won't be quite touching the bottom of the spinning drum. Right now the 100lbs (2 buckets) of green sand I have is enough to ram up about 2 molds in the flask I used to cast the axe head and the rammer, with a little left over. so Big Bucket Mull is gonna come in pretty handy in my foundry once I get him working a little better. He is also running too fast, I have my eyes open for a gearbox with greater reduction, which will be nice since a bit more torque will also be needed when the wheels start rolling and providing more resistance instead of just hanging there...

First test run (FAIL, duration 2:09):



First more or les ssuccessful test run (though I ran out of water of course, duration 4:08):



Here's a pic of his seamy underbelly that isn't shown in the videos, which are admittedly terribly badly shot:

IMG_20160808_201637955_zps6qefuex9.jpg

Kang Edited by Kang
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Before the rammer and muller was my oil furnace build. I built The Black Dread to replace / supplement the charcoal furnace I had built before. Oil fired furnaces get hotter, faster than charcoal furnaces, plus they don't make a big mess of ashes that needs to be cleaned out of the bottom of the furnace every so often, etc. The Black dread also has a 12" bore, compared to the old furnace's 8", so greater melt/pour capacity was also a goal.

Here's the old charcoal furnace in action, for the record:

Melt%201%20bigpic%20004_zpsscdjx3dj.jpg

And here are the lost foam casting patterns for the first castings I poured using the new furnace (minus a couple small lost foam skull patterns:

SnowflakeSprues_zpszr7tktzp.jpg

Video of the first pour in that session, AKA first pour of metal melted by Balerion's fiery fires:



The molds, just after pouring the last one:

NewFurnace_First2Pours_zps3iqqsuuh.jpg

The castings that resulted (and off to the right, the cut-off sprues):

NewFurnace_Castings_First2Pours_zps7dt14


Kang Edited by Kang
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What do you guys want to see next?

1) oil furnace build
2) more lost foam castings (skulls mostly, a few fails included)
3) bulk scrap melter with quench bucket (for making cast aluminum car wheels into small enough lumps to fit in a crucible)
4) q&a about the preceding posts
5) enough already, Kang is crazy, we get it
6) anthill castings
7) something else?

Kang

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Hmmm... Sounds like an overwhelming vote for option 5 so far, but I'm not so easily put off.

 

Here's #3 instead, quick and dirty, just the way you like it...

 

Here is my bulk scrap melter for processing large castings into small lumps that can fit in the crucible. This one was easy to build, I just had to cut and weld a stand out of bedframe rails and add a coarse grate, then stand a 55-gallon drum with both ends removed on top. The drum gets halfway filled with firewood (hardwood is best), then there's room for 3 car wheels on top. Aluminum car wheels (A356) are some of the best scrap to use for general purpose aluminum casting. The chromed ones can add some minor contamination, but you'd need to do spectroanalysis to tell the difference unless there was a lot more of it. For a backyard hobbyist like me who isn't trying to build moon rockets, this is negligible. The bottom third of another drum goes underneath, filled with water so the drips of molten metal freeze before they can fuse back together. More cold water needs to keep on being added or it will start to boil and the lumps start sticking together.

 

Lighting up the Beast (it's only smokey like that for a minute while it is getting going). the drum still had some of the grease it originally contained coating the inside of it; I save that and used it to get the fire going. One sheet of paper towel with grease wiped onto it was all it took:

 

BeastScrapper_Lighting_zpstelocp6v.jpg

 

Burning merrily, one of my favourite pix from my foundry:

 

BeastScrapper_Burnination_zpsmtf1sfuh.jp

 

Short clip showing the dripping aluminum, the drips sound really cool when they hit the water.

 

 

Here's a pic of the stand after those 3 wheels were all melted down. You can see that the stuff that froze to the grate was mostly on one side. That is because I did not put any feet on the stand's legs - it wants to sink into the ground, especially once a lot of water has spilled there. One day I'll add some feet so it can stay level when I use it, which isn't often. The darn thing actually toppled over on me one time when I tried to process 4 wheels - the one on the bottom of the stack got hot first and broke into pieces, so the ones on top shifted, and the whole works lost its balance and I had to jump out of the way pretty quick and pull the hose out of the way so it didn’t get melted before I could put out the fire. So yeah, 3 wheels only, and it needs some more stability via feet and maybe some diagonal braces up higher to secure the drum... Still, this beats the heck out of using a hacksaw or even a reciprocating saw with metal demolition blade, fun as those are for taking wheels apart. Some people have specialty blades on a table saw for chopping up wheels, but that method scares the heck out of me. And it is more expensive, especially if you don't have a table saw...

