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| Green Twin Oscillator Cast/Build |
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| MetalCaster:
I started trying to learn all the strange new terms required for casting, such as cope, drag, sprue, runner, gate, shrinkage allowance, machining allowance, ect. etc. I tried to melt cast iron with propane as I had seen Rob do, but no luck with that. I had to find a better burner, and without the problems of vaporization of the propane tank. I started playing around with kerosene and a paint sprayer, blowing huge flames across the driveway much to my wife and the neighbor's horror. I built a very ugly but well functioning furnace, and build an oil burner from a cutting torch tip. The cutting torch burner worked well, but required a heck of a lot of compressed air for atomization. Then I ran across a Delavan siphon nozzle, and made a great duel-fuel (propane-oil) burner which melts cast iron like butter. The cope/drag thing and moulding in general was very confusing, and I confess I hardly had a clue as to what I was trying to do other than fill the mould with molten metal. Here is an early attempt at a cope/drage layout. I would probably do it different now. This is before I read the "Basic Gates and Risering" book. |
| MetalCaster:
One very critical casting term that I was aware of, but an idea that was further impressed upon me as I progressed was the all critical "draft angle". Not a more important term in casting than that (in my humble opinion). I attempted to cast the base in aluminum, and had a lot of trouble with the lower mould breaking off (the part that protrudes up into the bottom of the base). I finally used a sodium silicate core in the drag, and petrobond in the cope. But who would dream that you have to put weights on top of your flask to counteract the hydraulic forces, and so while I was on track for an excellent cast, the mould blew out, and the casting was ruined. The sand used for the core was too coarse, and so the finish underneath was terrible. I have made several other attempts at casting the base, using various sand types, mixtures, grain sizes, mould layouts, etc. and each has been a failure for one reason or another. A good learning experience though, and I think I have the issues sorted out. |
| MetalCaster:
Another attempt at the base. Not a bad attempt, but poured too slow with too small a sprue, and aluminum too cold. The finish was better on the bottom. Was still trying to zero in on pour temps, gating/risering, and numerous other things. |
| tekfab:
Sorry to interrupt, what size of delevan nozzle did you use ? Mike PS Good stuff ! |
| MetalCaster:
This is a third attempt at pouring the base. My Petrobond was getting a bit dry, so I mulled some 30 weight non-detergent oil into it (too much oil), and started getting erosion as the sand/oil mix failed. This casting is probably usable, but I will save it and try to improve upon it. |
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