Why did the Titanic have one more rudder on a platform at the stern?

[Captain Puckett]

 

[Jason D. Tiller]

Hello Captain Puckett and welcome aboard,

This steering gear situated in the poop at the after end of the shelter deck, was simply a spare or standby. It would only come into use if "the quadrant and working tiller was disabled", or in need of repairs. The spare "was placed immediately above the quadrant". It "could also be worked by the working capstans on the same deck should the whole gear be disabled".

 

[brionboyles]

This is also referred to as a "docking bridge" or "docking platform". In addition to having a helm, there are several telegraphs to relay docking instructions from the pilothouse/bridge... such as when to cast off lines or tugboats. In this manner, the officer supervising activity on the stern could receive orders without being tethered to a telephone receiver. It was once a common feature on most ships.
Inasmuch as maneuvering in confined waters when entering or leaving port where the margin for error or delay during a steering casualty could be disastrous, most ships to this day have an "emergency steering" position manned and ready for such occasions should the need arise.
I have spent many, many boring hours at sea posted in the noisy confines of the steering gear room of US Navy ships as "After Steering Helmsman" during what we called "restricted maneuvering" conditions... entering/leaving port, underway replenishment alongside another ship, transitting minefields, etc...

 

[Stephen Carey]

This is also referred to as a "docking bridge" or "docking platform". In addition to having a helm, there are several telegraphs to relay docking instructions from the pilothouse/bridge... such as when to cast off lines or tugboats. In this manner, the officer supervising activity on the stern could receive orders without being tethered to a telephone receiver. It was once a common feature on most ships.
Inasmuch as maneuvering in confined waters when entering or leaving port where the margin for error or delay during a steering casualty could be disastrous, most ships to this day have an "emergency steering" position manned and ready for such occasions should the need arise.
I have spent many, many boring hours at sea posted in the noisy confines of the steering gear room of US Navy ships as "After Steering Helmsman" during what we called "restricted maneuvering" conditions... entering/leaving port, underway replenishment alongside another ship, transitting minefields, etc...

Navy ships maybe, but merchant ships don't have anyone stationed in the tiller flat/steering gear room, even on stand-by.