 

scrappinator%202_zpsv4lqzyzp.jpg

 

Underside of the stand. Those stalactites are razor sharp and love to draw blood! I spent an hour or so with hammer and angle grinder removing this mess so I could melt it to pour castings later:

 

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Here are the easiest lumps to separate out of the bucket after all is said and done:

 

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Here's the rest, mixed in with a bunch of mushy charcoal and ashes:

 

scrappinator%201_zpsqlqs7kby.jpg

 

And here is all 3 wheels' worth, from a different run (in the green water bottle buckets, plus one big lump that still shows some of its former wheelness):

 

image.jpg1_zpsmgipazyt.jpg

 

Also some sprue cutoffs, a bread pan ingot, a failed plaque casting, and the results of a crucible failure in my old charcoal furnace, which I have saved as a curiosity and a reminder.

 

Kang

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Building Balerion, the Black Dread: Step 1

Fabricating the furnace’s outer shell and the cart to wheel it around on:


Making brackets for the hinge that opens the lid - one short one shown here to attach to the lid, also one that's longer to attach to the furnace body:

Lid_Hinge_Bracket_zpsrztx9hte.jpg

Welding them to the barrel so they line up was easy - I just put one edge of the brackets aganst the seam that goes down the side of the drum. Attaching the hinges themselves to the edge-corners of the brackets was trickier; I had to get creative:

hinge_welding_setup_zpscog4oeum.jpg

Stainless steel "rebar" tacked to the inside of the lid, plus drain hole in the furnace floor:

Rebar_zpsay5uss9y.jpg

Test fitting the hinge pin, plus legs added (with feet for bolting it to its cart). Hinge pin needs trimming from the bottom so the flange up high sits just below the lid hinge bracket - a pedal on the cart will raise the pin so the flange lifts the lid by its hinge bracket:

Furnace_So_Far_zpsatcntyv7.jpg

Completed shell installed on completed cart. I made the cart ouf of some square tubing, sheet metal salvaged from our old oven's under-drawer, wheels from a lawn care machine called a "chipper vac" that I found in my back shed of mystery goodies:

Furnace_View_zpszzry1nru.jpg

Pedal works to lift up the lid just enough that it can be swung to the side without scraping the top of the furnace. Pedal cam:

Furnace_Pedal_zpscfkxnd1i.jpg

Lid goes up:

Lid_Up_zpsamr1e7hj.jpg

Lid goes down:

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Lid wide open:

Lid_Open_zpss0qxckg8.jpg

My first time welding, what fun!

Next step: Installing the furnace floor...

Kang

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Building Balerion, the Black Dread: Step 2

Installing the furnace floor


Shaped a half dozen 2300F-rated insulating firebricks (IFB's) to fill most of the bottom of the drum, yet making sure to leave gaps around the outside edge and around the drain hole. Castable refractory will be installed ("poured") to fill those gaps and form the actual floor of the furnace bore, while locking the firebrick subfloor in place. Unlike the dense firebrick you may have seen at the hardware store for repairing wood stoves, IFB's are very light and fragile, and really easy to cut or sand to a desired shape.

Floor_6Bricks_zps5axlsled.jpg

Built a form for the drain hole. The blue "fingers" will form channels that slope downwards slightly toward the drain. This will allow spilled molten metal to get underneath the plinth the crucible stands on so it can reach the drain in the center.

drain_form_1_zpsa10kwiyq.jpg

Castable refractory is sort of like concrete, but it is chemically different so that it can take high temperatures that would make portland-cement-based concrete explode, then begin to melt. The stuff I used is rated to 3200F, them's cast iron temps!  You mix it a lot less wet than concrete though. So saying that you actually "pour" it is a bit misleading. More like scooping it into place. I built a vibration tool to help settle it into place and debubble it. As dry as a mix as it is, it is amazing how much moisture comes to the surface when you start vibrating it! Like, actual drops of water splashing up out of the thick mortar-like mix. It's strange, I wish I had some video of that. Anyhow, here is my vibration tool (mark 1):

Vibro_Refracto_zps9sgdtemb.jpg

Dad's old sander sure didn't appreciate that kind of rough treatment - the vibration "wand" worked perfectly, but the sander shook itself to pieces by the time the floor was poured. I'm still hunting for one of its screws... But here is the finished floor after I did my best to pull the drain form from the refractory after it had set up. the wooden "fingers" pulled just fine, but the brass tube... Would. Not. Budge. you can see in the pic that I tried, but it was basically glued in there. I forgot to grease it before pouring the floor. I would not get that brass tube out until much later in the build.

furnacefloor_zps6bzhmtlr.jpg


Next post: building the lid


Kang

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Building Balerion, the Black Dread: Step 3

Building The Lid


First, tools and formwork:

I cast the bottom half of the lid against an old "Krazy Karpet" sled, since it was wide enough and designed to be smooth and non-sticky. the refractory would need to be "poured" to a level above the "rebar" and above the barrel rib that would lock it in place so it couldn't just fall out of the lid. But it needed a vent hole in the middle for the furnace exhaust, a wall of castable refractory surrounding the vent, another wall of castable around the outer edge, and a 2" deep recess in between those little walls. The lid took pretty much a whole 50lb bag of refractory, and I had a much better time mixing it appropriately dry this time.

