started with the base. It is 2 pieces of 6 duct about 3
tall connected together. That gives me a 12 furnace.
I installed three 7 legs made from ½ pipe. I
placed 1 fire brick in the center for the crucible to sit on. I
then packed it with my Home
Made Refractory. I let it sit in the sun for 2 days and
turned it over. Well the bottom dropped out soo
I carefully put it back in and made a metal pan for the bottom.
waiting for the bottom to dry I took 7 fire brick and cut 3/8 grooves ½
deep in them for the Home Made Element. I used a diamond
tipped masonry blade in the table saw. I then beveled the
edges to make an octagon. OK 7 brick doesnt make an
octagon. I sat the brick in a circle with the last un-grooved
brick. I marked the un-grooved brick at an angle so that the
element could go from one groove to another. After cutting
the grooves in the last brick I tied them together with some stainless wire and
sat them on the base. I took two 9½ lengths of duct and
connected them, put a handle on each side and rolled the
bottom ½ to give some support to the refractory. I
drilled 2 holes through the shell and brick top and bottom for the electrical
connections to the element.
pictures below shows the progress so far. The scary looking
electrical connection is temporary. I hooked it up to 110v
and left it sit overnight with 2 brick on top to keep in the heat. It
definitely got hot, but not enough to melt anything yet.
3/22/03 : Some more pics. I have used it about a dozen times so far. It does work! I have the control box disconnected right now. The home made element keeps burning off the ends where I connect it to the wires from the control box. Its hard to see but there is a Hard brick in the middle of the base. I was worried about the refractory being too soft to support a crucible.
Not very exciting. Just some pics of the control box. A regulator from an electric stove and a terminal block from a dryer. All housed in a printer switch box. I have a 5 foot dryer cord coming into the box and about 8 feet of wire to the connection on the furnace. Combined with the 8 feet of cord I have coming out of the sub panel, I can sit this anywhere in my garage. I have melted in the garage with the windows open for ventilation. I usually sit it just inside the garage door with the door open. It keeps everything out of the weather. All of this is legal in my area even the cord coming from the panel however, I suggest you check with your local building codes. This setup will also let me improve the control and keep it away from the heat of the furnace.
Some thought so far. The home made element does not seem to get hot enough to do a good job. I know I have been to cold on most of the things I have done. It also takes a long time to heat up. This is due to the brick. I used fire place brick instead of kiln brick, harder but less insulating. I am going to paint a coat of 3000 deg furnace cement on the inside to see if that helps. If not I will spring for some ITC coating from BCS. I an going to buy a real element and see if it is much better than the one I made. So far I have used mostly soup cans. I get about 2 melts then I toss them. Just not comfortable with their strength after that. I have also used stainless canisters. These take longer to heat up and I seem to get a pin hole in the bottom. I did finally complete a steel crucible but haven't used it yet. I will update this with more info as I make improvements.
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