540 counterweight

[Dorfie]

Can someone please explain the meaning of "one fifth and one sixth order
counterweights".
I think I got the fact that the fourth suffix in the engine designation indicates the counterweight setup, where the number 5 means "one fifth and one sixth order" and the number 6 in the fourth suffix means "one sixth and five third order counterweights". Don't know what these "order counterweights" mean though and google could not help.
Can all engines with the #5 as the fourth suffix turn 2700 RPM?
When looking at the suffixes then I often come across the statement "more effective counterweights" to accommodate a specific propeller, but the number 5 remains.
Thanks.
Johan

[rocketbob]

It means that there is a counterweight that dampens a vibration that occurs 5 times per revolution (5th order.) and another that dampens a vibration that occurs 6 times per revolution (6th order.)