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Rod End Bearings - Maintenance?

rvator51

rvator51

Well Known Member
What kind of lubrication have people been using on their rod end bearings for their control surfaces and how do they apply it?
I heard a silicon grease works best, but dont see how you can get it uniformly throughout the bearing.

The reason I asked is because I found the rod end bearings on my wifes rv-4 had froze up and the elevator was turning on the bolts. Its a 1989 rv-4 and I dont know if the elevators were ever removed or not. I dont know how you can lub the bearings without removing the elevators unless you use some kind of spray lub and dont know how effective that would be.
 
Tom, I've been using LPS No. 1 Greaseless Lubricant monthly and have been very happy with the results. I hold a rag under the bearing in one hand and spray with the other hand then twist the (aileron/flap) rod ends (what little they will) and call it a done-deal :D Rosie
 
Rosie said:
Tom, I've been using LPS No. 1 Greaseless Lubricant monthly and have been very happy with the results. I hold a rag under the bearing in one hand and spray with the other hand then twist the (aileron/flap) rod ends (what little they will) and call it a done-deal :D Rosie
Click to expand...
Thanks Paul, we will give it a try!
 
Use LPS #2

Rosie said:
Tom, I've been using LPS No. 1 Greaseless Lubricant monthly and have been very happy with the results. I hold a rag under the bearing in one hand and spray with the other hand then twist the (aileron/flap) rod ends (what little they will) and call it a done-deal :D Rosie
Click to expand...

Rosie... with LPS #1 you probably should be doing it monthly...

The LPS #1 data sheet says...

Dries fast and resists oil, dust and dirt build-up
Provides a dry, thin lubricating film
Fast acting penetration
Displaces moisture
Loosens rusted or frozen parts
Provides short term light corrosion resistant barrier

The mechanics working on my planes all have used LPS #2.

The LPS #2 data sheet says...

Strong, multi-purpose lubricant and penetrant with added corrosion protection
Provides a nondrying, light, oily film for use on indoor/outdoor equipment
Displaces moisture
Reduces wear caused by friction and corrosion
Provides up to one year protection

For use during annuals, the LPS #2 appears to be a better product, leaving more of a longer term lubrication film behind.

However, if the bearings are frozen, then LPS #1 first would free them up better, and then follow with LPS #2 when they are turning for a longer term lubrication...

gil in Tucson
 
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az_gila said:
The LPS #1 data sheet says...
<snip>...Provides a dry, thin lubricating film

The LPS #2 data sheet says...

<snip>...Provides a nondrying, light, oily film for use on indoor/outdoor equipment

gil in Tucson
Click to expand...

I can tell you first-hand that you truly do NOT want to use LPS-2 if you live in a windy, dusty, wind-howling-dirt-blowing environment ;) Rosie
 
Rod end bearings

Since someone else brought it up, also check flap link rod end bearings. They are made by Aurora Co., and if you check Aurora's web site, you will note that they are economy grade. On the RV6, the flap end rod bearing terminates unenclosed, and could possibly separate from the stud, if allowed to wear sufficiently. When preflighting the flaps, a clicking sound is likely heard where excess bearing play exists. Note that once removed, the bearing race vs. ball stud must be positioned at the installed angle to accurately check for play.
 
In this part of the world, people seem to use Tri-Flow and that was what was recommended by my A&P friends. Just another data point. I've also considered LPS-2 but figured I'd give the Tri-Flow a try... seems to work pretty good!
 
What lube to use on control connections?

I'm doing the condition inspection with an A&P and he suggested using a few drops of 30W oil on all the rod end balls in the controls. I was going to use silicone spray lube because with the little tube I can get it right on the ball. I've also seen people use one of the LPS brand lubricants that is kind of sticky so that it stays where it's put.

Any suggestions? What has worked for you?
 
LPS oils...

The specs are here.....

http://www.lpslabs.com/Products/Lubricants/LPS1.asp

http://www.lpslabs.com/Products/Lubricants/LPS2.asp

LPS-1 says -- Provides a short term, light, corrosion resistant barrier

LPS-2 says -- Nondrying, oily film for long lasting lubrication

My A&P likes the LPS-2

I think the LPS-1 is like WD-40, it works for a short time, but cleans and displaces water... then the oil disappears and the part rusts faster than before...:)

My Tiger, and old Pipers, call for MIL-7870 instrument oil... if you can find this, it seems to be better than LPS-2, but it's hard to locate.

gil A
 
Rod End bearing Lube.

