Home built "HOTPOT" foundry

 

The home made refractory was cast and rammed in as per picture and allowed to cure for a week. Two days in natural sunlight and later the 'OL LIGHTBULB' was stuffed in and left on for remainder. Looked quite nice at night - remnants of a medieval lampshade (it cured in the guestroom of course).   

I managed to get the steel crucible made up - I copied a similar design (with slight mods) I found on another site. Quite an impressive litle chap!  

The crucible in the furnace! Cant wait to fire it up!! You can see the idea used to retrieve/insert the crucible from/into the furnace. The bottom of the crucible (not shown clearly) has provision for a 'tiliting attachement' to allow for ease of pouring. 

The burner I used was a kinda mixed design between Ron Reils and other examples on the web. It is constructed out of 3/4" (19mm) piping about 200mm long. I turned up a nozzle to a press fit into one end of the pipe and worked on a jet diameter of 1mm. The air intake holes were slotted on either end and ± 10 mm away from the nozzle end. After a couple of first (unsatisfactory) tries of the burner I whipped up a 'choke' to allow for adjusting of the burner to get that "neutral" flame so needed. It worked great! (Gives me an idea to modify my gas barbecue to give a better output!)

 The "cope and drag" I slapped together (yes, did it that way). It did have a simple form in it but was sanctioned by "quality control" whilst preparing for the furnace light (whisper: Guess she couldnt get her big but into it!!).

 So then we're all set and we need some scrap Aluminium. Well  the compressor housing from the turbocharger I had served no purpose in the corner of the workshop - so here is the before picture.........

 And then a few hours later - the first ingot and a test sand casting!!! Excellent!!! The Mrs was quite impressed aswell!!!

 My recent doings in the backyard..... tried to go bigger and the eye fell on my helpful tool the, G-Clamp! Whats next.....?

HOTPOT Update 04/10/2010

My home foundry got an upgrade!! Initial operation was via an atmospheric burner. It worked....but was really slow! Got a melt after ± 45mins. Not good...so a little research on forced air burners led to the forced air gas inlet an the recent acquisition of a 12V blower (to blow up air matresses). Why 12V? Because I could use my PWM controller I built for my hot wire foam cutter to control the speed of the blower - It works GREAT! I will use this controller for controlling my spindle motor onmy CNC router when I get to that stage of the project!!!

I used a 3/4" pipe ±200mm long (cause I had it). The gas nozzle is a mere M12x70mm long bolt. This was chucked in my lathe and a hole -3mm dia-drilled halfway down the length of the bolt. Another hole drilled perpendicular to the length completes the gas supply into the air stream. The pipe was drilled (dia 12) ±50mm from air inlet and the bolt clamped in place with two nuts. The blower came with a range of adaptors and one fitted perfect into the 3/4"piping.

The light up of the furnace was a bit of a learning curve - until I got the hang of it. Open gas, light up, see the yellow flames and then crank up the PWM controller - the correct air/flow mix was achieved by looking down the inlet pipe and guaging the color of the crucible as it heated up. If too little air is added you will see the flame blow out off the vent hole on top of the furnace. Too much air and the flame blows out. "Sound" of the burner also gives you an idea of the performance - ever heard the exhaust of a gas turbine? After all we were up to a melt in 20mins!!!!

So why does the gas bottle freeze up causing intermittent bursts of gas into the furnace? LPG gas exists in its gas bottle in a liquid form. For it to burn it has to vaporize (I sound scientific-ish). To vaporize it requires energy - heat energy. It gets this energy from the surroundings. The more you burn (you are just dumping gas through a 3mm dia orifice!), the more vapour you need to generate, and the more heat you absorb causing the cylinder to freeze up. I think I kind of explained the way a refridgerator works?