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Control column installation and bearing stiffness (page 29-05 step 7)

iamtheari

Well Known Member
I got the bottom fuselage skins riveted together tonight and proceeded to install the control column. There is almost no play when one side's hardware is installed so I do not think I need any shims. But when the hardware is torqued to spec, the bearings seem rather stiff. It moves smoothly without binding, but it resists movement and will easily hold itself in position against gravity. How freely should the control column move?
 
You may need to try different combinations of washers/shims to eliminate bearing load. I believe there ought not be a change in friction as you torque the nuts. Shim with care.

If it's any consolation, as I look at my time lapse from when I completed that task on 4-Jul-15, it took me 3 hours to find the right combination. I obtained very smooth movement in both axes with no noticeable friction. It was frustrating but worth the time invested. It's best to do this now when access is so easy.

Not everyone's will be the same as mine, however my ultimate washer stack ended up being two NAS1149F0363 on the left inboard and single 363 and 332 washers on the left outboard (top image). The right side had two 363 washers with a single F-14146A shim (sandwiched between the washers so it won't contact anything) on the outboard side and a single 363 with the same size shim on the inboard side (bottom image).



 
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Thanks. I'll spend my weekend in that tedium, I guess, since it'll be worth it. My concern is that the bearings themselves are not working correctly but I don't know how to differentiate that from misalignment of the control column, nor how to fix them if they are sticking.
 
The RV 14 is a wonderful example of how new technology has improved the design, and quality of parts. I do have a concern about this particularly part of the airplane in terms of maintenance. If those bearings are ever to be replaced it is going to be a major job. The "bearing" holders are riveted to the fuselage and if I were to do it again I would use screws to fasten these parts to the airframe. This would allow you to easily remove those parts to replace the bearings. Airplanes can last a long time and 20 or 40 years down the road those bearings will need to be replaced.
 
The RV 14 is a wonderful example of how new technology has improved the design, and quality of parts. I do have a concern about this particularly part of the airplane in terms of maintenance. If those bearings are ever to be replaced it is going to be a major job. The "bearing" holders are riveted to the fuselage and if I were to do it again I would use screws to fasten these parts to the airframe. This would allow you to easily remove those parts to replace the bearings. Airplanes can last a long time and 20 or 40 years down the road those bearings will need to be replaced.

I wonder if I would be better off drilling those rivets out and re-engineering the bearing bracket mounts now, before I install the side skins and age an additional 20-40 years. I'm 36 now and, if there's a tedious job that must be done, I'd rather do it now than in retirement.
 
As always, be careful with any reengineering, particularly of the "eyeball" type. If Van's hasn't OK'ed a change and you don't have the experience to do the math yourself, then any structural deviation from plans (including substituting screws for rivets) is a bad idea, even when it seems obvious that it'll work fine in a given situation.

Be aware, too, that any such deviation from plans is a likely focal point for future legal action by a new owner (even should you document and fully disclose all such deviations, which you're absolutely going to do, right?) or his estate's attorney.

I build with the intention of enjoying the plane (or car, bike, etc.) for a few years and then selling it and moving on to the next project. I couldn't possibly care less about maintenance issues 20-40 years down the road. Your mileage, of course, will very likely vary.
 
I got the bottom fuselage skins riveted together tonight and proceeded to install the control column. There is almost no play when one side's hardware is installed so I do not think I need any shims. But when the hardware is torqued to spec, the bearings seem rather stiff. It moves smoothly without binding, but it resists movement and will easily hold itself in position against gravity. How freely should the control column move?

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.
 
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.

Thanks. I'll loosen one side at a time and see how that goes. I agree that any friction between my hand and the control surfaces would be best to avoid. My main concern is whether I somehow messed up the bearings themselves when sandwiching them into the bracket assemblies.
 
The RV 14 is a wonderful example of how new technology has improved the design, and quality of parts. I do have a concern about this particularly part of the airplane in terms of maintenance. If those bearings are ever to be replaced it is going to be a major job. The "bearing" holders are riveted to the fuselage and if I were to do it again I would use screws to fasten these parts to the airframe. This would allow you to easily remove those parts to replace the bearings. Airplanes can last a long time and 20 or 40 years down the road those bearings will need to be replaced.

I have been working on RV's for almost 30 years now (and work on the oldest side by side RV flying ;)) and have never had to replace one of these bearings.
If the control column is shimmed properly so that there is no side load on the bearing, and they are lubricated occasionally, they will last. That is the main reason that even though design effort is typically made to make things reasonably maintainable,maintainability was compromised in this instance because it is unheard of to have one of these bearings fail.
 
Thanks. I'll loosen one side at a time and see how that goes. I agree that any friction between my hand and the control surfaces would be best to avoid. My main concern is whether I somehow messed up the bearings themselves when sandwiching them into the bracket assemblies.

