Should I tap a primary flight control rod? F389

bobmarkert · #1 07-02-2013, 05:20 AM

This is a picture of the F-839 elevator push-pull tube on an RV8 that connects the front and rear stick together. It comes from the factory with the threaded ends pre-installed in the tube and powder coated. I can see a depression in the powder coating where the thread insert is attached to the tube. I cannot tell if it is attached with a weld or some sort of rivet holding it together. The directions are clear that at least half the threads of the rod-end-bearings must be engaged to protect against the scenario where the nuts come lose and the tube turns. The problem is there is a DEFINITE resistance (block) where the weld (?) is. I cannot (or am unwilling) to apply the amount of force it would take to insert the rod-ends in 1/2 way. The picture show the jam nut set at the depth where the bearing stops screwing in and it corresponds to where the weld is. I am considering running a tap through the threads. I would like the collective wisdom of the group to weigh in because this is a piece of the primary flight control system!!!!
Thank You
Bob

JanRV6UK · #2 07-02-2013, 05:45 AM

When you look on the paint - it looks like the inner sleeve has been plug welded in the tube .. if that is the case .. would expect some internal distortion that a tap would sort out ..

Pat Stewart · #3 07-02-2013, 05:58 AM

I would show vans the picture, sure looks like a pop rivet to me, also make sure you have the correct rod end, some are longer than others.

bobmarkert · #4 07-02-2013, 10:16 AM

Van's support answered my email question immediately. Here is their response:

It's a weld, and in this case it must have penetrated just a little too much. Chasing with a tap is fine, but do it with a light hand and plenty of lubricant. If the tap breaks, there's no practicalway to extract it.

Case closed. I'll run tap down it tonight

Mike S · #5 07-02-2013, 10:18 AM

Bob, thanks for closing the loop on this one, always good when folks do that.

JanRV6UK · #6 07-02-2013, 01:37 PM

When you run the tap down the hole - back it out frequently to clean it out ... if you use a cheap carbon tap they can break easily if you are not used to tap ... and oil .. plenty of it ..