WIRE ROPE, a variety of ropes of iron or steel wire extensively employed in raising and lowering apparatus in coal mines, as standing rigging for ships, as substitutes for chains in suspension bridges, and for telegraph cables. Endless wire ropes or cables arc also used on traction railways, and in transmitting power over long distances where ordinary belting would prove unsuitable. A special type is used for the controls in aeroplanes. Wire ropes were used in 1822 for a suspension bridge at Geneva, and for a similar structure of great span at Freiburg in 1835. Their manufacture, however, is of extreme antiquity, a section of a four strand wire rope 15 feet in length having been dug up at Pompeii. This rope was of bronze. A variety of machines are in use for making wire rope. The equivalents of round ropes of iron, steel and hemp are here tabulated: sheave shall equal 100 rope diameters Ex perience has demonstrated that the wear in creases with the speed. It is therefore better to increase the load than the speed. One-fifth ,1 the ultimate strength of rope is considered a fair working load. Five grades of wire rope are recognized according as they are made of iron . crucible cast steel; extra strong crucible cast steel; plow steel; and 'Monitor' plow steel — an exceptionally high grade. Each of these may in a general way be regarded as 10 per cent stronger than the grade preceding it. The Monitor rope, however, is quite stiff in propor tion to its diameter and requires a larger mini mum sheave in operation. The following table shows the minimum diameters of the sheaves required for the more commonly used varieties of wire rope, and the safe load which the sizes named will bear in common usage. The table is based on crucible cast steel, as the material gen erally employed. Wire rope must not be coded Dimensions and Durability.— In the United States the wire rope generally in use is com posed of a hemp centre around which are laid six strands of 7, 9, 12 or 19 wires, thus forming a rope of either 42, 54, 72 or 114 wires. Ropes with seven wires to the strand are generally used for elevators of all kinds, standing ropes, guys, transmission of power, etc. Ropes with nine wires are generally used for haulage ropes in mines, on inclines and for transmission of power. Those with 12 wires to the strand are
generally used for shiprigging and 19 wires for hoisting. 'Special flexible" rope has six strands of 37 wires each; and 'extra flexible" has eight strands of 19 wires each. These ropes are em ployed in hoisting, on dredges, cranes, etc. The standard haulage rope has six strands with seven wires to the strand. •Running rope' has ordinarily six strands of 12 wires each. Wire rope is as pliable as hemp rope of equal strength and can be operated over sheaves and drums (.1 (quivalcnt sizes and is far more dur able and efficient. Durability of wire rope depends prm. pally upon the diameter of the sheaves or drums; the greater the size of the •heavcs ur drums, the longer the rope will last. The rule commonly followed in wire trans mission is that the minimum diameter of the or uncoiled like a hemp rope. When not on a reel, roll on the ground like a wheel or hoop to prevent twisting or untwisting. Galvanized rope should never be used for running rope. To preserve wire rope under water or under ground, add one bushel of fresh slacked lime to a barrel of mineral or pine tar—boil and apply hot. On inclined planes the grooves of the pulleys or idlers should be lined with wood or babbitt metal. It is recommended to use as few idlers as possible. In a great many cases they do more harm than good For transmis sion of power the shoves should he lined with leather or India rubber, to secure increased ad hesion and prevent wear. The radius at the pit of the groove should always be greater than that t f the rope, so that the latter drives only by fric tion in the bottom of the groove. The use et cast-steel rope is becoming general because of its lightness, greater strength and duralselets To get th&c best results, steel rope should be of the best quality of crucible cast steel Ropes made from low grades of steel are in ferior to iron ropes. The use of Bessemer steel in running ropes is not advisable. Rope. should bc examined frequently and a new rope ordered before the old one is allowed to out. Attention to this will insure safety and prevent serious accidents.