The directional solidification rule is that  "solidification of the molten metal in a casting should occur in such a manner that liquid feed metal is always available for that portion that is just solidifying."

• Another way to describe directional solidification is that the casting should  -- "cool and solidify progressively from thin sections to heavy sections with constant metal feed into the heavy sections."

In the pivot frame, the heaviest section is the 2.5" diameter center hub.  The mold should be designed so that the hub section will solidify last and have good metal feed through the entire cooling process.