Same question...

I wondered the same thing, but after trying to find an answer in the plans and a book on building, I decided to torque to the same AN setting shown in the plans, i.e 20-25 in lbs for AN3, 50-70 in lbs for AN4, etc. Hopefully that was the right thing to do!

Sounds like we are at about the same place in construction as I just did that yesterday.
 
The jam nuts are thinner than regular nuts. Use the values in the torque tables for MS20364 or AN320 shear nuts. Every builder should have a copy of AC 43.13-1B. Its torque table shows:

thread size 10-32, normal torque of 12-15, with a max allowable torque of 25
thread size 1/4-28, normal torque of 30-40, with a max allowable torque of 60

All values are in-lb.
 
Here's a pointer to AC43.13

Kevin Horton said:
The jam nuts are thinner than regular nuts. Use the values in the torque tables for MS20364 or AN320 shear nuts. Every builder should have a copy of AC 43.13-1B. Its torque table shows:

thread size 10-32, normal torque of 12-15, with a max allowable torque of 25
thread size 1/4-28, normal torque of 30-40, with a max allowable torque of 60

All values are in-lb.
Click to expand...

http://rgl.faa.gov/Regulatory_and_G...99C827DB9BAAC81B86256B4500596C4E?OpenDocument

Chris Hepburn
RV8 - Wings
 
I could probably answer these questions by reading chapter 7, but...

1) That table gives Torque values for given thread-sizes. Our hardware callouts specify fasteners by their designation like "AN3-5A", etc. I don't know how to identify a thread size by looking at it. Does AC43-13 provide a table listing the thread-sizes for the fasteners we use, so that we can then use the Torque table on page 7-9? How would we determine the thread size of something like those threaded rod-end bearings that the jamnuts go on?

2) I've been using the small torque table Vans supplies in Chapter 5 of the build manual. It gives values for AN3 and AN4 bolts, irrespective of what type of nut is put on it. I presume that torque should really depend on on the particular combination of male and female threaded fastener? That table of Vans does does not list torque values for the jamnuts on rod-end bearings.

3) Also, the table on page 7-9 gives torque values in two categories, tension-type AN310 nuts and sear-type AN-320 nuts. What about things like nutplates, that have an altogether different identifier?

4) ALSO... on page 7-11, Para 2, the "prevailing torque" of self-locking nuts is mentioned, with table 7-2 giving values. I searched the chapter 7 PDF file for this term, and it does not appear to be defined anywhere.

There seems to be a lot of different information that needs to be assimilated regarding torquing fasteners, and I admit I haven't been able to sort it all out yet.
 
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Don't like them

These jam nuts have always bothered me. They are so critical to safety that it seems a belt and suspenders approach should be used.

That said, my RV4 just went through it's 18th condition inspection and they have never come loose. I think that on my own project, they will at least get a healthy dose of loctite.

FWIW

John
 
When asked specifically about jam nut torque, Van's tech support said "don't worry about it, just snug them down". They aren't as concerned about this as I expected. I torque mine when I can get a wrench on them.

Jekyll
 
For the aileron pushrods, I guess even if the jamnuts loosened, the rod end bearing is prevented from rotating (unscrewing) by the way it is bolted into the bellcrank.
 
prkaye said:
For the aileron pushrods, I guess even if the jamnuts loosened, the rod end bearing is prevented from rotating (unscrewing) by the way it is bolted into the bellcrank.
Click to expand...

true. the main reason for the jamnuts is to keep the threads from working and wearing against each other.
 
prkaye said:
For the aileron pushrods, I guess even if the jamnuts loosened, the rod end bearing is prevented from rotating (unscrewing) by the way it is bolted into the bellcrank.
Click to expand...
But, if the jamnut comes loose on both ends, (both tightened by the same person), the pushrod itself can unscrew and come off completely.
 
No it can't! The rod ends, if done correctly, are installed in such a way that the control rod itself jams against the shank of the opposite rod end. Very clearly the rod ends are installed with more than half of the threaded end engaged in the threads of the push rod end cap. Since both end caps are right handed threads one tightens while the other loosens. Nothing comes apart.
 
In the absence of solid guidance from any source (as wordy as it is, I consider AC43.13 to be pretty vague in certain areas - this is one of 'em), I default to Sikorsky's guidance on flight control rodend jamnuts:

Tighten all rodend jamnuts 1/6 to 1/3 past the sharp rise in torque.

In other words, one or two wrench-flats beyond when the nut snugs against the control rod.

This is in both military and civilian maintenance publications, on three different Sikorsky products - two of them are considered "FAA-approved technical data", so they've been blessed by the Administrator as being Gospel, graven in stone from on high....
 
prkaye said:
I could probably answer these questions by reading chapter 7, but...

1) That table gives Torque values for given thread-sizes. Our hardware callouts specify fasteners by their designation like "AN3-5A", etc. I don't know how to identify a thread size by looking at it.
Click to expand...
The first number in the thread size in the torque table is the diameter, and the second is the number of threads per inch.

AN3 bolts are #10 size, and they have 32 threads per inch. So for AN3 bolts use the values for 10-32. AN4 is 1/4 inch diameter, with 28 threads per inch. AN 5 is 5/16 inch, etc.

