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Lubricating


Roger Lee

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Loctite 480 is just black TOUGHENED superglue. It's not just at regular superglue. If those bearings are glued in place leave them alone. You can easily damage them. Just worry about loose ones and gluing them back in place. This is an easy job. Do not make more out of it than it is or you may in up with unintended consequences.

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Loctite 480 is just black TOUGHENED superglue. It's not just at regular superglue. If those bearings are glued in place leave them alone. You can easily damage them. Just worry about loose ones and gluing them back in place. This is an easy job. Do not make more out of it than it is or you may in up with unintended consequences.

 

Roger, He is talking about a bearing that is stuck or binding. If cleaning and lubricating doesn't resolve the issue, you advocate for leaving them alone? IMO if the bearing is bad it needs to be replaced.

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I have never seen or heard of a bearing so bad it needed replacement. They have very low stress on them. The center should turn, but if someone got glue on them they could stick which I have seen. That said the metal center bushing and the very small amount that this moves  allows this to work and operate just fine. If it is lubed like it should be every annual then it can rotate on the bolt within the metal bushing without any consequences. 

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The bearing was bad. Really bad. The middle would pop out of the outer ring with just finger pressure. The rest were getting pretty worn too. Replaced them because we already had the control surfaces off when it had to be trailered from a broken sprag.

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If it is lubed like it should be every annual then it can rotate on the bolt within the metal bushing without any consequences.

 

Roger, I don't always agree with what you say, but this time you are giving really bad advice. The bolt if installed and torqued properly will not rotate in the metal bushing.

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The bolt doesn't ever rotate the metal bushing it goes through will. If it didn't then the guys that glued the center part to the outer black ring would cause it to freeze up. Those bushings many times are so loose they just fall out of the center.

 

I would also replace a bearing if the center came out, but I haven't seen one, but all my customers get these bearing lubed every inspection and I check and fix any loose ones. I would imagine that if a complete bearing was loose in its mounting and it was never fixed then the movement and forces it was not supposed to have would cause this center to break out due to excessive wear. I have had first time customers come in with 3-5 loose bearings and they were never discovered by the last mechanic. 

 

 

Bottom line always lube them and always check for loose ones. This should be a pre-flight check and it only takes a minute to check all of them on both wings. 

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I have never seen or heard of a bearing so bad it needed replacement. They have very low stress on them. The center should turn, but if someone got glue on them they could stick which I have seen. That said the metal center bushing and the very small amount that this moves  allows this to work and operate just fine. If it is lubed like it should be every annual then it can rotate on the bolt within the metal bushing without any consequences. 

 

Flap bearing

 

This one was outworn. The ball moved freely in axial direction between 1 mm and 2 mm.

 

n.b. This is the source to buy the bearings:  http://www.igus.de/wpck/2492/igubal_Gelenklager_EGLM_mm

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Roger, I looked at 3 different airplanes. When the bolt is tightened down there is no way that the metal bushing will rotate in the plastic ball, regardless of ho much it has been lubricated. On 2 of the airplanes the bushing is shorter than the ball is thick, and the third was only .001 longer than the thickness of the ball. On the third the bushing was tight in the ball and would not rotate anyway.

 

Another interesting note from the link that Markus posted is that the bearings are plastic and self lubricating. It may be possible that the wrong type lubrication could do more harm than good.

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How can a dry plastic bearing be self lubricating unless it grinds away and causes a powder residue. That isn't lubricating that just excessive wear.

 

 

As a data point, motorcycle cables used to be notoriously unreliable and need periodic lubing.

 

Until they mostly switched to teflon-lined outer cables. Now they are virtually maintenance-free and can last the life of the bike. Lubing is actually discouraged since oil would just attract dust and grit.

 

Just pointing out that the "self-lubricating" can occur with essentially no wear. 

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Roger, I was just repeating what the manufacturer said.

igubal® pressfit bearing EGLM, mm

Special properties:

 

Spherical ball and housing made from high-performance plastics

Easy to install

Compensation for misalignment

Corrosion resistant

Lightweight

Self-lubricating, maintenance-free

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I've seen glued centers. If it isn't moving then something has to.

How can a dry plastic bearing be self lubricating unless it grinds away and causes a powder residue. That isn't lubricating that just excessive wear.

 

Oilite bearings are dry too. But they are neat and self lubricate. It's based on powder metallurgy.

 

https://en.wikipedia.org/wiki/Oilite

 

https://en.wikipedia.org/wiki/Powder_metallurgy

 

In plastics, the surface breaks tiny beads loose that roll up into a ball (some types of metal coatings can do this too). Or they can also be oil impregnated. But they definitely do not have the lifespan of their metal counterparts.

