Engine order telegraph
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An engine order telegraph or E.O.T., also referred to as a Chadburn,
Construction
In its original form, from the 19th century until about 1950, the device usually consisted of a round dial about 9 inches (230 mm) in diameter with a knob at the center attached to one or more handles, and an indicator pointer on the face of the dial. There would also be a revolutions per minute indicator, worked by a hand crank. Modern EOTs on vessels which still use them use electronic light and sound signals.
Operation
Traditional E.O.T.s required a pilot wanting to change speed to "ring" the telegraph on the bridge, moving the handle to a different position on the dial. This would ring a bell in the engine room and move their pointer to the position on the dial selected by the bridge. The engineers hear the bell and move their handle to the same position to signal their acknowledgment of the order, and adjust the engine speed accordingly. Such an order is called a "bell"; for example, the order for a ship's maximum speed, flank speed, is called a "flank bell".[2]
For urgent orders requiring rapid acceleration, the handle is moved three times so that the engine room bell is rung three times. This is called a "cavitate bell" because the rapid acceleration of the ship's propeller will cause the water around it to cavitate, causing a lot of noise and wear on the propellers. Such noise is undesirable during conflicts because it can give away a vessel's position.
Compared to remote control throttle
On most modern vessels with direct combustion engines or electric propulsors, the main control handle on the bridge acts as a direct
Remote control systems on modern ships usually have a control transfer system allowing control to be transferred between locations. Remote control is usually possible from two locations: the bridge and the Engine Control Room (ECR). Some ships lack a remote control handle in the ECR. When in bridge control mode, the bridge handle directly controls the engine set point. When in Engine Control Room mode the bridge handle sends a telegraph signal to the ECR and the ECR handle controls the set point of the control system. In local control, the remote control system is inactive and the bridge handle sends a telegraph signal to the local control position and the engine is operated by its manual controls in the engine room.
Order transmission
At least two telegraph units and alarms must be installed, one on the bridge and one in the engine room. The order is given by moving the bridge unit's handle to the desired position on the dial face. This sends an
Typical dial positions
Many past ships have the following dial indications:
- Flank ahead (1940–present) (US only)
- Full ahead
- Half ahead
- Slow ahead
- Dead slow ahead
- Standby
- Stop
- Finished with main engines
- Dead slow astern
- Slow astern
- Half astern
- Full astern
- Emergency astern (1940–present)
Any orders could also be accompanied by an RPM order, giving the precise engine speed desired. Many modern ships have the following dial indications:
- Full ahead navigation (on notice to increase or reduce)
- Full ahead
- Half ahead
- Slow ahead
- Dead slow ahead
- Stop
- Dead slow astern
- Slow astern
- Half astern
- Full astern
"Finished with engines" and "standby" conveyed via separate control panel.
See also
References
- ^ "The Chadburn Ships' Telegraph Society". Archived from the original on 27 November 2021. Retrieved 2 July 2011.
- ^ Halpern, Samuel (18 September 2007). "Speed and Revolutions". Encyclopedia Titanica. Retrieved 6 January 2013.