Shock disk tower bolt/bushing/nut

[Vance Harral]

Have the main gear shock disk towers off the airplane right now for shock disk replacement, including the bolt/bushing/nut that attaches the tower to the truss.  All the hardware is - not unexpectedly - showing some light surface corrosion.  We stripped, bead blasted and repainted the towers to address this.  I'd also like to replace the bolt, bushing, and nut.

The nut is an AN365-918 which can be overnighted from Spruce or maybe even obtained locally.  But the bolt and bushing have Mooney-specific part numbers.  As Mooney and the local service centers are closed today, I'm wondering if anyone knows if these parts are cross referenced to some standard part number.  I'm not particularly hopeful about the bushing, but the bolt just seems like a standard AN bolt, especially given that it takes an AN nut.  I'm a little surprised it has a Mooney-specific part number in the parts manual.

Does anyone know a quick source for these parts?  Alternatively, any advice for cleaning up the bolt and nut I already have?  I can run it on a wire wheel, but that would strip any cad-plating still left.  I'm not sure if painting the nut and the head of the bolt after doing so is kosher, or particularly useful for corrosion protection.  Any advice/tips would be appreciated.

[Mcstealth]

On February 4, 2017 at 8:58 AM, Vance Harral said:

Have the main gear shock disk towers off the airplane right now for shock disk replacement, including the bolt/bushing/nut that attaches the tower to the truss.  All the hardware is - not unexpectedly - showing some light surface corrosion.  We stripped, bead blasted and repainted the towers to address this.  I'd also like to replace the bolt, bushing, and nut.

The nut is an AN365-918 which can be overnighted from Spruce or maybe even obtained locally.  But the bolt and bushing have Mooney-specific part numbers.  As Mooney and the local service centers are closed today, I'm wondering if anyone knows if these parts are cross referenced to some standard part number.  I'm not particularly hopeful about the bushing, but the bolt just seems like a standard AN bolt, especially given that it takes an AN nut.  I'm a little surprised it has a Mooney-specific part number in the parts manual.

Does anyone know a quick source for these parts?  Alternatively, any advice for cleaning up the bolt and nut I already have?  I can run it on a wire wheel, but that would strip any cad-plating still left.  I'm not sure if painting the nut and the head of the bolt after doing so is kosher, or particularly useful for corrosion protection.  Any advice/tips would be appreciated.

Vance, I noticed there were no responses on your question. Did you already fix the issue?

[Vance Harral]

No, I didn't get any response.  In consultation with the mechanics, we decided to clean up the existing bolt and nut with a wire wheel and re-install.  The wire wheel removes any cadmium plating left on the parts (of which I suspect there was virtually none left anyway).  So after cleanup, I primed and painted the nut, and the head and end of the bolt for corrosion protection, then installed it with a heavy dose of LPS-3 corrosion protectant all around.  I'm confident the old bolt and nut have good holding strength, just wanted to replace with new for better corrosion protection.  Instead, I'll keep a close eye on the reinstalled bolt over the next year and look for signs of corrosion.

[kortopates]

One thing you can do easily is order the new bolts from Mooney and nuts from them or Spruce (the AN365-918 nuts are certified versions of AN364-524 as you probably already noticed). Then next time you get it up on jacks you can easily replace bolts and nuts after jacking it up just enough to get the required clearance.

I had to replace my shock link towers last time I did mine because of corrosion inside at the bottom of the tower. I think they get rain in them on approaches. So like you, I squirted a good dose of LP-3 into the towers and will do that at annuals. Plus Mooney also sells covers for these which are available from LASAR and very inexpensive. Don't know if they apply to the F, but they are good for mid-body's and long-body's. Don't know why, but Mooney made these optional on current production aircraft - so new ones are missing them.  

Edited February 7, 2017 by kortopates

[1964-M20E]

Order the bolts and have them on hand when you need them or decide to replace them,  Of course if you have my problem you forget where you put them and they are buried among other things.

[Vance Harral]

Yes, good advice to order new bolts/nuts/bushings for the next opportunity.  While I think my paint job on the bolt and nut will hold up OK in the short term, the act of installing the bolt takes some of the paint off, of course.  Also, the bushings were "usable', but have some scoring and should be replaced within the next year or so, too.  I think some of the bearing wear was a result of not really getting grease all the way through the bearing at past annuals.  It had become pretty difficult to push grease from the zerk out both sides of the bearing, seemed like it was always just squirting back out the zerk, or out one side of the bearing at best.  Easier now after disassembling and cleaning everything.

