Official Answer
Answer
Static thrust formulas do not account for 'impact' or 'shock' loads where the kinetic energy $E_k = \frac{1}{2} m v^2$ must be dissipated. For impact loading, the effective capacity of a spiral ring is reduced by $50\%$ or more. The designer must ensure that the ring does not undergo dynamic dishing. The impact capacity is often tested by drop-weight methods. To improve impact resistance, a 'heavy-duty' spiral ring with increased material thickness $t$ and a self-locking feature is used to prevent the ring from momentarily expanding and 'jumping' the groove during a high-G shock event, common in downhole drilling jars.
