| 摘要 |
An excavator has an undercarriage supported on three pair of driven ground wheels. The middle pair of wheels is disposed lower than the remaining wheels so as to enhance the skid-steering ability of the excavator. A dozer blade is mounted to the front of the undercarriage. A caster wheel assembly is mounted to the outer end of the excavator boom and actuators associated with the latter are operable to bring the caster wheel into ground contact ahead of the blade and to exert a down-pressure sufficient to cause the undercarriage to rock rearwardly about the middle pair of wheels to a stabilized condition, where the excavator weight is carried by the middle and rear pair of wheels. Grading operation can be done when the undercarriage is in its stabilized condition.
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