ENGINEMAN 1 & C
data, furnished by the contractor, should be
entered in prescribed records by the ships
engineering personnel when the ship is at the con-
tractors yard. They should include the crown
thickness readings and the clearances of the
original bearings, the thrust settings and
clearances, and the backlash and root clearances
for gear and pinion teeth. It is essential to have
this information available at the time when the
alignment must be checked.
All repairs, adjustments, readings, and
casualties should be reported in accordance with
3-M system procedures. All original bearing data,
as well as all additional bearing measurements,
should be entered in appropriate records.
The manufacturers technical manual, which
gives detailed information regarding repairs to be
made to reduction gears, is furnished to each ship.
Special tools and equipment are normally pro-
vided on board ship for (1) lifting some reduc-
tion gear covers, (2) handling the gear elements
when removing or replacing their bearings, (3)
making the required measurements, and (4) rebab-
Figure 4-1.Scribe lines used in measuring the crown
thickness of reduction gear bearings.
These special tools and equipment should be
available aboard ship in case repairs have to be
made by repair ships or at advanced bases. Bridge
gages are no longer used to check bearing wear
of the main reduction gears. When bearing wear
must be checked, the crown thickness method is
bearings are given in the manufacturers technical
manual. These clearances are also shown on the
blueprints for the main reduction gears.
A bearing shell consists of a pressure-bearing
half and a nonpressure-bearing half. The
nonpressure-bearing half has a radial scribe line
at one end of the geometric center. The pressure-
bearing half of every main reduction gear shell
has three radial scribe lines on each end of the
bearing shell (figure 4-1). As you can see one of
these scribe lines is located at the geometric center
of the shell and the remaining lines intersect the
center scribe line at a 45° angle.
On a multishaft ship, if a main reduction gear
bearing is wiped, the preferred procedure (if prac-
ticable) is to secure the shaft and the reduction
gear until the units can be inspected and repaired
by a repair activity.
A glance at figure 4-2 will indicate why the
replacement of a bearing in a main reduction gear
would be a major undertaking for the ships force.
However, emergency conditions may require
action by the ships force. When such action is
to be taken, a number of factors must be taken
into consideration before repairs are attempted.
The crown thickness of each shell at these
points should be measured with a micrometer at
a prescribed distance from the end of the shell.
These measurements should be recorded during
the initial alignment and should be permanently
marked adjacent to each scribe line.
The first factor to consider would be whether
or not to attempt the repair work.
The amount of bearing clearance should not
be allowed to become too great to cause incor-
rect tooth contact. The designed clearances for
The EN1 or the ENC must study the manufac-
turers instructions and the blueprints for the
reduction gear, so as to have a clear understanding
of the constructions details and the repair pro-
cedures and to be able to decide whether or not
the work should be done by the ships force. Other
factors which must be considered are the location