Paul, I took a good look at our shock link towers based on your comment about replacing them in your own thread.  They had some light surface corrosion on the exterior (i.e. the parts you can see when everything is assembled), as well as some wear on the tube that holds the disks.  But nothing significant in terms of wall thickness.  I took the exterior portions down to metal with a bead blaster, then primed and painted them.  The interior tube still had most of its original chromate coating intact, so I just cleaned it lightly with a scotch brite pad and solvent, then sprayed a liberal dose of LPS-3 on when installing the new disks.

I'm pleased with the way everything is going back together, and with getting a serious look at the state of the trusses and hardware.  The old paint and dirt was so gross that we worried every year about the possibility of a major crack or corrosion hiding in the paint chips and grime.  Cosmetically it's going to look much nicer, too.  I just wish it didn't require so much time and effort to really do things the right way.  I've been working on this in the shop about 8 hours a day for the last 4 weekdays, including getting some help from the "real" mechanics.  The labor bill at this year's annual is going to be a bit ugly vs. prior years...

[Vance Harral]

Here are some pictures, for the curious.  They attached in reverse order for whatever reason.  Bottom photo is lower truss taken down to bare metal.  Next above is post-paint, with all new fasteners (except for large shock disk tower bolt).  Next above is everything ready for re-install.  Top photo is post-installation.

Edited February 7, 2017 by Vance Harral

[Flymac]

Cool pics, thanks for sharing! About to replace our main discs as well...was gathering all the hardware/bushing/etcs to try and order ahead of time and just plan to replace while have it all apart.  You mentioned the bolt to attach the disc tower to the truss was mooney specific, but from my list I just see it as a standard AN?(below)

Also debating if its worth/any need to replace the collars.  Definitely nice you got to clean yours all up with fresh paint.

32-10-00	17	AN9-24A
MAIN	17	914007-005
GEAR	17	AN365-918

[kortopates]

10 hours ago, Flymac said:

Cool pics, thanks for sharing! About to replace our main discs as well...was gathering all the hardware/bushing/etcs to try and order ahead of time and just plan to replace while have it all apart.  You mentioned the bolt to attach the disc tower to the truss was mooney specific, but from my list I just see it as a standard AN?(below)

Also debating if its worth/any need to replace the collars.  Definitely nice you got to clean yours all up with fresh paint.

32-10-00	17	AN9-24A
MAIN	17	914007-005
GEAR	17	AN365-918

Without looking at the IPC, my recollection is the AN9 bolts are for the  two 9/16 bolts that secure the shock link towers to the spindles shown in the picture above. A different Mooney part (maybe the 914007-005?) is the top bolt - but it doesn't have a standard bolt head, it has an oval slotted end for a screw driver, which is what use to hold it as you put on the nuts. I don' see it in Vance's picture above.

[Vance Harral]

On review, I'm embarrassed to say I mis-read the parts manual.  Flymac is correct - the bolt I was looking for is the AN9-24A he references from the parts manual.  Apparently not available from Aircraft Spruce (at least not via online search, maybe they do have stock if you call).  But available from Skygeek, albeit at over $30 apiece.

The 914007-005 part number is the bushing associated with that large bolt.  That's a Mooney part number, not sure it cross-references to anything standard.  But when/if I replace that bolt, I intend to replace the bushing, too.  As I mentioned, ours has some score marks.

The special bolt with the oval head that goes through the collar is in the second picture above if you look closely.  It's at upper right, immediately below the shock disks themselves.

I'm not sure how much trouble it would be to replace those collars, Flymac.  They're definitely Mooney-specific parts, not sure if the factory has them in stock or what they charge.  I debated painting them, and did so only because I already had everything set up for paint.  The point wasn't to make them look pretty, but just for corrosion protection.  The collars appear to be a non-stainless variety of steel, and showed some light surface corrosion.  But a liberal dose of LPS-3 or similar on assembly, and periodic re-spray of same at annuals is probably just as good as paint in that department.  If you do paint yours, either mask the inside of the collar before painting or sand it smooth/thin after.  The fit of the collar over the top of the shock disk tower is tight, and any excess paint will make it harder to slide the collar in place.

[Yetti]

Those rockshields are pretty.  They are a beotch to get put back on.  I think I spent several hours on one.    The right side brake line was snaked around instead of removing and now I have to do an on the hoof paint job.

[Flymac]

Hey Vance, on the collars...I spoke with Paul at LASAR yesterday on all my potential parts, items etc as I'm also sending in our entire nose gear asm to get rebuilt. His opinion on the collars was he rarely replaces, and only might do so if he sees any major elongation of the holes(which I supposed would be a hard rebound of the gear extending after a bounce or such)...I dont think I'll end up replacing mine unless find a major surprise.

