torque jamnuts?

[prkaye]

The jamnuts for the aileron pushrods, should they be torqued? If so, what value?

[Spindrift]

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.

[Kevin Horton]

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.

[chepburn]

Originally Posted by Kevin Horton

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.

http://rgl.faa.gov/Regulatory_and_Gu...E?OpenDocument

Chris Hepburn
RV8 - Wings

[Kevin Horton]

Originally Posted by chepburn

http://rgl.faa.gov/Regulatory_and_Gu...E?OpenDocument

Chris Hepburn
RV8 - Wings

The torque table is in Chapter 7, on page 7-9.

[prkaye]

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.

[John_RV4]

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

[Jekyll]

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

[prkaye]

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.

[billdianne]

Originally Posted by prkaye

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.

true. the main reason for the jamnuts is to keep the threads from working and wearing against each other.