Answer
The radial wall $b$ is the width of the flat wire used to coil the ring. It determines the ring's radial stiffness and the amount of stress it undergoes during installation. The installation stress $S_a$ is calculated as $S_a = \frac{E b imes (D_g - D_f)}{D_f imes (D_g + b)}$, where $D_g$ is the groove diameter and $D_f$ is the free diameter. A larger radial wall increases the thrust capacity and centrifugal stability but also significantly increases the stress required to expand (external) or contract (internal) the ring for installation. If $b$ is too large, the material may exceed its yield point during installation, resulting in a 'loose' ring that does not seat properly in the groove. Optimal design balances the radial wall to provide sufficient groove engagement without exceeding the material's elastic limit.