For the bushing, he did note thats certainly the hardest working bushing in the gear taking all the brunt and its fairly common to replace...yes mooney specific but he has them, $69 per vs I think $100+ from mooney just FYI.

Can I ask on your media blasting process? Which media did you use? And in repainting, did you just primer and spray white by hand with a gun or such?  On your disc link did you also blast the outside and inside there to try and clean it out?  Seems thats a trouble area too inside the link where water can just sit with no escape.

[Vance Harral]

13 hours ago, Flymac said:

Can I ask on your media blasting process? Which media did you use?

The machine in the shop I'm using is set up with glass beads  It worked "OK" for removing the paint and underlying zinc chromate primer from the trusses, but took a lot of time and patience.  I did the first one "dry".  On the second one, I took the mechanic's advice to apply a chemical paint stripper first.  That took most of the paint off, leaving only the chromate, which still required a lot of bead blast work.  Actual sand is better for paint removal, but the more abrasive media you use, the more careful you have to be not to pit the target.  For a junior birdman, non-mechanic like myself, glass beads were probably the best choice.

I had and still have mixed emotions about removing the chromate primer along with the paint.  I had a number of spots where the primer was worn away and the exposed steel was exhibiting some surface corrosion, so full cleanup seemed best.  But the self-etching primer I used for the re-paint probably isn't as good as the original chromate.  ZC is also pretty nasty stuff.  I've sanded or media blasted parts with it on a couple of occasions including this one, but it always makes me a bit nervous from a health perspective.

 

13 hours ago, Flymac said:

And in repainting, did you just primer and spray white by hand with a gun or such?

I actually used rattle cans made up by a local automotive paint shop.  3 light coats of self-etching primer, followed by 3 fairly heavy coats of color.  I set the parts on a ladder underneath the shop's full-hangar heaters over the weekend, as a poor-man's baking oven.

It remains to be seen how well the job will hold up to use.  Our airplane isn't a showpiece, and I wasn't really trying to achieve a high-end result.  Just something to tide us over a few years until a theoretical future paint job.  The gold standard would probably be powder coat, but that would have required more time, money and logistical management than I was willing to spend

13 hours ago, Flymac said:

On your disc link did you also blast the outside and inside there to try and clean it out?  Seems thats a trouble area too inside the link where water can just sit with no escape.

I did shoot some beads at the inside of the tube, and also scrubbed it out with a wire brush, but I didn't try to make it pristine like the outside.  It probably still has some chromate on the inside, which I think is a good thing.  I'm relying on that and a heavy dose of LPS-3 for corrosion protection.  Now that I understand how to access the top of the tube, I'll probably re-shoot it with LPS once or twice a year.  I agree it's a potential trouble spot that could collect water, but the operating environment mitigates the concern in our case.  It's a pretty dry climate here, the airplane is hangared, and we rarely fly actual IMC (clouds around here tend to be full of ice in the winter and thunderstorms in the summer).

[Vance Harral]

15 hours ago, Yetti said:

Those rockshields are pretty.  They are a beotch to get put back on.  I think I spent several hours on one.    The right side brake line was snaked around instead of removing and now I have to do an on the hoof paint job.

Thanks for the complement, but they look better in the photos than in real life.  I didn't actually strip them down to bare metal.  I just did a "scuff and shoot", and you can see the old paint texture underneath.  I was running low on paint in the rattle cans, and it seemed like a reasonable compromise since almost no one ever sees them up close and personal.

Different models may attach the shields a different way, but I didn't have much trouble with mine.  They're held on with 10-32 machine screws, through Adel clamps, and into self-locking nuts.  The trick is to use safety wire to pull the Adel clamps together, then get the bolt/nut started, then cut and pull out the safety wire before tightening everything up.

Edited February 10, 2017 by Vance Harral

[Vance Harral]

At the risk of patting myself on the back a little... just downloaded all the photos from the annual to my phone, which allows for a better before/after comparison.  As you can see, the landing gear cleanup made a dramatic difference!

[outermarker]

Has anyone posted a video on actually removing the landing gear disks? I really didn't see anything posted here and didn't find anything on Utube. I read the manual and it is no road map to success. Has anyone actually used Mooney tools to do a disk replacement? 

albert

[cliffy]

For the main gear no special tools are needed 

Just remove the collar and bolt and then jack the airplane high enough to get the lower half and shock discs out.

Might have to take the wheel and tire off first

Reassemble with new discs and slide in then lower jack enough to compress the discs enough to get the collar back on. 

Nose gear discs take some doing with the tool or a press, Best left to the tool though.