🔍 Key Concepts

• Follow-up steering systems and how command vs. feedback motion are compared mechanically • Role of a planetary differential gear in comparing rudder order (from the helm) to actual rudder position (feedback linkage) • What happens immediately at the start of rudder movement before the follow-up linkage has time to respond

💭 Think About

• From the diagram, decide which shaft carries the order signal from the steering control and which shaft carries the feedback from the rudder stock/linkage • When a 15° starboard command is first given, which shaft must move first to create an error in the differential and drive the pump, and which shaft is initially held still? • In that brief initial period, is the motion of the feedback side being used to change linkage length, or is it temporarily cancelled/nullified until the rudder actually starts to move?

✅ Before You Answer

• Identify clearly which one of shaft K and shaft L is driven by the helm order and which is driven by the rudder feedback linkage • Trace through the planetary differential around labels K, L, and M: which element is the carrier, which are the sun/planet gears, and which one changes linkage length to reduce error? • Before choosing, verify that your option matches the idea that at the very start, there must be a difference (error) between order and feedback for the system to drive the rudder away from midships.