Mechanical Cooling Fan broke during 6000 rpm burnout.

i have one of those fans too and was pissed when i saw the rpm limit. i dont really know how to take it, when you compare it to a stock fan, there isnt a lot of difference. the one i have does have aluminum blades. i would really think an old used fan that has been flexed for many years would be more likely to fail. i had a fan come apart on my 31 essex, it fatigued over the years when it hame apart it ruined a perfect honeycomb core rad and went through the hood side. pissed me off but no one was hurt.