Eccentric bushing / bolt

[GAHorn]

I believe if the bolt and the bushings are removed you can view some of the interior with a boroscope. I don't know how far you wish to view, but the best way is to remove the wing completely and look all the way thru. (Then scrub it out with brushes and swab it with chromate.)

[c170b53]

With the top inboard panel off you can get a line of sight right on the bolt. With the nut of the bolt removed, use a long extension and wiggle the bushing, when it moves just a bit move it backand forth until you notice a spot of reduced resistance. Then take a drift and tap out the bolt. Use a smaller diameter drift to catch the wing, it will not go anywhere but will make the re-assembly easier. If you want to look down the rear spar then you must take out the rear block once the rear bolt holding the wing has been removed. But I think unless you have a good reason to go there, I wouldn't. I would change out the bolts than hold the block in the rear spar just to ensure there's no corrosion in them due dissimiliar metals.Don't forget to go crazy with the parker o-lube or your favorite assembly lube to make it easier next time you go deep.

[wa4jr]

I finally got the rear spar bolt out of the right wing. No corrosion damage evident The bolt was being held in by misaligned excentric bushings. So I should change out the two smaller bolts to the inboard of the AN7 bolt? Easier to do this now while I have the fairing strip down. I've been driving myself crazy working from under the wing...never thought of taking the small rear top panel off Would have saved a lot of work trying to get a 7/8 socket to properly grip the low-profile flats on the bushing from under the wing.

Looking at my left wing, which is the heavy wing, I thought I had found the problem. The rear excentric bushing is adjusted all the way up and I thought all I would have to do is run this bushing to neutral while bringing my right wing up to neutral. Then I look at the front bushing on the left wing and find that is exactly opposite of the rear bushing, which I can imagine is making the AN7 bolt very unhappy, and in a few minutes is going to make me very unhappy when I try to unjam the bushings My big question here is what if any damage could happen by having one excentric bushing all the way up, while the other is all the way down, and how on earth could one possibly get the bushings to do this without the use of a VERY long pipe on the end of the wrench I joke about my airplane having a "Billy Bob" paint job complete with runs, but I think Billy Bob played around with the wrenches after he put away his paint brush

[c170b53]

That Billy Bob has got talent. I think you're on the right track to change the small stuff while your at it. This is just from memory but if your still intent on removing the block, I think a block is held in by 4 bolts, 2 in the cabin, 2 on the outside. As for the L/H wing, you'll have to remove the bushings to see how they have been modified to permit them to be offset from each other as you have described and at best the shank of the AN7 bolt will be scored / shanked. Its all good to make it right.

[ak2711c]

I am going out on a limb here but I would take a very close look at your rear spar of the wing. I really don't think it would be possible to install the bolt through the bushings at that angle unless the rear spar was twisted slightly at the attach point, or if your carry through spar was twisted at he attach point. It has been my experience that those bushing have to be indexed almost exactly the same to get the bolt through them and the spar. Another possible might be that the holes are over sized enough to allow it to go in which is not a good thing ether. Good luck, I hope I am wrong.
Shawn

[jlwild]

Looking at my left wing, which is the heavy wing, I thought I had found the problem. The rear excentric bushing is adjusted all the way up and I thought all I would have to do is run this bushing to neutral while bringing my right wing up to neutral. Then I look at the front bushing on the left wing and find that is exactly opposite of the rear bushing, which I can imagine is making the AN7 bolt very unhappy, and in a few minutes is going to make me very unhappy when I try to unjam the bushings

John with reference to your quote above, please look at Fig.2-7 and Fig. 7-7 in the Model 170 Illustrated Parts Catalog. Note that there is NO excentric on the front spar. The excentrics are only located on the rear spars. Also, suggest you get with rigging expert before doing much more, as you can cause damage if not careful. FYI, Tom Hall, a C170 member and Part Coordinator before George has a complete write up on rigging the 170. Suggest you give him a call. He is in the club directory.

[Bruce Fenstermacher]

Jim I think John meant the front bushing on the rear spar.

[jlwild]

Jim I think John meant the front bushing on the rear spar.

Bruce, after rereading the prior note from John, you are right. WOW....those excentric bushings (Fig. 2&7-7 parts) were really installed wrong. It is a wonder they didn't shear the AN7-24 bolt (Fig. 2&7-4). Remember at Dearborn Convention Maintenace Forum how Tom Hall pointed out the danger of not turning both excentric bushings at the same time? George also talked about it earlier in this forum.

John, glad you found the problem and hope you find nothing else out of wack.

[wa4jr]

And it gets even better! When I went to remove the nut from the AN7 bolt on the rear spar, left wing, I found that it was just hand tight....I ran it off with my fingers Of course the bolt itself was not going anywhere since it was in a complete bind with the two excentric bushings 180 degrees from each other. I managed to use a long 1/2 inch torque wrench and gently work the front rear bushing around...extremely hard at first, but as I brought the bushing around, you could feel the metal relax, the bushing becoming easier to turn, and finally the AN7 bolt free to come out. As I removed the AN7, the wing, which is my heavy wing, popped down about a quarter inch or so...which is good as this means maybe my heavy wing will no longer be that way in flight. The AN7 bolt does not appear to have any outward signs of damage from binding, but I will go ahead and replace it. I removed two outboard AN3 bolts holding the bearing block, and they appeared in good shape with the exception of some very slight pitting from years of rust. The holes in the block appear solid, so I'm not so worried about corrosion anylonger. A final note on torque values for this AN7 bolt in the rear spar. My information says as a general rule, 450 to 500 inch pounds, working out to about 37 foot pounds. Does everybody agree on this torque value for the nut on the AN7 rear spar bolt? I'm still having the CPA rigger pay me a visit, but his job is now much easier now that I have the excentric bushings free and properly aligned

[Bruce Fenstermacher]

John

One thing I found after fooling with my eccentric bolts. In the neutral position the hole of the pair of eccentric bolts will be either closer or farther away from the fuselage than if the AN7 bolt hole where centered in the eccentrics.

One is actually slightly swinging the wing forward or aft as well as the trailing edge up and down when adjusting the eccentrics. What this does is change the length of the cable run from the controls to the flaps and aileron. You need to inspect your control cables for both interference and tension after any eccentric adjustments.

I adjusted my eccentrics like you just did from one extreme up on one wing and extreme down on the other to both neutral with the AN7 bolt positioned farthest away from the fuselage on each side. This lengthened the cable run to both wings. My cable tensions went from loose to off the scale high a fact I didn't realize for a week or so. I also found a cable that was close to the fuselage at the exit hole even closer.

[wa4jr]

I found that I could not rotate the eccentric bushings to have the spar bolt on the fuselage side without part of the wing spar contacting the fuselage skin. In other words, I can have the bolt up, neutral to the outside, or down. I was trying to take one set of bushings around from bolt high to bolt low and couldn't do it....then finally saw the wing spar butting up against the skin/carrythrough. Reversed course and went the other way, and all was well. When I get the new AN7 bolts in, I hope to have a good chance at having the luxury of being able to take my hands off the yoke long enough to read a chart without doing a wingover to the left I'll also be able to bring my left flap up again where it should be....as my A&P advised me to droop the left flap to pick up that wing in cruise