Page 18 - Cat Motor Grader Application Guide AEGQ0947-00

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Road Rebuilding

Moldboard Positions Used in Vee Ditching

Tip the blade to place the top of the moldboard slightly ahead of the cutting edge (approximately 2 inches or 5.1 centimeters). From this position, tip the blade forward or back as needed to meet the material requirement. This is the normal tip position used unless specified otherwise.

On the marking pass have the blade at a steep angle to the frame (near 45 degrees), with the toe of the moldboard at the outside edge of the front tire. The heel of moldboard should be raised nearly full height to place material between the tandem tires. Adjust the moldboard to cut a shallow marking pass.

Circle the moldboard to an extremely steep cutting angle.

Typical Ditch Cuts and Marking Ditch

Lean the top of the front wheels toward the heel of the moldboard, using only enough lean to counter side draft. Using excessive lean will cause the machine to wander off course.

On pass number 1, cut just deep enough to mark the intended line (4 to 6 inches deep or 10.2 to 15.2 centimeters deep). This pass should be made in first or second gear with the differential locked.

When marking a ditch through a tight curve, do not lock the differential. Keep as close to the intended line as possible. Some slight ditch line corrections can be made on succeeding passes. On pass number 2, place the front wheels into the marking ditch and cut deeper while holding the desired slope.

Succeeding cuts can normally be made at deeper and higher ground speeds than the marking pass. After several cutting passes, the shoulder windrow must be moved to the road center. Alternate between cutting passes and windrowing material toward the centerline as needed.

C A U T I O N

On straight sections of road use Straight Frame Mode for deep ditch cutting passes to avoid possible: • Tire Sidewall Damage. With articulation on straight sections, the front or rear tandem tire can be forced against the ditch backslope, possibly causing sidewall damage. Rocks or other objects can be trapped between the tire sidewall and ditch backslope, damaging the tire sidewall. In corners, articulation can prevent the rear tandem tires from tracking on the backslope.

• Loss of Air Pressure or Damage to the Rim. Using articulation on straight sections can force material between the tire bead and rim, causing loss of air pressure in the tire. • Have tire pressure at the proper level before starting any ditching work. Extended periods of deep ditching will require higher air pressure and/or tubes in the tires.

M S E R I E S M O T O R G R A D E R S A P P L I C A T I O N G U I D E

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Page 18 - Cat Motor Grader Application Guide AEGQ0947-00

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