THE ENGINE FRAME: The engine frame of a modern 4 stroke medium speed diesel can be produced as a single casting or fabricated from cast steel sections and steel plates welded together. With this design, there is no separate bedplate, frame and entablature as with a 2 stroke slow speed engine. The photograph above shows the frame of an engine with the liners and crankshaft in place. An alternative method of construction consists of a separate bedplate, which is bolted to an entablature which holds the underslung crankshaft. When the Crankshaft is underslung, the load on the bearing caps is transferred back to the frame by the use of tie bolts. Note the use of the side tie bolts - which locate the bearing cap, and prevent sideways movement. THE CONNECTING ROD : The connecting rod in a medium speed 4 stroke engine is subject to an inertia whip loading due to the mass of the con rod swinging about the piston pin. (Because of the lower speed of a 2 stroke engine...