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As a data point, motorcycle cables used to be notoriously unreliable and need periodic lubing.

 

Until they mostly switched to teflon-lined outer cables. Now they are virtually maintenance-free and can last the life of the bike. Lubing is actually discouraged since oil would just attract dust and grit.

 

Just pointing out that the "self-lubricating" can occur with essentially no wear. 

 

 

Oilite bearings are dry too. But they are neat and self lubricate. It's based on powder metallurgy.

 

https://en.wikipedia.org/wiki/Oilite

 

https://en.wikipedia.org/wiki/Powder_metallurgy

 

In plastics, the surface breaks tiny beads loose that roll up into a ball (some types of metal coatings can do this too). Or they can also be oil impregnated. But they definitely do not have the lifespan of their metal counterparts.

 

I think you are right! Lubricating the plastic bearings is not a good practice. I am changing my checklists for inspections at that point immediately.

 

This is what I found in the Maintenance Manual for the CTSW under chapter 4.3.2.4.4:

Inspect the bearings (С9997022 Spherical Bearing EGLM) for play. Do not lubricate them with anything. If

play exceeds 5 256 ” / 0.5 mm, replace the bearing (С9997022 Spherical Bearing EGLM). For bearing

installation use Loctite 480.

 

Thanks for the enlightment :-)

 

Markus

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Update.  I was going to leave the bearings alone but I couldn't let it go.  My bearings on the right aileron were both binding.  No amount of lubricant nor exercising of the ball in the housing would loosen this.  All I got was a ball that I couldn't move with a bolt thru it without screeching or groaning.  Today, I took over an hour to deal with this.  I removed my aileron completely. This is the only way one can get to the bearings.  I used emery cloth to polish the balls. (yes, I've now got polished balls!)  Working the ball so that it was angled, I worked my way completely around the surface 360 degrees.  Gradually, the ball loosened up where I could pinch it between my thumb and forefinger and rotate it.  I didn't loosen it.  The ball has no radial or axial play in the housing.  Even now lubrication seems to make no difference on how well this joint functions. The effort to turn the ball is the same with or without being lubed.  The materials used here appear to be impervious and don't allow the lubricant to penetrate.  Perhaps whoever installed these might have gotten adhesive on them?  It is very easy to do because the superglue is like water and goes everywhere if one isn't careful when installing these bearings.  I have asked my mechanic to mask off the bearing and go very easy on the amount of Loctite if a replacment is needed in the future.  The service done to my bearings also allowed me to lubricate the bellcrank assembly in the wing and inspect the leading edge of my aileron which cannot be accessed without removing from the wing. 

post-24-0-85497900-1471464115_thumb.jpg

 

Markus, thank you for providing the link for the bearings and for the additional information for part number and free play allowed.

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Use the right lubricant and it works well. I've been using Inox on these bearings since 2006 and tons of CT's so it has a long and proven history of success. This is better that FD's history that came with the manuals because they don't do annuals. I also use it on all rod ends and hinges on all LSA.  Not a single bearing has gone bad in a CT. Using a distillate, solvent or hydrocarbon based lube like many may have done isn't a good practice. If allowed to self lubricate then that means plastic material has to wear to produce the powder which in turn causes free play or gaps. As this happens material has to disappear until the bearing has that play and then needs replacement. I'm sure they had in mind people using lubes that were damaging which many are to some plastics, but Inox is not. They may have just considered these a consumable part that needs replacement every so often, but none of mine has and some are well into the 1100-2000 hour CT's. To me this is one of those common sense time tested application. FD Germany just had the idea of just tossing them from wear. Why, it isn't necessary.

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I think you are right! Lubricating the plastic bearings is not a good practice. I am changing my checklists for inspections at that point immediately.

 

This is what I found in the Maintenance Manual for the CTSW under chapter 4.3.2.4.4:

Inspect the bearings (С9997022 Spherical Bearing EGLM) for play. Do not lubricate them with anything. If

play exceeds 5 256 ” / 0.5 mm, replace the bearing (С9997022 Spherical Bearing EGLM). For bearing

installation use Loctite 480.

 

Thanks for the enlightment :-)

 

Markus

 

 

I actually disagree with the maintenance manual on this though FlyRatz.

 

Self lubricating bearings don't work in harsh conditions very well. Those bearings are exposed to rain and sun.

 

They SHOULD be lubricated with a plastic-safe lubricant. My post was simply to point out how things can be self-lubricating. 

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So are self lubricating bearings on motors. That's not really a factor :). If anything, constant movement is better for bearings. In general, when bearings sit, brinelling, false brinelling, and corrosion occur. Obviously the plastic bearings are less suseptible for obvious reasons, but I said in general :)

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