Tools and Machinery of the Granite Industry, Part II

Manila rope was used only for lifting light loadsrarely in the quarry. For the same breaking strength, hemp ropes were two to three times the diameter of wire ropes. For equal strength, steel wire rope was just as flexible as manila rope. Wire ropes were both more durable and more efficient (less friction) than hemp ropes. The typical wire rope had a hemp center with six surrounding wire strands, each strand with seven, nine, twelve, or nineteen wires. Wires for the best quality rope were made of crucible cast steel. Wire rope wear was greater for higher speeds and for smaller sheave diameters. Wire rope was used for boom derricks, cableways, and overhead traveling cranes. Seven-wires-per-strand rope (Figure 11) was normally used for standing ropes, such as guys, and nineteen-wires-per-strand rope (Figure 12) was used for hoisting (moving) ropes. The working load for ropes was usually kept at one-fifth or less of the breaking strain. Some example diameters and their corresponding breaking strains for H.H. Harvey's Hercules hemp-center, nineteen-wires-to-the-strand, tempered steel, hoisting rope were: Vs-inch (eight tons), 3/*-inch (29 tons), 1s/8-inch (95 tons), and 2'/4-inch (235 tons). In 1912, the Clyde Iron Works of Duluth, Minnesota, had for sale flattened-strand hoisting rope that presented a 150 percent greater wearing surface. This resulted in less wear to the rope and also less wear on the pulleys, sheaves, and drums over which the rope passed.

The hitches that wrapped around the stone and were suspended over the derrick, cableway, or crane hook to lift the stone were made of rope or chain. Chains could be formed into various sized loops to surround a stone by the use of a grab hook, round hook, or grab link at one end of the chain (Figure 13). However, ropes were considered safer than chains because a broken rope strand was usually easier to spot than a crack in the link of a chain. A quarryman requested a rope or chain of a certain size by the use of hand signals. For example, to call for 1 ½-inch rope-he passed his hand across his stomach; for 1 ¼inch rope he passed his hand across his throat; for 7/8-inch rope he would with one hand grab the thumb of the other hand and wiggle his fingers; and for ½-inch chain he faced both his palms toward each other.

Wire rope could be spliced very much like manila rope, and if properly done, the resulting splice was a very strong and secure join. To splice a rope, the ends were unraveled three feet back. The wire strands were taken two at a time one from each rope end, crossed over, wound around each other, and the ends tucked in so they wouldn't catch. Eyes could be formed by doubling back a rope over a thimble (to protect the rope from wear) and secured with multiple (usually five) rope clamps. Socket shackles (Figure 14) could be secured to the ends of a rope by pushing the unraveled end of the rope (cleaned with acid) into the socket into which molten zinc was then poured. The U-shaped shackle had a removable pin that was itself secured by cotter pins.