BACKHOE OPERATIONS

The backhoe attachment shown in figure 9-37 is used to dig hard material because of the positive pressure created by the hydraulic system. Its digging depth is limited by the length of the boom and dipper stick. The backhoe dumps the material into trucks to be hauled away or into piles alongside the excavation to be used as backfill material. Its dumping range is also limited to the length of the boom and dipper stick.

515 Dresser Backhoe

The 515 dresser backhoe attachment couples easily to the front of the loader frame, using hydraulic controlled pins and quick- disconnect hydraulic fittings. The procedure for setting up the backhoe attached to the 515 dresser is as follows:

1. After the backhoe has been coupled to the front of the front-end loader, raise the boom arm until the

Figure 9-37.-Backhoe attachment.

Figure 9-38.-Backhoe boom arm pivot point.

Figure 9-39.-Backhoe operation locking lever locking plate.

boom arm pivot point is approximately 20 inches from the ground, as shown in figure 9-38.

2. Using the bucket control lever, tilt the backhoe main frame until the top of the main frame is parallel with the ground.

3. For backhoe operations, place the two levers fiut.best from the operator in the hold position. Place the lever closest to the operator in the forward position. Move the locking plate in the position shown in figure 9-39, locking the lever in the forward position and the two other levers in the hold position.

Figure 9-40.-Remote hand throttle assembly.

4. The loader is equipped with a remote hand throttle assembly (fig. 9-40) located on the front cover of the loader, which is behind the backhoe operator's seat. The hand throttle is preset to the backhoe specifications to deliver the proper amount of hydraulic oil flow for backhoe operations. The speed of the engine determines the volume of hydraulic oil delivered to the backhoe and the speed of the cylinder movements. Because of this, you should set the engine at a low speed until you are familiar with the control lever pattern.

NOTE: The backhoe is designed to operate efficiently at a preset gallons per minute flow of hydraulic fluid. Setting the engine throttle in excess of that set for backhoe operations creates excessive hydraulic temperatures and pressures that can damage hydraulic and structural components.

5. Lower the backhoe stabilizer legs to fix the backhoe in position.

6. Warm up the backhoe hydraulic system by extending and retracting each hydraulic cylinder piston rod several times to circulate warm oil through the hydraulic system. When the backhoe hoses feel warm when touched, the backhoe is ready for operation.

WARNING

Before performing maintenance on the backhoe, you must extend the dipper stick fully and set the bucket and stabilizer on the ground. Shut down the engine, and actuate all of the control levers back and forth to relieve the hydraulic pressure in the system.