In line with agreements with SAE experts a research program aiming at the evaluation of these improvements was conducted by ACEA. It consisted of dummy preparation, static and pendulum tests involving the chest, and sled tests with driver and passenger dummies for different sled deceleration pulses and occupant restraints (three-point belt system or a combination with an airbag).

The objective of this paper is to highlight the chest deflection measurement approach that was implemented in the Hybrid Ill dummy and to present detailed results which were obtained in this program. During the static and pendulum tests, when the loadings to the chest have been moderate, the standard rod and the string potentiometers appeared to function without any obvious faults. However in sled tests some problems were observed:​ while the string potentiometers seemed to function well, the rod potentiometer has failed in a few cases, due to disengagement of the rod from the groove in the sternum plate. A general observation from all tests is, that the rod potentiometer in the large majority of cases shows an about 10 mm higher displacement than the one measured at the ends of the ribs. This is explained by the "hinge and lever effect“, permitting the sternum plate to move progressively much closer to the spine than the ends of the ribs do.

Different locations show different deflection values, so a complete chest deformation description would require more than one single measurement. Comparison of the rod potentiometer and a string potentiometer using the same installation was impossible for obvious reasons. Even attached to the ribs, with more variations in load transfer, the string potentiometer showed acceptable repeatability.

In order to solve the chest deflection issue, it is proposed to replace the standard rod potentiometer by a string potentiometer, using identical mounting position.