The Barn Find Build

[bbs428]

Had to do much the same on my build including the joystick torque tube supports and bearing. Build quality is something that cannot be ignored. Time well spent.

[Eric Page]

Thanks, gents. I really appreciate the kind words. Being a rookie builder, it's hard to accept my work being called "craftsmanship," but I'm trying!

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Today I spent an unbelievable amount of time cleaning a pile of really filthy parts. They had been laying on a furniture blanket on the garage floor collecting dust since I removed them from the fuselage several months ago.

IMG_0826.jpg

Another bucket of hot, soapy water and a rag made easy work of the dust and grime, but it quickly became apparent that I needed to disassemble every single item down to its constituent parts, because many assemblies weren't moving smoothly. I also found more hardware store fasteners, some mismatched hardware, and most alarming, three rod end bearings assembled without washers!

Luckily I found all of the rod end bearings in acceptable condition. A couple were a bit stiff, but some cleaning and a drop of Tri-Flow got them swiveling like new.

There are a few items that I need some advice on. The first relates to the four control stick pivot bearings that are pressed and Loctited into either end of the control column weldment.

ControlColumn.jpg

I think these four bearings in my assembly are shot. They weren't seized, but if I stick the rubber tip from an air gun into them to rotate the bearings, they feel like they have detents. I'm assuming there's corrosion inside their races. I tried to drift one out by hammering on it with a socket and nut driver, but it won't budge.

If I torque the nut on the pivot assembly just tight enough to make it turn on the bearings only, it feels pretty bad, but if I loosen it slightly so that the pivot rotates on the bolt, it's like butter. So, I could leave the crappy bearings in place and get an acceptable control feel, but I'm guessing the bearings are there for a reason, and it's not just to locate the bolt.

The other issue is that the flanges that carry the bearings at the left end are too far apart. When I torque the nut on the bearing races, it bends the flanges inward at a slight angle so that the ID of the bearings aren't in alignment. I've got the pivot out of the assembly and I don't see any way to get a washer in there to take up the space.

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So, three questions:

1. Is there an easy way to get the pivot bearings out without cooking the powder coat with a torch?
2. Does anyone know the generic part number for that size/style of bearing?
3. Is there a solution to the spacing issue on the bearing carrier flanges?

Anyway, here's the final beauty shot, with a table of clean parts, mostly ready to go back together. There's a Spruce box elsewhere in the garage with bags of new hardware, waiting for its place in the project.

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Finally, the aileron bellcrank and flap bellcrank assembly feels a little bit stiffer than it should be, given that the two parts are free to rotate on two greased clevis pins. I'm considering taking this apart to clean it and apply new grease. It will require drilling out four 1/8" stainless rivets that hold the pin retaining straps in place.

BellcrankStrap.jpg

This looks pretty straightforward, but if anyone has done it and has any advice to offer so I don't screw it up, I'd be grateful.

[Eric Page]

And the hits just keep on comin'...

I realized that I hadn't removed the control column braket assembly from the fuselage frame, and it needed to come off due to flaking primer and some black overspray, so I got to work taking it out. The two nuts/bolts in the rectangular part of the bracket came out fine, but the two through the L angle on the right side were a real pain. Here's the forward nut, from underneath (I cleaned up the Poly-Brush while I was under there!).

IMG_0831.jpg

As you can see, the first builder made a real mess of the nut because there's no room between the nut and the fuselage tube to get a socket or a box-end wrench onto the nut. The welds holding the tabs on get in the way too. There might have been room for an open end wrench, but whatever the first builder used to tighten the nuts chewed them up so badly that my wrench wouldn't go over them.

In the end I had to roll the fuselage onto its side in order to have any leverage, then grab the nuts with a pair of duck bill pliers and turn them in multiple 10° rotations to get them off. By the time I got them free, this is what they looked like.

IMG_0834.jpg

Obviously I don't want a repeat of that performance when I reassemble. So, how the h*** do you get a nut onto those two bolts, and get them torqued properly, when you can't get a socket onto them because of interference from the tube and the tab weld?

