Ronald J. Tabar

A Low Modulus, High Fatigue Life Elastomer Compound for Suspension Applications

Abstract Soft elastomeric suspension bushing compounds have been developed which are based on natural rubber/polybutadiene (NR/BR) blends which have been softened with polyisobutylene (IM). The new compounds have a Shore A hardness of 45 and a fatigue life of 97 kc and 80 kc for the urethane cured and semi-EV cured compounds respectively. This compares with a fatigue life of 62 kc for the current production compound (Shore A 65). It appears that the mechanical behavior, i.e. resistance to crack growth, of natural rubber based compounds is unaffected by the addition of IM. Fatigue life, compression set and retention of physical properties after heat aging of the new compounds are also superior to the production compound. The dynamic mechanical properties of the new compounds were evaluated and found to have a slightly greater temperature sensitivity than the production compounds.

A Fatigue Resistant Polychloroprene Compound for High Temperature Dynamic Applications

Abstract A polychloroprene material has been developed which can replace the natural rubber materials traditionally used in dynamic, fatigue-producing applications, when these applications require high temperature stability. An optimized compound based on a mercaptan modified polychloroprene with large particle high structure carbon black, silica filler and rapeseed oil has superior compression set, improved heat aged fatigue life and comparable dynamic properties to current NR compounds. This CR compound was designed to have good fatigue life while keeping compression set to a minimum. A positive correlation between tear resistance and fatigue life has been demonstrated for a series of CR compounds.

An Elastomeric Energy Storage Device for Automotive Engine Restart

Abstract An elastomeric spring starter using rubber in shear has been designed. Design criteria have been established and used to develop potential compounds for use in the device. Natural rubber proved to be the elastomer of choice primarily because of its excellent fatigue resistance. To reconcile bonding requirements and requirements for low hysteresis, the individual rings were fabricated from two elastomer compounds. Limitations on the thermal stability of the adhesive system were identified which put constraints on the operating conditions for the starter. A prototype starter has been assembled and installed in a vehicle. This prototype starter provides quiet, rapid starting of the test car. Questions of cost effectiveness, reliability, durability or manufacturing feasibility of this device have not been addressed. The starter was built for experimental purposes only and development of such a concept for mass production has not been explored.