Development of an Alternative Shoulder for the THOR-50M

Hagedorn, Alena V.; Carlson, Michael; Millis, William · 2026 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This report details the development and evaluation of alternative shoulder designs for the THOR-50M anthropomorphic test device (ATD), sponsored by the National Highway Traffic Safety Administration (NHTSA). The primary motivation was to create a shoulder assembly that avoids infringing on existing U.S. patents held for the baseline THOR-50M shoulder while maintaining identical fit, function, and range of motion. The baseline design, patented in 2014, utilizes a spring and an adjustable friction element. To circumvent patent infringement, the alternative designs eliminated these specific components. Two alternative concepts were developed: Option “A” and Option “B.” Option “A” replaced the baseline spring and friction mechanism with a cylindrical molded rubber torque element, where stiffness could be tuned by altering the rubber compound hardness or the cylinder’s void pattern. Option “B” utilized molded rubber straps wrapped around spools to generate resistance through stretching during rotation. A right-side Option “A” and a left-side Option “B” were fabricated. Patent assessments confirmed that neither design literally infringed on existing claims or the doctrine of equivalents, as they lacked the adjustable friction features present in the baseline. The alternatives were evaluated through fit tests, quasi-static rotation tests, qualification tests, sled tests, and biofidelity tests. Fit tests confirmed that both options installed correctly without interference. Quasi-static tests assessed stiffness and range of motion, targeting the baseline’s 62° total range and approximately 40 in-lb torque. Multiple variations of Option “A” were tested using different rubber materials (Nitrile, XNBR, Neoprene) and hole patterns to match baseline stiffness. Option “B” was tested with fewer variations due to initial favorable results from Option “A.” Qualification and sled tests ensured that the alternative shoulders did not adversely affect the ATD’s overall performance during impact simulations. Biofidelity tests compared arm pull responses against human injury criteria corridors. The study concluded that the alternative shoulder designs successfully met the objective of providing a non-infringing replacement for the THOR-50M shoulder. Option “A,” particularly with specific rubber compounds like XNBR 80A, demonstrated the ability to match the baseline’s mechanical properties and biofidelity performance. The elimination of the spring and friction adjustment elements effectively avoided patent issues while preserving the necessary functional characteristics for crash testing applications. This development supports the continued use and advancement of the THOR-50M ATD in motor vehicle safety research without legal encumbrances.

Key finding

The Option A alternative shoulder design using XNBR 80A rubber springs demonstrated equivalent fit, function, range of motion, and biofidelity to the baseline THOR-50M shoulder while avoiding patent infringement.

Methodology

lab_experiment

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (5 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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