Determine the shear area $A_s$ for a two-turn spiral retaining ring and its relation to axial load capacity.

For a spiral retaining ring, the shear area is not simply the circumference times thickness. Because it is a continuous spiral, the shear area $A_s = \pi D t \times (n)$ where $n$ is the number of turns. For a standard 2-turn ring, the shear area is $2\pi D t$. The axial load capacity $P_r$ is then $P_r = \frac{A_s S_s}{K}$. Interestingly, while a 2-turn ring has twice the shear area of a 1-turn ring, the groove yield $P_g$ often remains the bottleneck. Therefore, adding turns increases the ring's strength but does not help if the housing material is the weak link.