Why are tie-rods provided on a 2-stroke main engine, why are they placed close to the crankshaft centerline, and what is a tie-rod pinch screw and its purpose?

flowchart TD
    A[Tie-rods] -->|keep structure in compression| B[Counteract firing/inertial tensile stresses]
    A -->|placed near| C[Crankshaft centerline]
    C -->|minimises| D[Bending stress on bedplate]
    C -->|maintains| E[Alignment under cyclic loads]
    F[Pinch screws] -->|located at| G[Bottom of cylinder block / top of A-frame]
    F -->|positioned at| H[Antinodal point of tie rod]
    H -->|limits| I[Transverse vibration]
    H -->|prevents| J[Fatigue failure]

• Tie-rod purpose: keep the engine structure under compression to counteract firing and inertial tensile stresses
• Placement: close to the crankshaft centerline to minimise bending stress on the bedplate and maintain alignment under cyclic loads
• Pinch screw: located at the bottom of the cylinder block near the top of the A-frame; usually three in number
• Pinch screw purpose: positioned at the antinodal point of the tie rod to limit transverse vibration and prevent fatigue failure