[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]

Safety issue

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]

What Webb said, plus....

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]

Further Q

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]

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]

Thanks Mel

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]

Tubing Locally

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]

Why 4 bearings

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.

 

[Mel]

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?

Webb, Since the connections at each end of the push rod are not in the same "plane", the push rod needs to rotate slightly as it moves back and forth. A rod end on only one end would not allow enough of this movement. When you install the aileron push rod you need to adjust the rod ends so that the push rod can "rock" slightly when held at each end of the stroke. If not, it can cause binding. I've seen this problem on more than one airplane.

 

[Webb]

Let me re-phrase

Webb, Since the connections at each end of the push rod are not in the same "plane", the push rod needs to rotate slightly as it moves back and forth. A rod end on only one end would not allow enough of this movement. When you install the aileron push rod you need to adjust the rod ends so that the push rod can "rock" slightly when held at each end of the stroke. If not, it can cause binding. I've seen this problem on more than one airplane.

I should have said, one not 2 longer ones (a total of 4). Sorry, I wasn't clear about that. I meant order 2 long ones, keep 2 short.

Sorry

 

[Mel]

Sorry, I missunderstood.

Yes. One "longer" rod end bearing for each push rod should work.

 

[flydjd]

Update..

Sorry for the delay in responding...I have been back at work in the UK !

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?

The Heim M3616M bearings are $14.66 each at the moment which is still cheaper than replacing the tubing and 4x VA-111 threaded rod ends (plus there are some other bits and pieces that I need to order from Van's and shipping costs will be less)...the bellcranks are both properly aligned.....

I just was thinking - why 4 bearings? Wouldn't just 2 work?

Yes. One "longer" rod end bearing for each push rod should work.

and I had come to the same conclusion that this will work in my case....(and I already have 2 M3616M's that I haven't used yet to make the elevator pushrod)
I emailed Gus at Van's for approval to substitute the longer bearings...I plan to substitute them at the bellcrank ends only where the movement is mostly in one plane only and the only adjustment is to shorten the AT6 W-929 aileron bellcrank spacer by 1/16" (rather than at the stick end where the range of movement is much greater...and there would be more fiddling to set up the wider bearing in the stick weldment)

 

[jrvssgl]

Just curious if Gus at Vans has implied that no one else has had the problem of short push tubes. I had to rebuild my tubes as well a couple of weeks back, and suggest that they add a little length to their plans. He said they would consider it if more people had the problem. After reading on VAF there obviously is a problem.

If you use a different bearing make double sure that when everything is installed and the jamnuts are tight that the tube is not binding on the bearings through the full motion of the stick. There really isn't a lot of free play to deal with.

Anyways for added length I made the new push tubes 1/2 inch longer than what was indicated in the drawings. perfect length.

 

[Steve]

where to buy?

I could also use an extra 3/8" or so push rod length. Where can a guy purchase the M3616M long length rod end bearings? Is all the sizing info included in that part number?

Steve

 

[flydjd]

Where can a guy purchase the M3616M long length rod end bearings? Is all the sizing info included in that part number?

Steve

Hi Steve,

Vans sells them as 3/16X3/8M LONG RD END BEARING MD3616M.....there doesn't appear to be any more sizing shown...I found the detailed dims by looking in the A/c Spruce catalogue that I have and then by measuring the 3616 bearings that were with my kit

Hope this helps