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  #1  
Old 08-23-2022, 06:56 AM
uk_figs's Avatar
uk_figs uk_figs is offline
 
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Location: Tulsa, OK
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Default Pilot stick play

I have a small amount of play in the pilot stick elevator axis on my -7, it has been there a long time but is beginning to bug me. I remember a thread discussion a long time ago about the bushing being captured and the stick rotating around the bushing or the bushing being free and rotating around the bolt. I plan on fixing this at the next condition inspection and am interested in people who have had the same issue and if (and how) they fixed it.

Probably over anal about it but it is irritating in an otherwise very smooth control setup.
Figs
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  #2  
Old 08-23-2022, 07:25 AM
BH1166 BH1166 is offline
 
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Location: Eatonton Georgia
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Default

Id guess it is the linkage that has play. I thought all pilot side sticks are NOT removable, canít wobble. Check all rod end bearings, pivot points. Good luck.
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  #3  
Old 08-23-2022, 07:59 AM
lr172 lr172 is offline
 
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Very common. A flaw in the weldment execution. The stick has a small tube that is welded on and a bronze busing goes through it. This provides the left / right rotation rotation. However, any play in that interface causes fore/aft movement of the stick. That bushing is held captive and the tube rotates around it. When that small tube is welded, it warps a bit and looses some of it's roundness. This is compounded by tolerance slop in the bushing OD. I machined a custom bushing that was a tighter fit and also .0015 different from one side to the other and it is much better than the stock part, but can still notice the play if I am paying attention. There is no good way to get rid of the out of round condition other than reaming. However, the tube is not that thick and wouldn't want to take away more than 2 or 3 thou, as it is a critical structural part. That would require reamers I don't own.

IMHO, this part should start thicker and then reamed post welding. I am told they ream post weld, but obviously they are not starting with enough meat, as it is still not round after reaming. It is a shame because the rest of the control system is so tight.

Larry
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Last edited by lr172 : 08-23-2022 at 08:12 AM.
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  #4  
Old 08-23-2022, 08:16 AM
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PaulvS PaulvS is offline
 
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Default Bushing length.

If the play is in the pilot stick only and definitely not in the co-pilot stick then that would eliminate the source of play from anywhere else in the control linkage, other than the bronze bushing in the pilot stick.

During construction the bushing length needs to be filed to be just slightly longer than the steel tube on the stick. If the bushing is too long then the stick will slide fore and aft on the bushing and create slop. It should be easy to visually check for movement at the bushing by removing the stick boot and observing for play while moving the stick back and forth.

Alternatively, as Larry said, there may be play or wear between the bushing and the tube, which is causing the slop. A new bushing (cheap) may fix the problem.
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Last edited by PaulvS : 08-23-2022 at 08:21 AM.
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  #5  
Old 08-23-2022, 08:38 AM
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BillL BillL is offline
 
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Default My stick was the problem.

I had this and wrestled with it. A new stick & bushing was purchased and it was the same way. The basic issue is the cross tube welded to the stick has some weld distortion. Production has a drill bit run through to size it. The production bushing is supposed to be firmly held with between the flanges and have no compression of the stick, its ends need to fit square against the bushing.

Larry has a perfect description of the problem.

You can check all this on yours.

1. is the through bolt tight?
2. If so, remove the stick and see if the bushing is loose. It probably is.
3. Machine a new bushing with a relieved diameter section in the center by -.010" then carefully fit each ends diameter to your stick tube. Deburr/polish the inside to ensure no bumps or burrs are there first. Allow some end play and a little extra to allow for compression by the through bolt.
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Last edited by BillL : 08-23-2022 at 10:57 AM.
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  #6  
Old 08-23-2022, 09:11 AM
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What Larry and Bill said.
I too machined new bushings that only improved the condition.
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  #7  
Old 08-23-2022, 09:36 AM
Desert Rat Desert Rat is offline
 
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I has this happen. I thought that I had the brass bushings the exact perfect length, but when I got the elevator linkage all hooked up, I had a perceptible bit of play in the stick.

People say that it isn't even noticeable in flight, but it seemed easier to deal with before I have everything buttoned up, so I ordered a new bushing from Vans and made it about 1/64" longer. That cured it in my case.

FYI- Those bushings need to be a very precise length otherwise the stick is free to slide back and forth on them. This causes just as much slop as if the hole is out of round.
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Last edited by Desert Rat : 08-23-2022 at 09:40 AM.
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  #8  
Old 08-23-2022, 10:05 AM
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uk_figs uk_figs is offline
 
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Thanks for the responses, guess I will dig up the drawing and order a new bushing and take it from there.
Figs
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  #9  
Old 08-23-2022, 11:10 AM
Ralph Inkster Ralph Inkster is offline
 
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A new factory bushing might not do it. The weld that holds the tube to the control stick distorts the internal diameter midway down it - to get a consistent ID requires the tube be reamed - which for best results calls for a custom brass bushing be used there after. Your friendly local machine shop can easily help you out here. Note to tell them the bolt & bushing are solid, the weldment should swivel around the bushing with minimal play, they will know what to do.
I've fixed more than a few wobblers using Larry's approach.
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Last edited by Ralph Inkster : 08-23-2022 at 12:06 PM.
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  #10  
Old 08-23-2022, 12:24 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Desert Rat View Post
I has this happen. I thought that I had the brass bushings the exact perfect length, but when I got the elevator linkage all hooked up, I had a perceptible bit of play in the stick.

People say that it isn't even noticeable in flight, but it seemed easier to deal with before I have everything buttoned up, so I ordered a new bushing from Vans and made it about 1/64" longer. That cured it in my case.

This causes just as much slop as if the hole is out of round.
I disagree. If the bushing was a true slip fit (.001") and truly round, it could slide around inches laterally and would not result in the noticeable clicking and fore/aft movement caused by the excessive clearance between the parts. Same way that your crankshaft can move .025" axially without rocking around radially.

Larry
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Last edited by lr172 : 08-23-2022 at 12:27 PM.
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