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  #11  
Old 06-08-2021, 11:44 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
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Quote:
Originally Posted by printbr View Post
I have always wondered the same thing. It seems completely unnecessary.
I recall back when ‘Aviation Maintenance’ was a paperback publication. They called wheel bearing greasing “…the most over-performed maintenance out there”. At least, they said, it was cheap and hard to screw up.
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  #12  
Old 06-09-2021, 11:38 AM
fr0gpil0t fr0gpil0t is offline
 
Join Date: Apr 2013
Location: Colorado Springs
Posts: 62
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My understanding sealed bearing - mean that "sealed". No need to replace the grease and anyway you can't get to it.

The RV-12 main wheel bearings have some sort of rubber shield which makes it hard to add/refresh the grease. But they are not truly sealed meaning the grease still needs to added/maintained.

Robert
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  #13  
Old 06-09-2021, 01:29 PM
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Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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The rubber seals on the RV-12 main wheels are indeed lip seals. They are removable and not integral with the bearing.

Tapered roller bearings are excellent for radial and axial loads. Also, very good at absorbing static loads such as hard landing. Tapered rollers have large surface area in contact bearing race to distribute force. These bearings do not have integral seals and required either removable lip seal or dust cup like on front wheel of automobile. Tapered roller bearings consist of two separate pieces – inner race with roller/cage and separate outer race.

Ball bearings have point contact between balls and bearing race which is poor for absorbing static loads. Some ball bearings are designed for combined radial and axial loads but don’t approach robust design of tapered roller. Ball bearings can have integral shield or seal. This is possible because the bearing is assembled as a single unit with inner/outer races and ball/cage.
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