A. MOTOR ORDER TELEGRAPH SYSTEM|
11A1. Description. The motor order telegraph
system consists of 2 separate electrical
circuits. The starboard circuit is designated 1MB
and the port circuit, 2MB. Electrically both
circuits are identical. The system is operated on
115-volt, 60-cycle, single-phase, alternating current.
Each circuit receives its supply from the
a.c. bus of the I.C. switchboard through fused
The purpose of the motor order telegraph
system is to transmit electrically any desired
orders for the direction and speed of the propellers
from the transmitting stations located
in the conning tower and control room to the
maneuvering room and to repeat those orders
back to the transmitting station from the
The circuits are controlled through rotary
switches on the action cutout switchboard. One
switch selects the conning tower or the control
room as the transmitting station for both 1MB
and 2MB circuits. Two more switches select
either the conning tower, control room, or both,
as the receiving station for the repeat back
orders from the maneuvering room. One of these
2 switches is for the 1 MB, the other for the 2 MB
The conning tower and control room units
consist essentially of a type "A" transmitter and
pointer, a type "M" indicator and pointer, 2
sets of contacts for bell-ringing circuits, and
necessary operating gears. The assembly is
mounted in a case.
The transmitter is operated by a knob type
handle fastened to a shaft on the front cover of
the instrument. This shaft is connected to the
transmitter rotor by means of a positive engaging clutch.
A star wheel mounted on the transmitter shaft holds the
transmitter in the desired
position by means of a spring loaded main bell
contact actuating lever. This lever also operates
the contacts for the bell signal at the indicator
station. The bell signal rings whenever the transmitter
is being moved from one position to another. Auxiliary
contacts for the bell signal are
operated by a push button on the cover of the
instrument. They are connected in parallel with
the contacts operated by the star wheel. The
auxiliary bell-ringing circuit is energized at any
time the push button is operated. The indicator
pointer is connected directly to the rotor of the
indicator through an extension shaft.
The maneuvering room instruments are
similar except for an additional mechanism
consisting of a cam mounted on the transmitter
shaft which operates a contact for wrong direction
warning. These contacts are connected with
contacts on the reverser levers of the main control
cubicle. If the reverser levers are moved in
a direction opposite to that indicated by the
transmitter pointers of the maneuvering room
instruments, a visual and audible signal informs
the operator of the error.
11A2. Operation. In order to energize the
system, the- IMB and 2MB circuit switches on
the I.C. switchboard must be turned to the ON
position. On the action cutout switchboard, turn
the 1MB-2MB transmitter selector switch to the
station that is to control transmission. This
switch is marked CONNING TOWER, OFF,
and CONTROL ROOM. Next, turn the 1MB
and the 2MB indicator selector switches to those
stations that are to receive a repeat indication
of the transmitter order. These switches are
marked CONNING TOWER, OFF, CONTROL
ROOM, and CONTROL ROOM AND CONNING TOWER.
NOTE. Before transferring control from
one station to another, be sure that the station
you are transferring to has its transmitters set
on the same order, otherwise, the maneuvering
room will receive whatever order is indicated at
the new transmitting station.
Figure 11-1. Schematic diagram of motor order telegraph system.
Figure 11-2. Schematic diagram of motor order telegraph, two units.
Figure 11-3. Motor order telegraph transmitter
indicator unit, maneuvering room.
Figure 11-4. Side view of motor order telegraph transmitter indicator unit, maneuvering room.
Figure 11-5. Elementary wiring diagram of motor order telegraph transmitter indicator, conning tower and control room units.
Figure 11-6. Elementary wiring diagram of motor order telegraph transmitter indicator, maneuvering room unit.
Figure 11-7. Schematic diagram of motor order telegraph transmitter and indicator.
11A3. Maintenance. The bearings, gears,
cams, and other moving parts should be
inspected periodically to see that they are in
proper alignment and working freely. A drop or
two of fine-grade mineral oil may be applied to
the bearings if necessary. Contacts should be
checked for signs of pitting and wear. Slightly
worn or pitted contacts may be dressed with
very fine sandpaper and crocus cloth.
