Which capstan drive arrangement requires a flexible coupling between the reduction gear output shaft and the capstan head input shaft?

Correct Answer: Option C — The drive arrangement where the drive motor, electric brake, gear reducer are mounted on the deck below the weather deck, and only the capstan head is located on the weather deck.

When the drive motor and gear reducer are mounted on a separate deck from the capstan head, a flexible coupling is mandatory to accommodate minor structural deflections and shaft misalignments. This prevents excessive stress on the bearings and gear train caused by hull working or thermal expansion.