🔍 Key Concepts

• Follow-up hydraulic control system – how a small control movement (A) positions a larger power piston (B) through oil ports D and E • Relative motion between pilot spool (A) and power piston (B) in a servo: which one moves first and which one ‘follows up’ to re‑center the ports • Mechanical linkage at C – how the motion of the tilting box control arm feeds back to the pilot valve body

💭 Think About

• Trace the oil flow when A is moved to the right: which port (D or E) is opened to pressure and which to return? What does that do to the piston at B? • Once B starts to move, what happens to the valve body and the linkage at C? Does this motion tend to reduce the offset between A and B, or increase it? • In a follow‑up system used to control pump swashplate angle, should the large output motion (at C) occur instantly with A, or should it lag until pressure has moved B?

✅ Before You Answer

• Be clear on which part is the spool (A) and which is the power piston (B); they do NOT move simultaneously at first • Verify whether the motion of C is a direct mechanical connection to B or a feedback motion that re‑centers A relative to B • Check if the drawing implies that B’s motion is in the same direction or the opposite direction to the pilot spool movement when a given side of the piston is pressurized