Saw a post on Facebook in June 2020 NAPARS page about damage measurement:
- Measuring Crush.
- An investigator for NHTSA came to an inspection of this car which experienced a serious frontal impact. He brought a pair of folding music stands, and set them at a common distance from the undamaged rear axle to serve as a reference baseline. He tied a string at bumper height and used tape on the string to flag the locations for his 6 crush measurements (equidistant on the original face, now distorted on the car). Low tech, but also low cost, easily transportable on a plane, highly adjustable, easy to explain, and repeatable enough for the task of measuring crush. He let me take a picture of it. Thanks, NHTSA-guy!
- i just browsed down to the page...LOTS of informative posts by Wade on that Facbook thread...here's the specific thread on Facebook to Measuring Crush
- An investigator for NHTSA came to an inspection of this car which experienced a serious frontal impact. He brought a pair of folding music stands, and set them at a common distance from the undamaged rear axle to serve as a reference baseline. He tied a string at bumper height and used tape on the string to flag the locations for his 6 crush measurements (equidistant on the original face, now distorted on the car). Low tech, but also low cost, easily transportable on a plane, highly adjustable, easy to explain, and repeatable enough for the task of measuring crush. He let me take a picture of it. Thanks, NHTSA-guy!
- Love it! I'll take on ANY cloud scan in damage analysis with my plumb bob and ruler! There have been tests/papers on comparing different measurement techniques when applying damage analysis and it all boils down to that a cloud scan for data in crush analysis is like using an electron microscope to measure something to the nearest inch!! what's the point? Whole lotta gigabytes for a crude technique.(yea they sure make purdy looking pictures which has jury appeal!!)
CRASH (on which all damage analyses techniques are based) was invented by Ray McHenry as a quick/fast way to get starting speeds for NHTSA to start a SMAC analysis!- ...and yea, NHTSA decided crude was OK and good enough for their NASS statistical studies mainly because they simply wanted/needed uniform interpretation of crash evidence so they could look for trends, etc. etc.
- See our many papers on CRASH
- and let me add...many 'instantaneous momentum exchange' analysis program vendors now try to bolster their results by including damage analysis results.
- Please exercise caution when using these (or ANY) techniques for crash reconstruction.
- Be sure to perform sensitivity tests on any results. See:
- ...and yea, NHTSA decided crude was OK and good enough for their NASS statistical studies mainly because they simply wanted/needed uniform interpretation of crash evidence so they could look for trends, etc. etc.
For additional information on damage analysis & CRASH, please see:
- The Algorithms of CRASH, paper presented at 2001 SECCC, Aug 2001
- NHTSA CRASH3 Technical Manual - 1986 NHTSA collection/summary of CRASH papers
- From the McHenry Forum Topic on CRASH:
- Why was the CRASH program created?
- What Speed Should I Use to Calculate CRASH3 A&B Coeff?
- Is CRASH damage analysis a virtual relationship?
- Should a CRASH type damage analysis include induced damage?
- What is the "No Damage Intercept" of CRASH
- Can You Use Maximum Crush For CRASH A&B Crush Coefficients?
- Crush Coefficients Conversions: CRASH (McHenry), Campbell, WinSMASH (Prasad)
..and more, see the McHenry Forum and specifically the McHenry Forum topic CRASH and Damage Analysis