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Attaching points for rudder cables - nylock nuts?

JackinMichigan

Well Known Member
We had a very experienced builder go over our RV-10 recently, and one of the many things he suggested was to glop JB Weld or Proseal over the rudder cable attachment nuts down by the pedals. The reason is that eventually my foot was going to get caught on one of the cotter pins and either break it or pull it out.

Sound advice, but after he left I thought of replacing the castlated nuts with nylock nuts (and the appropriate bolt) and not only remove the problem but make it more maintainable. Nylock nuts seem sufficient for all the other control surfaces, so why not there?
 
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Nylocs will not work as you have relative motion on the bolt (the cable ends rotate on the pedal bracket).

While this might look like a shoelace grab hazard, it never happened to me.

One tip - add a piece of UHMW tape on the side of the tunnel to protect the rudder cable bolt heads from scratching the interior paint.

Carl
 
Locking nuts are not appropriate for any bolt subject to rotation. Nylocs are OK on the control surface hinges because they are tightened down on rod end bearings and are not subject to rotation.

In this situation can you not reverse the direction of the bolt, putting the "head" of the bolt near your foot?
 
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SNIP
In this situation can you not reverse the direction of the bolt, putting the "head" of the bolt near your foot?

Not in the RV-10 - there is not enough clearance on the tunnel wall to have the nut and cotter pin on the other side.

Carl
 
M517825 nuts

I had this happen and damaged my rv4 including a prop strike. I had used epoxy over the cotter pin which broke and the nut backed off.
I replaced the nut with a combination self-locking and castled nut which I safety wired with wire instead of a cotter pin. I used a slightly longer bolt to leave room for a thin stainless jam nut. The jam nut protects the safety wire and is more visible for pre-flight checks (in the 4 the peddles are in a well and hard to see)
Chuck Ross RV4 Vernon BC
 
I agree with Carl and Mel and sympathise with Chuck and his experience with the RV4. .........but I did away with the castellated nut and split pins on the RV10 for the same reasons you mentioned, .......the split pins just made to catch your socks/shoes etc, harder assembly and later maintenance,....... and nylocs just simply look better/neater. Notwithstanding as has been said, that any bolt subject to rotation should be split pin retained, the RV10 rudder linkage is subject to very little rotation as the action of rudder applications basically only results in an inline movement back and forth. I put on the standard size nylocs (not the mini width style) The rudder linkage on the RV10 is very visible at all times, my aircraft has now flown 150hours and the retainer nylocs haven't moved on either the pilot or copilot side. Just my experience. Cheers from Western Australia
 
Not in the RV-10 - there is not enough clearance on the tunnel wall to have the nut and cotter pin on the other side. Carl

Then how about replacing the bolt with a clevis pin? The "pinned" side of a clevis with a washer and cotter pin would be much shorter than a nut and should fit nicely between the cable and the tunnel wall.
 
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....... and nylocs just simply look better/neater.

Really? That's a good reason for deviating from standard practice? If it is subject to rotation then you use a bolt/castellated nut or cotter pin/split pin. End of..... The fact that your installation has shown no signs of issues does not mean it is right. Every non-standard fitting behaves impeccably right up to the moment it doesn't. I simply don't see any need for this kind of deviation on a primary flight control.

Harsh words, maybe, but sorry......
 
Can't you use safety wire instead of the cotter pins? Right now I have mine just cleco'd but looking at the picture and seems you could do that. Or is the issue snagging on the castle nut tops?
 
Why not use a castellated nut and cotter key with one of these:


https://www.mcmaster.com/#nut-caps/=19n20q2

You need to keep the cotter pin from catching in shoe laces, etc. If the plastic cover shown at the bottom of your reference will fit snugly over the cotter pin, it may be a good option. (Harder to inspect the actual hardware, though).
I have never had an issue. It may be because, with short legs, I mounted my rudder pedals in the aft position, which then requires a shorter link, which moves the cotter pin closer to the soles of my shoes, away from socks and shoelaces.
 