These bearings can tolerate no side load without there being a large increase on friction.
That is the reason for the emphases on using shims and it is likely the cause of your friction as well.
 
These bearings can tolerate no side load without there being a large increase on friction.
That is the reason for the emphases on using shims and it is likely the cause of your friction as well.

Thanks for your posts above. I'll hope for the best with shims and report back. Shouldn't take more than a month or two of dropping washers and cursing my lot in life. :)
 
It sounds like there should be no issues with this bearing, if, as Scott mentions, it is installed properly. The fact that this tightness has been discussed on this list by folks who are conscientious likely means that there is a good chance that someone might get it wrong.
I have been fixing machinery for over 50 years, building and maintaining RV/Rockets for 25 of those years and I always think of how I am going to fix moving parts when they need to be fixed. I often add extra inspection holes as things that are easy to be inspected will likely be inspected more often.
 
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With one side completely loosened, there is much less friction on the control column. There are visible gaps on both sides so I will have to get some shims in there. I am still working on honing my ability to use The Force to hold the washers and shims in place while inserting the bolt.

However, I wanted to post because there still is some friction with only one side torqued down. If I lift the control column all the way up (full back elevator direction) and let go, it will stay there. If I push down to overcome the stiction, it will drop all the way down easily.

My guess is that I'll need shims on both sides and I'm really going to wish I had magical powers for this process. It was frustrating enough putting those bolts and washers in just once.
 
... I am still working on honing my ability to use The Force to hold the washers and shims in place while inserting the bolt.

My trick, take a small drill bit thinner or the same thickness as the washer and super glue the last washer to the flat end of the drill bit. You poke it in and the bit will snap right off.

It may still take a try or two but it will be much easier.
 
Well, I spent an hour on it tonight, mostly dropping washers and cursing. With two thick washers and a shim on the outboard side and a thin and thick washer on the inboard side, the copilot side of the control column is as tightly shimmed as it can get. So I torqued it down and loosened the pilot side to isolate the copilot side bearing. And it is very sticky, just like my original situation.

This is the most frustrating part of the build so far. Mostly because I spent an hour of very tedious work and cannot see any results at all and have no idea why I don't have any results. I hope someone can help me out before I completely lose my mind. Thanks everyone! :)
 
Well, I spent an hour on it tonight, mostly dropping washers and cursing. With two thick washers and a shim on the outboard side and a thin and thick washer on the inboard side, the copilot side of the control column is as tightly shimmed as it can get. So I torqued it down and loosened the pilot side to isolate the copilot side bearing. And it is very sticky, just like my original situation.

This is the most frustrating part of the build so far. Mostly because I spent an hour of very tedious work and cannot see any results at all and have no idea why I don't have any results. I hope someone can help me out before I completely lose my mind. Thanks everyone! :)

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....
 
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.

Be sure to get washer holders or make them. This process is used for other pivot bearings as well. Gluing the majority of the washers/shims together is a major positive step in the final assembly, so only one is left to be inserted with the holder. Leaving the .063 one separate is most easy. Proper technique and this whole process is easy and straight forward.
 
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.

Be sure to get washer holders or make them. This process is used for other pivot bearings as well. Gluing the majority of the washers/shims together is a major positive step in the final assembly, so only one is left to be inserted with the holder. Leaving the .063 one separate is most easy. Proper technique and this whole process is easy and straight forward.

The challenge isn't just the overall shim thickness. I don't know how the -14 compares to other models, but I found that some of the issue is how one side moves when the other is tightened. I can't tell you how many times I tightened one side, all was good, carefully followed the shim process on the other side and found stiffness. I tried carefully alternating sides as I tightened them etc. Just never found the exact perfect combination. (And I did try making custom shims, using feeler gauges etc.)
 
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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/2016/08/section-29-hours-5-after-finishing-up.html
 
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/2016/08/section-29-hours-5-after-finishing-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. :(
 
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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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
 
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.
 
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!
 
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
 
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
 
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.
 
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?

I?m 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??
 
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?

I?m 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.
 
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?




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.
 
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.
 
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
 
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.
 
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?
 
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.
 
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
 
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.
 
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.
 
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
 
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I've just come in from wrestling with my control column installation.

I got my slightly stiff bearing free with very little effort (some penetrating oil and a couple of taps) and secured that side with the nominal washer stackup. With the nut torqued, the column moves as effortlessly as it should.

The issue now is that the other side (with the perfect bearing) stiffens markedly when it's torqued down. I can't seem to find a combination of thick washers, thin washers, and shims that will get it right, though some are slightly better than others. What am I missing?

I'll go back to it tomorrow afternoon and try any suggestions received. Argh!!!!
 
Had the same bearing issue -- tried a couple of fixes... will the bearing fail?

