Step 1: Begging and Buying
This is a really fun project that doesnt take much time at all and once completed enables you to melt metal!
::Warning::This activity does involve fire and very high temperatures, so bring your common sense and competence along. You should engage in metal melting activities fully covered, wear leather boots, jeans, and a long sleeve shirt. Use eye protection and gloves over your hands.
- 2 used Papa Johns sauce cans (just walk in and ask for a couple, early morning or early afternoon is usually when they prep sauce)
- 1 used bean can
- 4 inch diameter x 24 inch length Galvanized Oven Vent
- Blower with a power source
- A few screws or rivets
- Foundry stand (jackstands and a grate in my case)
- Can opener
- Flathead Screwdriver
- Drill with proper bits
- Sheet metal bender (in my version)
- Tin Snips (scissors might get it done too)
- Cans or other forms of aluminum
- Welding Gloves
- Lighter Fluid (optional)
- Tongs or a coat hanger for holding the crucible
- Spoon with extended handle for dross Removal
- Eye Protection
- Somewhere to put the molten metal, I used a muffin tin.
If there's something in this list that you dont have or cant get then try and improvise (except on the safety stuff). The first time I made one of these furnaces the duct was made from left over rain gutters. And the blower came out of a microwave. Just give it a little thought and start building and see what you can come up with.
Step 2: The Duct
Wrap a piece of paper around the stove pipe, line up one edge even all the way around. Then grab the sharpie and mark a line all the way around the duct. This needs to be about a foot from the sharp edge of the duct (to make about a nine inch to one foot long duct)
Then pop open the seam of the duct, take your snips out, and cut it along the line.
Next we have to deform it into a rectangular shape, this is alot easier than it looks.
Take the duct in your hand and press it against a hard flat surface (your table) it will form 2 seams approximately equidistant from each other
Then grab the duct about an inch or two from the one of the creases and press it against the table again making another crease.
Now press the wide flat part of the duct against the table, holding it approximately the same distance as the other shorter face and bend in the last crease.
The duct is finished, now for the Can....
Step 3: The Can
Or alternatively some clamps :]
Clamp the can down, get out your hammer and screwdriver (i guess a chisel would work too). Place the screwdriver towards the bottom of the can about as far from the bottom as you duct is tall. Start pounding the screwdriver in across the circumfrence of the can, making a hole big enough for your snips to go in.
Once your snips can be inserted start cutting away at the can, be careful not to be too zealous and cut it too big. But you want a hole not quite as wide as your duct and just about as tall.
Step 4: The Adapter
In this step we have to adapt the blower to the duct size.
This is the step that will require you to adapt to the blower you picked out, mine was an A/C Fan from an 86 honda crx. :)
The way that I made the adapter, I took the blower and sat it on my sheet metal and tried to trace around the outlet (you can see how well that went). Then I trace inside that around my duct.
Then I used a straight edge to draw in some flaps on the inside (duct) and the outside (blower), in order to rivet the adapter to the duct and tape it to the blower.
Step 5: Diverter and Grate
The diverter should be made from some of the left over duct sheet metal. trace the outline of the can, then add about a 3/4in flap to one side. Cut this shape out, and bend out the flap. It will have to be adijusted till it just fits in the can. Just cut off a little at a time with your snips till it just slides down into the bottom of the can.
Then bend the first 2 inches or so opposite the flap, the purpose of this piece is to ramp the air into the furnace, so it should look like a ramp.
Next we need a grate.
Take the second salvaged can, and a phillips head screwdriver, and you hammer. Place the screwdriver on the bottom of the second can and hit it with the hammer till it pops through...
Continue until the bottom is riddled with a nearly even distribution of holes.
Now cut out the bottom out with a can opener.
Step 6: Mating
First we need to prepare a place for the grate. Take out your drill, and drill a few (3-4) holes around the circumference of the can about half an inch above where you cut the hole for the duct. Screw in a few short screws, these are for the grate to rest on.
Now we need to modify the duct so it can be riveted or screwed onto the can. Use the can to mark an arc line on the wider side of the duct opposite the seam. Then add two more lines perpendicular to the edge for a flap. (see picture below) After cutting along these lines bend the flap out perpendicular to the duct.