2) I've been using the small torque table Vans supplies in Chapter 5 of the build manual. It gives values for AN3 and AN4 bolts, irrespective of what type of nut is put on it. I presume that torque should really depend on on the particular combination of male and female threaded fastener? That table of Vans does does not list torque values for the jamnuts on rod-end bearings.
Click to expand...
The jam nuts on rod end bearings are thin shear nuts, so that is the torque values I would use, if I chose to put a torque wrench on them. As others have mentioned, if you have assembled things correctly, it should be impossible for the pushrod to completely unscrew.

3) Also, the table on page 7-9 gives torque values in two categories, tension-type AN310 nuts and sear-type AN-320 nuts. What about things like nutplates, that have an altogether different identifier?
Click to expand...
The reason for the different torque values between regular tension nuts, and the AN320 shear nuts is that the shear nuts are thinner. The thinner nuts have fewer threads, so you need less torque to put the same amount of load on each thread. Platenuts seem to have about the same thickness as regular nuts, so for better or worse, I have used the torque value for regular tension nuts.

4) ALSO... on page 7-11, Para 2, the "prevailing torque" of self-locking nuts is mentioned, with table 7-2 giving values. I searched the chapter 7 PDF file for this term, and it does not appear to be defined anywhere.
Click to expand...
Prevailing torque is the torque required to turn the nut against any drag from the self-locking function of the nut. You need to add the prevailing torque value to the value from the table to get the target torque value.
 
Rivethead said:
No it can't! The rod ends, if done correctly, are installed in such a way that the control rod itself jams against the shank of the opposite rod end. Very clearly the rod ends are installed with more than half of the threaded end engaged in the threads of the push rod end cap. Since both end caps are right handed threads one tightens while the other loosens. Nothing comes apart.
Click to expand...
Never say "can't", Jim. Things that "can't happen" happen every day.
 
Ya know Mel I think I'll go ahead and stick with ?can't? With the condition of ?properly installed? applied. It's a given that the jam nuts on this arrangement are going to come loose at some point. Extra security could be gotten by wire tying.
 
NEVER

Had a friend finish his glasair II. The elevator tube is the same kind of setup. jam nuts backed off, lost elevator, used power to "pancake" the airplane home. Luckily no one was hurt.

I think I will use nylock nuts in addition to the jam nuts.....Anyone agree? Thoughts?
 
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ncarmon said:
Had a friend finish his glasair II. The elevator tube is the same kind of setup. Nutplates backed off, lost elevator, used power to "pancake" the airplane home. Luckily no one was hurt.

I think I will use nylock nuts in addition to the jam nuts.....Anyone agree? Thoughts?
Click to expand...
then he didnt assemble them correctly, not sure what you mean with nutplate.

nylocks would be ok but you would have to thread them nylon first.:confused:
 
While Van's intent is that each bearing be more-than-half engaged so that the pushrod can never completely fall off, I have found on my airplane that many bearings end up being exactly half engaged -- not much margin for error (the width of one jamnut). So I have been adding an extra jamnut onto the threaded portion of each bearing whenever I have to work on them. In this way, the opposite bearing has less room to rotate to come undone.

Of course you need to look out for any new interference issues caused by the extra nut.

I asked Van's about this and they said it was an acceptable practice, but that for strength reasons the bearing must be at least half-engaged.
 
As above - the important issue is to make sure the push/pull rod is long enough to ensure sufficient engagement of the threads at both ends. It should be such that if the jam nut loosens and the rod is free to rotate then it will bottom out at one end while still leaving sufficient engagement at the opposite end to carry the required loads. On the female rod ends there is a small "check" hole. The male thread should be sufficiently engaged in the rod end so that you can't pass a wire through the hole. I'd aim for way more than half engaged.

Jim Sharkey
RV6 Tip-up finishing
 
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jsharkey said:
As above - the important issue is to make sure the push/pull rod is long enough to ensure sufficient engagement of the threads at both ends. It should be such that if the jam nut loosens and the rod is free to rotate then it will bottom out at one end while still leaving sufficient engagement at the opposite end to carry the required loads. On the female rod ends there is a small "check" hole. The male thread should be sufficiently engaged in the rod end so that you can't pass a wire through the hole. I'd aim for way more than half engaged.

Jim Sharkey
RV6 Tip-up finishing
Click to expand...

Yes, ideally Van's would not give such a critical length callout such that the pushrods end up only just barely long enough. Hard to know the proper length at the point they have you build the pushrods...

By adding nut(s) on one end, you give less room for the other end to become disengaged. By adding nut(s) on both ends, the whole thing can rotate less.
 
Correct installation

ok, I get it. I didn't understand that if you thread them on beyond the "check hole" that one would bottom out before the other end drops out. Learn something new everyday.

Corrected my earlier post, jam (jamb) nuts backed off, not nutplates...sorry :eek:

As to cytoxin's post, why would I have to put the nylocks on nylon first? All I want to do is stop the movement of the jam nut. I could even leave them 1 thread away from the jam nut. If the jam nut moves out to the nylon side of the nylock, it would still stop the movement. I don't have to use the nylock nut as a stop nut against the jam nut...do I?

This is a really interesting safety topic and the only one, aside from fuel system that I've spent much time thinking about.

N7NC
 
I am with the add an extra nut on both ends crowd. When I built my pushrods, I ordered a whole pile of extra jam nuts to add to them.

I just did not feel comfortable with the fact that if they had come loose, I would only have two or three threads holding the bearing to the pushrod. With the extra nut, this is no longer a problem.

I think Vans should change the plans to give everyone a little more wiggle room on these pushrods. They really seem to cut it too close and from what I can see, there is absolutely no reason for this to be that close.
 
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