I use LPS 1 every year during annual inspection. One drop from a drop oiler right on the ball of the rod end and I wipe off the excess. I did rebuild a 20 year old wrecked RV 4 which had flown continually until the mishap. It's control sticks felt like you were stirring mud when moved until I lubed the rod ends after cleaning them. It did not take much LPS 1 but the difference was actually remarkable so I now repeat this every year with my own RV. I doubt that LPS1 is in compliance with any Mil spec but It is good stuff and readily available!

Dick DeCramer
RV6 N500DD 200 hours
Northfield, MN
 
I lubed mine with Lubriplate when I built the airplane. (10-years ago)

Motor oil it the old standard used by most A&Ps. I am not crazy about the dirt that motor oil attracts. It lubes well but the dirt it attracts can cause more wear.

Many builders have used LPS-1. I have used it also. It is light like WD40 but is suppose to leave a dry film behind. LPS-2 may be a better choice. I do know that using LPS-1, the rod ends will be squeaking again after a month but I also know that it has never attracted dust or dirt on my airplane.

If anyone finds a MIRACLE lube for the rod ends, please let the rest of us know.

This could turn into another PRIMER thread as I am sure there are as many different solutions as there are lubricants.
 
Thanks!

My thanks to everyone for their input. My A&P said 30w motor oil, but I have also seen it attract dirt and get gritty.

John
 
How about this.

Has anyone tried "Break Free" It works pretty good on guns which have both sliding and rotating mechanisms that require consistent reliability.

My Uncle Jim told me that the CHP changed over to this from WD 40 years ago to resolve weapons jamming issues.:rolleyes:
 
Silicone

Bubblehead said:
I was going to use silicone spray lube because with the little tube I can get it right on the ball.
Click to expand...

I wouldn't advise using spray silicone within 100 yards of any airplane. It is handy stuff, stays slick after it drys. But once you get it on a surface you can almost forget getting paint to stick. Paints will "fisheye" even after careful cleaning. I can imagine the uglyness you could encounter if the airplane was lubed with silicone before painting. Just don't do it. LPS, motor oil, no problem.

John Clark
RV8 N18U "Sunshine"
KSBA
 
GAHco said:
Has anyone tried "Break Free" It works pretty good on guns which have both sliding and rotating mechanisms that require consistent reliability.

My Uncle Jim told me that the CHP changed over to this from WD 40 years ago to resolve weapons jamming issues.:rolleyes:
Click to expand...

I still would like to know, before I use it, does anyone have experience with Breakfree on there low velocity, low load bearing areas?
 
Break Free

Tom, I've never seen break free used anywhere on an aircraft other than cleaning of cordite from weapons racks and gun systems. It does leave an oily film and made the next days weapons releases easier to clean up after. In the bearing applications I'd stick with the LPS products or the tri-flow.
 
WilburD2 said:
Tom, I've never seen break free used anywhere on an aircraft other than cleaning of cordite from weapons racks and gun systems. It does leave an oily film and made the next days weapons releases easier to clean up after. In the bearing applications I'd stick with the LPS products or the tri-flow.
Click to expand...

Thanks for the well educated response,

Thinking about it, I know it has some supended teflon it it and who knows maybe some silicone lube too.

It does seem to work good for a lot of the smaller stuff.

I am trying to put in all MS ball bearing rod ends in my controls, but I might run out of money first they are a little pricey.:rolleyes:
 
Do rod end bearings need lubricating?

After 16 hours of flying, I could feel some drag in the ailerons during control inputs. I traced it to the rod end bearing on the bellcrank leading to the right aileron. I removed the bearing and could not rotate the ball with my fingers. Inserting a punch in the bolt hole, I rotated it and sprayed it with penetrant/lubricant. After a little working, it now rotates freely with light finger pressure- just about spins actually. Inspecting the ball, there are no scratches, just a little polishing around the circumference at the mid diameter (the equator, if you will) of the ball. There is no indication that there is a possibility of failure, but I suppose it could end up dragging again if lubrication was not a long term fix.

Question to those in the know is; should the rod end bearing be permanently lubricated, or is it a common practice to occasionally lubricate these? Is wheel bearing grease acceptable or should a white grease like lubriplate be used?

