Rev. 2002-11-14, 2003-07-20, -10-30, 2006-05-26, 2008-01-06, 2011-01-14, 2013-03-09
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Simply said, what I am discussing is a cylinder of insulating castable refractory, supported by a sheet metal skin, heated by a blower driven propane burner, held by a rectangular steel tubing cage that supports the lid, etc. The burner is a simple design and in fact, I use the same burner with a different head to melt aluminum cans in a cast iron pan. Melting Metal
HOW IT DIFFERS FROM A GLORY HOLE - Besides it being smaller, this hole has no back up insulation - frax or board which increases the insulation value. It will heat up and cool down faster and use more fuel at any given temperature.
This unit was built by making an inside form of a fairly stiff piece of sheet metal, about 22 gauge (0.030") and bending it to an overlapping cylinder about 3" smaller in diameter than the can. It was held in shape with fiberglass strapping tape and inserted in the can.. A fairly thick mixture of insulating castable was made up and troweled into the space between the can and the shell; the thickness preventing flow of castable below the shell. When set, the form edge was pulled inside to reduce its diameter and free the tape and then pulled out. The burner hole was cut, first in the sheet metal with a hole saw and then in the castable with an old paddle bit -THIS IS NOT A GOOD IDEA unless you have a use afterward for a really dull paddle bit. A better idea would have been to cut the shape of the burner port from Styrofoam or rolled paper, cut the hole in the can before pouring the castable, inserting the core and sealing it with tape, then removing the core, by burning or tugging, after the castable is set. 2001-09-29
Firehole after stripping of rusted shell, adding painted sheet
metal held in place with stainless steel hose clamps [each made of 2 long ones connected end
to end] and welded
tubing frame of 1/2" steel to support unit when placed on
side and to support the lid when raised or swung aside. The tension bolt
[above] of the lid band and the welded on loop [lower right center of picture] are lifting and
Today, I welded spacers at the bottom to keep the cylinder centered and corner plates to keep it from falling through when picked up by the frame. (Shown below) 2001-12-02
Construction of this from scratch is below.
Below, left to right, the framed hole standing on a larger frame holding other hot stuff. In the first image the PVC to the right is where the blower for the burner attaches. The lid is set to one side in one parking position on fire brick. The center image shows the rain shield raised up and the pole that supports two hooks. The lower hook catches the chain from one side of the lid like a hinge or pivot - the chain runs from the lid in the picture. The right image shows the lid hung by the other chain to the upper hook, which I use so I don't need a layer of firebrick to lay it on. 2008-01-06
These 3 pictures show the hole with the lid in place and the large link chain resting on top. The two chains are attached to the compression band around the lid, one welded and the other to the tightening bolt. The center image shows one of the crucibles in the open hole resting on firebrick to raise it near the top. The heating flame comes in from the right rear behind the pot which is centered when in use. The corner and centering pieces can be seen at the bottom of the frame. Tools on right described below image. 2008-01-06
Tools for handling the foundry pot. The pot must be lifted out straight up with a grip below the lip, the gripper having to fit between the pot and the wall. The loop is set on a fire resistant surface (sand in the casting pit) and the pot set inside the loop which is then lifted to pick up the pot for pouring. The image shows one end in the main picture and the other in the insert. The loops at each end of 1/2" square tubing for different sized pots. The clamps for lifting the pot had to be quickly adjusted to squeeze between the walls of the hole and the pot. Note that they overlap when closed for a smaller opening. I rebuilt [2003-10-30] the lifting tongs, welding 1/2" square steel tubing to the straight sides for strength, still keeping the bottom end thin. The original clamps were pretty weak when lifting several pounds of molten brass that might splash on my legs.
BUILDING A FIREHOLE STEP BY STEP
It has occurred to me today, (2002-01-13) after reading
Dudley's book again, that the fire hole could be a glass melter
for a vertical access furnace! Duh. It could then later be a
small glory hole when a furnace was built.
This is a mini version of the Firehole, cast from insulating castable around a shaped Styrofoam core with a piece of clay to form the burner port. While casting was done the sheet metal outer covering was held with a large hose clamp which was replaced with a piece of wire twisted to tighten it. It has a bottom/back wall. A Hot Head torch is used to heat it. So far it has been used to heat the ends of rods for forging and heat for annealing copper and brass being hammered for bowls, etc. The rough clay crucible shown is about the size of a muffin. 2003-07-20.
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