| 摘要 |
Disclosed is a polar crane supported by a rail and having a bridge and a bridge-supporting end truck at each end of the bridge. Each end truck has, for either direction of revolving bridge motion, a leading wheel contacting the rail. In the improvement, the leading wheel of each end truck has a single flange and the flange is inward of the rail. Skewed crane "lock-up" is thereby substantially prevented. A related method for modifying a polar crane includes raising the first end truck away from the rail, removing a two-flange wheel (the leading wheel) from the first end truck and installing a one-flange wheel in place thereof.
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