Official Answer
Answer
For a spiral retaining ring, the moment of inertia $I$ of the cross-section is calculated as $I = \frac{b \cdot t^3}{12}$, where $b$ is the radial wall width and $t$ is the thickness. However, the radial stiffness of the ring—its ability to resist expansion or contraction—is also governed by the 'curved beam' theory. The stiffness is proportional to $E \cdot I / R^3$. This means that even a small increase in the radial wall $b$ significantly increases the force required to install the ring and its ability to remain in the groove. Designers must balance the radial wall width $b$ to ensure the ring is stiff enough to hold the load but flexible enough to be installed without exceeding the yield strength $\sigma_y$ during expansion.
