fashion and offsets the dynamic unbalance due to the eccentric 30 4 orbiting scroll 21 and oldham coupling 36 referring now to fig1 20 the numeral 14 generally designates a scroll compressor which has a three piece shell 15 made up of top shell 15 1 middle shell 15 2 and bottom shell 15 3 shells 15 1 to 3 are welded together such that top shell 15 1 and bottom shell 15 3 are partially within middle shell 15 2 and their ends define shoulders which serve to hold the compressor structure in place as will be explained below suction tube 16 and discharge tube 17 extend through and are suitably sealed to middle shell 15 2 and top shell 15 1 respectively as by welding suction tube 16 additionally is received in bore 20 6 of fixed scroll 20 and is sealed from the interior of sell 15 by 0 ring 18 which is located in internal groove 20 7 in bore 20 6 eccentric 30 4 of crankshaft 30 is received in bore 21 2 of tubular boss 21 1 of orbiting scroll 21 and as shown in fig1 20 the end of eccentric 30 4 is in an enlarged portion of bore 21 2 and not in contact therewith so that edge effects are avoided crankshaft 30 and orbiting scroll 21 move as a unit.