Notchy blade grips

[philipjdall]

The way I see it is; when we tighten up our feathering spindle we pull the grips towards the head block, and the grip can actually be compressed against the washer/main hub. When you pull the grips outward (simulating load) the load transfers to the thrust bearing, and as such turns freely. Therefore the notchiness isn't coming from the bearing, but the friction of the grip against the washer/hub,

Now I'm not an engineer, but this confused me too so have spent quite a bit of time trying to diagnose this!

As for one side being tight, the other not. Very often on new builds (with tight dampeners) the spindle hasn't reached it's natural centre, so we just need to fly it..

[Grumpy]

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 ?

As far as I'm concerned this issue is always down to excessivly pre-loaded bearings. For instance the Goblin 630 I just built was quite notchy, I removed the 0.2mm pre-load shims and it was smooth as silk (the instructions say to remove them if it's notchy). I may have to put the shims back once the dampers compress a bit.

Problem is often that once the bearing has been pre-loaded enough to make it 'notchy' it becomes brinelled and remains slightly notchy even when slackened off, replacing being the only option in that case. Answer is to slowly tighten the feathering shaft bolts checking for the first onset of any slight notchiness, and if there is any sort it out with the shims before tightening fully down.

PS.. in response to the highlighted part about pulling the grips out.....The compression in the grip is taken on a thrust bearing on the outer side and a radial bearing on the inner side. The radial bearing not being designed for axial load will be the first bearing to get 'notchy'.. So it will be the inner radial bearing that you feel, hance why pulling out reduced the notchy feeling. In flight it's probably not an issue because all the load is taken on the thrust bearing.

[scallybert]

PS.. in response to the highlighted part about pulling the grips out.....The compression in the grip is taken on a thrust bearing on the outer side and a radial bearing on the inner side. The radial bearing not being designed for axial load will be the first bearing to get 'notchy'.. So it will be the inner radial bearing that you feel, hance why pulling out reduced the notchy feeling. In flight it's probably not an issue for the same reason.

Cool, that makes way more sense.

BTW, 'Brinelling' took me to here..: https://www.applied.com/static/catal...ingfailure.pdf

[james_2k]

My 570 head was notchy in the same way as you described. With all new components. After the crash I replaced the grips (and bearings) and now it's very smooth. Didn't effect flight from what my crappy skills can discern though. Same spindle tightness though.