[alexM]

Those nuts on the underside of the right control column end can be a b****. Sockets need not apply because the nuts are so close to the fuselage tube there. Being AN364 nuts makes it even more challenging since there is less to grab on to. I think I can barely get a box end wrench on one of mine but on the other I'm laying under the plane very carefully using an open end and getting 10-15 degrees per cycle. I'm a german car owner so stuff like this seems normal.

Just go with new hardware and take your time, working from the bottom side so you can see the wrench on the nut.

On your other situation (Question 3.3) with the control column, you're aware of the "L" washers right? You should have AN960-10 and -10L. L is supposed to be "light" but it really means thin. There are plenty of places in the control system (especially when it comes to brake master cylinders and rudder pedal cables) where you'll be stacking different combinations of washers to make up a gap.

[efwd]

Click Bond Nut Plates.

[jrevens]

Hi Eric,

You’re doing good work! I have just a couple of comments that might be helpful (or not). First, yes you’ll probably have to use heat to break the Loctite bond on the bearings. Definitely don’t want to be spinning on the bolt. Just touch up with some black paint afterwards. Sorry I don’t know the numbers on the bearings, but they’re nothing very special. Kitfox can tell you. About the clearance problem with the nuts and tubes/tabs, you might consider using MS21042 all-metal locknuts. They have equivalent strength but are lighter & have a smaller hex head. You should have plenty of clearance for a socket then. Get the ones with dry lube (gray color). I think they have an “L” in the part number. Aircraft Spruce will have them.

[Eric Page]

Just go with new hardware and take your time, working from the bottom side so you can see the wrench on the nut.

Yes, and I think I'll get that part re-installed ASAP, while the fuselage is still laying on its side. The part is sitting in a paint stripper bath at the moment, to get the failing primer off of it. I'll Alodine it once that's done cooking, then reinstall.

...you're aware of the "L" washers right?

I have a bag of them. It didn't appear to me that there would be enough room between the ends of the pivot arms and the inside face of the bearing to fit the OD of a -10 washer, but I'll definitely give it a try. If they fit, that'll solve the problem.

Click Bond Nut Plates.

That might work, but I very much doubt there's enough space on those two little tabs to center a nut plate. There's barely room for the diameter of an AN364 nut. Given that this is a part that's very unlikely to ever be removed, I'm not willing to use four $7 fasteners anyway. I'm cheap enough to endure 30 minutes of frustration to save $28!

First, yes you’ll probably have to use heat to break the Loctite bond on the bearings. Definitely don’t want to be spinning on the bolt. Just touch up with some black paint afterwards. Sorry I don’t know the numbers on the bearings, but they’re nothing very special.

That's kinda what I figured. There's a PA-12 replica builder a few minutes away who has a very well-equipped shop; I'll take my torch over there and see if he has a press I can borrow. Once I have the bearings out and can measure them, I'm sure I'll find a suitable replacement.

...you might consider using MS21042 all-metal locknuts. They have equivalent strength but are lighter & have a smaller hex head. You should have plenty of clearance for a socket then. Get the ones with dry lube (gray color). I think they have an “L” in the part number.

Now that's a good idea right there! There might not be enough depth available in that spot for a standard height nut (Kitfox specifies an AN364), or enough bolt length to get a couple threads' worth of protrusion, but I'll put a couple in my next Spruce order and give them a try. Thanks.

[jrevens]

. ... Now that's a good idea right there! There might not be enough depth available in that spot for a standard height nut (Kitfox specifies an AN364), or enough bolt length to get a couple threads' worth of protrusion, but I'll put a couple in my next Spruce order and give them a try. Thanks.

The nuts are also shorter... you don’t have the extra height that houses the nylon locking material. They should work.

[efwd]

I have sacrificed a 3/8" socket once by grinding the the socket to a very thin wall. The torque on those is minimal.

[Eric Page]

The nuts are also shorter... you don’t have the extra height that houses the nylon locking material. They should work.

Excellent, thanks.

I have sacrificed a 3/8" socket once by grinding the the socket to a very thin wall. The torque on those is minimal.

Hmmm, good idea. There happens to be a new Harbor Freight store nearby. Sounds like a good use for one of their tools!