The instrument cases are sealed. If a
pressure test is to be conducted in a compartment
in which an instrument is located, make certain
that the plug located on the case is opened.
With the plug opened, the air pressure in the
compartment necessary to conduct the test, and
the pressure in the case will be equalized, thus
avoiding possible damage to the instrument.
The transmitters and indicators should be
maintained as outlined in the maintenance
instructions for selsyn units (Section 10B2).
Figure 11-8. Schematic diagram of rudder angle indicator system.
B. RUDDER ANGLE INDICATOR SYSTEM|
11B1. Description. The rudder angle indicator
system is designated as circuit N. It is operated
on 115-volt, 60-cycle, single-phase, alternating
current and receives its supply from the
a.c. bus of the I.C. switchboard through a fused
The purpose of the system is to transmit
electrically the angular position of the rudder
various stations in the control room, conning
tower, and bridge.
The circuit is controlled through 2 rotary
contact switches on the action cutout switchboard.
One switch energizes the conning tower
and bridge indicators, the other switch energizes
Figure 11-9. Rudder angle indicator and case.
Figure 11-10. Rudder angle transmitter.
Figure 11-11. Rear view of rudder angle transmitter.
the indicators located in the control room.
The transmitting instrument consists essentially of a type "A" transmitter mounted in a
case. Any movement of the rudder is transmitted
mechanically through a linkage or gear arrangement
that causes the rotor of the type "A"
those stations at which an indication of the rudder
angle is desired. One of these switches controls
the bridge and conning tower indicators.
It is marked BRIDGE, OFF, CONNING
TOWER, and BRIDGE AND CONNING
TOWER. The other switch controls the control
Figure 11-12. Cross-sectional view of rudder angle transmitter.
transmitter to rotate in a corresponding direction.
The indicating instrument consists essentially of a
type "M" indicator, a pointer, and a
dial mounted in a case. The indicator pointer
is secured to the indicator rotor shaft.
11B2. Operation. In order to energize the
system, the circuit N switch on the I.C. switchboard
must be turned to the ON position. On
the action cutout switchboard, the circuit
N indicator selector switches should be turned to
room indicators and is marked STEERING
STATION, OFF, DIVING STATION, and
DIVING AND STEERING STATION.
11B3. Maintenance. The operating mechanism
between the transmitter instrument and
the rudder should be examined periodically to
make certain that it is operating freely but
without any backlash. For maintenance of the
selsyn units, the procedure outlined in Section
10B2 should be followed.
Figure 11-13. Wiring diagram of rudder angle Indicator.
Figure 11-14. Rudder angle Indicator, showing pressure-proof construction for bridge installation.
C. BOW AND STERN PLANE ANGLE INDICATING SYSTEMS|
11C1. Description. The bow plane angle indicating
system is designated as circuit NB.
The stern plane angle indicating system is designated
as circuit NS. Both of the systems are
operated on 115-volt, 60-cycle, single-phase, alternating
current, and receive their supply from
the a.c. bus of the I.C. switchboard individually,
through fused switches.
The purpose of the systems is to transmit
electrically the angular position of the bow and
stern diving planes to the diving station in the
control room. The instruments and the mechanical
arrangements connected to them are similar to those
employed in the rudder angle indicator system.
Auxiliary circuits XNB (bow plane) and
XNS (stern plane) are provided for use in the
event of failure of the selsyn-operated systems
(see Section 11C4).
11C2. Operation. The bow plane angle indicator
system is energized by turning the
switch labeled for this system on the I.C.
switchboard to the ON position. The stern plane angle
indicating system switch is also on the I.C.
switchboard; turning it to the ON position
energizes the system.
11C3. Maintenance. The mechanical operating mechanism
between the transmitters and
the diving planes should be examined periodically
to see that proper alignment and free
movement without backlash are maintained. See
Section 10B2 for maintenance of selsyn units.
