Official Answer
Answer
The installation stress $S_i$ for a spiral ring is calculated as $S_i = _x000c_rac{E imes t imes ext{expansion}}{D^2}$. However, the radial wall $w$ (the width of the wire) also determines the force required to expand (external) or contract (internal) the ring. A wider radial wall $w$ increases the ring's moment of inertia $I = _x000c_rac{t w^3}{12}$, making it more difficult to install and increasing the risk of permanent deformation if the expansion exceeds the material's elastic limit. Engineers must optimize $w$ to ensure sufficient 'cling' on the shaft without making the ring so stiff that it cannot be installed over the shaft end.
