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  #11  
Old 08-14-2018, 01:17 PM
TimO TimO is offline
 
Join Date: Feb 2005
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Actually, I just got a note back from a friend who said that Bob Kauffman crashed his RV-10 nose first from that exact problem...that the rod end unscrewed. (I think that was on landing).

This is second hand info, so I can't make any guarantee to it's accuracy, and my memory is fuzzy on that one. But, if this is true, then this has indeed actually been a factor in at least one incident.
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  #12  
Old 08-14-2018, 01:31 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by TimO View Post
Actually, I just got a note back from a friend who said that Bob Kauffman crashed his RV-10 nose first from that exact problem...that the rod end unscrewed. (I think that was on landing).

This is second hand info, so I can't make any guarantee to it's accuracy, and my memory is fuzzy on that one. But, if this is true, then this has indeed actually been a factor in at least one incident.
Tim, I heard (3rd hand) a different version: The nut securing the bolt thru the rod end bearing was removed to allow the alignment jig to be placed on the bolt end, during control alignment. Afterwards the nut was forgotten, and eventually the unsecured, horizontal bolt worked out of the bearing. Same general area but it was not the rod end that came loose.
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  #13  
Old 08-14-2018, 02:32 PM
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9GT 9GT is offline
 
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When I rigged my control rods, I put a drop of green wicking Loc-Tite on the threads of the bearing thread next to the threaded insert, then ran up and tightened up the jam nut and put another drop in front of it. I did the per plans safety wire also. You know the Loc-Tite is doing its thing if you need to adjust down the road, but it does not make it overly difficult to turn. I don't think it would back out on its own if the jam nut came loose.
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  #14  
Old 08-14-2018, 03:00 PM
mdaniell mdaniell is offline
 
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I replaced the jam nut with an AN364 low profile elastic stop nut, plus the stop wire after reading something somewhere on the same issue.
Martin
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  #15  
Old 08-14-2018, 03:04 PM
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Jesse Jesse is offline
 
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I’ve seen a couple of cases where the safety wire was broken, but never a jam but being loose. Both jam nuts would have to come loose for the rod to turn, which would indicate that they weren’t tightened correctly in the first place, imho. If you’re not comfortable with the stock setup get a rod end for the back of that rod that is the same as the front so there is no way for it to come apart, which is a scary scenario.
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  #16  
Old 08-14-2018, 04:55 PM
jwilbur jwilbur is offline
 
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I got in there and fixed it today. Followed the plans (as I did before). The difference this time is I made sure the safety wire was routed thoroughly along the side (actually kind of under), of the tube and not so tightly wound as I had done originally.

Regarding the discussion that has been happening. In my case, the tube did not rotate. The rear jamb nut was so tight I couldn't even loosen it today.

As I evaluate this, I had two errors:

1... The jamb nut was not tight enough. This time I got it as tight as I could in the tight space and used thread locker as others have suggested.

2... The bigger problem in my case was the safety wire. It actually caused the problem (likely as a result of me doing something wrong). Somehow it ended up working itself over the top of the nut. It either broke first and ended up there or it ended up there and the interference caused it to brake. No idea which. This time I routed it thoroughly down the side - almost below the push tube. I still am not happy about it but the majority of builders have not had this problem. It could be that I just wound it too tight and it broke from vibrations. As I stated originally, I didn't know it broke until I loosened the nut. The broken ends were still in place around the bolt/bearing. For all I know, it broke when I installed it. ... I stress, however, that there was NO interference or scraping of any kind when I got my FAA inspection. This developed over the course of the past year.

So another comment about the issue. This is not just about preventing one of the ends from coming out (as important as that is). The tube can NOT be allowed to rotate. If it were to rotate forward, even if there were enough threads on the far side to keep it all together, it would severely hinder up elevator performance. The push tube would become your new up-elevator stop.

The whole point of this (apparently controversial) design is to keep the push tube away from that cross bar (see pictures in first post). Any improvement in the design has to not only keep the two ends from separating, but has to keep the push tube well away from that cross-bar. ... Note in the plans how it states even to position the jamb nut so as to have increased clearance. If designed to plans, full aft stick puts the cross bar right over the jamb nut. Rotate the nut off the flat and the bar can touch it.

Is there any reason the push-tube must be the diameter that it is? Something like the size of the cross-brace would eliminate the interference or any chance of it, I think. Not sure what the engineering reasons are for the push tube we're using, so I'll be leaving it alone. But just wondering. Maybe someone else would have an idea why the tube is what it is.
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  #17  
Old 08-14-2018, 10:00 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by BobTurner View Post
Tim, I heard (3rd hand) a different version: The nut securing the bolt thru the rod end bearing was removed to allow the alignment jig to be placed on the bolt end, during control alignment. Afterwards the nut was forgotten, and eventually the unsecured, horizontal bolt worked out of the bearing. Same general area but it was not the rod end that came loose.
This was the cause that I heard as well.
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  #18  
Old 08-14-2018, 10:06 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by TimO View Post
This is most definitely NOT the first time that this has happened on a customer built RV-10. Forgive the tone if that came off wrong, as I'm not being argumentative. This isn't the only forum, and I'm not sure which forum it was reported on, but I know its happened to at least 2 other builders. One of them I think it actually unscrewed all the way out. One of them is a good friend of mine.

I checked on mine immediately after he reported this and found that mine looked good, but I was a bit paranoid after hearing what happened to him.

So far, I have done nothing additional to mine, as it's built per-plans and working fine. BUT, if someone comes up with an improved design or some sort of anti-rotation method, I would surely be interested in it. Also, I would think that in this application, loctite would be appropriate, as well as the jamb nut.
If the screwed all the way out instance is the one that you thought resulted in the landing accident at north Las Vegas, that was not the cause of that accident ( see other post in this thread).
So maybe that leaves one other? (Note: I said I hadn't heard of any...... I didn't say i knew for a fact that it hadn't)
Do you hav any specific details? ( such as a thread name on the RV-10 list to search for)
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  #19  
Old 08-15-2018, 12:00 AM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by jwilbur View Post
.. Well, as soon as I started removing the nut/bolt holding the rod-end bearing, the safety wire fell out. The safety wire loop on the bearing side had broken and the safety wire was being held only by being compressed in the assembly.
From the plans. Page 39-10

I believe the root cause here may be a subtle but important deviation from the instructions. You state the safety wire was being held by being compressed in the [rod end] assembly. But the plans say that the wire should not interfere in any way with the rod end, e.g., it should go around the part of the rod end in contact with the clevis, and not be ‘compressed in the assembly’. Properly assembled, the wire ROTATES a small amount, with respect to the clevis/rod end, with fore-aft stick movement. But compressed by the assembly, as yours was, will subject it to an up-down flexing with fore-aft stick movement, leading to work hardening, fatigue, failure.
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  #20  
Old 08-15-2018, 03:26 AM
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Lenny Iszak Lenny Iszak is offline
 
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I did what Jessie said, same length rod bearing on the aft end of the push rod. I think there was a discussion about it in the forums at that time.

Lenny

Quote:
Originally Posted by Jesse View Post
If you’re not comfortable with the stock setup get a rod end for the back of that rod that is the same as the front so there is no way for it to come apart, which is a scary scenario.
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