where the balls 24 30 will not excessively penetrate the surfaces of the races 20 22 26 28 and accordingly also will prevent damage to the ball bearing assemblies 16 17 referring now to fig2 the spindle drive motor 10 of fig1 is illustrated with crash stop rings 60 and 62 crash stop ring 60 is inserted into engagement with and supported by the interior surface 64 of rotor 18 crash stop ring 60 is fabricated to a dimension which will leave a small gap or clearance 66 between the inner diameter 68 of crash stop ring 60 and shaft 12 similarly crash stop ring 62 is inserted into and supported by the inner cylindrical surface 64 of rotor 18 and is manufactured to provide a gap 70 between crash stop ring 62 and shaft 12 the gaps 66 and 70 must be sufficient to prevent any inhibition of rotation of rotor 18 with respect to the shaft 12 however when rotor 18 is attempted to be rotated about point p2 or any other similar point along the axis of shaft 12 stop ring 60 and stop ring 62 will be shifted substantially in a radial direction toward the circumference of shaft 12 resulting in engagement when the gaps 66 and 70 are closed once either or both gaps 66 70 are closed at any point between.