212 ACTIVE TYPE OF STABILIZING GYRO. 



This feature is of great value when appUed to ships in icebound waters, 

 inasmuch as it enables them to keep free of the ice. In the case of the S. S. 

 Ashtabula, we have a ship of about 5,000 tons displacement plying regularly 

 between ports of this country and Canada across Lake Erie. Her general 

 dimensions are as follows: Length, 370 feet; beam, 56 feet; displacement 

 loaded, 4,500 tons; draught, 11 feet; period, from 5.5 to 6.6 seconds. In 

 stormy weather she has rolled in the neighborhood of 35 degrees or through a 

 70-degree arc. In this instance and on Lake Erie this rolling is usually due 

 to a succession of comparatively small increments, the magnitude of which 

 has been ascertained. 



In Fig. 14, Plate 87, and Fig. 15, Plate 88, are shown an active gyro and 

 damping tanks of equivalent stabilizing power which have been carefully 

 calculated from known formulae, the analyses of which have been brought to 

 conform exactly to the formulae of Herr Frahm. These formulae have also 

 been used in the diagrammatic analysis. The metric system has been used 

 throughout to facilitate the comparison. The period of this ship varies from 

 5.6 to 6 seconds according to the number, weight and distribution of railway 

 cars upon her four tracks. The total net load capacity of this vessel is about 

 1 ,500 tons. The tanks in each instance have been designed for taking care 

 of one-degree wave slope increment. Since the trips are of comparatively 

 short duration and the load varies through quite a large range, the adjustment 

 of the tanks would be imperative to bring them into synchronism. There 

 would be no reserve quenching power available in the tanks shown, the free 

 space necessarily being small. There being no available space above the 

 main deck for the tanks, they are placed below. 



Keeping the characteristic displacement X period X M. G. constant, 

 we have the following results as to tanks and gyro : — 



