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  #21  
Old 09-29-2018, 09:59 AM
iamtheari iamtheari is offline
 
Join Date: Nov 2017
Location: ND
Posts: 196
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Quote:
Originally Posted by smash View Post
I had a problem getting the control column to move freely. When built correctly, there is almost no friction and mine was sticky no matter how I adjusted the shims.

I discovered that while back riveting the bearing bracket assembly, I had accidentally positioned the backing plate under the bearing and slightly marred the bearing surface. I didn't realize this until I tried shimming and could not get the assembly to move freely.

The solution was painful- I had to remove the cover rib to gain access to the bearing bracket assembly and then disassemble it. When I removed the bearing, it was stiff when I tried to move it with my fingers and on closer examination I found some scoring on the bearing surface.

Remove the control column and try moving the empty bearing with your fingers- it should move absolutely freely with no catching.

Here's my build log writeup: http://www.smashsrv-14build.com/2016...ishing-up.html
I hope it doesn't come to that for me. But can you share some insight on why you removed the rib rather than removing the bearing bracket from the rib and leaving the rib in place? It seems to me like it will be at least as hard to drill the rib out of the fuselage assembly (especially from the bulkhead) as it would be to drill the bearing bracket off of the rib.

Although despite it not being ideal, I kind of like the castle nut solution posted by mturnerb because it lowers the risk of damaging things while trying to remove and reinstall them after the fuselage forward and mid sections have been riveted together.
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  #22  
Old 09-29-2018, 10:28 AM
mturnerb mturnerb is offline
 
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Location: Ponte Vedra, FL
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Quote:
Originally Posted by iamtheari View Post
I hope it doesn't come to that for me. But can you share some insight on why you removed the rib rather than removing the bearing bracket from the rib and leaving the rib in place? It seems to me like it will be at least as hard to drill the rib out of the fuselage assembly (especially from the bulkhead) as it would be to drill the bearing bracket off of the rib.

Although despite it not being ideal, I kind of like the castle nut solution posted by mturnerb because it lowers the risk of damaging things while trying to remove and reinstall them after the fuselage forward and mid sections have been riveted together.
Just don't take my solution as being recommended safe or best practice. I am sharing my experience and my comfort level (based on what I believe to be good advice). I would guess the biggest risk of my approach might be wear over time, so I will keep a close eye out. FYI I did carefully check the bearings for free movement and I'm sure there's no binding related to assembly of the bearing bracket. And I was careful to tighten the castle nut enough that the bearing is moving, not the nut/bolt. I found that there is a very big effect on binding between this level of tightness versus torquing a locknut. I was also careful to use the right length drilled bolt and/or washers as required so that castle nut lined up correctly with the drilled hole.
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Last edited by mturnerb : 09-29-2018 at 10:34 AM.
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  #23  
Old 09-29-2018, 12:29 PM
smash smash is offline
 
Join Date: Apr 2013
Location: Fair Oaks,CA
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Quote:
I hope it doesn't come to that for me. But can you share some insight on why you removed the rib rather than removing the bearing bracket from the rib and leaving the rib in place? It seems to me like it will be at least as hard to drill the rib out of the fuselage assembly (especially from the bulkhead) as it would be to drill the bearing bracket off of the rib.
Agreed- if you can remove the bearing bracket without removing the rib, go for it. I wasn't able to get my drill in-between the ribs to do that and I didn't want to attempt to remove that many rivets using my 90 degree drill. Also, it would have been very difficult to drive the rivet stems out in the confined space. YMMV
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  #24  
Old 10-02-2018, 10:22 PM
iamtheari iamtheari is offline
 
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Location: ND
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After removing the control column completely, I can see that both bearings are stiff. I can insert a screwdriver through them and rotate them with mild stiffness, but I can't rotate them in the direction they need to rotate with my fingers. I guess I'm going to be doing a whole bunch of rivet-drilling.
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  #25  
Old 10-05-2018, 06:44 PM
iamtheari iamtheari is offline
 
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My A&P friend who is helping me with the build helped me evaluate this situation and decide on a solution. We will use a 90-degree drill to remove the 8 rivets holding each bearing bracket to the rib, disassemble the bearing brackets, replace the bearings, rivet the brackets back together, and then use flush Cherrymax rivets to reinstall the bearing brackets. Wish me luck!
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  #26  
Old 10-05-2018, 11:49 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by mturnerb View Post
I had the same situation - spent many hours trying every possible combination of washers/shims I could: finally discussed at length with my tech counselor. He advised me to replace the standard bolt/locknut with a drilled bolt/castle nut/cotter pin: having a bit less torque keeps the bearing from binding. I settled for this compromise since at some point you have to move on....
Be cautious with this approach. The inner part of the bearing needs to be help captive in the arms of the control rod. If this is too loose, the bearing won't rotate and you'll be rotating on the bolt.

