TESTING WIRE ROPES. 665 



certificates of the ultimate stress, it is found that a variation of 8 

 per cent, below the guarantee is permissible, as it is impossible to 

 make steel wire perfectly uniform in temper, strength, and composi- 

 tion. Exception has sometimes been taken to laboratoiy tests of 

 M'ire ropes on the ground that there is no guarantee that the piece 

 so dealt with will reveal the defects in the whole rope. This at (he 

 first glance may appear to be a very strong objection, and there are 

 those who argue that the only way to test a wire rope is to attach to 

 it a weight equal to about one and a half times its usual working 

 load. Then, if it does not bi-eak, it is said to be safe. To this 

 argument it may be replied that a dead-weight test is, if unintelli- 

 gently applied, a source of considerable danger. The writer has 

 known a new piece of rope 500 ft. long, when subjected to this test, tO' 

 stretch 11 ft., and take tliree weeks to shrink to its former length. 

 During this time it will be readily understood that the engine-driver 

 was subjected to considerable annoyance. When applied to a rope 

 that has seen sei'vice, the dead-weight test may be a death trap, since 

 having stretched very much while working it will require very close 

 oljservation to determine the amount of elongation, if any, under 

 test. The rope's limit of elasticity may be exceeded, and what may 

 be called " a permanent set " put in it which may cause it to break 

 in the near future. The customary examination of winding ropes at 

 mines is generally made once a week, when the ropes are run through 

 some cotton waste held in a man's hands, and unless broken wires are 

 found the rope is said to be in good order. As a rule, little notice is 

 taken of the flattening of tlie wires, and no efi'ort is made to ascer- 

 tain the amount of corrosion. The chief causes of deterioi-ation in 

 winding ropes are wear, corrosion, and crystallisation. In a vertical 

 shaft Avear is caused by the rope coiling on the drum, and passing 

 over the pulley wheel; this causes frequently a flattening of the wires, 

 more especially when the drum is narrow and the rope coils several 

 times on it. Sometimes also a new rope is damaged by being put 

 over an old pulley wheel which has been grooved by a smaller rope- 

 In an underlay shaft there is, in addition to these causes, wear 

 due to the rope passing over rollers in the shaft, wear caused 

 by changes of grade causing the rope to bang up and down between 

 the hanging and foot walls of the shaft, and in a flat and underlay 

 shaft wear is caused by the rope being dragged along the footwalL 

 In many vertical shafts in metalliferous mines the shaft traffic is 

 so small that after three or four years' work the wires show hardly 

 any flattening. Corrosion may be either internal or external. If the 

 former, it is probably caused by water getting into the heart of the 

 rope. This kind of con-osion is extremely difficult to find out, and 

 frequently it is not suspected imtil the rope breaks. Water often 

 finds its way into the centre of a rope owing to neglect to properlv 

 clean and oil it, and owing to the use of a stiff lubricant which does 

 not penetrate beyond the outside of the rope. Some lubricants that 

 act very well in a cold climate become gummy in Australia. Outside 

 corrosion may be caused by bad lubricants failing to protect the 

 wires, or by water in the shaft. When selecting a lubricant for a 

 roi)e, the greatest care is necessary, as acids in a lubricant may do 

 great damage. Formerly a favourite lubricant consisted of Stock- 

 liolm tar and castor oil. Since it was discovered that Stockholm tar 



