a compressor , as well as a lightweight and strong casting for a compressor , are disclosed . the compressor , which may be a reciprocating compressor for use in compressing high - pressure refrigerants such as co 2 , includes substantially reduced wall thicknesses compared to prior art castings . the side walls of the compressor can be manufactured to such reduced thicknesses through the use of a bridge spanning across the crankcase . this not only allows the opposing side walls to be manufactured of a thinner material , but the bottom cover removably mounted to the crankcase can be manufactured from a thinner and lighter material as well . through the use of such a bridge , the resulting compressor is not only able to satisfy current strength requirements , but at significant weight , size and cost savings as well .