I'm pretty sure I know where the problem originated. Years back I had someone in my local chapter weld the threaded portion onto the tubing, since I didn't like the rivet idea on these critical push/pull tubes. They didn't remove the bearing and I think it cooked the provided lubricant. I'll be inspecting the 3 remaining bearings. Bit of a setback, but so far the only problem identified in the test program.:)
 
Short Answer, Yes

I use LPS-2 on protected ball joints (inside the fuselage, wings, under the cowl) and LPS-1 on external ones (like rudder, elevator).....
Frequency depends on operating environment.
 
I was taught to use LPS-2 on my old Bonanza and have continued with the RV-10. I had one beginning to squeak a bit a while back, so now check frequently.
 
Mooney calls out

Triflow on all the rod end bearings. Worked well for me. You can get it at bicycle shops and some hardware stores. I'm now using on my 7A...:)
 
That lubricating tool is just too cool. Only problem of course is you have to disassemble the joint. LPS-2 is what I used to lubricate it in the first place.
 
Lube

frazitl said:
Triflow on all the rod end bearings. Worked well for me. You can get it at bicycle shops and some hardware stores. I'm now using on my 7A...:)
Click to expand...

I used to use LPS-2. I now use TRIFLOW as recommended by Mooney. It's a bit pricey, but worth it in my experience.
 
Welding is usually a Bad Idea

I'm pretty sure I know where the problem originated. Years back I had someone in my local chapter weld the threaded portion onto the tubing, since I didn't like the rivet idea on these critical push/pull tubes. They didn't remove the bearing and I think it cooked the provided lubricant. I'll be inspecting the 3 remaining bearings. Bit of a setback, but so far the only problem identified in the test program.
__________________
Tim Ribble

Tim:
Not sure about the particular bearings you used, but I believe some rod-end bearings utilize a polymer insert or "cage" as part of the assembly. If so, you risk trashing the assembly with too much heat. At the least, cooking the lubricant out of a bearing is never a good idea. If you already have a wear pattern visible on the bearing, it's probably beyond the point where it's useful. Add some lube, keep an eye on it, but it sounds like you're in need of replacement.
Terry, CFI
RV-9A N323TP
 
trib said:
I'm pretty sure I know where the problem originated. Years back I had someone in my local chapter weld the threaded portion onto the tubing, since I didn't like the rivet idea on these critical push/pull tubes. They didn't remove the bearing and I think it cooked the provided lubricant. I'll be inspecting the 3 remaining bearings. Bit of a setback, but so far the only problem identified in the test program.:)
Click to expand...

The practice of welding pushrod ends has been addressed in the past. I am particularly attuned to the issue because a good friend of mine lost his airplane because a welded elevator puchrod failed in flight. Dan Horton offers some good reading in this thread.
 
LPS-2 every bearing, every annual conditional inspection. A little squirt, a little wiggling back and forth of the bearing and for/aft of the control rod, wipe up the overspray, done.
 
Riveted connections are fine.

I am with Terry and Ron. Riveted pushrods held in the UH-60A Blackhawk helicopter, they should hold in my RV-10. The airframe will bend before the rivets shear. The rod ends as well as much of the hardware that comes with our kits is not top of the line. It is affordable, aviation grade and sufficient for most of our needs.
 
Started the thread with a grease question and end up discussing heat stresses, bending moments, ductile and brittle failure modes along with some vibration harmonics thrown in. Being an engineer myself, all of the replies make me think of the old joke about not asking an engineer what time is it, since they'll tell you how to build a watch!:p
 
trib said:
Being an engineer myself, all of the replies make me think of the old joke about not asking an engineer what time is it, since they'll tell you how to build a watch!:p
Click to expand...

Good thing no politicians responded. If you asked them what time it was they would try to convince you that what is best for you, is not knowing the time, but knowing if it is day or night outside.
 
You really should have a good engineering reason to weld a joint that was designed to be riveted. There are numerous invisible things that can go wrong with a welded joint. You could make it more brittle (if it's annealed) you could make it weaker (if it were heat treated) you could introduce changes to the alloy at a critical joint, introduce stress concentrations at joint or any number of other problems.

It may not be a problem on this particular part but don't assume that a weld is better than a rivet on principle. Welds are just easier, they are not necessarily better.

Oh and one more vote for LPS-2. Works great, lasts long time. Well, it works great anyway.
 
Lubrication is required on any bearing surface.

Welding can be bad. One thing not mentioned: if the grease was cooked out due to high heat, the bearing race may also be deformed.
 
For the aileron push rods...

Toobuilder said:
Lubrication is required on any bearing surface.

