Galvanized Steel Cables are largely used for suspension bridges and are composed of six strands with wire centre.
These ropes are exceedingly flexible and are less liable to the crushing action which fre quently takes place in other ropes. They are made up with the wires in the strands and the i strands in the rope laid in the same direction or reversely. Owing to the comparatively little wear which takes place in these ropes, so large a margin between working load and breaking strain is not required as in ropes of ordinary construction. Flattened strand ropes are free from all tendency to spin or kink and a con siderable saving in wear of pulleys and sheaves is effected by their smooth surface which is shown in the two following illustrations: Galvanized Steel Hawsers are usually 37 wires to the strand and combine great strength with pliability. The demand for towing a num ber of heavy loaded barges, practically in all kinds of weather, has called for a wire hawser stronger than any Manila hawser made. The two grades presented in the table — Cast-steel and Special—are made with a hemp centre and six strands of 37 wires each, and of six 24-wire strands and seven hemp cores.
The end sections show a comparison of structure and wearing surface of round and flat tened strand rope.
A flat or ribbon-like form of this rope is made by laying as many strands as desired side by side, and them together with a soft iron wire. The latter wears away and has to be renewed at intervals Flattened Strand Instead of being made up of strands of circular form in cross section, flattened strand ropes are constructed with strands, each of which has one or more flattened surfaces, so that one flattened surface is exposed on the outside of the full length of rope. with the result that a plurality of wires in each strand must at all times take the wear in stead of there being only one external wire in peripheral working in each strand, as is the case with ropes of ordinary construction while new. Until the wear has greatly advanced and consequently a considerable diminution of strength has taken place in an ordinary rope, the friction is borne in a very marked manner upon the crown of the one wire nearest the periphery of the rope in each strand, and in cases where small wire is used it is rapidly worn through, while heavier wire has a tendency to fracture where the abrasion has taken place. Owing to the number of wires that are at all times ex posed to wear in a flattened strand rope for a considerable distance along their re4)ective lengths, a smooth or comparatively smooth sur face is presented even while new, and the wear is consequently light upon any individual wire and the tendency to become brittle is minimized.
Hercules Wire This is a very high grade of rope, the steel for which is specially prepared for it under a patent process and then the wire tempered and drawn by a patent proc ess, producing a steel strong and tough and that is uniform in density, texture, elasticity, elongation and strength, every wire being care fully tested for these points and the tests regis tered for reference. It is a rope that was evolved originally for use in extrahazardous places and where there is liability for rough usage.
A special hoisting rope of 18 seven-wire strands, six of which are laid around the hemp core to the left and the other 12 outside of them around to the right. This rope will hold a load steady without twist ing and spinning.
Aerial Wire Rope Aerial tramways may be used to advantage both in operation and construction for transporting ma terial from one place to another. This is especially true with ores, coal, stone, lime, rock, gravel, earth, sand and cord wood. Packages, lumber, logs, light merchandise and water may also be transported economically. Usually the material is loaded on the cables at one terminal or an intermediate loading station and carried to the opposite terminal where it is discharged.
By means of various devices it can be arranged for the discharging of the material at any point along the line for use in such work as construct ing dams, carrying refuse from plants, etc. Aerial trams can be constructed in a hilly coun try without the necessity of making tunnels, cuts, embankments or bridges as in railway construction. Rivers and ravines are spanned while hills and other constructions are overcome by the line directly over them and supporting it by towers or derricks at the high points. Grades are no barrier to this con struction as they can be built to surmount prac tically any grade and in fact where the loads are carried down grade and the grade is sufficient the entire tramway will be self-propelled, due to the forces of gravity. An aerial tramway is free from surface traffic, so that the underlying ground may be used for other purposes. Tram ways are not affected by the elements, such as snow, sleet, rain or frost and may be operated irrespective of the weather.