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.


I tried this method -- lots of lubricant/penetrating oil and also using a small peening hammer on either side of the bearing (not directly to the bearing) to try and dislodge it. I also fastened a bolt w/ washers onto the bearing and used a drill to rotate the bearing 500-1000 times (estimated based on drill rpm). I did notice a slight improvement regarding the bearing loosening up but I still have a slight amount of friction on the control column (it does not drop from gravity alone when I lift if up and then let go of it).

Now, I'm wondering, having manipulated the bearing so much, is it more likely to fail? Should I be worried that it's going to seize up and cause a control stick jam?

Something that was discussed here by another member was using a bolt/castle nut/cotter pin here and letting the bolt rotate inside the bearing hole. Seems like this could be a good solution, but the bolt would need to be checked for wear on the shank and on the bolt head every year, no?

Thanks,
 
After several hours of consternation trying a number of different shim combinations, I was unable to obtain friction-free movement of my control column. I then removed the column column and put a bolt and washers directly on what I suspected was my sticky bearing. Sure enough, when torqued, this bearing was a little sticky when rotated by hand. If I rotate it quickly, it moves smoothly, but if I slow down or stop, it binds up slightly. As I understand it, there should be no net side-load at all in this configuration and so the bearing should be able to rotate freely.

So I'm wondering if I'm chasing a unicorn here trying all the different shims given that I have a slightly sticky bearing in the first place? I've lubed up the bearing with Boelube and have given it a few gentle taps, but it still binds up slightly. My concern is that the bracket was not aligned correctly from Van's and this may be contributing to the friction. I also learned late that maybe I shouldn't have primed the inner surface of the bracket, although I don't completely follow that reasoning as there should be no net reduction in bearing space after priming.

Anyway, any other suggestions to free up this very slightly sticky bearing?
 
After several hours of consternation trying a number of different shim combinations, I was unable to obtain friction-free movement of my control column. I then removed the column column and put a bolt and washers directly on what I suspected was my sticky bearing. Sure enough, when torqued, this bearing was a little sticky when rotated by hand. If I rotate it quickly, it moves smoothly, but if I slow down or stop, it binds up slightly. As I understand it, there should be no net side-load at all in this configuration and so the bearing should be able to rotate freely.

So I'm wondering if I'm chasing a unicorn here trying all the different shims given that I have a slightly sticky bearing in the first place? I've lubed up the bearing with Boelube and have given it a few gentle taps, but it still binds up slightly. My concern is that the bracket was not aligned correctly from Van's and this may be contributing to the friction. I also learned late that maybe I shouldn't have primed the inner surface of the bracket, although I don't completely follow that reasoning as there should be no net reduction in bearing space after priming.

Anyway, any other suggestions to free up this very slightly sticky bearing?
I think I replaced the bearings while I had the brackets out of the plane, but in my case I had sticky bearings with the interior surfaces of the brackets primed and did not have sticky bearings with the interior surfaces of the brackets cleaned. With two variables (new brackets and removal of primer) I can't tell you if the problem was one, the other, or both items. But I can tell you that a clean bracket interior surface and a fresh bearing left me with perfectly free moving control sticks, even now after two years of flying.
 
I think I replaced the bearings while I had the brackets out of the plane, but in my case I had sticky bearings with the interior surfaces of the brackets primed and did not have sticky bearings with the interior surfaces of the brackets cleaned. With two variables (new brackets and removal of primer) I can't tell you if the problem was one, the other, or both items. But I can tell you that a clean bracket interior surface and a fresh bearing left me with perfectly free moving control sticks, even now after two years of flying.

Good to know, thanks. I'm a little hesitant to drill out the brackets at this time, but may resort to this if I can't free it up any other way.

Did you find it difficult to shim once you had free-moving bearings?
 
Good to know, thanks. I'm a little hesitant to drill out the brackets at this time, but may resort to this if I can't free it up any other way.

Did you find it difficult to shim once you had free-moving bearings?

I remembered now (and probably posted above, this was after all several years ago) that the old bearings moved freely once I removed them from the primed-interior brackets.

I didn't find it hard to shim the control columns at all.

The biggest challenge was impatiently awaiting the arrival of my tight-places 90-degree drill kit so I could drill the brackets out of the plane.
 
I remembered now (and probably posted above, this was after all several years ago) that the old bearings moved freely once I removed them from the primed-interior brackets.

I didn't find it hard to shim the control columns at all.

The biggest challenge was impatiently awaiting the arrival of my tight-places 90-degree drill kit so I could drill the brackets out of the plane.

LOL. I think I agree. With the one good bearing I have, I think I've recognized that it shouldn't be that hard to find the right combination of shims. I think the problem people may have is that if there is the slightest amount of friction, then it just gets worse upon torquing.
 
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