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  #31  
Old 12-09-2018, 06:37 AM
markelliott markelliott is offline
 
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Location: minneaopolis, mn
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Scott-

I understand what you are saying as far as when the second side is torqued - however how about the first side? Since only one side is torqued at this point the stiffness is purely in the bearing. How much friction is ok? My bearing was tight to move using your fingers after riveting. When only one side is torqued the control tube will stay in any position it is set. It will not "float" down.

I did measure, tried a few combinations, and have it now where there is no difference when the second side is torqued however the control rod will not float due to the stiffness in the bearing - not the side load.

Anyone? Thoughts?




Quote:
Originally Posted by rvbuilder2002 View Post
As freely as as it does when only one side is torqued up.

The fact that it tightens up is an indicator that you do need shims.

Any noticeable friction at his point in the system will have an influence on flight characteristics. Most notably... pitch stability, and the ability for the airplane to return to trimmed flight after even a slight upset.
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  #32  
Old 12-10-2018, 07:14 AM
iamtheari iamtheari is offline
 
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Quote:
Originally Posted by markelliott View Post
Scott-

I understand what you are saying as far as when the second side is torqued - however how about the first side? Since only one side is torqued at this point the stiffness is purely in the bearing. How much friction is ok? My bearing was tight to move using your fingers after riveting. When only one side is torqued the control tube will stay in any position it is set. It will not "float" down.

I did measure, tried a few combinations, and have it now where there is no difference when the second side is torqued however the control rod will not float due to the stiffness in the bearing - not the side load.

Anyone? Thoughts?
If the bearing is stiff without the column mounted on it, then you have a problem like I had. Did you prime the brackets? Or is there any chance that you have any contamination in them? Just the thin layer of primer in mine was enough pressure on the bearings to keep them from turning freely.
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  #33  
Old 12-10-2018, 09:44 AM
markelliott markelliott is offline
 
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Yes I primed and I agree it is likely the same senerio you described. If it is indeed the same maybe they should add a note when you build the bearing bracket to be sure it is 100% free?? I knew it was slightly stiff but didn?t see that it was to rotate thinking it would move side to side slightly which loosened up nicely when a bolt was inserted

Looking like I am going to remove the bearing bracket after it is installed. Ugh
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  #34  
Old 12-10-2018, 09:54 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by markelliott View Post
Yes I primed and I agree it is likely the same senerio you described. If it is indeed the same maybe they should add a note when you build the bearing bracket to be sure it is 100% free?? I knew it was slightly stiff but didn?t see that it was to rotate thinking it would move side to side slightly which loosened up nicely when a bolt was inserted

Looking like I am going to remove the bearing bracket after it is installed. Ugh
Sorry Mark,
I hadn't seen your other post.
Before resorting to removing the bracket, I would try and free up the bearing with it in place.
Flood it with some penetrating lubricant and manipulate it a lot to see it it helps.
Occasionally the a bearing will get stiff when riveting into a bracket.
It can sometimes be freed up with a light hammer tap laterally on the bearing. Don't hammer on the bearing directly... bolt the control column in place with spacers (on the stiff bearing only... leave it free floating on just the bolt on the good bearing) and tap on both ends of the control column with a rubber mallet and see it it improves.
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  #35  
Old 12-10-2018, 12:00 PM
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kbalch kbalch is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Before resorting to removing the bracket, I would try and free up the bearing with it in place.
Flood it with some penetrating lubricant and manipulate it a lot to see it it helps.
Occasionally the a bearing will get stiff when riveting into a bracket.
It can sometimes be freed up with a light hammer tap laterally on the bearing. Don't hammer on the bearing directly... bolt the control column in place with spacers (on the stiff bearing only... leave it free floating on just the bolt on the good bearing) and tap on both ends of the control column with a rubber mallet and see it it improves.
I'm nearly at this point myself and have a similar issue with one bearing. In my case, one is perfect and the other isn't stuck (can be turned with fingers), but is perceptibly tighter than the good one. Is it worth preemptively trying the lubricant or am I not likely to have a problem once everything is tightened up?
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  #36  
Old 12-10-2018, 12:02 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by kbalch View Post
I'm nearly at this point myself and have a similar issue with one bearing. In my case, one is perfect and the other isn't stuck (can be turned with fingers), but is perceptibly tighter than the good one. Is it worth preemptively trying the lubricant or am I not likely to have a problem once everything is tightened up?
If I was working on it, I would get the bearing working freely before proceeding.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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  #37  
Old 12-10-2018, 01:46 PM
markelliott markelliott is offline
 
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Both bearings of mine are identical as far as stiffness. I had lubed it liberally with oil before I left for a few days. Working is getting in the way of building. I will try to loosen one end keeping the other torqued and see if I can?t nudge it free as Scott has suggested. If the bearing bracket does have to come out I think I am leaning toward removing the rib - less rivets to remove while working inside the structure plus the bracket when reassembled will not have to be cherry max back in.

If I do decide to just remove the bracket I?m sure vans would approve cherry max replacements - but I think they are AN426AD4-8. Someone earlier had said they put in -5 CM. That sounds short to me as a replacement but I also don?t have anything longer than a -6 in my collection........

When I build my next one I will not prime the brackets until after they are fabricated. I gotta say - and many would disagree - but building is way more fun than flying. Flame on
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  #38  
Old 12-10-2018, 03:22 PM
Tom Martin Tom Martin is offline
 
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In post number 4 I suggested that screws and nuts would be a better way to secure those brackets. This would have been helpful to those building as well as for future maintenance.
Perhaps a paragraph in the manual about making sure these bearings move freely both before and after assembly should be stressed.
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  #39  
Old 12-10-2018, 06:46 PM
iamtheari iamtheari is offline
 
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Quote:
Originally Posted by markelliott View Post
Both bearings of mine are identical as far as stiffness. I had lubed it liberally with oil before I left for a few days. Working is getting in the way of building. I will try to loosen one end keeping the other torqued and see if I can?t nudge it free as Scott has suggested. If the bearing bracket does have to come out I think I am leaning toward removing the rib - less rivets to remove while working inside the structure plus the bracket when reassembled will not have to be cherry max back in.

If I do decide to just remove the bracket I?m sure vans would approve cherry max replacements - but I think they are AN426AD4-8. Someone earlier had said they put in -5 CM. That sounds short to me as a replacement but I also don?t have anything longer than a -6 in my collection........

When I build my next one I will not prime the brackets until after they are fabricated. I gotta say - and many would disagree - but building is way more fun than flying. Flame on
I think that cherry max rivet lengths are the grip rather than the entire shank, as with AN470 rivet sizes.
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  #40  
Old 12-12-2018, 01:32 PM
markelliott markelliott is offline
 
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SOLVED!!!

Scott - I owe you a beer. Just a light tap on the side loosened it right up! It did take another few hours of playing with shims to get it perfect however I think it is worth it. Just as a side note - I did remove the entire control rod and used a bolt with washers directly on each bearing. With this setup I was able to use my 24" socket extension to tap directly onto the bearing. I did this on both sides and it magically opened up. Hindsight: I wouldn't prime between the bearing brackets, BoeLube before installing the bearing into the bracket, and squeeze slowly on each rivet before the final set.

Building on.........
Mark

Last edited by markelliott : 12-12-2018 at 01:36 PM.
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