Following upon the development and implementation of the 50th percentile male Thor-Lx lower extremity, the NHTSA has directed the development of a companion design sized to fit the small 5% female Thor dummy, and which optionally can retrofit directly to the 5th percentile female Hybrid III at the distal femur interface. The resulting design is denoted as Thor-FLx (5th percentile female lower extremity), while the stand-alone Hybrid III retrofit product is designated as Thor-FLx/ HIIIr.
Figure 1 shows the complete Thor-FLx/ HIIIr assembly with tibia flesh removed for clarity. 
Figure 1: Thor-FLx/HIIIr Assembly (Tibia Flesh Removed)
The leg and ankle response characteristics of the Thor-FLx/ HIIIr were scaled from the data sets previously utilized to design the 50th percentile male leg. As was the case for the Thor-Lx/ HIIIr, the Thor-FLx/ HIIIr design is based upon recent biomechanical data which includes the following: a) guidelines for the geometric dimensions of the lower extremity, b) location of the ankle and subtalar joints, c) inertial properties of the leg and foot, d) static and dynamic response characteristics associated with axial loading at the heel, and e) static and dynamic moment-angle characteristics at the dorsiflexion/ plantar flexion and inversion/ eversion joint centers of rotation.
In accordance with these guidelines, Thor-FLx/ HIIIr includes a compliant element in the tibia to assist in the generation of biofidelic axial force response, an Achilles tendon to simulate passive resistance of the musculature to dorsiflexion, separate locations of dorsiflexion/ plantar flexion and inversion/ eversion joint centers of rotation, continuous moment-angle joint characteristics, and more human-like range of motion at both the ankle and subtalar joints. In addition, a degree of freedom for internal and external rotation (foot rotation about the axis of the leg) has been incorporated.
As noted above, the Thor-FLx/ HIIIr mounts to the Hybrid III 5th percentile female dummy at the distal femur interface, and an available low friction ball bearing knee slider is incorporated into the stock Hybrid III female knee housing. Additionally, molded and shaped urethane covers are integrated into the sides of the housing to provide more realistic knee penetration contour at the knee/ bolster interface. Because of inherent space constraints in the small female design, Thor-FLx/ HIIIr embodies a shaped-cam ankle design which differs somewhat from that of the 50th percentile male Thor-Lx/ HIIIr unit. However, the two designs are fully analogous in function. The mechanical elements of the Thor-FLx/ HIIIr design are shown in Figure 2.
Figure 2: Thor-FLx/HIIIr 5th Percentile Female Hybrid III Retrofit Assembly - Mechanical Components
Instrumentation provided in the Thor-FLx/ HIIIr parallels that provided with Thor-Lx/ HIIIr, with the exception that Thor-FLx/HIIIr can additionally accommodate an optional angular displacement measurement device to track knee flexion angle. Thor-FLx/ HIIIr instrumentation elements are shown in Figure 3.
Figure 3: Thor-FLx/HIIIr 5th Percentile Female Hybrid III Retrofit Assembly - Instrumentation Elements
The four- axis upper tibia load cell (Denton no. 4825 or equivalent) of Thor-FLx/ HIIIr is lower in mass and smaller than the load cell currently supplied with the 5th percentile female HIII/ Denton design, to facilitate conformance with Thor-FLx assembly mass targets. The five- axis lower tibia load cell (Denton no. 4826 or equivalent) of Thor-FLx/ HIIIr is also of custom design. As of July 31, 2001, NHTSA has released version 1.0 of the Thor-FLx/ HIIIr (Thor-FLx Advanced Lower Extremity- Fifth Percentile Adult Female Hybrid III Retrofit Version) design to the public domain. This release consists of the following downloadable components: PLEASE NOTE: The NHTSA has stipulated that all Thor-FLx/ HIIIr hardware manufactured and delivered for use must conform to the specifications and certification performance requirements as defined within this release. Further, the NHTSA has stipulated that all certification performance data must accompany newly manufactured and delivered Thor-FLx/ HIIIr hardware.
For further information with regard to the Thor-FLx/ HIIIr, Thor–Lx/ HIIIr, or the Thor Advanced Frontal ATD please contact Mr. Mark Haffner, Thor Program Manager, NHTSA National Transportation Biomechanics Research Center, at (202) 366-4719 or at mhaffner@nhtsa.dot.gov. |
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