Squat-method landing gear disc replacement

[FlyingDude]

How do I tell if my '67 M20E has the new or old style donuts/gear? I have 3 donuts in the nose gear whereas the diagrams in the parts manual show 4 donuts in the nose gear. Can we say that the 4-donut version is the old style and 3-donut solution is the new style?

Thank you.

Edited January 13, 2021 by FlyingDude

[mike20papa]

AN9 -24A is what is called out in my A model book for the bolt at bottom of shock tower.  Double check the grip length, but I bet these are the same thru the J.

[Andy95W]

1 hour ago, FlyingDude said:

How do I tell if my '67 M20E has the new or old style donuts/gear? I have 3 donuts in the nose gear whereas the diagrams in the parts manual show 4 donuts in the nose gear. Can we say that the 4-donut version is the old style and 3-donut solution is the new style?

Thank you.

Yes, that is correct.  Nosegear 3 discs=new style.

[carusoam]

The old Firestone donuts look like spindly legs...

They would stand out when parked next to any other Mooney.... each stack had an extra donut count...

Essentially the same height, just different donut dimensions....

PP thoughts only, not a mechanic...

Best regards,

-a-

[Prior owner]

Firestone

[carusoam]

Spindly!

 

That first donut has been completely compressed...

Go MS!

-a-

[cliffy]

How much do you want to bet that the "special" bolts are in fact standard AN bolts that have been ground or milled to the design needed to fit the application?

[mike20papa]

Just as a note .. when changing out the donuts on my (low time) A model - the most worn parts in the gear where the two pivot bolts that attach the nose wheel trunnion to the airframe.  They were deformed and allowing play into the retract mechanism. Would suggest inspecting these at nose gear OH.  Joe

[Andy95W]

1 hour ago, mike20papa said:

Just as a note .. when changing out the donuts on my (low time) A model - the most worn parts in the gear where the two pivot bolts that attach the nose wheel trunnion to the airframe.  They were deformed and allowing play into the retract mechanism. Would suggest inspecting these at nose gear OH.  Joe

⬆️⬆️⬆️ I second that recommendation. 

LASAR has oversized bushings and bearings that are PMA’ed for our landing gear.

[EricJ]

16 hours ago, carusoam said:

Spindly!

 

That first donut has been completely compressed...

Go MS!

-a-

I noticed that, too, and was wondering whether the Firestone units were designed for a progressive rate or something.

[FlyingDude]

Hey guys,

Alright, today after 5hrs of work, most of which was done by me, the mains are fitted with new donuts

Tomorrow we'll do the nose. It was getting late, so we put it off.

What's the trick to remove the top collar bolt in the nose? We don't want to remove the gear door to avoid having to rig it. It seems like it's almost impossible to put any wrenches in there! How did you remove the top collar bolts off without losing your temper??

Some notes on the mains: one of them had the screw driver head towards the gear door! Removing that was a PITA. Then, when you remove the top collar, and lift the plane all the way up, the top of the rod doesn't slide off. We had to remove the bottom bolt to slide it off. We were going to replace that bolt but couldn't find the nut, so I'll replace it later on. The weight of the plane was good to squish the pucks but e have extended tanks. I wonder if it would work smoothly on planes with standard tanks. One Last thing, there was some surface rust on the parts. We cleaned them and smothered then with rust inhibiting LPV.

2 down 1 more to go...

Edited January 31, 2021 by FlyingDude

[FlyingDude]

Well... Found my answer

This post explains the procedure in detail. I had read it but apparently forgot about it... 

[carusoam]

When inspecting tube shaped items for rust...

Be sure to look down the center of the tube as well...

Some tubes rust from the inside outwards...

There are pics of some rust destroyed gear tubes around here somewhere.

Haven’t seen any fail yet, that I remember...

PP thoughts only, not a mechanic...

Best regards,

-a-

[FlyingDude]

11 minutes ago, carusoam said:

When inspecting tube shaped items for rust...

Be sure to look down the center of the tube as well...

Some tubes rust from the inside outwards...

There are pics of some rust destroyed gear tubes around here somewhere.

Haven’t seen any fail yet, that I remember...

PP thoughts only, not a mechanic...

Best regards,

-a-

Oh man... It's like... too late for the mains... Well, now you put a bug in my ear. I'll look at them with a borescope... Thanks for the tip

[carusoam]

The outside of tubes get painted...

The insides of tubes often get ignored... same with the cabin frame...

For the gear tubes... the outside is kept clean by rubber constantly moving against them...

Rust doesn’t have much opportunity to form and propagate that way..(?)

Make sure the tubes aren’t collecting any standing water in them... (?)

I don’t recall many deeper details about these tubes...  

PP thoughts only...

Best regards,

-a-

[FlyingDude]

Hey guys,

Yeah so I told my mechanic about the inside of the tubes and he said that he checked them because "that's a standard check any time you inspect any metal". You look outside AND inside. Well, learned something valuable   Thanks for bringing it up. He wouldn't have told me because that's just common practice for him. 

So the nose was a BITCH. Compressing with turnbuckle method worked great. I used the bolts and nuts removed from the main gears at the eyebolts. I helped the turnbuckle with the weight of the plane. At the end, after 2 cycles of compression, the threads looked worn out...

I recall someone here mentioning 4 hrs for all 3 landing gears and I wonder if it's Earth hours or Jupiter hours. I admit that the 2nd main gear took 1.5 hrs, less than half the first main gear, so yeah maybe 1.5 hrs per wheel is doable but I also add the time setting up and cleaning up, which is like 0.5hrs. If I were to do it again tomorrow, I would quote myself 5-6 hrs... 

[Nathaniel Reece]

On 1/11/2021 at 6:53 PM, FlyingDude said:

my AP said lifting by engine mounts is a good way, because we're lifting the engine in the end. 

I also found the bolts but they're damn expensive. Let me ask it this way: 

"Has anyone used AN bolts instead and regretted it?" 

"How/why are these bolts so Special?" They only thing I notice is that they're smooth (no threads) along their shaft and have threads only at the tips. Is that it?

 

See figure 2-1 jacking in mooney service manual.

[A64Pilot]

On 1/14/2021 at 10:34 PM, cliffy said:

How much do you want to bet that the "special" bolts are in fact standard AN bolts that have been ground or milled to the design needed to fit the application?

That would be standard practice, if it were in fact specially made and not machined from a standard bolt it’s likely it would be stupid expensive.

‘However if it were machined, then standard practice is also to send it off to be re-cad plated again, that only makes sense for batches of bolts, isn’t all that expensive, but adds time, shipping both ways etc.

So $70 a bolt really isn’t price gouging, I’ve seen and paid over a couple of hundred a bolt for larger NAS bolts, that were not special.

‘When I overhaul an engine, I send every piece of common hardware off of it, nuts, bolts etc to Aerospace defense coatings in Macon Ga and have it cad plated in gold cad plate, it’s actually very reasonable.

I’d bet though if you bought AN or NAS whichever is correct and had them machined and then cad plated as an owner produced part, I’d bet it would cost a least what Lazar charges, maybe more?

 

Edited May 2, 2021 by A64Pilot

[carusoam]

Welcome aboard Nathaniel!

Best regards,

-a-