| 摘要 |
PROBLEM TO BE SOLVED: To prevent a wheel on a rear side of a machine or a crawler mechanism from scraping a ground surface with considerable resistance when the wheel or the crawler mechanism is positioned at a retracted position in a frame. SOLUTION: At least one rear side wheel or a crawler mechanism 4 has a horizontal shaft 7 pertaining to a chassis 8 which is a part of a frame 2. At least one first actuator 9 operated by a steering device 10 operable from a driver's stand 5 for turning the rear side wheel or the crawler mechanism 4 around a vertical shaft 13 while the direction of a front side wheel or crawler mechanisms 3, 3' is changed is provided on the chassis.
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