Main Engine Structure The crankshaft rest in 1 built into cross girders of the bedplate. These bearings, known main bearings, each consist of two 2 which are secured by means of studs and bearing caps. The thrust 3 or thrust bearing, located at the aft end of the engine, may be integral with, or separate 4 the bedplate. On the flat upper surface of the bedplate 5 a number of A-shaped frames 6 may be manufactured of cast iron or fabricated steel. The frames are mounted on and 7 the bed-plate cross girders. At the top of the A-frames there is a strong cast iron frame called 8 , which is built of a number of sections provided with vertical flanges enabling them 9 together to form a block for 1-3 cylinders in front of the chain transmission, and a block with 4-6 cylinders aft of the chain transmission. The chain transmission, forming the connection between the crankshaft and the camshaft, is enclosed in a cast iron casing known as 10 casing.