Can You Repair A Damaged Rod Journal On A Crankshaft?

Figure 3-28.—Checking the alignment of a connecting rod. REPAIRING CRANKSHAFTS AND Journal BEARINGS The repair of crankshafts and bearings varies depending on the extent of impairment. There is no doubt about the necessity for replacing such items equally broken or bent crankshafts. Out-of-round journals may be reground and undersize begetting shells may exist installed, simply this requires personnel skilled in the apply of precision tools. If a new shaft is available, it should exist installed and the damaged shaft should be sent to a relieve reclamation centre. Under certain conditions, scored crankshaft journals or damaged journal bearings may exist kept in service if proper repair is performed. Repair of SCORED JOURNALS depends on the extent of scoring. If a crankshaft has been overheated, the effect of the original heat handling will accept been destroyed. In this case, the crankshaft should be replaced. If journal scoring is only slight, you can use an oilstone for dressing purposes if you take precautionary measures with respect to abrasives during the process. During the dressing operation, plug all oil passages within the journal and those connecting the mainbearing journal and the adjacent connecting rod journal. In the dressing procedure, use a fine oilstone, followed with crocus cloth, to smoothen the surface. After dressing journals, always wash them with diesel oil. This procedure must include washing the internal oil passages too as the outside journal surfaces. Some passages are large enough to accommodate a cleaning castor; smaller passages tin be cleaned by blowing them out with compressed air. Always dry the passages by blowing compressed air through them. NEVER STOW A CRANKSHAFT OR Bearing PART ON Whatever Metal SURFACE. When you remove a shaft from an engine, place it on a wooden plank with Figure 3-29.—Using a strain or deflection gauge between creepo webs. all journal surfaces protected. If the shaft is to be exposed for some time, protect each periodical surface with a coating of heavy grease. Ever place bearings on wooden boards or clean cloths. CRANKSHAFT overhaul consists of an inspection, servicing for scoring and wear, and a determination of each crank spider web deflection. Take crank web deflection readings according to the Planned Maintenance Organization (PMS). A strain gauge, often called a crank web deflection indicator, is used to take deflection readings. The gauge is only a dial-reading within micrometer used to measure the variation in the distance between next crank webs as the engine shaft is barred over. Figure 3-29 shows a strain judge between creepo webs. When you lot install the gauge, or indicator, betwixt the webs of a crank throw, be certain to place the judge as far equally possible from the axis of the connecting rod journal. Balance the ends of the indicator in prick-punch marks in the crank webs. If these marks are not nowadays, make them and so that the indicator tin can be placed in its correct position. Consult the manufacturer'south technical transmission for the proper location of new marks. Readings are generally taken at the four crank positions: tiptop dead center, inboard, most or at lesser expressionless eye, and outboard. In some engines, it is possible to take readings at bottom dead centre. In others, the connecting rod may interfere, making it necessary to take the reading as most as possible to lesser expressionless center without having the gauge come in contact with the connecting rod. When the gauge is in its lowest iii-19