Refractory Vibration Tool Mk II was based on my reciprocating saw. I took the original "wand" and filed the back end of it to match the shape of a recip. saw blade, then just installed it in the saw like any other blade. I can’t believe how perfectly this worked! Saw is still in good working order too, no missing fasteners...

Tobho_s_RefractoryVibratorTool_Detail_zp

Tobho_s_RefractoryVibratorTool_zpsy3tfxs

Forming the vent

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Styrofoam doughnut to form the recess

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Then, the pour:

Improvised hold-downs to keep the doughnut from floating out of position during the pour:

image3_zps6xsdxxs2.jpg

Hold-downs removed after the refractory set up

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Foam doughnut removed (ripped out)

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Vent hole with form removed

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Underside of lid

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Doughnut made of two 1" layers of 2600F-rated ceramic fiber blanket insulation (just one layer shown in this pic)

LidInsulatingDonut_zpslnhjwdp6.jpg

First doughnut layer installed

LidHalfInsulated_zpsozvvutm0.jpg

Note the turnbuckles attached to the hinge. They will help support the weight of the lid when it is not closed and lowered onto the rim of the furnace body.

Ceramic fiber insulation covered, to keep those fibers from going airborne - they are a respiratory hazard.  The cover also makes a nice place to put scrap to preheat before going into the crucible. The cover is supported by the little walls of castable refractory protruding into the upper half of the lid, and was made from one end of another used oil drum.

image.jpg1_zps4yqzvmrf.jpg


Next post: Lining the furnace's main body


Kang

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Building Balerion, the Black Dread: Step 4

Lining the Furnace's Main Body



3 forms were needed to cast the refractory "hot face" - one for the outside of the 1"-thick wall, one for the inside of the wall, and one for the tuyere (the hole the burner gets inserted into so it can blast flames into the furnace). Another member of the Alloy Avenue forums who has access to CAD software was kind enough to post some printable customized templates based on the diameters of my forms and outer shell and tuyere form so that I could cut out the holes for the tuyere. They aren't quite just circles, because the tuyere has to enter the furnace at a tangent to the inside surface of the hot face wall - this promotes a swirl of flames surrounding the crucible, so each hole (one in the outer shell, one more in each of the hot face forms). The one in the outer shell is the most round, but as the holes are located farther and farther toward the center of the furnace, they get more teardrop shaped - that way the piece of pipe used to form the tuyere fits snug through the holes in the increasingly curved surfaces.

Tuyere%20_Templates_zpsgwgwtfib.jpg

(that is not the actual form I used for the outermost form (the metal one) - I decided there was not going to be any way to remove that one after casting the hot face, so I switched it out for a length or rolled up aluminum flashing secured with some metallic tape.)

Here you can see how the holes appear round from the angle the tuyere comes in at, once the forms are in place.  Also that I have ground off the blue paint.  It would be replaced with a layer of high-temp BBQ paint during this step as well.  Black, natch.

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I wrapped the innermost form (the 12" sono tube) with cling-wrap to help it pull out later, also to help it not get soggy - those cardboard tubes are meant for casting concrete, but they are only waxed on the inside, and not intended to have the concrete poured around their exterior. I would also backfill the furnace bore with sand before pouring the hot face, so that there would be no risk of the cardboard form collapsing (this has happened to others). The outer form (the 14" roll of aluminum flashing) got greased on the inside to help it get removed later - at this point, that brass tube I used to form the drain hole is still glued in place...

Because the outer form was taped into a ring shape and not originally built that way, it wanted to go teardrop shaped. My solution to that, and to getting the form centered inside the shell, was to cut a bunch of 2" wide styrofoam spacers. Once those were wedged into place, the form naturally became round and centered in place. The spacers were squishy enough to allow for slight mis-measurement and still have the form end up centered.  After that the inner form was easy to position by just eyeballing it. That left a 1" gap between the forms, which is where the castable refractory would go. Just a matter of positioning the forms so that the tuyere hoes lined up as seen above, inserting the tuyere form, and plugging the inside end of the tuyere form and the drain to keep the sand backfill from leaking out.

