The engine cylinders are contain ed in the engine block. The block has traditionally been made of gray cast iron because of its good wear resistance and low cost. Paasages for the cooling water are cast into the block. Heavy-duty and truck engines often use removable cylinder sleeves pressed into the block that can be replaced when worn. There are called wet lines or dry liners depending on whether the sleeve is in direct contact with the cooling water. Aluminum is being used increasingly in smaller SI engine block to reduce engine weight. Iron cylinder liners may be inserted at the casting stage, or later on in the machining and assembly process. The crankcase is often intergral with the cylinder block.
The crankshaft has tranditionally been a steel forging; nodular cast iron crankshafts are also accepted normal practice in antomotive engines. The crankshaft is supported in main bearings. The maximum number of main bearings is one more than the number of cylinders; there may be less. The crank has eccentric portions; the connecting rod big-end bearings attach to the crank pin on each throw. Both main and connecting rod bearings use steel backed precision inserts with bronze. The crankcase is sealed at the bottom with a pressed-steel or cast alumimum oil pan which acts as an oil reservoir for the lubricating system.
Piston are made of aluminum in small engines or cast iron in large slow-speed engines. The piston both seals the cylinder and transmits the combustion-generated gas pressure to the crank pin via the connecting rod. The connecting rod, usually a steel or alloy forging, is fastened to the piston by means of a steel pistonpin through the rod upper end. The piston pin is usually hollow to reduce its weight.
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The crankshaft has tranditionally been a steel forging; nodular cast iron crankshafts are also accepted normal practice in antomotive engines. The crankshaft is supported in main bearings. The maximum number of main bearings is one more than the number of cylinders; there may be less. The crank has eccentric portions; the connecting rod big-end bearings attach to the crank pin on each throw. Both main and connecting rod bearings use steel backed precision inserts with bronze. The crankcase is sealed at the bottom with a pressed-steel or cast alumimum oil pan which acts as an oil reservoir for the lubricating system.
Piston are made of aluminum in small engines or cast iron in large slow-speed engines. The piston both seals the cylinder and transmits the combustion-generated gas pressure to the crank pin via the connecting rod. The connecting rod, usually a steel or alloy forging, is fastened to the piston by means of a steel pistonpin through the rod upper end. The piston pin is usually hollow to reduce its weight.
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