Basically Contruction of Engine is carried out in five parts :-
1.Bed Plate :-
It is the base of engine which carries the whole load and stress of the engine due to the different moving parts.Bed plate should be rigid enough to support the weight of the engine, and maintain the crankshaft.Also it must be flexible enough to withstand hogging and sagging.For fulfilling this purpose,the bedplate is made of Cast Iron and Mild Steel.
Bedplate consists of two longitudinal girders .Transverse girders Connect these longitudinal girders which are positioned between each crankshaft row.Main bearing pockets are built into the transverse girders for the crankshaft to run in.The small bore engines-made from cast iron as a single casting and the larger engines have a fabricated bedplate-welded together from steel sections, steel castings and plate.The modern bedplate is constructed from fabricated longitudinal girders with cast steel transverse sections containing the bearing pockets and tie bolt holes.The bedplate should be inspected regularly for evidence of cracking.
These carry the cross head guides and support the engine entablature (the cylinder block). In earlier engines, the A frames were individually erected on the bed plate directly above the transverse girders. When boxed in with plating they formed the crankcase. The trend nowadays is to build the frame box as a separate fabricated construction and then, after stress relieving and machining the mating surfaces, to mount it on the bed plate. This has the advantage of saving weight.When the frames are aligned on the bed plate they are secured together by drilling and reaming and using fitted bolts. Cracking in A frames can occur leading to misalignment and excessive wear of the running gear.
It is made of cast iron. It incorporates the scavenge air space ,the cooling water space and housing for the cylinder liner.
Tie Bolts or Tie Rods :-
Tie bolts and tie rods are used to fix the whole engine structure to its bed plate.