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  #1  
Old 05-11-2020, 12:55 PM
Aluminum Aluminum is offline
 
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Location: San Jose, CA
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Default Lubricate Heim bearings?

My search-fu doesn't seem to be up to this task today:

Is one supposed to lubricate Heim bearings? If so, how?

They ship with a film of light oil, which may be just a preservative. Is the bearing action designed as steel-on-brass dry, or is this oil meant to be replenished as it creeps out? Tribologists opine please.
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  #2  
Old 05-11-2020, 01:01 PM
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LPS-2. I shove a paper towel under to catch the excess.
LPS-2 is pretty much what I use on everything except the wheel bearings!
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  #3  
Old 05-11-2020, 01:45 PM
PhatRV PhatRV is offline
 
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Location: Buena Park, California
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Quote:
Originally Posted by Aluminum View Post
My search-fu doesn't seem to be up to this task today:

Is one supposed to lubricate Heim bearings? If so, how?

They ship with a film of light oil, which may be just a preservative. Is the bearing action designed as steel-on-brass dry, or is this oil meant to be replenished as it creeps out? Tribologists opine please.
Some of the bearings are already lubricated with grease such as on the aileron pushrod so I suppose you don't want to lubricated these with other solvents.
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  #4  
Old 05-11-2020, 11:20 PM
JDeanda JDeanda is offline
 
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Location: Ventura, CA
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Spherical bearings should Not be dry. I use LPS-3. It?s waxy and stays on the bearing for a while. LPS-2 is about as good. Some folks use engine oil, and that?s OK.
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  #5  
Old 05-12-2020, 12:10 AM
rongawer rongawer is offline
 
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Depending on which rod end bearings you have, you can buy these ACS Regreasers, but for an RV, I'm with the others: LPS-2, although honestly, just about any comparable heavy spray grease will do the job. Like the grease people like to say, the best grease is the one that gets used. If you spray your internal rod ends at annual, you'll be fine.

For the external ones, I recommend LPS-1 to minimize dust and dirt build-up and then spray them more often. I do mine monthly, but I fly a lot too, so YMMV.

LPS-1 is great on those piano hinges too and keeps the trim tab from getting gummed up vs LPS-2.
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  #6  
Old 05-12-2020, 05:44 AM
fixnflyguy fixnflyguy is offline
 
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Default LPS 1

The LPS 1 "greasless"is the go-to-lube for me. We use it on the big birds by the gallons, as it provides lube without dust and dirt sticking to it. hard to find at local retail stores, but worth every penny to mail order it.
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  #7  
Old 05-12-2020, 06:50 AM
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Triflow is also a highly recommended lubricant for these bearing.
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  #8  
Old 05-12-2020, 07:43 AM
WingsOnWheels WingsOnWheels is offline
 
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Quote:
Originally Posted by Walt View Post
Triflow is also a highly recommended lubricant for these bearing.
That is what I use, with a fine-point applicator.
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  #9  
Old 05-12-2020, 07:51 AM
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rv8ch rv8ch is offline
 
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Default Sewing machine oil

I could have sworn I read it here on VAF somewhere, but can't find it. Someone suggested sewing machine oil.

Looking up sewing machine oil on the google has shown me that there are about 100 different varieties of that as well, so not sure if this is a helpful tip or not. It does seem very clean with very low viscosity, and applying it to some of my old stiff rod end bearings helped them move very smoothly.
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  #10  
Old 05-12-2020, 07:33 PM
Aluminum Aluminum is offline
 
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Thanks for all the suggestions. The consensus seems to be that yes, periodic lubrication is indicated.

To clarify: my concern was less about what type of oil, more about what is the action that creates the film where the surfaces are bearing on one another.

There are two kinds of uses I've encountered so far. One is on rod ends. These can be tilted one way and then the other, so the new oil/grease can be worked into the bearing. But the other kind of use, like the one on the rudder, is more confusing. These bearings are static-loaded in one direction 99% of the time, so oil film will disappear on that side after a few days/weeks of sitting idle and metal-on-metal contact will occur. My mental model is that at next rotation of the rudder, any oil/grease from the unloaded side will work itself in between the bearing surfaces. But clearly these don't have a tendency to gall after years of sitting, so is the oil film necessary or are the metals self-lubricating? Oil would still help with corrosion, but not have a significant role in bearing operation.

To add to my confusion, there are also models with a zerk.

It would be nice to find an engineering reference and understand how these things work. It's baffling enough thinking about how they are constructed!
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