Abstract: A system is provided for automatically clamping a cable drum in the event of mechanical failure of the drive train that connects the cable drum to its prime mover. The system monitors the mechanical continuity of the drive train by comparing the number of revolutions of the prime mover with the number of revolutions made by the cable drum in the same time interval. The system actuates a caliper disc brake mounted with the drum if a discontinuity of the drive train is detected. In the electrica system, shaft encoders are used on both the cable drum axle and prime mover shaft. The cable drum encoder is selected such that the number of pulses it produces per revolution of the cable drum is approximately equal to the number of pulses produced by prime mover shaft encoder per revolution of its shaft divided by the speed reduction ratio of the drive train.

Abstract: A convertible crane is provided with a main trolley which carries a powered hoist along a horizontal path. A trailer trolley also carries a hoist which is powered from the main trolley. Each of the hoists thus have a powered drum which will increase the total line capacity of the crane allowing the crane to be used for temporary longer load travel or higher capacity lifting depending upon the amount of reeving or parts of line used to support the load from the trolleys.