Thrust Bearing - Replace or Lube

[TheBigE]

All,

I have 77 flights on my E7.  Still flies great, however, recently I have noticed some tail holding issues in backward rolls.   I noticed that there is some outward play in the tail grips.  I checked the bolts and they are tight, so I suspect the thrust bearings perhaps are starting to show some wear.

Was thinking about just ordering and installing new bearings in the tail.   Possible that just adding some grease will help the issue as well   Thoughts?  How often do you replace the Thrust Bearings in your E7?

Erik

[Chris Sexton]

Grease might prolong the issue, but if you are having binding and slop, I would replace the bearings.


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[Anthony Oxlade]

I periodically inspect my thrust bearings for wear. You can usually spot wear as marks on the bearing races.

My first set of head thrust bearings lasted 250 flights (including two crashes). The tails thrust bearings still looked perfect at this point but i replaced them anyway.

My e7 has a small amount of axial play in the tail grips, even with brand new bearings.

[RichL]

My e7 has a small amount of axial play in the tail grips, even with brand new bearings.




+1,  there should be a little axial play due to the thrust bearings themselves.


Rich

[TheBigE]

Yeah.  I have to admit I did not look at axial play in the beginning.  Overall the tail holds fine, but just noticed some loss of tail control during backwards rolls.   However it could be from cross input too. 

I will grab a set and replace at next opportunity.  Not a big deal

Thanks
Erik

[Jean-Luc Bolduc]

I have not replaced the tail thrust bearings yet on my E7's after each 500 flights, so I don't think yours are worn 

[KevinM]

Just to add, I just finished my E7 and flew it today and mine out the box you could pull/push with a little slop and the screws are very tight! 

[trhammonds]

Guys on the tail hub if you take and sand the ends just a taste it will take the play out of the hub or you can put a small shim behind the screw and it will also disappear as well.. My bearings have a little over 200 flights and my bearings look good.. I'm actually trying to see how many flights I can get before I have to replace them..

Rock

[GAR]

Several hundred flights on the same tail bearings here.
I did have to file the shaft to make both sides equal in length

[Anthony Oxlade]

Are you sure modifying the hub is a good idea? I assumed the small amount of axial play was part of the design. I have the same amount on both sides. Most tail designs i've seen at the field have some.

[RichL]

Are you sure modifying the hub is a good idea? I assumed the small amount of axial play was part of the design. I have the same amount on both sides. Most tail designs i've seen at the field have some.

Rock's post was referring to removal of in / out play on the blade grip not axial play.  Removing the in / out play will not remove the axial play on the tail rotor grip because, the diameters of the thrust bearings are not identical.  The in / out play exists because of tolerances that have to be allowed for in the machining process.  If the tolerances are too tight the spindle could end up being a couple of thousandths to short which would mean that the blade grip retaining bolt would bind the bearings before it became tight.  By sanding the ends of the ends of the spindle Rock is removing a small amount of in / out play but, removing too much would allow the above mentioned scenario to take place.


Rich

[Anthony Oxlade]

Maybe i'm confused... By axial play i was referring to play along the axis of the tail rotor hub, i.e blade grips moving towards/away from centre of rotation. Isn't this what they are trying to remove by filing down the hub?

[RichL]

By axial play I was referring to the slight side to side movement (or wobble around center) in the the blade grip which exists because of the thrust bearings.  Maybe I have my definitions confused.


Rich   

[Anthony Oxlade]

ah ok i'm following you now. We were both thinking of different wobbles!

[trhammonds]

+1 on Rich's statement.


It will not do any harm to the geometry of the tail rotor system or throw anything out of tolerance on the tail. If you fill uncomfortable on sanding the tail hub you can add a very tiny washer behind the bolt to tighten  up the blade grips.

Rock