Casting Aluminum Horn Ring?
seems to me you are not worried about plaster making a good mold of your object, but the object casting properlyI think it depends mainly on how you arrange your system of spruesIf you are thinking of adding just a single feed, chances are against the metal flowing around the entire circle before it freezesI would try adding quite a number of sprues to the entire roundAlso heating your mold will helpTo avoid any water remaining in the plaster I would heat the entire mold anyway to a minimum of 250F for a few hours, as water and hot metal never should mix (unless you are into creating volcanoes.)Cast into hot mold, so your metal will cool off more slowlyGenerally the thermal resistance of plaster will be increased if it contains silica (silicon sand)Don't know how much mechanical stress resistance your cast needs, not sure about a108 (308.0)I am only somewhat familiar with 319.0, which however seems to be fairly similarCast aluminum tends to be pretty brittle, so I wouldn't really use it for anything where it's important that it doesn't ever break (is the ring only a decorative addition or a structural part of the steering wheel?)Though I'm not an engineer, just use metals for sculpture a lotBut I would tend to fabricate that ring out of steelStainless steel if necessary.
