Melting and Casting Aluminium
Back in 2008 when I was about 15 I saw a video of someone melting down some scrap aluminium with a homemade foundry. I first experimented by making one out of a plant pot and actually managed to melt some aluminium using coal as a fuel source. I wanted something bigger and better so decided I wanted to make one from an old gas bottle. I spent a lot of time searching around for a suitable insulating refractory material, there were a couple of people making it from cat litter and cement. I managed to get a large sack of refractory cement from a local supplier for about £20 which was cheaper that making the fake stuff, which was great because I was in school and had little money at the time.
All I had was an old stick welder with huge rods and a hacksaw, I managed to get someone to grind the top off an old gas bottle for me and then proceeded to sawing up some scrap metal I had. I made a progression of holes at the base of the bottle and welded a couple of steel tubes coming off it to supply air, the whole thing was then welded down to an old sack barrow. I mixed up some cement and lined the bottle, it was more like a putty and took me quite a bit of time to do, ensuring there were no air pockets. I left it to set for a couple of days and then lit a coal fire inside of it using a hair drier as a source of air. I used an old mug as the crucible and hey presto I had some molten aluminium.
A few days after I got hold of an empty disposable welding bottle, chopped the top off it and used it as a crucible. Coal really stunk so I opted to go for charcoal instead and it seemed to transfer heat a little better towards the crucible. I had managed to melt a litre of aluminium and cast myself some 30mm aluminium rod to use in the lathe, which was great. I remember running it for a few hours at a time and the refractory cement worked so well that I could still touch the outside. I didn't have enough money to make any moulds and the foundry couldn't be used as a forge so I left it in a shed. A year after my computer hard drive failed so unforunately I lost all of the constructional photo's.
10/02/2016 - February
Eight years later and I still have the foundry so I thought it was about time that I did something with it. It's about 14 inch deep and the bore is 8 inch wide. The lid has no frame to it and I fear that it will likely break in half, so if I come across another bottle I may make a proper lid for it. I'm not even sure if the blower I've found will supply enough air to melt metal in a resonable time.
I chose to recycle one of my empty CO2 welding bottles. I first drilled a hole in it to ensure that it was completely empty, then chopped the bottom off at a height of 12 inch and then ground around the edge to remove burrs. This will serve as my crucible, I now need to create some kind of a handle as this thing will nearly hold 4L or 10.5kg of aluminium.
I thought that I would first clean up the foundry before melting anything in it. I had quite a lot of bed liner left from a past project so I figured I could use this as it shouldn't get too hot. (Bed liner is two part resin used for the pickup truck bed for protection). I first ground down the exterior and then proceeded with trying to spray the liner, the temperature was 5 degrees and it wouldn't spray through the gun. Instead I chose to brush paint it, and the only brush I had was a half inch one, so it took a while, but overall it came out ok, there were brush marks but considering it's viscosity and what I had I think I did rather well.
The next step was to fix the blower to the induction pipes, so I held it in place with duct tape, mixed up some epoxy resin and wrapped it in place, I used denim fabric as it was free and is surprisingly strong. I wasn't too sure if the blower would be big enough but it did come from a 25kW gas boiler, I am running charcoal and I'm sure power will be less, but I'm not sure how much less.
The next day the epoxy had set and there was no reason why I couldn't run the furnace. I first wired up the blower motor and ensured that the previously exposed terminals were covered, safety first. I created a sturdy handle for the crucible as dropping it would be unthinkable and drilled some holes in the crucible itself. I also cut up a load of scrap aluminium from past projects, it was ready to melt. I picked up a cheap bag of coal, not my first choice but it was all they had. At first all seemed to be going well but as more of the coal caught fire I started to get more smoke, it got so bad that it was billowing yellow smog and I had to douse the fire with sand. It was so bad that I didn't get any pictures but the inside is lined with thick black soot, I need some clean burning charcoal.
My first test with coal proved to me that the blower was sufficient for the task, but coal as a fuel was not.
We ended up with a string of bad weather for a while andsomehow with all the confusion of selling all fo my workshop I managed to forget about firing up the forge again. As of (May 2016) I'm living in Canada, I left it in the UK but I doubt it will be there if I go back.
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