It's amazing to me that someone would post that they are using nylocs in place of castellated nuts because they look better! These are airplanes we are talking about and the use of non-standard hardware on flight controls is not really acceptable. It is also wrong. There are lots of ways to solve the problem of a cotter key snagging your foot. Just because it has worked for 150 hours is not really good proof of anything. We still see AD's on a fleet with millions of hours.

And what about the unsuspecting second owner who buys the airplane? Is there a preflight check list item for checking the rudder cable bolts for security?

There are a lot of first-time builders on this site that look for guidance. Please be mindful of that. 😀

Vic
 
not a split pin..

.040 safety wire would be the best solution around those particular fasteners. Make the tail long enough to wrap around the nut, and cover with RTV. Keep an eye on it too - while you are boarding is easy enough.

The cable coming loose from the pedal is a too-common occurrence in the other RV models...as Mr Cross has related.

Best,
Mark
 
Trying to understand

I know the standard and accepted practice is castellated nut and cotter pin as per plans. I have used that in my own construction for this reason. I am not questioning the validity of the aforementioned.

What I don't understand is how it will be possible for the nylock nut to separate from the bolt in this installation. The complete nut/bolt assembly is free turning in this installation. I cannot visualize a force that will hold either the nut or the bolt, at the same time apply a force on the other side that will unscrew the nylock nut. You need a wrench on both ends to separate or install to overcome the friction of the nylock nut.

Again, I'm not trying to change accepted practices. Only trying to understand a situation as described.

Thanks.

Johan
 
I too would like to know how this application will cause a nyloc nut to rotate on the bolt. Just looking to learn something here.
 
While I would agree it is unlikely the nyloc would magically rotate off the bolt, if there was a side load caused by a foot or ? holding the steel joiner, it might cause the nut to turn on the bolt as the pedal was depressed. Given enough cycles, who knows. Long shot in my mind, but....
There are quite a few areas in the RV construction that one could argue no harm could come by not following convention, but there are also quite a few that are critical.
"Good practice" is just that. There may be hidden concerns that are not obvious to any of us until they bite.
 
JonJay hit the nail on the head. It's hard for one to imagine howa fiber nut could fail in this particualr case. But keep in mind the fleet is young. Who knows what happens over the years as the fleet ages, bolts corrode, fiber in the nuts gets brittle, etc. That's why it is best to use an accepted best practice.

Vic
 
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Not to get off subject, but if the rudder bolt - nylon nut could come lose, couldn't the flaps or aileron bolt - nylon nuts come lose?

I have my rudders done with a castellated nut and cotter pin as per plans and my ailerons with the nylon lock nut as per plans. Should I be worried about them? After reading this thread, it gives me cause to rethink the wings.
 
Not to get off subject, but if the rudder bolt - nylon nut could come lose, couldn't the flaps or aileron bolt - nylon nuts come lose?

I have my rudders done with a castellated nut and cotter pin as per plans and my ailerons with the nylon lock nut as per plans. Should I be worried about them? After reading this thread, it gives me cause to rethink the wings.

Rod end bearings do not require a castellated nut and cotter pin because the fitting gets torqued up tight against the ball of the bearing. The bolt and bearing ball do not rotate--the bearing race rotates on the secured ball of the bearing.
 
If you are really worried about it, check out:

MS17826 nut

It is both self locking (nyloc) and castellated.

http://www.aircraftspruce.com/catalog/hapages/MS17826.php?clickkey=42362

http://www.gen-aircraft-hardware.com/newSearch.asp?ProductNumber=MS17826&Submit=Search

Probably overkill, but peace of mind for some.

Or put a lock nut on top of a nyloc.

I personally think that in this particular application, it is more likely that a cotter pin will get damaged and fall out leaving a castle nut loose, than it would be for a new self-locking nut to come off.

Flame suit on.
 
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