The Traffic Accident Reconstruction Origin -ARnews-
|
|
Re: equivalent barrier speeds for sideswipe pole impacts
Wilt Nelson (WIL7MO@aol.com)
Mon, 1 Jun 1998 16:14:23 -0400 (EDT)
EBS is a term that started many years ago when I did a LSB study of field crashes for GM. It was based, solely and completely upon a guess of the speed required to duplicate the damage if the field car ran into the concrete test barrier. The damage on the car had to be a flat, distributed, frontal damage pattern that looked like it had run into the concrete barrier. Not all the field crash cars were distributed frontal damage, some were offset frontals--so if you can guess at one why not the other. So pretty soon all the cars in the study had EBSs. Then I made a presentation of the effectivness of LSB to NHTSA and the EBS term was used and pretty soon everybody was using the term. You realize of course that in the field these vehicles were not running into concrete barriers nor cars of equal mass and shape. The other vehicle or object in the crash was not considered in that estimate. So EBS is really quite hokey. Now and then someone wants to know the EBS of a sideswipe. Th
ere is no such number. Perhaps what you want is the Delta V over time for a sideswipe. In a sideswipe type crash the car does not go from some travel speed to zero mph. And the stiffness coefficients which are typically measured orthogonally to the vehicle are not much help. Basically a sideswipe is a slow down that might be calculatable if you knew the coefficient of friction of the car's side and the object struck. Sometimes the object struck "pockets" in front of the rear axle, which means the decel experienced by the car was not uniform. The sides of a car for glancing impacts is not uniform and the variables are many. The program by Hans-Herbert Scheier, called MacCar, and given in an SAE paper does calculate glance-off impacts, and expresses some of the results as DELTA V. You may want to try that. So your question is really one without an answer, even though I used up a lot of space saying so. Wilt
Wilt Nelson
WIL7MO@aol.com
Quick Reply
Use this form to reply to
this Thread