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

[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.

[RJK_Omaha]

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

[Oregonfox]

I’m not sure folks are still reading this thread but, do you know how much torque is supposed to go on the nuts attached to the through bolts? I’ve had issues done all that is previously suggested on this thread ( bending the elevator straight, filing the weldments for space between the tabs, creating free movement of the steel bushing between the bronze bearing and the bolt while keeping the original length) and as soon as the nut are tightened beyond a just snug fit, the elevator seriously binds. I can even see the tabs move inward toward the bearings/bushings when tightening. The nearest torque value I can find is on the chart given in the builder’s manual, which is 25 in/lb.

[FlyinFish N928M]

I’m not sure folks are still reading this thread but, do you know how much torque is supposed to go on the nuts attached to the through bolts? I’ve had issues done all that is previously suggested on this thread ( bending the elevator straight, filing the weldments…..…The nearest torque value I can find is on the chart given in the builder’s manual, which is 25 in/lb.

It might be a manufacturing problem that you may consider bringing up with KF. You may want to consider mounting the leading edge of you horizontal stab to the airplane, along with your v-braces properly adjusted, then attach the elevator to see what kind of movement or binding you are getting. By filling the bushing weldments down to allow for your elevator tabs to align properly seems like the proper corrective action. The bolt you snug down is meant to compress onto the bushing, only the bushing should move in a freely rotating, lubricated weldment on the horizontal stab. Maybe the weldment on the stab are out of alignment. If things are grossly out of alignment, video and photo document your issues and send them to John and Brandon at KF and let them formerly address before going to far any one direction.

[patrick.hvac]

This stuff isn't NASA precise. If the barrel is longer than the bushing, the tabs will bind.
Either need to shorten the barrel or make a longer bushing. By the location of your tabs in the photo, you don't have much of a choice.