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ENGINE FRAMES

The term frame is sometimes used to identify a single part of an engine. It is also used to identify several stationary parts that are fastened together. These stationary parts support most of the moving engine parts and engine accessories. When we talk about the frame, we will use the latter meaning in our discussion. As the load-carrying part of the engine, the frame may include such parts as the cylinder block, base, sump or oil pan, and end plates.

CYLINDER BLOCKS

A cylinder block is the part of the engine frame that supports the engine’s cylinder liners, head (or heads), and crankshaft. (In modern engines, the term crankcase identifies the location of the crankshaft, and not a separate component of the frame.) The blocks for most large engines are of welded-steel construction. In this type of construction, the block is made of steel forgings and plates that are welded horizontally and vertically for strength and rigidity. These plates are located where loads occur. Deck plates are generally fashioned to house and hold the cylinder liners. The uprights and other members are welded with the deck plates into one rigid unit. Blocks of small high-speed engines are often of cast iron en bloc (in one piece) construction.

A cylinder block may contain passages to allow circulation of cooling water around the liners for cooling of the cylinder. However, if the liner is constructed with integral cooling passages, the cylinder block generally will not have cooling passages. Many blocks have drilled lube oil passages. Most 2-stroke cycle engines have air passages in the block.

In other words, a passage that is an integral part of an engine block may serve as a part of the cooling, lubricating, or air system. Generally, we think of one cylinder block in connection with all cylinders of an engine. Some engines, however, may have a separate block for each group of cylinders. Examples of cylinder blocks common to Navy service are shown in figures 3-1, 3-2, 3-3, and 3-4. Figure 3-l shows an example of an in-line, 6-cylinder block; and figure 3-2 shows the same block in a cutaway view.

In figure 3-1, the entire unit is a one-piece casting of alloy cast iron. Transverse members provide rigidity and strength, ensuring alignment of the bores and bearings under all loads. The block is bored to receive the cylinder liners. Note the air inlet ports in the cylinder bores and the water jackets which extend to the full length of the bores. Air space surrounds the water jackets. Through this space, commonly called the air box, air is conducted from the blower to the inlet ports of the cylinder liner. Other parts, which are cast integral with this type of block, are the upper halves of the main bearing seats, handholes, bore for the cam or balance shaft, lubricating oil passages, and coolant passages.

The cylinder block shown in figure 3-3 is made up of two 8-cylinder alloy cast iron sections. The front and rear block sections are bolted together to form a rigid self-supporting, 16-cylinder,

Figure 3-1.—A General Motors in-line, 6-cylinder block.

Figure 3-2.—Cutaway view of a cylinder block showing air and water passages.

Figure 3-3.—A 16-cylinder, 2-piece block (16 V series 149).

Figure 3-4.—A Colt-Pielstick PC 2.5 16-cylinder block.

V-type arrangement which accommodates the cylinder assemblies, crankshaft, and engine-mounted components. Water passages are cast in the block to provide coolant to the cylinder liners and the cylinder heads. Main oil galleries are drilled in the block to direct lubricating oil to the crankshaft main bearings and related parts. The front and rear block sections are not interchangeable.

A cylinder block for a large diesel engine that consists of steel plates and forgings is shown in figure 3-4. The steel plates and forgings are welded together to provide the structural support for the stationary and moving components. The upper deck contains the cylinder assemblies and related gear. The lower deck, which forms the crankcase, is mounted with an oil pan to the bedplates. (The oil pan is not shown in fig. 3-4.)



   


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