Ross - sanity check - radius is 12.5 not 25 - they were 25mm beams.
duh me stupid

I just spent 3 weeks revising, slope defection by equation and integration, stress and strain, and dynamics:- centripetal force, Dynamic amplification factor, Euler rule etc etc. and the question was how to calculate the Natural freq.........F**kin typical

told you my brain was fried.......

ok so r= 12.5 didn't you read the caveat ( see first paragraph)

Lee ,Sure I will sort something out for you. But better get Irving to check it eh......