WALKING MACHINERY CONTROL

The walking process can be separated into 4 distinct phases, as follows:

• During the first quarter turn of the eccentric, the walking shoe moves from its “top dead center” or parked position toward the rear of the machine and down until it contacts the ground. Refer to PHASE 1 on the previous page. Just before the eccentric turns into the second quarter of its rotation, the rear of the machine and the rear edge of the tub raise and move slightly forward. This movement raises the tub out of any depression formed while digging and breaks any suction between the tub and the ground.

• During the second quarter turn of the eccentric, (PHASE 2) the shoes cause the machine to move rearward, dragging the front edge of the tub along the ground.

• The third quarter turn of the eccentric (PHASE 3) completes the propel movement of the machine. Near the end of this quarter turn, the machine is slowly lowered and the tub settles down onto the ground again.

• The fourth and final quarter turn of the eccentric raises the shoes into their park position (top dead center). The shoe return mechanism on each shoe realigns it parallel to the rotating frame as it is raised.

WALKING MACHINERY CONTROL

The Drag-Propel Contactors, located in a cabinet on the machinery deck in front of MG set #1 on the left side of the machine, electrically move the drag motors and the propel motors into and out of the drag generators loop, depending on what machine control mode the operator selects. In the DIG mode, the drag (left) controller in the cab controls the drag motors for digging. In the PROPEL mode, this same lever controls the propel motors for walking.

The walking shoes at each side of the machine are not mechanically connected. The position of the two shoes is electrically monitored to keep them in time/synchronized. This timing system detects when one shoe gets ahead of the other and generates an error signal to slow down the leading shoe and speed up the trailing shoe. This timing system functions to align the shoes only when they are approaching or have lifted off the ground and when the tub is nearing the ground after the step. This provides a smooth, shock-free propel movement. Once the shoes have contacted the ground and commenced the propel motion, the timing system will not alter their speed. The propel portion of the step will be completed. The encoders in this timing system are also used to detect when the shoes are at their “top dead center” or PARK position.