ACC Users Group › ACC Users Group Discussion Forums › Fans & Gearboxes › ACC Fan U-bolts › Reply To: ACC Fan U-bolts January 31, 2018 at 3:44 pm #1852 nick_romanoParticipant Is the wet cool type running at the same speed? Do you know the blade natural frequency? The ratio between the BNF and the fan RPM can be tricky and causing troubles.
