Newbie Question

[Av8r3400]

A rod end bearing only requires a locking nut because there is no movement on the hardware. A cotter pin and castle nut is only needed when the hardware is the rotation element of the joint.

A rod end bearing should be tightened in it's mating fork such that the ball of the bearing does not turn against the hardware. The ball should only turn in it's socket.

Using castle nuts on a rod end bearing is not the correct usage of hardware and will result in unwanted wear on the bolt itself instead of the ball of the bearing as it's design intended.

[Dave S]

During the construction of the aircraft, I had three EAA tech counselor inspections. Two of them were done by a person who was a long time Airline A & P (& RV builder), the other was an EAA tech counselor, FAA employee who worked on certification of in service components for transport aircraft. The DAR also liked the drilled bolts. The A & P tech counselor suggested the switch to drilled bolts/castle nuts & cotter keys. What I didn't put in my original post on the subject was the fact that this also included the use of select fitting, as needed, of thin washers to allow the correct tension ("Feels right") and have correct cotter pin alignment.

For what it's worth,

Sincerely,

Dave S
KF7 Trigear

[Dave Holl]

Dave
I did the same on my installation and it's what I expect to see on Boeing and Airbus installations with flying controls
Dave

[Av8r3400]

We can disagree, I guess.

I will go on what I was instructed in my LSA Repairman class. After a long discussion on this very subject, the instructor (an A&P with AI) made perfect sense to my engineering perspective. A mechanically locked nut and bolt, by definition, must be loosened to align the cotter pin. This will allow the hardened ball of the rod end bearing to rotate on the soft bolt shaft, which will cause wear.

Using a nyloc bolt allows the hardware to be tight on the flat sides of the ball in the bearing, making this hardened ball rotate in the socket it was designed to move in. There is no movement of the hardware in relation to the ball or the actuating fork in the joint. So there is no concern of loosening the nut on the bolt or grinding wear thinning the shaft of the bolt.

[SkyPirate]

I agree with you Av8r3400, my
Mechanical mindset says the same thing, if it were tapered like a tie rod end it would be a different story because then a castle nut and cotter pin would be exceptable because there are 2 forces working to keep it in check , where the bore of the hiem joint is not tapered you must rely on friction of the nut and bolt compressing the flat sides of the ball/ bearing

[airlina]

What swayed me to the castle nut camp on my Series 5 was walkarounds on my work airplane. If Boeing did it I figured it had to be tried and true.

[Sabre]

Thanks for all the replies, interesting discussion. I had another question: As I'm working through hooking up the connecting rods I came to the rear belcrank for the elevator. With everything square I can only get one washer (960-10L) between the bearings and the mounting tabs (as in one on one side of the assembly), there should be two, one on each side between the mounting tab and bearing surface. This fit is perfect with the exception of missing a washer. Is it preferred to remove material from the bearing surface? Removing material from the mounting tab doesn’t seem like a good choice although I removed the powder coating from both tabs on the inside. Is not having a washer satisfactory on one side? Manual states to shim as required but I am assuming that means to use a combination of 960-10 and 960-10L to achieve the proper fit with a washer on both side of the bearing mounting tab surfaces? Thanks for your input.