My second homemade foundry

This is my second foundry and I made it from empty gas cylinder. First I made sure the cylinder is empty then I drilled 2 holes. One hole to fill the cylinder with water the other as air hole makes it easy to empty the water and to fill it again.
After all gas is gone I marked where I want to cut and used my small grinder for that job. When I cut the cylinder I had it full of water, just to be on the safe side. It took me less then 10min to cut the cylinder handle, top nozzle and cylinder top including grinding the rough bits of metal.
It is a good idea to mark lines over cutting so later on when welding, the lid will fitt well.
When using the grinder It is recommanded wearing eye and ears protection.
If you don't know what you are doing take it to a professional. Misuse of pressured gas cylinders can cause injury and even fatalities.
This is not an instruction or a guide how to do it, I am sharing with you how I used a gas cylinder based on my own experience and knowledge.
Anyone who attempts this he/she will do it on their own risk,
I will not be liable for any injuries/damage in anyway.

I cut the inlet air hole and welded 2.5" pipe in an angle so the air will swivel and create more heat in the center. I kept the pipe 2" inside that will be the thickness of the refractory in the furnace. I found my welding magnets very usefull for holding the pipe in place. After getting all my welding gear ready the pipe was perfectly welded into place. Small tip, when placing the cylinder on the side 2 wood battens under it will prevent it from rolling aside when using the grinder on it.

Next thing I made was the hinge system for the furnace lid. I used 20x20mm box iron from scrap metal I kept for "rainy day". I used my drill press for accurate 10mm holes. The 2 box iron that I welded to the lid I made longer to act as stopper preventing the lid from falling back.
Before welding I set the lid in the correct position using the blue mark as guide. After lid was in place I secured it with large welding magnets and welded the hinge into place. I am very happy with the result and the hinge is very strong and sturdy.
After finishing with the hinge I cut the outlet hole on the top of the cylinder (lid).

Sometimes the refractory shrink or move so in order to keep refractory in place I used metal screws all around the furnace body and lid part.

At this stage the foundry is almost ready for the refractory stage. I used plastic can of paint with a bit of extra cardboard on top to form the inner furnace core leaving 2" space around for the refractory. For the lid I used cardboad pipe from empty gravy box to form the outlet lid hole.
The refractory I used is ready made fire cement comes in big 25kg bags all that is needed is to add a bit of water. I started mixing it using very small amount of water until I got a sticky paste.

Too much water is bad for any refractory. On the net many home made refractorys are combined of Perlite (cruashed)+cement+silica sand and fireclay. Good refractory means good insulation, good insulation keeps the needed high temperture in the furnace. I started filling the furnace from the base ramming the refractory with timber block to get all the air bubbles out, then I placed the plastic core into position and filled it all the way up with refractory keeping 2" width and after that I filled the lid.

Every type of refractory have its own curing time and manufacture guidelines. If refractory is not cured properly it might crack under high temperature. The type of refractory I used had to be cured by lighting the foundry for a few hours keeping the temperature at 100°C this type of refractory is good for up to 1200°C (cured). After refractory was cured I lit the foundry first time with charcoal and after one hour when the temperature was over 1000°C I placed my hand on the outerside of the furnace and it just felt worm. So that was a good sign that the refractory doing its insulating part by keeping the heat inside the furnace.
After the furance body was cured I welded handle for the furnace lid and welded 4 support washers to hold the refractory in the lid.

The foundry was ready for action at this stage but I found moving it quite a task with all that heavy refractory. So I welded handles from 5mm rebars I took from my first furnace broken lid.
After that I welded a small trolley for the furnace made out of scrap metal and hand trolley with 2 good wheels I found in a rubbish skip.

Now its time for some melting, My furnace is HUNGRY time to feed it with some aluminum. I collected some aluminum from my house, some unused items. I made some tools for my old furnace and they are still good for this one. To get rid of the dross I used big spoon with holes.
Cheaking the temp with multimiter at some stage showed over 1000°C.
I used characoals and hair dryer connected to a hoover pipe as a air blower and pot as crucible.
My first melt was parts of aluminum ladder, I used my muffin tray to cast the aluminum ingot.
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July 2011

Small upgrade. I found the lid hinges too long getting in my way a few times so I decided to make them a bit shorter using my angle grinder and welding a metal L angle.