[Gary F Deitering]

It could be rocking on the shaft, not the bearing failing, just not tight on the shaft. If that’s the case you might not see any heat buildup. Trouble with that is , the shaft is probably being worn down and might eventually fail. Most bearings should be Lock Tited on installation to prevent this from happening. Long driveshafts and harmonics can be an engineering nightmare. Look at the way the tail drive shaft is mounted in the R22, pretty interesting design. But over-speeding the rotor system in these ships with drive shafts is a big no no, don’t do that. However in a RW with belts, 120%, no harm done, very forgiving.

I experienced that on my first ship.  On run down you would hear a 'click-click-click (for lack of a better sound.  Believe it or not I put some  'wicking lock tight' on each side of the pulley, rechecked the tightness of the bolt (it was fine).  Let it cure overnight and it took care of the noise.  Something like this is hard to find as the noise travels.  Evidently the pulley ID was a tad too large.  This took place at Oshkosh of course.

[Orv Neisingh]

I have also experienced this on a few ships over the years working with students in their Rotorways. This is not something to ignore. If the pulley is tight on the shaft then I have also discovered that if one side of the tail rotor belt adjustment had been tightened more than the other side there can be a side load on the tail rotor shaft bearings and as the shaft rotates the bearing is forced to shift in the bearing holder clamshell causing a one per rotation tick. This can be fixed by loosening the clamshell bolt and then hand rotating the tail rotor a few times, slightly tighten the bolts, rotate the shaft, tighten and rotate and continue until the nuts are at torque and the click is no longer present. If this does not solve the issue, look at the pulley.