testing is a very complex engineering function
Things like cell phones and LCD TVs are tested after they are assembled for functionality. In a product with that many parts and assembly sequences, if 99 out of 100 TVs tested work correctly, you have a very good design and production line. The 1% that fails the functional test would be sent back, the defect identified and repaired, and the unit would be tested again. About 90% of those reworked failed units pass on the 2nd test. At some point they stop trying to debug a failed unit, and it gets scrapped - because after a certain point of debugging and rework, you spend more time trying to fix them then it cost to make another one.
A production line with a 1% failure rate would be happy as can be. For complex products its normally between 90 and 95%.
To have a production line in which 100% of all units pass the functional test, they would have to use very expensive components, and the assembly process would have to be very precise and meticulous. That would drive the cost of the cell phone or TV thru the roof.
That is all non-destructive testing. If you understand that, now jump to the DOT and SNELL testing.
They are destructive tests. If they tested every helmet at the factory, then every helmet would be destroyed by the test, and there would be nothing to sell. In production they call that "testing bullets". You have to shoot them all to test them all.
Just like the functional tests on the TVs, it would be extremely expensive to make helmets in such a way that every single one was perfect. The test is a very high threshold for quality - its not like the ones that fail the test are falling apart like they are made of paper and paste.
I dont think its as bad as the report makes it sound. What actually happens to your head in an accident is different for every accident - there is no ideal pass/fail test that will emulate the worse case accident that you are expecting to survive.
In the end it all comes down to bell curves and statistics. Imagine you are dopping hard boiled eggs on the floor - each one will break and crush a bit, and each one will break a little different. If you started dropping raw eggs, they would just splat splat splat...
Its kinda like that. None of these helmets that fail the random sample test are exploding on impact like you dropped a crystal punch bowl. If they were I would hope that DOT or SNELL would have some other level of failure - for example, if someone was selling counterfeit Arai helmets from china that are actually made of painted sugar.
Last edited by KCW; 07-08-2018 at 07:07 AM.