The past week we’ve been trying to get a better mold making Green Sand mixture to use. Sifting the sand and using only fine particles works pretty well, but the large particles are prone to clumping still. Part of the reason for this is probably because the “bentonite” we’ve been using is probably just clay and filler from the cat litter. Clay is still supposed to work, since it is supposed to naturally bind to sand particles. Or you could say we’ve been playing with dirt for a week. “Indian Clay” in grade school nomenclature.
Lukas purchased a coffee grinder from Walmart to try to grind the insoluble clumps in the cat litter. Not only can it grind clay, apparently it can turn sand into smaller sand dust. We are using that as our molding mixture now, but it’s still just wet sand. It is very difficult to remove the negative from the mold with the wet sand adhering to it. We managed to make a rudimentary mold that is much higher resolution than the last attempt.
The issue with removing the negative however is making an uneven mold, so a double cope and drag isn’t possible yet. The next attempt will hopefully include a casting flue and a completely enclosed casting space so the product won’t oxidize as much (opposed to the muffin tin we have now).
Melting was facilitated by simply adding a steel cap to the steel grass jelly drink can. By melting smaller bits of aluminum at a time and using the cap, we were able to melt .75 lbs of aluminum in half the amount of time as attempt #1.
Our mistake was letting the coals die down by the time we were ready to cast, so the resulting pour was only partially liquid. Since we’ll be having to cast this same piece four times, I’ll probably keep the coals fully loaded the entire time.
The pour was “too cold.”
The resulting cast looks much better than attempt #1. There is little oxidation on the surface, and little slag due to the cap on the crucible while heating. There was virtually no steam from the mold, but the backside still has the impressions of the sand from the mold.
Hopefully the third time around will be a charm. The two part mold and hopefully improved negative removal technique will bring this motor mount to acceptable standards for use.