Elevator Binding

[P Johnson]

Morning,

So I got to fit the elevator onto the aircraft yesterday, everything was nice and free until I started tightening up the bolts, actually it only needed anyone of the bolts to be tightened and the elevator became very stiff. When I initially assembled the elevator and horizontal stabiliser after doing the reaming and inserting the bushes I noticed that the elevator hinge hinge tabs were tight on the horizontal tail hinge bushings, not the brass bushing but the steel weldment they were not too big but would catch on the tabs some on the left side and some on the right side so as soon as you start to tighten a bolt the little steel bearings which are silky smooth become redundant as you now have metal tab against metal bushing on several of the hinges due to the lateral offset of the tabs and bushings.
The remedy as I see it is to identify the offending steel bushings and file either left or right side until there is a small clearance which will then let the little steel bearing do its job. I have attached a photo of one hinge that is biased to the right and if you can imagine the next one that would be biased to the left creating a brake when either bolts is tightened. The one thing that concerns me is that I have searched this forum and have not found anyone else whom has had this problem?3D3ADA65-609A-4441-805F-0EEBA16AB445.jpg

[Hardwood]

Hello Mr. Johnson,

I would recommend you give KitFox a call or send them an e-mail directly with the picture and ask for some guidance. I just finished installing my elevator to the horizontal stab. & I didn’t have any of the issues which you are showing in your photos and describing. I have however had some issues with some other parts, e-mailed KitFox and they usually get back to me the next day or answer the e-mail. I’m working on a Model 7 Sti. Good luck and I hope that you will hear back from the quickly after you message them.

Matt

[FlyinFish N928M]

Based on the photo you are showing, the tab looks extremely tight to the bushing block. I agree, a call to KF is a good place to start. I think the remedy minus returning you parts is to file as best you can one or both sides of the bushing block.

More importantly, if you so choose to modify yourself, use a flat edge razor and cut away the powder coat on the bushing block alone to get to the steel below and see where this gets you. After painting on my stab, I had to do exactly this in order to get my parts to fit nicely. Then consider touch up paint to cover any exposed steel. Not ideal but a solution instead of returning parts. Ideally, in my opinion, these tolerances should be set up at the factory to accommodate powder coat and paint build up to allow for weather tight connections.

This is where you get to exercise your craftsmanship

[Pushboy]

Hi Oregonfox,

I had this exact same issue just a couple weeks ago. Free movement when the fasteners are not torqued, but at 25 there was restriction of movement - especially at the extremes of rotation.

The factory gave me the same advice about horizontal and elevator spar alignment. They also told me that the "free movement" should be the elevator wanting to fall down on its own. (More on that in a bit.) I did try the string down the center of the weldments and tabs but found that eyeing it was the best way to get close. As mentioned here before, I went with what seemed like the best average "close" colinear. Like you that was better but wasn't enough. Further advice from the factory was to focus on the actual range of the elevator - approx 40degrees up and 20 degrees down. Restricted movement above or below that - is out of range and thus not really worth the work. Lastly, they suggested to carefully remove powder coat on the weldments and/or tabs to get free movement. This did take quite a bit of time. Initially I had the horizontal/elevator mounted in the fuse for this -- however I found it far less time consuming to work these two parts off the fuse until I had something more workable. Also, it allowed me to turn the entire assembly upside down to assess "free movement" in the other direction. I carefully and meticulously watched and marked every hinge point during rotation to see where things were binding. With a small jeweler file and razor blade I removed powder coat in these areas. I did have to remove more powder coat than I initially wanted to or felt comfortable with -- however there is now a very small visible gap between the tab and the weldment... and more importantly free range/movement.

So a few thoughts for you to consider,

There is possibly more powder coat on each surface than anticipated/expected.
Also -- if I recall correctly the recommended range of torque for AN-3 is 20-25"lbs. The idea behind this attach point is that the bearing rotates within bronze sleeve and the bolt hold fast in one position on the tab. Possibly you could attempt your assembly with a torque of 20"lbs and see what the rotation restriction is with the bolts holding fast. If you have less or no restriction at 20 - then you can individually increase the torque to 25 at each hinge point and assess/correct the binding any offending points before moving on to the next one -- not all hinge points may be binding.

I hope that helps.

Incidentally I find if kinda funny that in the builder's tips section of the manual, it mentions not chasing every 1/64 or 128th of an inch or something to that effect cuz you will drive yourself crazy... -- yet the first chapter has you doing exactly that... I feel your pain -- I asked myself a couple times during that ordeal -- what am I doing here? Am I crazy? What have I gotten myself into?

Dave.

