A rotor-stator structure including plural bumper elements that may employ synthetic sliding bearing surfaces, mounted to the stator, and designed to contact a machined surface on the rotor if generator structural deflection occurs during operation. During normal operation, the bearing surface is not in contact with the machine rotor. If extreme loads are imposed on the rotor or stator structures, or other issue like bearing failure, causes the air gap to close, the bumper elements will “touch down” on a machined surface on the rotor to maintain a minimum air gap.