500 Blade Grip bearings notchy

[dillwhacker]

Hi all,
Im rebuilding the head on a Trex 500 after a crash. The blade grips felt very notchy with the links disconnected. So new feathering spindle, pair of new radial bearings and new thrust bearing in each grip. Old bearings came out OK and the new ones slid in nicely.
But when I tighten the bolts fully, the bearings still feel very stiff and a bit notchy. They feel smooth if one bolt is slackened off by a turn or two. Definitely got the thrust bearings in the right way, and got the ali washers between them and the outer radial bearing, and got the brass washer touching the dampener rubber, so I think its all OK assembly wise. Seems like the feathering shaft is too short and squeezing up the dampeners really tight. Tried another spindle - no different.
Any ideas / help gratefully received!

[Baldie]

Are they still notchy if you pull the blades outwards whilst moving them ?

[dillwhacker]

Thanks Silverlyx, well, less so but still notchy & very stiff.

After a bit of a faff and some shouting, I could see what was happening. Its a tolerance issue with the grip and the 'inner' race of the thrust bearings.
The blade grip is sort-of bored to 12.00 mm dia, give or take the bad machining / surface finish.
The inner race of the new bearing set I got measured 12.03mm ish (they're not circular - 12.02 to 12.05 measured).
So the thrust bearing cannot be pulled snug up against the ali washer between it and the outer of the two radial bearings - it gust gets stuck in the grip and so the whole lot goes tight when you clamp up the two screws in the ends of the feathering shaft...
So I took the two inner thrust races and screwed them to the end of an old shaft, and twissled them against a Dremel wheel for a minute, until they measured 11.95 mm dia all round.
PERFECT. Now the two screws clamp up nice and tight, and everything feels silky smooth, just the friction of the rubber dampeners. Lovely.
Thanks Align for your precision machining. Nice one.
Cheers all, have fun!

Are they still notchy if you pull the blades outwards whilst moving them ?

[Si Goodchild]

Thanks Silverlyx, well, less so but still notchy & very stiff.

After a bit of a faff and some shouting, I could see what was happening. Its a tolerance issue with the grip and the 'inner' race of the thrust bearings.
The blade grip is sort-of bored to 12.00 mm dia, give or take the bad machining / surface finish.
The inner race of the new bearing set I got measured 12.03mm ish (they're not circular - 12.02 to 12.05 measured).
So the thrust bearing cannot be pulled snug up against the ali washer between it and the outer of the two radial bearings - it gust gets stuck in the grip and so the whole lot goes tight when you clamp up the two screws in the ends of the feathering shaft...
So I took the two inner thrust races and screwed them to the end of an old shaft, and twissled them against a Dremel wheel for a minute, until they measured 11.95 mm dia all round.
PERFECT. Now the two screws clamp up nice and tight, and everything feels silky smooth, just the friction of the rubber dampeners. Lovely.
Thanks Align for your precision machining. Nice one.
Cheers all, have fun!

Sounds like a solid technical investigation and solution to me.

[dillwhacker]

Hi Si!!
Well, not too technical, just trying to see what fits where and what doesnt fit!!
Not your bird - only hovered that so far - this belongs to a mate - I said I'd fix it and fly it for him, and I blooming crashed it for him...
Let you know when I fly yours - I'm sure it will be fine! Now I can get on to setting it up on the DX8.
Cheers for now buddy!
Trev

Sounds like a solid technical investigation and solution to me.