The applications of wire ropes are very numerous, an important one being for winding and hauling purposes in mines. For aerial ropeways they are extensively employed, and are of high value in bridge building, the suspension bridge being sustained by them. The strength of the steel wire used for ropes varies from seventy to over one hundred tons per square inch of sectional area, the weight of a hemp rope being about three times that of a wire rope of equal strength.
Pine Tar for Ropes.
Who does not know of the tarred rigging that once meant so much to the rope maker? Its very odor seems to cling to the pages of seafaring books. When steam power took the place of wind power in ships the use of tarred rigging naturally declined, yet tarred goods still form an important branch of the rope business. Pine tar is the kind best suited for cordage, the yellow, longleaf, or Georgia pine holding the first rank in the United States for tar making. This tree is found along the coast region from North Carolina to Texas.
In tar-kiln burning only dead wood is used, the green tree yielding less tar and of lower quality. It is a slow process, as a brisk fire would consume the wood without yielding tar. As the tar comes from the kiln it is caught in a hole dug before the outlet and is dipped up and poured into barrels, the average yield being one barrel of tar to the cord of wood. As above said, it is indispensable to protect cordage exposed to the effects of moisture, except in the case of coir ropes. Oiling is also an important process in the manufacture of ropes from hard fibers, as Manila, Sisal and New Zealand. This softens them and makes them more workable, and it also acts as a preservative.
Inspecting Manila Fiber at Dock
Shipping Platform of a Large Factory