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Winches used in oceanographic investigations vary so widely in construction that it is impossible to describe any standard designs. The type and design of winches depend not only upon the character of the work contemplated but also upon the size of the vessel, the space available for the installation, the length of wire rope to be carried, and the power for operating the winch. Details of construction and installation of the winches on the vessels listed in table 57 may be found in the references cited.

Winches may be classified under three headings, depending almost entirely upon the strength of the wire rope they carry.

Sounding winches are relatively light. They carry single or multistrand wire of small diameter and are designed for sounding and for obtaining bottom samples with light gear. Sometimes they can be used for other types of oceanographic work. An electric powered deep-sea sounding winch is described by Parker (1932).

Hydrographic winches are moderately stout. They carry somewhat heavier wire than the sounding winches and are designed for handling water-sampling devices, thermometers, and plankton nets. Since the introduction of sonic sounding methods, winches especially designed for taking wire soundings are not so common, and hence hydrographic

winches may be used when it is necessary to take wire soundings or bottom samples.

Heavy winches are strongly built to carry the largest and strongest cables. They are used for dredging, trawling, anchoring in deep water, and for any other work requiring heavy equipment or the ability to withstand a great strain.

The construction of winches depends not only upon the size of wire rope handled, but also upon its length, since those carrying small amounts need not be so large or so strong as those that must handle several thousand meters of wire rope. For investigations in the open sea, winches should carry at least 5000 m of cable, and for studies in the deeps, more than 10,000 m may be required. Winches carrying only a few hundred meters of wire rope can be cheaply built and, if necessary, operated by hand. However, heavy winches and those carrying large amounts of wire are always power driven. Winches may be operated by steam, as on the Discovery II, by gasoline or diesel motors coupled directly to the winch, by the main engine through some suitable mechanism, or by electric motors. Because of its economy of operation and its flexibility, steam is in many ways the most desirable source of power for winches, but it is practical only on steam-driven vessels. Oceanographic winches are now most commonly operated by electric motors. It is essential that all winches, particularly those used in handling water-sampling devices and nets, have a considerable range in speed of lowering and hauling in. They must also be capable of being controlled quickly and accurately so that instruments can be lowered to a predetermined depth and raised to a convenient level above the water for examination or removal from the wire. The maximum rate of haul on the hydrographic winch should be about 200 m/min. If electric motors are used to operate winches, speed control is obtained by the use of rheostats. In certain installations, reduction in speed also reduces the horsepower of the motor, but such designs should be avoided, because heavy loads must be hauled in slowly.

Electric motors mounted on deck must be waterproof, and the winches themselves must be so constructed that they can be readily lubricated and protected from corrosion by salt water. Winches carrying large amounts of wire rope must have drums with extremely staunch flanges; otherwise, the packing of the wire may break the flanges away from the core when the winch is hauling in under tension.

Spreaders of some type are necessary to lay the wire smoothly and evenly on winch drums that carry large amounts of wire rope. If no provision is made for such spreaders, the wire may accumulate unevenly on the drum, causing the strands to break down and, what is more serious, causing the wire to slip down between the underlying coils in such a way that when payed out again it may be badly snarled. Spreaders may be

operated by hand, but are generally an integral part of the winch and are mechanically operated.

The hydrographic and sounding winches are customarily placed on deck near the rail, where they can be conveniently operated and where the wire rope will clear obstructions on deck and on the hull. The heavy winch, which is more bulky, must be installed in such a way that it can be strongly supported, can withstand heavy loads, and will not affect the stability of the vessel. On smaller craft it is commonly installed amidships below deck or, sometimes, half sunk below the deck level. The axis of rotation of the heavy winch is generally athwartships.

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