Elevator Mid-Hinge Bushing Replacement

[Tarfu43]

Hi, Folks! I don't have a 170, I have a 1961 172B, but I'm a member of this Forum due to the obvious similarities of the aircraft. I'm in the process of doing the annual on my aircraft and need to remove the r/h elevator in order to swap the bushings because the otbd hinge has some wear. I replaced all the bushings and hardware on the l/h elevator in the past with no problem. My dilemma right now is that the mid-hinge bushing has corroded and frozen to the bolt, so I can't remove the bolt. The bolt and bushing will rotate, but I can't get the bolt out because the otbd hinge bracket attached to the elevator is "trapped" between the head of the bolt and the bushing. I've doused it with Kroil for days, but still no joy. There is no space to try and hold the bushing with vice-grips and turn the head of the bolt because the bushing is still within the bracket attached to the stabilizer. I haven't tried fishing a 10" drift into the leading-edge of the elevator to try and bang on the end of the bolt yet, but that's probably what I will try if nothing else works. I am hoping there is a less-impactful option.

Has anyone experienced this issue? Any ideas on how to get the bolt out without removing the otbd hinge bracket entirely or trying to beat on the bolt?

[ghostflyer]

I feel you pain. There is no short cut allowed. I wouldn’t attack it with a hammer and drift. I would dismantle it carefully ,if removal of other structure is necessary , so be it. However on reassembly of the elevator system , Hingers ,structure in these areas check for cracking . I would be replacing all hardware with new and New bearings . This area is the most vital part of the airframe . I would be also checking the rear spar carefully as on the inside of the spar [very hard to see when elevator is attached ] often gets corrosion in this area. I spray LPS 3 every where .
Due to the salt air environment in my region a lot of aircraft have corrosion issues in the balance horns on the elevators. If you loose a balance horn or it becomes dislodged you are going to have bad day.

[cessnut]

I once had an aileron bolt seized in the rod end inside the aileron. I tried every trick in the book, then wound up using a pneumatic angle drill to remove the head of the bolt. With the bolt head removed, I stacked washers under the nut and tightened the nut to pull the shank through the bearing. I'm not sure this will work in your situation, but it's worth considering.

[Tarfu43]

Cessnut,

When you tightened the nut to pull the bolt shank thru the bearing, how did you keep the bearing from spinning? (Or was it seized in the bearing housing along with the bolt?)

My dilemma is a bit different because the bolt and bushing rotate freely. Even if I removed the bolt head, when I turn the nut, it will just rotate the entire assembly so there’s no counter-pressure to draw the shank.

[GAHorn]

A C-clamp on the threaded-end… can press a bolt out of a bearing by placing a larger “socket” on the “Head” end…. and pressing the bolt out. If you intend to preserve the bearing/bushing it’s important the socket supports the bushing from moving.

[n2582d]

George, I like your idea except I don’t see how one could possibly get a C-clamp into an attached elevator. I wonder if modifying a couple of cheap wrenches might do the trick. Braze a 7/16” nut to one closed end wrench and loosely screw it on the stuck bolt. The other closed end wrench will slide over the stuck bolt head. Now, drill and/or tap two points at equal points on each wrench to come up with a lever arrangement. The fulcrum can be in the middle or at the end. Here’s a photo of a Briggs & Stratton valve spring compressor to illustrate the concept. It’s too large to fit in an attached elevator. A circle compass illustrates the same idea. A custom set of tongs that a squeezed together with an c-clamp might be the simplest. Or a heavy-duty custom hemostat. Alternatively, could one braze tooling on an adjustable wrench? Probably not enough leverage. Modified Channellocks perhaps?

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[GAHorn]

Cleco pliers….

[Tarfu43]

I'm liking all the thought here. That's how problems get solved. I was really hoping someone had this same problem and maybe had fabricated a custom tool to press the bolt out of the bushing while on-wing. I'll keep at it and if I come-up with something that works I'll be sure and report back. Keep the suggestions coming.....

[n2582d]

You might try calling Steve Knoff at P.Ponk. They make a replacement elevator bushing as seen at the bottom of this page. Wouldn't be surprised if they have a tool for this problem for they write, "After years of replacing frozen, corroded steel bearings from the tails of Cessna aircraft, we decided there must be a better way!"