The forced-synchronization type of clutch requires
ships service air and MRG LO availability before
normal engagement can occur. The clutch is made up
of a friction pack and dental clutch assembly. The
friction pack is needed to bring the GTM input shaft
speed to within 11 rpm of the first reduction pinion.
Once the speed permissive are met, air pressure is
applied to the dental clutch to complete engagement.
When the dental clutch is engaged, all torque is
transmitted from the GTM input shaft to the MRG's first
reduction pinion. This clutch assembly also houses a
friction-type PT brake that serves two purposes. The
primary purpose of the PT brake is to stop and hold the
PT stationary. If the PT brake is used with an engaged
clutch, the PT brake also acts as a shaft brake. The
forced-synchronization clutch is being phased out of
Navy service in favor of the SSS clutch.
Synchro Self-Shifting Clutch
Like the forced-synchronization clutch, the SSS
clutch performs the same functions by transmitting
engine torque through the input shaft to the MRG first
It does not, however, require any
external controls to perform the engagement sequence.
For clutch engagement to occur, the SSS clutch requires
only that the input shaft speed be greater than the speed
of the first reduction pinion. The SSS clutch is fully
automatic. By design, centrifugal force causes the main
sliding member to move and engage with the output
Depending on the ship class, the SSS clutch system
uses two different types of PT brake assemblies. The
CG-47 and DD-963 class ships have a similar PT brake
assembly. The PT brake assembly is an internally
housed friction clutch design that is mounted to, but
operates independently of, the SSS clutch assembly.
There is one main difference between the CG-47 class
ships brake and the one installed on the DD-963 class
ships. The CG-47 brake cannot be used as a shaft brake.
Because of the SSS clutch design, even if the brake is
applied with the clutch engaged, the clutch will
disengage once the PT input speed drops below the
speed of the first pinion.
The other type of PT brake assembly is the one
installed on the DDG-51 and FFG-7 class ships. This is
a single-disc caliper brake assembly that is externally
mounted to each PT input shaft. These brakes are used
with the SSS type of clutch in which their only purpose
is to stop and hold the PT stationary when required.
The last type of brake assembly we will discuss is
the shaft brake assembly. Shaft brake assemblies are
installed only on FFG-7 class ships. The shaft brake
assembly is also a single-disc caliper brake assembly,
such as the PT brake assembly we just described
Consisting of two complete units, a shaft brake
assembly is mounted on each starboard first reduction
quill shaft. Once all permissive are met, the single
purpose of thiS brake is to stop MRG rotation.
MAINTENANCE OF EQUIPMENT AND
The maintenance of the clutch and brake assemblies
and associated equipment and components is normally
done according to the PMS. General cleaning, tests, and
inspections will be your primary concern. Because of
the good operational track record associated with the
SSS clutches, troubleshooting and repairs should be
minimal. This good operational record is the main
r e a s o n
p h a s i n g
o u t t h e
forced-synchronization type of clutch in favor of the
In the following paragraphs, we will discuss some
general maintenance and repair practices associated
with clutch and brake assemblies. You, the GS
supervisor, must be familiar with these practices so you
can properly supervise maintenance and repairs.
The cleaning of the clutch and brake assemblies is
done primarily when the MRG is cleaned Cleaning the
clutch assembly is limited to external cleaning. Pay
attention to the areas around the inspection and access
cover plates and the clutch position indicating ports.
The cleaning of externally mounted brake
assemblies requires a little more effort. To properly and
thoroughly clean any of the external brake assemblies,
you must remove the guard screen. Once you remove
the screen, pay particular attention to removing any dust
accumulation on the brake and to the cleanliness of the
disc. It is important that you keep dust accumulation to
Once dust mixes with oil, it can be
deposited on the brake disc or absorbed into the pads.
Excessive dust and/or oil accumulation can seriously
degrade the brakes operation.
Tests and Inspections
Unless a casualty occurs to either the clutch or brake
assemblies, all tests and inspections are performed