Rod end bearings Q

[flydjd]

Hi all,

I have seen it quoted in various posts with ref to control rigging that rod end bearings need at least 1/2 of their threads engaged - does anyone know where this comes from...I cannot find it in AC 43.13-1B Acceptable methods, Techniques and Practices....or is it just "good practice"

Thks

[Webb]

My understanding is it is a safety issue. Notice on the push rods there are 2 rod end bearings.

If at least 1/2 of the threads are showing on each end and you have a stop nut on it which makes thread coverage even greater than half, it prevents the tube/rod from unscrewing at either end when attached and in place.

[Mel]

Another issue is leverage. The more overlap you have, the stronger the joint. Try screwing in only a couple of threads. Now wriggle the joint. Now screw the rod in to beyond the 1/2 thread point and feel how much less wriggle you have.

[flydjd]

Hi Webb and Mel,

Thanks for the replys but for clarification are you saying that as long as 1/2 (or more) of the rod end bearing is covered (within) by the threaded rod end AND jam nut together then that is sufficient.....if so mine are probably Ok (esp if I double up the jam nuts) but if at least 1/2 needs to be within the threaded rod end alone then they are not OK.
If they are not OK is it OK to substitute Heim M3616M bearings for M3614M's...as far as I can tell the only differences are that they have a longer threaded shaft and slightly wider ball width.
As a side Q why do these bearings have a hold drilled up the middle ...are we supposed to lubricate the inside at initial installation and at service intervals ?

I have taken the L wing aileron bellcrank to stick pushrod back to the bench to re-measure and it is 1/32 shorter than plans but that should not make that much of a difference....
Also whilst checking the plans I noticed that there have been several revisions to this particular items length...my plans go up to R3 on Dwg 15A....does anyone have any later edition of the plans maybe with yet another change ? For ref my plans for the 7 show the AT6 tube length as 65 25/32 and middle of rod end bearing to bearing as 69 9/32.

[Mel]

Originally Posted by flydjd

Thanks for the replys but for clarification are you saying that as long as 1/2 (or more) of the rod end bearing is covered (within) by the threaded rod end AND jam nut together then that is sufficient.....if so mine are probably Ok (esp if I double up the jam nuts) but if at least 1/2 needs to be within the threaded rod end alone then they are not OK.
If they are not OK is it OK to substitute Heim M3616M bearings for M3614M's...as far as I can tell the only differences are that they have a longer threaded shaft and slightly wider ball width.

You need at least 1/2 the threads covered, NOT including the jam nut.
No problem at all using the longer threaded bearings.

[flydjd]

for the quick response.... (without the Internet my build would be even slower than it is !)

It looks like Van's is getting more of my money as I shall order 4 longer bearings...at least that will be cheaper for shipping costs across the Pond than replacing the 6' long pushrods !

[caryr]

Actually there is a safety wire sized hole drilled into the threaded bearing housing.

If safety wire pushed into the hole hits the male theaded part, -- it is good to go.

cary

[Webb]

Originally Posted by flydjd

for the quick response.... (without the Internet my build would be even slower than it is !)

It looks like Van's is getting more of my money as I shall order 4 longer bearings...at least that will be cheaper for shipping costs across the Pond than replacing the 6' long pushrods !

Before you order those bearings, note price. They are $$$. Can you find aluminum tubing locally at a better price?

Also, before you do anything, be sure your bellcranks are properly oriented and use the alignment pattern that Van's gives you. Is it possible that you don't have the bellcrank in proper position to measure?

[Webb]

I just was thinking - why 4 bearings? Wouldn't just 2 work? One on each rod but use several stop nuts so it would take the majority of threads out of play so it can't back itself off?

[DanH]

<< substitute Heim M3616M bearings for M3614M's.>>

I think we get Aurora bearings in the kits, less expensive and probably easier to find on a shelf in Europe. GMM-3M-670 standard, GMM-3M-680 has the longer shank. GMB prefix is left hand.