More Estevan Pictures
From Steve Wolken
A great close uo of the shoe and walking cam on the Prarie Queen.
This setup is known as the " Cam And Frame " system.
Each turn of the walking cam,moves the machine 1 step.
The Walking cucle can best be described in 4 steps, relating to one quarter turns of the walking cam.
Beginning at the PARK position ( shown here)
First Quarter Turn of the walking cycle forces the shoe toward the rear and down to the ground.
The Second quarter turn begins to lift the dragline and force it to the rear.
The Third Quarter continues to force the machine to the rear, and qently sets it back on the ground.
The fourth quarter finally lifts the shoe back off of the ground and returns it to the park position.