[RJK_Omaha]

I would just quickly add that I am struggling with similar elevator to HS connection issues. I wanted to fit the two pieces to set the proper ribs locations and ensure rib alignment. Dry fitting (no lubricant) the six connection points leaves the elevator demonstrating some binding and not freely moving. Additionally, I struggled to get all six bolts through both hinge tabs. I assume part of the issue is no lube, but likely this is not the only issue. In examining the parts I have noticed the following:

- Definitely have some points where the hinge tabs are contacting the bearing/bushing weldment rather than the steel bushings. Suggests too much powder coating and/or potentially undersized steel bushings (unlikely). Plan on removing (sanding/razoring) excess powder coat (as suggested in this thread).
- Shooting a laser through the six sets of hinge tabs, shows that 2 sets (two adjacent sets on the outer side) are slightly out of alignment suggesting a very slight bow in the elevator. Factory guidance suggest carefully removing this slight bow by force. Will give this a try by placing between two sawhorses and applying controlled pressure.
- The final possible issue may be a set of hinge tab holes that appear to not be exactly parallel to elevator. This can be seen when a reamer inserted in this specific hinge tab does not run parallel to the elevator tube. Not sure what to do about this other than to first try to ream the tabs with a slightly larger reamer. Removing and rewelding the tab would be the last resort if I can't solve by some other means.

Of course...maybe the lubrication will make all the difference and I'm overworking this problem.

[Hardwood]

I must say I have been lucky to not have too many issues with the horizontal tail section. During that phase of the build initially I didn’t have the big reamer needed so I only lined them up, clamped them together and laid out my rib locations. I never actually tried to connect them again until I put the horizontal stabilizer on the fuselage and then attached the elevator. I did have to wiggle things together a little but by that point I had already reamed them, inserted the bushings and bearings. A clamp was necessary on a few of the bushings while I inserted the bolts, however after all was in I did have pretty good range of motion. I wish you both good luck going forward and that there will not be a need to have them removed and welded on again.

[P Johnson]

Hi Richard,

Your problem sounds just like how mine was! When I mated the stabiliser and elevator I found that the bushings and tabs were a tight fit and the bolt holes did not line up, some of the holes were not even visible, I inserted the two outer bolts first and swung the elevator through its travel at certain points the holes become more visible and the bolts could be inserted more easily but some manipulation of the spar along with some gentle persuasion of the bolts was needed, when the nuts were tightened the elevator became very stiff (locked), I noticed two of the horizontal tail hinge bushings and elevator hinge hinge tabs were binding on right and four on the left, I marked all of the offending bushing on the side that they were making contact and removed a 1/64th of a inch I then did another trial fit and repeated the above until I had a 1/64th gap between the elevator hinge hinge tabs and the horizontal tail hinge bushings and you could see the tabs nipping up on the steel bearings.
A few of things to note, wrap some thin aluminium around the spar to protect it whilst filing the horizontal tail hinge bushings. As the hinges are not perfectly inline there is no side float when the bolts are tight this will change when the bearings bed in so make sure that you have clearance either side of the bushing before tightening them, I assembled mine with a little WD40 as this will be easy to remove before paint, everything is now super smooth with no binding.

Hope this helps

Paul.

I would just quickly add that I am struggling with similar elevator to HS connection issues. I wanted to fit the two pieces to set the proper ribs locations and ensure rib alignment. Dry fitting (no lubricant) the six connection points leaves the elevator demonstrating some binding and not freely moving. Additionally, I struggled to get all six bolts through both hinge tabs. I assume part of the issue is no lube, but likely this is not the only issue. In examining the parts I have noticed the following:

- Definitely have some points where the hinge tabs are contacting the bearing/bushing weldment rather than the steel bushings. Suggests too much powder coating and/or potentially undersized steel bushings (unlikely). Plan on removing (sanding/razoring) excess powder coat (as suggested in this thread)……..Of course...maybe the lubrication will make all the difference and I'm overworking this problem.

[jiott]

Don't worry, it's not all like this. The only other area you may get frustrated is getting free rotation on the brake/rudder pedal assembly; oh, and maybe the delrin block for the control stick assembly. In all these areas it is usually the powder coating causing the problems.

[Oregonfox]

A big thank you to everyone who replied to my questions regarding the Elevator/Stabilizer hinge issues. Yesterday, after a few weeks of experimenting, head scratching, emails to the factory, and research we met with success! Things most helpful steps were 1) bending the elevator spar in two different directions, 2) filing down the stabilizer weldments to fit between the elevator tabs, 3) sanding and polishing the steel bushings down to a fine shine and 4) using motorcycle oil (what we had on hand) to temporarily lightly lube the weldments.

The advice Pushboy gave regarding the factory recommendation to focus on the elevator range of 40 degrees up and 20 degrees down was the most helpful. That made a lot of sense since the range of motion in the elevator when installed will not need to go further.

I am new to forums and this is my first post. Thank you all for your patience and also your kind and thoughtful answers.

The first attatched photo is one of the simple platform we built to hold the elevator/Stab off the table while I put the ribs on next. I saw this on Swiftfox’s videos and would like to thank him for this good idea! The stuffed fox is a gift from my husband, given to me when the fuselage arrived. Her name is, “Kit.”

[RJK_Omaha]

I like how you approached this Paul and appreciate the recommendations that led to a good outcome.