Then cut two flaps out of the sides of the hole that you cut in the can for the duct, and bend them both out too.
Drill through the top flap and the two side ones, through both the can and the duct. Put the flap on the top side of the duct inside the can. Place the holes together and insert a pop rivet, or screw.
You can now place the grate down inside the can, resting on the screws...
Then you need to stick the adapter and the other end of the duct together. Doing this is very similar to the other end of the duct. Just drill a hole through each flap and place a rivet or a screw through it.
That's it :D
Just tape the adapter to the blower and your done.
Kick back and view your handiwork.
Step 7: Preparations...
Your going to need some supplies first.
Get some gloves, charcoal, Tongs (or other crucible holder), a spoon, a lighter, and some lighter fluid.
The tongs, the spoon and the Crucible need to be slightly modified.
We'll do the tongs first. Clamp them into your vise and take some pliers and bend out the end. After its bent out some take them out of the vise and place the very end in the vise and clamp down, we want them straight out to the end. After they are straight clamp them in the vise again with about 3/4 of an inch protruding out of the vise. Take a hammer and whack the protruding end till it is flush with the vise surface. Do this to both sides of the tongs.
That makes a handy crucible holder.
Now take the spoon and mate it with tape to some long object (like an aluminum pipe in my example). I tried to use the spoon as it was and my hands got QUITE toasty, within my gloves.
Now for the crucible, you simply need to drill or poke two holes in the top of the can (the crucible is a bean can). The holes need to be big enough to recieve the crucible holder.
Next test your blower and power source to make sure air is coming through the duct and into the furnace.
Once everything is ready, its time to burn!
Step 8: The Burn
I place mine on a barbecue grate held off the ground by jack stands, on a concrete slab.
First we need to line the furnace with charcoal. Place the crucible on top of the bottom layer so subsequent briquettes can be placed around the inside of the furnace.
Douse the briquettes well in lighter fluid, then light them....
Making a device that contains fire gives a different feeling from just about anything else. It is beautiful. :D
Let the charcoal burn for about 5-15min and get good and started, you dont want to have to relight it.
After it is going good, turn on the power. Within a minute or two all the metal around the charcoal should be glowing red.
Now start placing aluminum in the crucible, make sure to use your gloves and tongs (hold the cans/etc over the crucible and drop them in) and eye protection.
Cans are fairly low grade aluminum something better would be preferred, like broken castings or overly painted welded aluminum joints (from high class lawn furniture). Most things are gonna flame up and put on a great show when they go in the fire. This part really is fun, for all its danger.
Step 9: The Pour
Well, if you know how to pour a casting that would be a really great thing to do with it. I dont, so I just poured it into an ingot. Later, when I learn how to cast a part then I can melt the ingot down (free of dross), and make it into something.
So first we need to remove as much material that is not aluminum as possible. Aluminum will be a shiny, shiny liquid at the bottom of the crucible, the dross will be anything floating on top of it.
Grab the spoon and jam it into the crucible (carefully), you should be able to see/feel what is liquid and what is not, remove as much of what is not as possible. Likely you'll come out like me, after sticking it down there once and bringing a wad of gunk out, the wad as well as some aluminum was stuck to the spoon.
But thats good enough...
Now we need to pour, first turn off your blower, then just place the ends of your crucible holder into the holes in the crucible CAREFULLY!! You REALLY have the chance to severly hurt yourself here!! Lift the crucible carefully out of the furnace. It will virtually instantly make crackling and popping sounds of very rapidly cooling down. I hope your cast was nearby...
Use the spoon in your other hand to gently lift the bottom of the crucible, pouring out the aluminum below the remaining dross.
WOW!! Look at that shiny stuff, isnt that amazing!
It will QUICKLY become dull and begin to solidify, and the muffin tin (if your using one) will become dull red .
Let it cool upwards of an hour before trying to touch it.
After pouring, place the crucible back in the furnace, and let everything die down and cool. Your charcoal should still be burning and everything will be hot for several hours, try to just let them be.
If you have some marshmallows break them out, and roast them over the remaining fire (might as well).
Congratulations, you can now make liquid metal, and form it into things. The whole world is open before you (or at least it feels that way).