quite conceivable that hydraulic drives will find increased future application. The double-drum units may have
two-drive units which can be clutched separately, one to each drum, or in tandem to a single drum for
increased power. Less-sophisticated units use a self-contained diesel engine drive connected through a torque
converter and/or an appropriate mechanical transmission.
K-3.1.4 Automatic Features. All machines have brake systems that will slip at some point. However, the set
level may not be very reliable, and the drum is often locked by a dog or pawl. The next level of sophistication is
an automatic payout capability when the tension exceeds a set level. There may be a limit on the total length of
hawser permitted to be paid out automatically. Finally, the most sophisticated machines have an automatic
reclaim capability, with a limitation on the net allowable length to be reclaimed.
K-3.1.5 Instrumentation and Controls. All units have local control capability and many have a remote
operation station. Instrumentation generally includes cable tension, length of cable paid out, motor speed
indicator and automatic payout/reclaim set points. Some of the instrumentation may be repeated on the bridge.
K-3.2 TRACTION WINCHES . In the U.S. Navy, traction winches were introduced for use with the large
synthetic hawsers that gained popularity in the 1960s. Traction winches also are finding application with wire
hawsers in powerful commercial tugs.
K-3.2.1 General Description. Traction winches always have two parallel cylinders with grooves sized to accept
the intended hawser. There are four or more complete wraps of the hawser around the two cylinders. Both
cylinders are powered to transport the hawser. The orientation of the cylinders or drums can be either horizontal
or vertical In principle, traction winches are similar to capstans. The two-drum arrangement eliminates the axial
skidding of the rope inherent in capstans, and permits the grooving that improves support and reduces wear on
In contrast to requirements of drum-type winches, a long line can be loaded onto a traction winch at any point
within its total length. This is useful for mooring purposes and was the reason for their first marine use-for
control of mooring lines on large ships and for Single Point Moorings used in the offshore oil industry.
K-3.2.2 Hawser Storage. Conventional winch designs are not used with fiber towing hawsers for two reasons-
the large size required and problems inherent in wrapping and storing a tensioned, highly elastic line on itself.
Storing the untensioned fiber hawser on a drum is feasible, but storage bins are universally used. The traction
winch can easily pull the hawser from its storage location, via appropriate fairleads. Re-stowing the hawser as it
is recovered is more difficult and sometimes requires hands-on effort.
K-3.2.3 Traction Winch Operation. Traction winches are motor-driven, sometimes with variable speed
capabilities. They have brakes and clutches for control When de-clutched, they can be overhauled by the
hawser to provide for free release of the hawser in emergency. Some traction winches have an automatic
tension payout capability, but automatic reclaim is rare on fiber line systems because of the hawser storage
system described in the previous sub-section.
K-3.2.4 Controls and Instrumentation . Traction winches have local and/or remote station controls. Most have
tension readouts and some have hawser scope (without stretch compensation) instrumentation. Some traction
winches will have end-of-hawser warning or shutdown systems.