ring 302 of this rotor assembly is illustrated in fig5 lamination stack 101 is clamped on a mandrel 301 and a ceramic adhesive coating 204 is applied to the interior surface of slots 111 as described above foam end ring patterns 302 and 303 each include fan blades and balance posts as is typical in die cast rotors a short protrusion typically about 0 10 u2033 in length which extends into each rotor slot 111 serves to position the end ring relative to the lamination stack upper end ring pattern 302 includes vents 306 from each slot 111 to enable gas to escape through vent tubes 307 during the casting process the end ring patterns are adhesively secured to lamination stack 101 the interior volume of closed slots 111 is left open except for the protrusions described above fig5 is an enlarged cross sectional view through end ring pattern 302 this end ring includes the fan blades vent 306 through the foam and vent tube 307 the vent tube is supported by a collar 308 the rotor assembly of fig4 is prepared for lost foam casting in the conventional way with foam gates 304 attached to lower end ring 303 to feed molten metal into the end ring from the larger cross sectional area of a sprue 305 the assembly is then coated with a gas permeable layer 309 of clay or other material and air dried fig6 illustrates an enlarged view of end ring 302 as shown in fig5 after the end ring has been coated with gas permeable layer 309 completed rotor assembly 300 which is now coated with gas permeable layer 309 is placed in a flask oriented with upper end ring 302 at.