Analysis of a Dirt Track Sprint Car Accident 942548


Open-wheel dirt-track racing represents one of the most dangerous forms of motor racing. The potential for touching and/or interlocking of rotating wheels, combined with the frangible and rutted nature of the track surface itself, makes the occurrence of x-axis [8] rollovers routine. In addition, the rollovers themselves are usually at a high enough speed so that very violent dynamics and occupant accelerations occur. The accelerative vectors present an unusual set of challenges to the restraint systems employed.

In this work, we examine a single dirt-track rollover event. The purposes of the investigation were (a) to attempt to characterize the dynamics of the vehicle motion through videographic analysis, (b) to estimate the accelerative loadings to which the driver would be exposed, (c) to develop a first order analysis model for car and suspension motions which ensue following interlocking of counterrotating wheels, and (d) to determine whether current restraint technology is acceptably strong enough to face such accidents.

To begin, a short introductory section characterizing dirt-track midget car racing in general is presented. Dirt-track racing presents a very high potential for rollover accidents whenever a sprint car is presented sideways to its direction of travel.

A short description of the accident event is presented next, followed by a discussion of the mechanism of tripped and untripped rollover. A frame-by-frame videotape analysis was used to examine the rollover motion. Combining driver position information with the video analysis enabled estimates to be made of the accelerations experienced by the driver. Standard anthropometric correlations were used to estimate body segment masses from driver weight. Estimating accelerative restraint loadings through the use of videographic analysis and anthropometry was necessary because of the impossibility of duplicating realistic motion in the laboratory.

To examine vehicle motion further, a first-order analysis of vehicle dynamics involving interlocking, counterrotating exposed wheels was performed. Simple calculations show that such engagements develop significant whole-vehicle and component forces and kinetic energies.

Belt and buckle strengths were measured under quasistatic conditions. A total of five arm restraints and five arm restraint hardware sets were tested. Strengths for the larger belts used in the restraint system (lap, torso and antisubmarine) were extrapolated from arm restraint data. Finally, belt and hardware rupture loads were compared to expected inertia loads to determine the potential for belt failure. Results showed that there is potential for such failures to occur, and failures did in fact occur during the actual accident. A discussion of the restrictions, assumptions and test conditions follows the above analysis.


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