What are full-floating piston pins designed to allow motion between?

Full-floating piston pins are specifically designed to permit motion between the piston and the large end of the connecting rod. In this configuration, the piston pin does not directly attach to the piston but instead fits loosely in both the piston and the large end of the connecting rod. This allows for relative motion between these two components, which is essential for accommodating thermal expansion and other dynamic movements that occur during engine operation.

When a full-floating pin is used, it provides ease in assembly and helps maintain the alignment of the piston and connecting rod while also allowing for efficient transfer of forces during the engine's cycle. This design helps reduce mechanical wear and promotes smoother operation, as any misalignment or distortion is mitigated by the design of the pin's floating capability.

Other options present misunderstandings about the design's purpose. The pin and the piston option suggests a fixed relationship that contradicts the floating functionality. The idea of motion between the piston and the small end of the connecting rod implies an inappropriate connection that doesn't exist in a full-floating arrangement. The connecting rod and crankshaft option does not relate directly to the specific interaction that occurs with the floating piston pins. Each of these options neglects the key aspect of what the full-floating design achieves specifically between the piston and the large