| The materials of ship propeller are manganse bronze and aluminum bronze which have short freezing ranges, freeze by "skin formation" in a straightforward way and tend to form symmetrical pipes at the open heat centers. In this paper, the relations between various castings and risers by the molding design for determining the optimum size of riser were investigated when a fixed pitch propeller was marufactured. Two types of patterns were used, that is, metal and strickle sweep pattern. The optimum allowance of shrinkage are 15/1000 in the case of manganse bronze and 20/1000 in the case of aluminum bronze. The size of sprues and runners which have some skin bob were determined by pouring weigh, and insulating riser sleeve was used for the riser. As the result, the pouring weight can be determined by the weight of propeller, and the diameter and height of riser which have a core in the center can be determined by the diameter and height of boss in propeller for manganse bronze and aluminum bronze castings. |
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