Case Study – TOMCAR Data Acquisition and CAE Analysis
Originally conceived and still used as a rugged military off-road vehicle, civilian versions of the TOMCAR all-terrain vehicle are now used in the mining, agricultural, recreation and tourism industries. Smaller than conventional sport utility vehicles and faster, safer and more nimble than conventional ATVs, the TOMCAR is designed and built to exacting standards.

Pratt & Miller Engineering provides analysis and data acquisition support for TOMCAR. For example, Pratt & Miller performed computer-aided engineering (CAE) analysis of the roll-over protective structure (ROPS). Several organizations publish ROPS standards that are used to certify off-road vehicles for roll-over safety. Recognizing the need to team with an engineering partner familiar with tubular structures and safety requirements, TOMCAR called Pratt & Miller Engineering.

Using advanced finite element analysis, Pratt & Miller engineers duplicated the physical ROPS testing procedures digitally. This enables design changes to be evaluated quickly using the computer, and will help ensure that the ROPS passes the physical certification test without expensive retesting.

Pratt & Miller Engineering also supported a full vehicle road load data acquisition project with TOMCAR. The objective was to collect data that could be used to create an ADAMS model and develop load cases for strength and fatigue optimization. The vehicle was instrumented at Pratt & Miller using the same technology used to acquire race car data.

DESIGN:
Design iterations were completed to evaluate different materials and frame geometries for the roll-over protective structure. An explicit analysis program was utilized to characterize the non-linear, high strain rate seen in the ROPS testing sequence. In the data acquisition program, a test plan and sensor package were designed to support the project objectives.

DEVELOP:
A number of design iterations were completed to evaluate different materials and frame geometries for the roll-over protective structure. The data acquisition test plan and sensor package were refined to support the project objectives.

BUILD:
The optimum solution for the ROPS will be constructed using an existing frame and modifying critical elements of the structure that were revealed in the CAE analysis. In the data acquisition program, a vehicle was instrumented and damper designs were tested on Pratt & Miller’s in-house shock dynamometer to characterize their force vs. velocity curves.

RACE:
The TOMCAR was tested at Chrysler’s Chelsea Proving Grounds on several off-road courses, including severe sine wave bumps and large jumps. Standard braking, acceleration, and handling events were also run and data was collected. A max/min file for each of the tests was created to list the maximum values for each channel seen on each road. Data also was collected for both sets of dampers and comparisons were made between the original and alternative dampers.

WIN:
CAE analysis of the TOMCAR rollover protective structure dramatically increases the likelihood that the ROPS will be certified in its initial test. The data collected by Pratt & Miller was used by TOMCAR to generate an ADAMS model and load cases for strength and fatigue optimization. TOMCAR now has the data to complete additional modeling and analysis without supplementary physical testing. This will accelerate product development and design optimization while reducing overall cost.