Notchy blade grips

[tomatwalden]

What's the main cause of notchy(*) blade grips? Radial or thrust bearings?

(*) ie. with pitch links removed, the blade grip turns in almost fixed points rather than smooth movement.

[jimmyhorns]

Could be either Tom, but I would have thought the radials are more likely to be the point of failure.

If im replacing a single bearing in a head I do the whole lot. For a fiver it doesnt make sense not to...

[jimmyhorns]

I've also noticed it happening when I havent correctly shimmed the head - so that the bearings are under compression.

[chrisleematt21]

+1 on the radials

[philipjdall]

Remember to pull the grips apart by hand when checking, to simulate the centrifugal force of the blades.

[Planehazza]

Remember to pull the grips apart by hand when checking, to simulate the centrifugal force of the blades.

In my own experience, notchy grips have always been too much tension on the thrust bearings due to the assembly being too tight. As said, pull them outwards gently to simulate the centrifugal effect - if they're still notchy, use thinner spacers between the head block and the grips.

[tomatwalden]

Thanks all!

Yes, if I pull the grips, the notchiness pretty much disappears. I have replaced one set of radials (on both grips) and the thrust bearings after a crash but couldn't get the innermost set of radials out - even after being in the oven for a bit I've got the spare radials in a drawer otherwise waiting to be used! Thing is, this is my little 300CFX so the bearings are so blooming fiddly anyway that getting those last ones out is something I gave up on ...

But as you all rightly pointed out, under (simulated!) centrifugal load, it seems that they become smooth anyway so I'll stop worrying and just fly it!

[philipjdall]

Yeah just fly it

On my helis (particularly smaller ones) I actually try to get it as tight as possible as it just makes the heli feel nicer in the air. A lot to be said for shimming the head IMO!

[scallybert]

In my own experience, notchy grips have always been too much tension on the thrust bearings due to the assembly being too tight. As said, pull them outwards gently to simulate the centrifugal effect - if they're still notchy, use thinner spacers between the head block and the grips.

But surely puling the grips outwards *increases* the tension/load on the thrust bearings ? So that seems logically inconsistent.

It is, however, exactly what I've seen with heads that feel notchy. [Including a brand new, carefully assembled Goblin 500 head. In that case, one grip is notchier than the other.]

BTW, in motorcycle steering head bearings, this notchy effect is due to the bearings having worn where the balls generally sit in use. So you have a kind of 'détente' effect. This doesn't explain why brand new bearings should behave like this.

[waveydavey]

Depressions or tension, I've had both small dents in the thrust races. Too much tension means the balls fight against each other, you're trying to flatten them in effect so the balls are skidding rather than rolling

[Jez N]

I rebuilt my warp the other night and took apart the blade grip that was notchy from before. Thrust hearings were correct and all re greased but still notchy when everything tight. Loosened the feathering shaft bolt a quarter turn and the notchiness gone. Trust the thread lock!!

Bolts need to be tight but not too tight

[Mike Sanders]

Loosened the feathering shaft bolt a quarter turn

.

Brave man. Trusting the threadlock!

[philipjdall]

.

Brave man. Trusting the threadlock!

Couldn't agree more!

Threadlock is Anaerobic; i.e. if there is any air in the thread then it WILL NOT work.

Slight notchiness is fine, will ease under load; better than a blade in your face!!

[Jez N]

Couldn't agree more!

Threadlock is Anaerobic; i.e. if there is any air in the thread then it WILL NOT work.

Slight notchiness is fine, will ease under load; better than a blade in your face!!

Everyone could (over) tighten their bolts up another quarter turn. All I am trying to point out was that I had overtightented the bolt and by loosening it a small amount (it's still tight!) I have taken off the stress in the system and resolved the blade notchiness. The threadlock is fine, there is no air gap and the blade grip will not come loose. If it does, i promise to come here, admit all and eat humble pie!

[scallybert]

There's still something not right here...

If the notchiness is down to the thrust bearings being over-pre-loaded (ie by the screws being too tight), then why would pulling the grips apart (simulating centrifugal force) ease the notchiness; rather than make it worse ?