Journal of Sound and Vibration (1998) 218 (2), 269–292 Article No . sv981832 UNIVER SAL BUMPER ED VIBR ATION ISOLATOR FOR SEVERE ENVIRONMENT V. I. B  A. M. V† Department of Mechanical Engineering , Loughborough University , Leicestershire LE11 3TU, England (Received 27 October 1997, and in final form 22 June 1998) Modern compact design often does not permit the effective use of linear vibration isolation in the case of the intense environmental disturbances. Demands for limitation of the dynamic deflections lead to the use of heavy damped vibration isolators, sometimes in combination with the bumpers installed with the maximal free travel. The increase in isolator damping improves the low frequency resonant response at the expense of an inferior isolation performance in the high-frequency range. The installation of bumpers with enlarged travel reduces the probability of the accidental impacts and effectively trims the excessive deflections in an emergency. However, it turns the isolator into a vibro-impact structure, where the appearance of intense impulsive accelerations and high-powered non-linear resonance becomes the subject of concern. The idea of the present novel concept is based on co-operative use of an undamped , low frequency vibration isolator in combination with optimally damped bumpers installed with minimal free travel . Such an isolator demonstrates the advantages of the linear undamped isolator under low level ambient and operational high frequency excitation. However, under severe ambient disturbances, for any excessive deflections, it becomes strongly non-linear and takes on the quality of an optimal shock absorber. The approach formulated has been applied successfully to a design of a gimballed electro-optical device based on the linear split Sterling cryocooler for a focal array.  1998 Academic Press 1. INTRODUCTION The limiting of vibratory energy transmission from a machine to its foundation and vice versa may be achieved by the proper use of a flexural suspension. If the natural frequencies of the resiliently suspended machine are located well below the lowest frequency in the excitation spectrum, a significant attenuation of vibration transmission may be achieved in a certain high-frequency range. In this case, it is recommended to use a soft and undamped flexural suspension [1]. In fact, such a simple vibration isolator is feasible in a limited number of cases of moderate environmental disturbances. As soon as an application involves exposure to severe environmental disturbances such as shock or broadband † Formerly Ricor Cyogenic & Vacuum Systems, En Harod Ihud 18960, Israel. 0022–460X/98/470269 + 24 $30.00/0  1998 Academic Press