tensile force 
ocean surface 
turning moment ocean surface 
Eee ee NS 
tensile force 
cable 
20,000 feet 
20,000 feet 
pump or 
generator 
ocean floor ocean floor 
Figure 19. Schematic of linear-motion Figure 20. Schematic of rotary-motion 
cable power transmission cable power transmission 
system. system. 
The rotating cable system was analyzed by applying Petroff's equation 
for a journal bearing with no radial load (Shaw and Macks, 1949): 
= @rrt(m 2atN) (6) 
where F = friction force (Ib) 
r = radius (in.) 
L = length (in.) 
M = viscosity (reyns) 
N = rotation speed (rpm) 
c = boundary (in.) 
The results for rotating a galvanized bridge rope at three different angular 
velocities are presented in Table 2. It should be noted that with low angular 
velocities, the skin friction and input horsepower are low. However, to 
transfer power equal to that of a higher angular velocity, a low angular 
velocity requires a large power torque necessitating a larger and heavier 
cable. 
19 
