Minimum Allowable Pin Load Reversal
Crosshead pin reversal is a reversal of compression and tension loads at the crosshead pin to connecting rod bushing. Without proper reversing loads, this bushing will not be provided with sufficient lubrication and bushing failure will occur. Pin reversal is defined by two components, degrees and percent. These represent the duration of the reversal and the magnitude of the reversal. Both of these values must meet or exceed minimum values. Ariel's requirements for reversal are 30 degrees of crank rotation, and 25% magnitude. The percent magnitude is defined by the smaller of the tension or compression force divided by the larger of the two. The combined gas plus inertia loading at the crosshead pin is used for the reversal calculations. The inertia load component includes the weights of the piston and rod assembly, balance nut and crosshead with crosshead bushings.