Welding can be bad. One thing not mentioned: if the grease was cooked out due to high heat, the bearing race may also be deformed.
Click to expand...

...where Vans plans give welding as an option, no bearings are involved. This is the part that is welded...

9329_c.jpg


I welded mine and cad. plated the assy..
 
Some Rod End Bearings Should Not be Lubricated

From Aurora Bearing Company
* What maintenance do I need to perform on my rod ends and spherical bearings to keep them operating properly?
* For metal-to-metal rod ends and spherical bearings, a thin layer of grease applied occasionally to ball outside diameter will assist in extending the life of these products. Rod ends and spherical bearings that are Teflon lined are self-lubricating and are designed to be maintenance free and should not be lubricated.

Excess heat can destroy a bearing with a teflon (PTFE) or nylon lining. Putting grease on after the fact is pretty much pointless, and in the case of nylon, can actually destroy a new bearing. In the opening post, mention was made of a wear or witness line on the bearing. Usually a sign that it's already shot. I'd probably replace the assembly, but it's up to the builder.
Terry
 
terrykohler said:
From Aurora Bearing Company
* What maintenance do I need to perform on my rod ends and spherical bearings to keep them operating properly?
* For metal-to-metal rod ends and spherical bearings, a thin layer of grease applied occasionally to ball outside diameter will assist in extending the life of these products. Rod ends and spherical bearings that are Teflon lined are self-lubricating and are designed to be maintenance free and should not be lubricated.

Excess heat can destroy a bearing with a teflon (PTFE) or nylon lining. Putting grease on after the fact is pretty much pointless, and in the case of nylon, can actually destroy a new bearing. In the opening post, mention was made of a wear or witness line on the bearing. Usually a sign that it's already shot. I'd probably replace the assembly, but it's up to the builder.
Terry
Click to expand...

Yep. Good point, I always forget the "plastic fantastic" races (and almost ALWAYS get caught with an "absolute" statement ;) ). Welding on an unprotected teflon/nylon bearing is really bad, for the points you mention.
 
az_gila said:
...where Vans plans give welding as an option, no bearings are involved. This is the part that is welded...

9329_c.jpg


I welded mine and cad. plated the assy..
Click to expand...

Let me be clearer. The rod end failure which caused the loss of my friend's Velux (mentioned in a previous post) was not a failure of the bearing but a failure of the threaded terminal fitting, pictured in the above quote, to which the female rod end is attached. No, the rod end was not attached when the fitting was welded. The heat applied during the welding changed the properties of the threaded portion of the terminal fitting such that the part failed in flight. Van's instructions not withstanding, I would caution anyone who decides to weld this fitting consider the effect of heat on the ultimate strength of the fitting. Personally, I have not and will not weld these fittings.
 
A way to test them?

I had mine TIG welded and they look very good. I have not installed them permanently yet. Any idea how I could test them (non destructive)?

Regards, Tonny.
 
ronschreck said:
......The heat applied during the welding changed the properties of the threaded portion of the terminal fitting such that the part failed in flight.
Click to expand...

Ron, what properties changed, and why do you feel a change of properties caused the failure?
 
DanH said:
Ron, what properties changed, and why do you feel a change of properties caused the failure?
Click to expand...

Dan,

You're looking for an expert opinion here and I'm no metalurgy expert. My information came from the builder/owner of the aircraft, not from my personnal evaluation/testing of the part. I can say with some assurance that any such part which is heated to the extent required to weld will have a change in tensile strength and brittleness. The exact amount of change could only be determined by testing. Specifications of the parts, as purchased are usually described on a specification sheet. The properties of the part you purchase can reasonably be expected to conform to the manufacturer's specifications. Once you weld the part all bets are off and you no longer know what properties you have in the part. (You could anneal and heat treat the part after welding. If you know what you are doing, this may be a satisfactory solution.)

The fact that the part in question failed under stresses considerably less than specified by the manufacturer indicate to me that welding of the part in all probablility caused the failure of the part and subsequently the loss of the aircraft.

I have tried to find the NTSB report for the accident but have been unsuccessful. If someone finds it, please let me know. Here are the details:
Aircraft: Experimental, "Velux" single engine aerobatic. Day, VFR. Owner: Dan McCan. Departed Lakeland, FL (Not sure if the accident is in Lakeland or a nearby community. Date: Early late 80's or early 90's. It was being flown by the Russion unlimited aerobatic champion at the time. He parachuted to safety.
 
ronschreck said:
You're looking for an expert opinion here and I'm no metalurgy expert. My information came from the builder/owner of the aircraft, not from my personnal evaluation/testing of the part.
Click to expand...

