GYRO STATIC ACTION 



29 



arrow T represents the torque which must act on the propeller shaft. 

 This torque is exerted upon the propeller shaft by the bearings as 

 indicated by the arrows FF' in the top view, Fig. 20. The high 

 speed and great weight of the rotating parts of a steam turbine 

 represent a very great spin-momentum (arrows 8 and S' in Fig. 19 



Pig. 20. 



very long) so that the increment of spin-momentum A$ which corre- 

 sponds to a given angular movement of the ship is very considerable, 

 and the torque T is great. Therefore the forces FF' in Fig. 20 may 

 be very great. These forces are transmitted to the bearings of the 

 propeller shaft through the hull of the vessel from the middle and 

 forward parts of the vessel, and therefore excessive stresses may be 

 brought into existence in the hull. It is supposed that the loss of the 



Fig. 21. 



British torpedo boat Viper several years ago in a rough sea was due to 

 this action. 



Figs. 21 and 22 represent the details of the gyrostatic action of a 

 high-speed steam engine, such as is used for driving dynamos on board 

 ship, the shaft of the engine being athwartship. In Fig. 21 the ship is 

 represented as rolling in the direction of the curved dotted arrow, 

 and T in the vector diagram represents the torque which must act upon 

 the engine shaft. The details of this torque action are shown in Fig. 



