124 



CABLE-RAILWAYS. 



made sufficiently heavy to take up the slack of 

 the cable and render the friction around the 

 pulleys C and C' ample for the required traction. 

 The foregoing contemplates the simplest pos- 

 sible conditions, namely, a straight, level course, 

 with the driving machinery in direct continua- 

 tion of the line of rails. In practice, these con- 

 ditions are always complicated. The engine- 

 house must usu- 

 ally be at one 

 sideofthetrack, 

 so that the ca- 

 bles must be de- 

 livered and re- 

 ceived at right 

 angles with 

 the service-line. 

 This is easily 



three feet apart. In this case the grip is not 

 released, but a nice adjustment is required, so 

 that the grip-bar shall fairly clear the sheaves 

 and yet not receive too much lateral strain 

 from the tension of the cable. This adjustment 

 is effected by an iron guard, just above and a 

 little in advance of the sheaves. Against this 

 guard an attachment of the grip-bar bears 

 while the car is rounding the curve. 



In some situations the tunnel is unnecessary 

 such, for instance, is the bridge between 

 New York and Brooklyn, where the track is 

 given exclusively to car-traffic. In such case, 

 while the same general rules govern the con- 

 struction, the cable and carrying-sheaves are 

 easily accessible for inspection and repair, while 

 frequent traps or man-holes are required in a 

 tunnel line. On the other hand, the cable, 



effected by passing each cable 

 around a grooved wheel, F, F', 

 Fig. 4. Again, there are usually 

 changes of grade, and horizontal 

 changes of direction. In chang- 

 ing from a level to a downward 

 incline, or from an upward in- 

 cline to a level, the weight of 

 the cable will keep it in place ; 

 but the change from a level to an upward in- 

 cline tends to lift the cable from its carrying- 

 sheaves. At such angles depression-sheaves 

 are placed at the top of the tunnel. They are 

 exactly like the carrying-sheaves, and are hung 

 so that the grip will pass below tnem by about 

 as much as it passes above the carrying-sheaves. 

 The same rule applies in a change of grade from 

 a downward incline to a level. When the 

 grip has hold of the cable, the latter is lifted 

 clear ot the carrying-sheaves at that point, but 

 must, either by gravity or some mechanical de- 

 vice, return to them as soon as the grip passes. 

 In changing direction horizontally, two 

 different methods may be followed. (See Fig. 

 5.) The heavy black line represents the cable, 

 and the broken lines the rails. At the left the 

 direction is changed by passing the cable around 

 a sheave turning on a vertical 

 axis, and with its periphery 

 , touching the two lines of direc- 



tion. In such a case as this the 

 I cable is released, while the car 



goes around the curve by its own 

 momentum, aided, if possible, by 

 gravity. At the right of Fig. 5 



\ the cable bears sidewise against 



a series of sheaves, set about 



Fio. 4. TENSION ARRANGEMENTS. 



being exposed to the weather, becomes wet, 

 and often more or less coated with ice for its 

 entire length. 



The life of a cable appears to depend mainlj 

 upon the grip, and much ingenuity has been 

 expended upon devices that can be trusted to 

 bear any probable strain and yet will not wear 

 out the cable. A grip that clasps the cable 

 like a vise is the simplest and most trustworthy, 

 but it is very destructive to the cable, because, 

 while it is tightening, the friction must of 

 necessity be great. On a railway in Hoboken, 

 N. J., a cable was recently worn out in less 

 than three months by a grip of this kind, while 

 that on the Brooklyn Bridge lasted for three 

 years, and even then did not show much ex- 

 ternal wear. Its inside strands, however, had 

 been crushed by pressure and incessant use, for 

 this cable runs day and night 

 without stopping, and during the 

 busy hours draws heavy trains 

 at intervals of one minute and a 

 half; 26,000,000 passengers were 

 transported by this cable during 

 the year. This difference in 

 wear of cable is due to the use 

 of a grip devised by W. H. Paine, 



J3 



Fio. 5. HORIZONTAL CHANGES OF DIRECTION. 