The Velox crash is here:
http://www.ntsb.gov/NTSB/brief2.asp?ev_id=20001212X20878&ntsbno=MIA00LA131&akey=1

Note "fractured through the end fitting and tube section".

The report specifies failure in bending. It doesn't make clear how a bending load was applied to a pushrod. Think about that.

A nice lady at the NTSB is sending a copy of lab report 00-077.

The fact that the part in question failed under stresses considerably less than specified by the manufacturer indicate to me that welding of the part in all probablility caused the failure of the part and subsequently the loss of the aircraft.
Click to expand...

We really don't know the stress applied to that Velox elevator pushrod, do we?
 
Weld in adaptors for Rod End Bearings are commonly available.

They are designed specifically for this purpose, to be welded. Unless you are doing something unusual, like quenching, you should yield little loss of strength as the materials are normalized when aircooled.
I have welded push rods. I will guarantee that the wall of the push rod will bend, tear, or break long before the fitting. I use 4130 tubing, its temper is also normalized when aircooled.
The bigger risk is not knowing what you are doing and not using a proper fitting adaptor or not getting enough penetration of the weld into the adaptor. The adpator has significantly more mass than the thin wall tubing and you have to take care that your weld is penetrating. For these low load applications a butt weld, properly penetrated is more than enough but if you are concerned, drill through the tube into the adaptor and rosetta weld it along with the butt weld. That is what is commonly done on tie rods for high end 4x4 rock crawlers and such. That is a pretty severe application.
Sorry for contributing to this thread drift but I believe these to be the facts in regard to welding rod end apaptors.
 
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JonJay said:
They are designed specifically for this purpose, to be welded. Unless you are doing something unusual, like quenching, you should yield no loss of strength as the materials are normalized when aircooled.
I have welded push rods. I will guarantee that the wall of the push rod will bend, tear, or break long before the fitting. I use 4130 tubing, its temper is also normalized when aircooled.
The bigger risk is not knowing what you are doing and not using a proper fitting adaptor or not getting enough penetration of the weld into the adaptor. The adpator has significantly more mass than the thin wall tubing and you have to take care that your weld is penetrating. For these low load applications a butt weld, properly penetrated is more than enough but if you are concerned, drill through the tube into the adaptor and rosetta weld it along with the butt weld. That is what is commonly done on tie rods for high end 4x4 rock crawlers and such. That is a pretty severe application.
Sorry for contributing to this thread drift but I believe these to be the facts in regard to welding rod end apaptors.
Click to expand...

JonJay,
Sounds like you know what you are doing, and that's the point I was trying to make. Without knowing the proper way to weld and how to treat the welded structure there is a risk of weakening the structure. I am not qualified to do the job or know if another person is doing it right, so I prefer not to weld these very critical control components on my aircraft.

Dan, I would be very interested to see that NTSB Materials Lab Report. Dan McCan told me that the Russian pilot that was flying was very rough on the airplane. Makes me wonder if he was hitting the control stops, bending the push rods, etc. Thanks for your input.
 
Xray

Pilottonny said:
I had mine TIG welded and they look very good. I have not installed them permanently yet. Any idea how I could test them (non destructive)?

Regards, Tonny.
Click to expand...

An Xray would be the only non destructive way that I know of and you would need an expert to read the result. If you took them to someone who operates a Tig welder professionaly, they probably know what they are doing. It is not an easy skill to aquire.
 
If the rod ends...

JonJay said:
They are designed specifically for this purpose, to be welded. Unless you are doing something unusual, like quenching, you should yield no loss of strength as the materials are normalized when aircooled.
........
Sorry for contributing to this thread drift but I believe these to be the facts in regard to welding rod end apaptors.
Click to expand...

...you are referring to are AN490's (the ones Vans calls out) then your statement is not quite correct.

They come heat treated to Rockwell C25 to C30 which puts them at a strength well above "normalized".

However, in our pushrod application, I'm sure the loads are not that high.
I would think that a Mil-Spec application would call for a heat treat of the finished welded parts assembly to retain full strength.

Is there another part number you are referring to that is "weldable"?

AN490 spec here --

http://www.gen-aircraft-hardware.com/images/pdf/Rod_End_Terminals.pdf
 
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