Evaporable foam pattern for casting an engine block of a two-cycle engine

Abstract

The assembled evaporable pattern, which is substantially identical in shape to the cast metal two-cycle engine block, includes a plurality of in-line cylinders each having an end open to the crankcase end of the pattern. Each cylinder includes an exhaust passage that communicates with an exhaust manifold that extends to the exterior of the pattern and each cylinder has at least one longitudinally extending transfer passage. The assembled pattern also includes cooling passages that surround each cylinder, as well as surrounding the exhaust manifold passage. The foam pattern is composed of a plurality of separate foam sections joined together by an adhesive along planar interfaces. A first of the sections extends from the crankcase end of the pattern to the lower end of the transfer passages, and a second section extends from the lower end of the transfer passages to a location intersecting the exhaust passages of the cylinders. A third section extends from the exhaust passages to the cylinder heads. In addition, a fourth pattern section encloses the water passages at the head end of the block, while a fifth section encloses the water passage that borders the exhaust manifold.