CHAPTER 11 u Crankshaft and Bearings u Piston and Rods u Page 276 Classroom Manual u Page 276 Lab Manual

CHAPTER OBJECTIVES u Analyze wear & damage to Crank & Bearings. u Analyze wear & damage to Piston and Rods u Select the most appropriate repairs to perform. u Explain theory of engine balancing. u Describe related theory of Pistons, Rings, Bearings

CHAPTER INTRODUCTION u This chapter deals with Crank, Pistons, and Rods. u These parts are called the lower end. u This chapter will deal with procedures for the lower end.

THE CRANKSHAFT u Cast Iron u Nodular Iron u Forged Steel u Do NOT store crankshafts laying down. u Lube and place in plastic bag. u Stood on end to prevent warping. u Or hung to prevent warping. Page 276

CRANKSHAFT DESIGN u Crank converts reciprocating motion to rotary motion. u Polished bearing surfaces are called Journals. u Main and Rod Journals. u Rod journals are also called crank pins. u Crank has drilled passages from the main to rod journals.

COUNTERWEIGHTS u Opposite each rod journal is a counterweight. u In-line engines have a separate rod journal for each rod. u V-8 and some V-6’s have rod journals for two rods. u V-6’s with 90 degree have splayed rod journals. Page 279

CRANK END THRUST u Crank is pushed forward by converter and clutch. u One main journal is ground on sides to provide bearing surface - Thrust. u Flanged bearing to control end play. u Thrust inserts - half washers - some imports. Page 279

CRANK CONSTRUCTION u Gray Cast Iron u Nodular Iron u Forged Medium-Carbon Steel u Forged Chrome-Moly steel u Some cranks are hardened. u Ion Nitriding Page 279

CHECKING CRANK CONDITION u Keep bearings in order during disassembly. u Bent forged cranks can be straitened. u Bent cast cranks should be replaced. u To check for straightness use front and rear bearings u In block and a dial indicator Page 280

CHECKING FOR CRACKS u More accurate to use wet magnaflux. u Disadvantage only works on ferrous metals.

CRANKSHAFT WEAR u Cranks wear because of abrasives in the oil. u Out-of-round maximum is.0005” u Taper u Clean and polish all cranks before reuse.

REGRINDING CRANKS u Standard undersizes are.010”,.020”,.030” u Main and rod journals can be ground to different sizes. Page 281

POLISHING THE CRANK u Polishing only removes approximately.0002” u Belt must travel across crank in direction of rotation. u Do NOT hand polish crankshaft. Page 282

WELDING CRANKSHAFTS u Acceptable to buildup undersize. u Not acceptable to repair a crack. Page 283