Transmitters

ends of links 20 support swinging shaft 31. Gear 26 is

PROPELLER REVOLUTION

attached to shaft 31. Friction blocks 23 are held in

INDICATOR SYSTEM

contact with the hubs of gears 25 and 26 by spring 24.

The propeller revolution indicator system (circuit

The friction blocks restrain the rotation of gears 25 and

K ) is used to indicate instantaneously and

26 and swing the links assembly, including shaft 31

continuously the revolutions per minute, direction of

and gear 26, in the direction of rotation of gear 25. This

rotation, and total revolutions of the individual

action engages gear 26 with one of the two gears 27,

propeller shafts. The information is indicated in the

the selection depending on the direction of rotation of

engine rooms, pilothouse, and other required

gear 25. Screws 80 limit the angular swing of the links

locations.

assembly.

There are two types of propeller revolution

Gears 27 are secured to respective side shafts 35,

indicator systems, the synchro system and the

which also carry gears 29 and 69. These gears are

magneto-voltmeter system. The synchro system is

meshed and drive each other alternately, depending on

installed in large combatant ships and in many newly

which one of the two gears 27 is engaged with the

constructed small ships. The magneto-voltmeter

swinging idler gear 26. Gears 29 and 69 do not reverse

system is less complicated and is installed in small

when the propeller shaft reverses because idler gear

ships. Only the synchro system will be discussed in

26 reverses rotation each time it swings from side to

this training manual.

side. The same is true for gears 28 and 57 because they

are mounted on the hubs of gears 29 and 69,

A representative synchro-type propeller

respectively. Gear 57 engages gear 58, which is

revolution indicator system installed in a DDG is

mounted directly on the shaft of synchro transmitter

discussed in the following paragraphs. The system

37. The overall gear ratio between transmitter shaft 56

consists of transmitters, indicator-transmitters, and

and the shaft of the synchro transmitter is such that the

indicators.

synchro shaft is always driven at twice the propeller

speed in a constant clockwise direction.

Transmitters

Revolution counter 38, which is driven at

The transmitters, one for each propeller shaft,

one-tenth the propeller speed, is driven through helical

indicate the revolutions of the propeller shaft. They

gears 28, 48, 47, and 30. The reading is directly in

also transmit the speed and direction of rotation of the

terms of propeller revolutions because each revolution

propeller shaft to the associated indicator-transmitter.

of the counter shaft registers a count of 10. Brake

The transmitters are installed on the actual propeller

shoes 50 prevent synchro transmitter 37 from driving

shaft usually near the reduction gear. They are

counter 38 backward during brief periods of rapid

electrically connected to indicator-transmitters

speed reduction.

located in their respective throttle stations.

The contact assembly is actuated by small

Figure 10-33 is the gearing diagram of a

insulating block 22, attached to one of the swinging

transmitter. The transmitter consists of a running

links 20. The block moves up and down as the link

synchro transmitter, revolution counter, and contact

swings with reversals of driving rotation. This action

assembly. These components, which are actuated by

moves center spring contact 44 from the bottom to the

suitable gearing, are mounted in a watertight housing.

top stationary contact 42, and vice versa. The center

The transmitter is either gear driven from the propeller

contact and one of the stationary contacts energize the

shaft or is directly coupled to the end of a stub shaft

signal lights in the remote indicator when the propeller

of the propulsion machinery, as required by the

shaft rotates in the astern direction,

particular installation. The synchro transmitter is

always driven at twice the propeller speed in a constant

Indicator-Transmitters

clockwise direction.

The indicator-transmitter installed in each throttle

A drive worm, cut integral with shaft 56, meshes

station is used to convert the running speeds received

with worm gear 12, which is secured to shaft 14. The

from the associated shaft transmitters into angular

ratio is such that shaft 14 is driven at exactly one-tenth

synchro displacements, which are transmitted to the

the propeller speed. Gear 25 is attached to shaft 14,

various indicators.

and links 20 are free to swing on the shaft. The lower

10-18