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Then I mixed up several small batches of refractory and vibrated them into the gap. It worked great, hardly any bubbles remained, no gaps underneath the tuyere where it was hard to get the vibration wand into, etc. I filled it up pretty close to the upper rim of the furnace shell.

Just-cast hot face, set up just enough to remove the foam spacers.

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Removing the forms

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Next post: The name tag


Kang

Edited by Kang
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Building Balerion, the Black Dread: Step 5

The Name Tag



Cut the pattern out of some of that 2" thick insulation extruded ploystyrene foam AKA XPS styrofoam. It's much easier to work with than the white beaded expanded polystyrene EPS styrofoam like you see in packaging materials, due to the lack of that beady grain.

I matched the back side of the pattern to the curve of the barrel by slappingsome sandpaper on the outside of it and rubbing the foam on that to shape it, seemed to work pretty well. The letters were printed out, glued to the styrofoam, carved out with my dremel w/router attachment (cutting bits, not grinding bits - the grinding stone attachments heat up the foam too much, it melts and sticks to the stone, then freezes as hard plastic that messes up the profile of the bit, which does not get noticed until the smooth surface you were trying to carve gets all wobbly. Ask me how I know...)

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The big blocky risers I used were probably overkill, I was worrying about shrinkage due to the fact that the middle of the casting is thinner than the edges. Note the bolts embedded in the foam. They are now embedded in the cast aluminum name tag, where they serve to hold the tag to the side of my furnace.

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Not a perfect casting, but it would be getting a coat of paint anyhow...

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Success! You can see it installed upthread somewhere, I'm sure. Here it is all painted up (using RMS paints of course). It was much easier to install now, before the insulation get stuffed into the 2" gap on the outside of the hot face.  There never really was any choice about what colours it should be...

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Next post: Insulation and finishing touches on the main furnace body


Kang

Edited by Kang
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Building Balerion, the Black Dread: Step 6

Insulation and Finishing Touches



All that was left at this point was to install the ceramic fiber blanket insulation in the 2" gap between the outside of the hot face and the inside of the steel drum, then add a bt more castable refractory to cap off the insulation and give the lid a wider surface to rest on.

Cutting out two 1" thick strips of the ceramic blanket

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I wrapped the blanket strips around the hot face. This was more difficult than it sounds, it was a snug fit and my hands don't fit too far down into that gap. but I fiddled around with it for a while and eventually got the insulation slid into place. Then I cut some strips off of a sheet of 1/4" compressed fiber blanket which is normally used for making gaskets for furnace lids to sit on when they don't seal properly otherwise, or for lining the inside of the shell for furnaces that are built as a solid monolithic hot face with no insulation. Compressed like this, it's not so great at actually insulating anything. I used the strips to lay down on top of the layers of blanket, since being compressed hopefully meant they would not wick away as much moisture from the castable I would install in the top inch or two of the gap.

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Then one last small batch of refractory vibrated into the top of the remaining gap to cover the ceramic fiber - again, it's not good to leave that stuff exposed due to the respiratory hazard the fibers pose.

I laid out my old Krazy Karpet sled on top of the wet refractory, then I sat the lid on top of that. the idea was that the lid would squish the top bit of refractory flat against the bottom of the lid so it would seal up well when closed and in use. This worked pretty great I must say - I get a little smoke coming out from under the lid occasionally, but no flames shooting out.

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Then I inserted the tuyere pipe. This is a piece of an automotive exhaust extension. The end on the outside of the furnace is a little wider than the rest, so these pipes can interlock end to end with one sticking into the wide end of the next. I cut the skinny (inside) end on an angle, so that the whole inside end would be resting on the tuyere hole in the cast hot face - no exposed ceramic fiber, and plenty of support for the burner. I gave the tuyere pipe a bit of a twist to get a friction fit, so it would not fall out. some day maybe I will weld it to the outer shell, but for now I like the idea of being able to replace it if needed.

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Then I cut another piece of the skinny end of that exhaust pipe to slip into the flared end. This "burner sleeve" got bolted/clamped onto the burner (since its tube is smaller than the tuyere) in such a way as to keep the burner centred within it, and (with a little adjustment) the correct distance into the furnace when fully inserted into the flare on the tueyre pipe. I ended up having to stuff the space between the sleeve and the burner tube with scraps of ceramic fiber, to keep flames from shooting back out through the gap at my fuel lines, but the stuffing is not shown here.

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Burner in place

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All ready to fire the refractory.


Next post: Lighting a fire!


Kang

Edited by Kang
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