Attaboy Vic - Page 2

lucaperazzolli · #11 12-13-2019, 09:57 AM

just watched the webinar, great job : very informative and .... scary

Thank you Vic !

FinnFlyer · #12 12-13-2019, 11:55 AM

There is a thread on jam nuts, but Vic closed it.

No argument on jam nuts on horz/vert stabilizers. Vital for shank to provide sufficient strength.

But on push rods where one has ensured that the rod can rotate all the way to both ends and still be engaged to the safety hole (minimum threads always engaged at both ends), what really is the importance of jam nuts?

Worried that threads will wear out over time, if the rod should actually rotate?

Finn

Steve Melton · #13 12-13-2019, 12:36 PM

for those, the jam nut is intended to be secondary retention to prevent the rod end from turning but they don't work very well because there is no distance between the nut and rod end to stretch the threaded portion to maintain clamp. they will become loose. put loctite on all jam nuts!

really good stuff from Vic. thank-you

rvbuilder2002 · #14 12-13-2019, 01:18 PM

Quote:

Originally Posted by FinnFlyer

Worried that threads will wear out over time?

Yes, that is a very real failure mode.

Vibration (aircraft have a lot of it) can cause a push/pull rod to vibrate around the play/clearance that exists between two threaded components that are not locked tightly together (because of a loose jam nut).
Under the correct circumstances it is even possible for the vibration to excite a natural resonance which would greatly accelerate the wear. If the wear went undetected long enough, it get bad enough that a tension or compression load failure of the threads could occur.

This would be much more likely on assemblies that have softer thread material like the aluminum plug ends of the larger diameter push pull tubes but I have found severe wear in the threaded connections on engine control cable connections with a loose jam nut, where the rod end and cable end were both steel.

Av8safe · #15 12-13-2019, 02:01 PM

Thanks Vic,

I watched the recorded version last night...more good insight for us non-builder types. Enjoyed the first pre-buy process you participated in and hope we can soon find an exceptional replacement for "Bucky" and try it again.

moosepileit · #16 12-13-2019, 02:50 PM

Great webinar and screenshots galore.

Earlier this year I found my FAB was eating the carb heat flapper hinge.

Rather than try it myself, I contacted Vic and he agreed to fix it.

Boxed it up, went on my work trip and it was back when I got back at a reasonable fee!

vic syracuse · #17 12-13-2019, 03:04 PM

But on push rods where one has ensured that the rod can rotate all the way to both ends and still be engaged to the safety hole (minimum threads always engaged at both ends), what really is the importance of jam nuts?

Scott already addressed the threads wearing out. Dead on.

But, yes, it is possible to roate the tube enough such that one end could come completely disconnected. It is a very serious safety of flight issue.

Vic

vic syracuse · #18 12-13-2019, 03:04 PM

But on push rods where one has ensured that the rod can rotate all the way to both ends and still be engaged to the safety hole (minimum threads always engaged at both ends), what really is the importance of jam nuts?

Scott already addressed the threads wearing out. Dead on.

But, yes, it is possible to roate the tube enough such that one end could come completely disconnected. It is a very serious safety of flight issue.

Vic

FinnFlyer · #19 12-13-2019, 04:03 PM

Quote:

Originally Posted by vic syracuse

...

But, yes, it is possible to roate the tube enough such that one end could come completely disconnected. It is a very serious safety of flight issue.

Vic

How would that be possible when one have made the length of the tube so long that adequate thread will always be engaged at either end no matter how much it rotates.

Anyhow, the thread wear argument has me convinced of the need for (tight) jam nuts even when the tube cannot rotate out of threads.

Finn

mbauer · #20 12-13-2019, 04:25 PM

Received my email link yesterday, plan to sit down this Saturday and watch, will have pen paper ready for notes. Hoping to get an updated checklist item or two.

Did not know until the other day that these webinars from EAA are available after the main presentation. Have seen a few I wanted to take, but my work hours here in Alaska mean they start before I get off from work to watch them.

Will be going back through the archives to watch the ones I've missed.

Best regards,
Mike Bauer