Larry
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  #27  
Old 10-05-2018, 11:52 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by BillL View Post
Using feeler gauges to determine the last thickness needed is one method of positively determining the shim needed. If an even # of .030 shims don't fit the bill then you can always machine a spacer the exact length needed or Make your own shim the proper thickness.

.
I just did this the other day. Using a feeler gauge is problematic, because the arms are usually not parallel. Your shim must fit when torqued, not when loose. As the bolt is tightened, the arms straighten out.

Don't forget that the L washers are only about 23 thou, so two of those is smaller than one std washer. Mix and matching may get you closer without making a shim.

Larry
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  #28  
Old 10-16-2018, 08:22 PM
iamtheari iamtheari is offline
 
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I successfully completed this repair with lots of help from my A&P friend. We used a tight-fit drill attachment to drill out the 8 rivets holding each bearing bracket assembly to the rib, then removed the two screws and removed the brackets. Then we drilled out the double flush rivets from the brackets. We reassembled the brackets with new bearings and then used CR3212-4-5 CherryMax rivets to attach the brackets to the ribs, then re-torqued the screws. (I also bought CR3242-4-5 rivets, the oversize type, just in case we weren't lucky with the drilling.) It was really tight to reach the two aftmost rivets with my puller, but I remembered that my dad loaned me a NAPA store brand rivet set and, voila, that puller fit perfectly in the tight space.

The sad thing is what we discovered to be the cause of the stiffness in the bearings. As soon as the bearing bracket halves were loose, so were the bearings. They both turned freely once the pressure of the bearing bracket assembly was off of them. Our conclusion is that priming the entire surface of the bearing bracket halves was a mistake, as the primer thickness was enough inside the bearing housing to make the bearing tight. We replaced the bearings anyhow because we had fresh ones. The solution was to use acetone and Q-tips to remove the primer from the inside of the bearing housings in the bracket halves. I'm using Stewart Eko Prime, which is sturdy but thankfully washes away easily with acetone so we didn't have to break out the MEK.

If I were to do it over, I would have assembled the bearing brackets before priming them. The interior surfaces are not likely to see any corrosion no matter what happens, especially if you don't scuff up the alclad surface before riveting them together.

I hope nobody follows my footsteps, but if anyone does I hope they find this post so they can see a repair method that worked out without removing the ribs.
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  #29  
Old 10-17-2018, 04:28 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
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Quote:
Originally Posted by iamtheari View Post
Our conclusion is that priming the entire surface of the bearing bracket halves was a mistake, as the primer thickness was enough inside the bearing housing to make the bearing tight.
Hi Ari,

Thanks for this info - just wondering if you could clarify what you mean? Are you saying that the pressure the brackets put on the bearing housing caused it to possibly distort etc so that the spherical part has some friction on it?

Iím not anywhere near this section yet but trying to understand anyway.

Out of interest, in this design by Vans, what stops the bearing housing from rotating in the brackets other than clamping pressure when you double flush rivet them together? If not enough pressure the housing may rotate? So you need some pressure but not too much??
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  #30  
Old 10-17-2018, 04:35 PM
iamtheari iamtheari is offline
 
Join Date: Nov 2017
Location: ND
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Quote:
Originally Posted by TASEsq View Post
Hi Ari,

Thanks for this info - just wondering if you could clarify what you mean? Are you saying that the pressure the brackets put on the bearing housing caused it to possibly distort etc so that the spherical part has some friction on it?

Iím not anywhere near this section yet but trying to understand anyway.

Out of interest, in this design by Vans, what stops the bearing housing from rotating in the brackets other than clamping pressure when you double flush rivet them together? If not enough pressure the housing may rotate? So you need some pressure but not too much??
The bearing bracket halves appear to be perfectly machined to clamp the bearings in place. I don't know if they clamp on the outer circumference of the bearing's outer race, on the flat sides of the outer race, or both. In any event, primer in that area was apparently just thick enough to cause the clamping force in one direction or the other to prevent the bearing from turning freely. It could have been a distortion out of spherical, or a compression that maintained the spherical shape, or anything else under the sun. All I know for certain is that removing the halves from the bearings allowed the bearings to turn freely again and removing the primer from that area allowed the replacement bearings to turn freely after assembly.

Maybe someone else can weigh in on the design and how exactly the bearings are prevented from turning inside the brackets. But I know this much: The bearings themselves turn so easily when properly installed that it is doubtful anything would cause the outer race to turn relative to the bracket.
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