🔍 Key Concepts

• Radial piston pump stroke – oil enters the cylinder during the suction (intake) stroke when the piston moves outward and the cylinder volume increases. • The direction of rotation shown by the arrow determines whether a given piston position is on the suction or discharge side of the pintle ports. • Look at the eccentricity between the rotor/reaction ring and the cylinder block – as the rotor turns, pistons move in where the distance to the ring decreases and move out where that distance increases.

💭 Think About

• On the illustrated rotation direction, between which numbered positions is the piston tip moving away from the pintle/center, increasing the volume of the cylinder? • Identify which side of the pintle would logically be the low‑pressure (inlet) side: is it where pistons are being pushed inward or pulled outward by the reaction ring? • Trace one full revolution of a piston around positions 1–4 and note in which segment its radial position changes from more inward to more outward.

✅ Before You Answer

• Verify which segment (1–2, 2–3, 3–4, or 4–1) shows the greatest increase in distance between the piston and the center as the rotor turns in the indicated direction. • Confirm that on that segment the cylinder volume is increasing, meaning it must be connected to the inlet port on the pintle. • Before choosing, double‑check that the other segments correspond sensibly to discharge (piston moving inward) and transition regions, so the stroke sequence is consistent around the circle.