Figure 11-15. Schematic diagram of bow and stern plane angle indicating systems.
Figure 11-16. Wiring diagram of bow and stern plane angle indicating systems.
Figure 11-17. Bow and stern plane angle indicators installed at diving station.
11C4. Auxiliary bow and stern plane angle
indicating systems. The auxiliary bow and
stern plane angle indicating systems are provided
for use in the event of failure of the regular
selsyn-operated systems (Section 11C1) or
of the I.C. power.
The circuits are designated XNB (bow
plane) and XNS (stern plane) and consist of
mechanical transmitters connected to the diving
plane mechanisms, a group of dry cell batteries,
and lamp type indicators located in the control
Motion of the diving planes moves the mechanical
transmitters across a number of contacts, thus
closing the circuits to the lamps
mounted on a panel in the control room. The
dry cells are connected to produce an output of
6 volts for each of the circuits which are
energized by means of a snap switch in the control
Figure 11-18. Schematic diagram of auxiliary haw and stern plane angle indicating systems.
Figure 11-19. Auxiliary bow plane angle indicator at diving station.
11C5. Bow plane rigging electrical indicator system.
The anchor windlass, bow capstan and bow plane rigging
gear is electrically
operated through hydraulic gearing and has an
electric indicating system. The indicating system
takes power at 120 volts d.c. through a snap
switch and fuses on the I.C. switchboard in the
control room, and shows indications at the diving station.
A contact maker on the rig windlass clutch
in the forward torpedo room lights a
CLUTCH IN RIG indicator at the diving station and
closes a circuit to another contact maker on the
windlass control valve in the forward torpedo
room. This contact maker is closed when the
control valve is in neutral.
When both these contact makers are closed,
the WINDLASS VALVE IN NEUTRAL indicator at the diving
station is lighted and the
circuit is completed to an interlock on the
tilting gear which is closed only when the planes
are at zero tilt.
When all three of these contact makers are
closed, indicating that the clutch in the rig
windlass control valve is in neutral and that the
planes are at zero tilt, a PLANES AT ZERO
indicator at the diving station is lighted. The
circuit is then completed to a RIGGING
LEVER RELEASE push button, also located
at the diving station. Pressing this push button
releases a solenoid latch on the rigging lever,
allowing the planes to be rigged either in or out.
A traveling nut type limit switch on the
rigging gear in the forward torpedo room closes
a circuit at either end of its travel through the
rig-windlass clutch and windlass control valve
contact makers to PLANES OUT or PLANES
IN indicators at the diving station.
An intermediate contact maker operated
from the hydraulic interlock shaft of the
rigging mechanism makes a series of intermittent
contacts while the planes are rigging in or out
and flashes an indicating light at the diving
station to indicate that the planes are moving
in or out. The circuit for this indicating light
goes through the traveling nut limit switch so
that the circuit is opened when the planes are
full IN or full OUT.
Figure 11-20. Schematic diagram of bow plane rigging indicator circuit.
Figure 11-21. Bow plane rigging indicator, bow plane rigging and windlass clutch indicator, bow and stern plane motor ON lights and controllers at diving station.
D. ENGINE GOVERNOR CONTROL SYSTEM|
11D1. Description. a. General. The engine
governor control system is the system through
which the maneuvering room controls the speed
of the engines. On vessels having single unit
propulsion control cubicles, the system consists
of 4 selsyn transmitters mounted in the governor
control cabinet in the maneuvering room.
Each transmitter is connected to a selsyn
indicator (motor) mounted on the mechanical
governor control of each engine. The indicators
geared to the rack shafts of the engine
governors. When a change in the speed setting
at the transmitters, the indicators move the
shafts. They in turn transmit motion to mechanical
linkage to establish an engine speed in
accordance with the transmitter setting.
