MOTOR GP-HYD 10R3339 - Caterpillar

Gear Drive Units
Remote mounted gear drive units must be supported by the same base or rails as the engine. These units are not fastened to the engine except through a driveshaft and flexible coupling. To install these units, the gear drive must first be aligned with the equipment that is driving; and then the engine must be aligned with the gear drive unit.Alignment between the gear drive unit and its driven equipment is usually line-to-line alignment. The centerline of the gear drive output shaft is in line with the centerline of the input shaft of the driven equipment. Depending upon the application, it may be necessary to use a flexible coupling between the gear drive unit and the driven equipment.Alignment between the gear drive unit and the engine is always an "offset" alignment. The centerline of the engine crankshaft is positioned below the centerline of the gear drive input shaft. This compensates for the thermal growth of the engine, flywheel sag and main bearing clearances during cold alignment. With this vertical "offset" in the cold condition, the crankshaft and gear drive input shaft will be in correct alignment at operating temperature. Because of this "offset" alignment, the coupling between the engine and gear drive unit must be a flexible coupling.Use shims as necessary between the mounting pads of the gear drive unit and the base to put the gear drive unit in alignment with the driven equipment. There must be solid contact between the mounting pads and the base at all locations without the anchor bolts installed. If all mounting pads are not solidly supported, distortion of the gear drive unit may result when the anchor bolts are tightened.Install a ground body bolt (fitted bolt) at the rear of the engine right rail to direct horizontal thermal growth of the engine away from the coupling. Use clearance type bolts at all other mounting locations.The allowable misalignment between the output shaft of the gear drive unit and the input shaft of the driven equipment must be within the coupling manufacturer's tolerances.After the gear drive unit is aligned and mounted, align the engine with the gear drive unit. Use dial indicators fastened to the input shaft of the gear drive unit to check for correct bore and face alignment with the engine.When aligning the engine to the gear drive unit, the coupling misalignment limits must not exceed the limits established for a Caterpillar viscous damped coupling. See Special Instruction Form SEHS7073, "ALIGNMENT OF TWO BEARING GENERATORS" for specifications on the Caterpillar viscous damped coupling.Check crankshaft end play before and after alignment with the gear drive unit, and again with the units at operating temperature. There must be no reduction in end play after alignment of the engine or at operating temperature.After the engine is in correct alignment with the gear drive unit, install shims as necessary between the engine rails and base to maintain this alignment. There must be solid contact between the rails and base at all mounting locations