PURPOSE: To use casting without taking out core, to freely produce shape of the core, to hold rigidity even in thin thickness and to enable further lightening by forming the core for hollow part of light alloy casting by foaming aluminum.
CONSTITUTION: Part of rim 1 and part of hub 2 are integrately formed as casting by spokes 3. A shaft hole core 6 made of sand core is set in an outer die 5 and further, the core made of the foaming aluminum is set at the spoke part 3. And the light alloy casting is poured and after cooling, the light alloy casting is taken out and a sprue is removed and the shaft hole core 6 is crushed to remove. As the core 7 made of the foaming aluminum has little thermal capacity, high heat insulating, light weight, good machinability and good permeability, blow hole in the light alloy casting is scarcely developed.
KAWAI MAKOTO
MASUDA KYOJI
