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CHAPTER 11

CHAPTER 11. Crankshaft and Bearings Piston and Rods Page 276 Classroom Manual Page 276 Lab Manual. CHAPTER OBJECTIVES. Analyze wear & damage to Crank & Bearings. Analyze wear & damage to Piston and Rods Select the most appropriate repairs to perform. Explain theory of engine balancing.

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CHAPTER 11

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  1. CHAPTER 11 • Crankshaft and Bearings • Piston and Rods • Page 276 Classroom Manual • Page 276 Lab Manual

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

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

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

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

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

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

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

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

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

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

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

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

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

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