Main gear stationary wobble?

[Planehazza]

A weird one... It has probably always done this, but I've just noticed mid maintenance. If I spin the rotor head so that the tail drive gear spins, but with the motor and main gear stationary, the main gear will oscillate up and down as in the video. Does this mean the OWB assembly is not on straight?


https://goo.gl/photos/SFTLEL9QvST6PYFm7

[Grumpy]

Bent main shaft?

Theoretically (if it has a sleeve that fits over the main shaft on which the OWB runs) then that sleeve could be machined or worn eccentrically, it's unlikely but is a possibility.

[waveydavey]

Maybe the hub isn't sat correctly in the main gear and up slightly one side

[Grumpy]

For it to wobble like that the part that's out of alignment and causing the wobble must be rotating. A misalignment of the static parts such as the gear itself or the hub or even the OWB case couldn't cause the wobble because those parts arent turning.

[waveydavey]

I see what you're saying youre right, ignore me Harry.

[Planehazza]

Hi all, and greetings from sunny Skiathos!

Thanks for the responses. I've replaced the main shaft and checked the old one which appears to be straight, but replaced it anyway. I've had the main gear assembly stripped, flushed with IPA and regreased. It still does it.i made sure to fit the owb as centrally and evenly as I could but there is no room for adjustment.

[Planehazza]

Bent main shaft?

Theoretically (if it has a sleeve that fits over the main shaft on which the OWB runs) then that sleeve could be machined or worn eccentrically, it's unlikely but is a possibility.

There was a smooth wear mark, but nothing too serious or worse than I've seen before and it hasn't slipped as far as I can tell.

[Grumpy]

Only thing I can think of then is the sleeve that slides over the main shaft is either slightly oversize so not fitting tight on the main shaft, or it's machined eccentrically. I cant think of any other cause?

To be honest though if you have ruled out the bent mainshaft then it's probably nothing to worry about.

[Planehazza]

Only thing I can think of then is the sleeve that slides over the main shaft is either slightly oversize so not fitting tight on the main shaft, or it's machined eccentrically. I cant think of any other cause?

To be honest though if you have ruled out the bent mainshaft then it's probably nothing to worry about.

Sorry mate, I hadn't spotted this reply until now. I'll keep an eye on it to see if it worsens.