The system is designated as circuit EG and
on earlier vessels is operated on 115-volt,
60-cycle, single-phase, alternating current
from the a.c. bus of the I.C. switchboard in the
control room. On SS 313 and subsequent vessels,
the governor control transmitters and receivers
are of the direct current type described
below and receive their power from the lighting
b. Engine governor control, direct current.
The direct current position transmitters and
receivers used in this type of governor control
(Figure 11-23), while in external appearance
similar to the a.c. types, are in reality
different both in principle of operation and in
construction. The transmitter unit consists
essentially of a continuous, cylindrical wire
resistor unit. Two taps, diametrically opposite,
are connected to slip rings which are fed through
brushes from the 115-volt lighting circuit.
Equally spaced around the fixed part of the
transmitter shell are 4 more brushes which make
contact directly on the wires of the resistor. The
transmitter shaft turns the resistor unit mounted
Figure 11-22. Schematic diagram of engine governor control system.
on the shaft. A friction device is also included
to prevent too rapid turning of the transmitter.
Unlike the a.c. selsyns, none of the effort used to
turn the receiver is supplied by the transmitter.
It is all supplied electrically.
The receiver consists of a stator, wound as
a 2-phase motor as shown in Figure 11-23, and
transmitter dial should be matched with the
tachometer. This is necessary because the large
gear ratio between the dial and the transmitter
makes it possible for the transmitter to be
synchronized with the receiver at several
A mechanical clutching device is provided
Figure 11-23. Elementary wiring diagram of d.c. governor control, Allis-Chalmers pointer transmitter.
a magnetized solid iron rotor with 2 poles.
As the transmitter resistor is rotated, the
voltage across each of the 2 windings varies and
reverses its direction. The permanent magnet
rotor follows until its poles are lined up with
the magnetic field which is the resultant of the
11D2. Operation. Each of the governor control
units is provided with an OFF-ON switch
mounted at the transmitter station. Governor
control from the maneuvering room may be cut
in or out as desired. Before an engine is started,
care should be taken to see that its individual
governor control switch is in the OFF position
and kept there until the engine room signals
READY. Before turning the switch to ON, the
by which any single governor control transmitter
may be operated individually; or any number of
them may be clutched together for common operation
through a master control handle.
NOTE. On vessels having split type propulsion
control cubicles, the governor control
transmitters are also split into 2 cabinets
are somewhat different in operation from those
described above. Each cabinet has 3 transmitters
and 2 selector switches. The arrangement
is such that the third transmitter on either side
may be connected to the receiver of either of
the engines associated with the other side. It is
thus possible to operate any 3 engines in unison.
However, it is not possible to operate 4 engines
Figure 11-24. Engine governor control panel on main
in unison. This can be done only with the single
unit type governor control.
11D3. Maintenance. Maintenance of a.c. selsyn
units is described in Section 10B2. For d.c.
selsyns, the general comments of Section 10B2
apply, but the symptoms and remedies do not.
If the rotor of the receiver sticks, no damage
results. If the receiver rotates in the wrong
direction, one pair of leads is reversed (A1 + A2)
or (B1 + B2). If it does not rotate in either
direction, and is not stuck, the A and B leads
Figure 11-25. Engine governor control unit at engine.
are interconnected; for example A1 to B1, and
A2 to B2.
11D4. Tachometer system. The tachometer
system consists of a magnetic generator on each
engine and an indicator electrically connected to
each of them. The system, by means of a flexible
shaft connected to the driving gear of the magneto,
also drives a mechanical tachometer located on the engine gage board.
The magneto is mechanically driven by the
engine and generates a voltage as a function of
its speed. This voltage is impressed on the
indicator, which is basically a voltmeter with
calibrated in rpm. The 4 indicators are mounted
on the engine governor control panel in the
Figure 11-26. Fairbanks-Morse tachometer installation.
Figure 11-27. Electric Tachometer engine unit and indicator.
Figure 11-28. Weston electric tachometer magneto, engine unit.
Copyright (C) 2004-2005 Maritime Park Association
All Rights Reserved
Version 1.11, 27 June 2005