Squat-method landing gear disc replacement

[FlyingDude]

Hey guys,

I read the other threads and saw the various methods of how to compress the pucks. Many people say that the discs on mains can be compressed by the plane's own weight. Does that hold true for an E? I just wanted to make sure that this quick method is not only for the newer & heavier models ...

Thanks guys.

Edited January 9, 2021 by FlyingDude

[MooneyMitch]

My experience..... yes, it will work on the E model.

[FlyingDude]

Great, thanks. Did you have to remove the bolt on the bottom (shock link) or was it sufficient to remove the top bolt (leg truss assy) only? Can you slide the old donuts off and slide the new ones on and insert the center rod into the leg truss assy with only the top bolt removed?

Thanks

[Super Phreek]

When I replaced the donuts on my C, I was able to leave the lower bolt in place.  The donuts just slid off with only the top bolt removed.  Make sure your tanks are full to get compression on the new donuts.

Derek

[FlyingDude]

Awesome. Thanks for your help guys

[FlyingDude]

I guess I won't have to bother to do the puck rotation test... Lol

[LOCOLJ]

It does work on an E, we just did it.  Perhaps you may find this useful, we placed  2x4s under the tires to not have to draw the jacks so far down to the floor.  It also allowed us to manipulate the shaft and bolt into place by using a bit of leverage. 

[FlyingDude]

This is a good tip. Thanks. How high do you jack the plane up? I built my own jack with a threaded central rod. Same height adjustment range as the ones on spruce. I just don't trust myself with lowering those hydraulic lifts... Bounced the car on the ground too many times. Don't want to repeat it with the plane

How do you lift the nose? By the engine lift, jack under the prop or pull down on the tail? The engine method should be the official method now but finding a hoist is not that easy around here...

Thank you.

[Bob E]

2 hours ago, FlyingDude said:

How do you lift the nose? By the engine lift, jack under the prop or pull down on the tail?

 

This works to lift the nose.  A solid steel bar (such as a breaker bar) is pretty stable.  Use a longer bar than in the photo if you want to lower the nose onto jack stands.

[Prior owner]

If you plan to change the nose discs and you have a spacer installed under the collar (per the SB), you will probably need to rent/borrow the Mooney nose gear compression tool (or add lots of weight to the nose with a method shown above). It takes a lot of pressure to compress a new set of discs with a spacer installed.

Also- two 3 ft lift straps wrapped around the top engine mount tubes (at the firewall) with a shop crane is an easy way to lift without having to remove the doghouse. The engine hoist point on a Lycoming uses a one small bolt through the aluminum case- most shops frown upon lifting from the engine hoist point. Not good for the engine or for you....don’t weight the tail, and don’t lift by the prop.

Edited January 9, 2021 by PilotCoyote

[FlyingDude]

Thanks guys. Bob E's method is a pretty smart one. You can use it if you remove the wheel but the donuts still bear the plane's weight. You can't use this method while changing the nose donuts, but it'll work to keep the nose high while replacing the mains donuts.

PilotCoyote that's a pretty nice method. I'll check that with my AP and see if I can find a hoist. I don't know if I have the spacer. I'll look into that. Do you have a picture/link to the SB at hand? I'll Google it but you know...

Anyway, I was planning on using a compression tool for the nose. 

Is a gear swing mandatory after puck replacement? How do you make sure that the gear won't lock at landing?

Thanks again

Edited January 9, 2021 by FlyingDude

[Prior owner]

Mooney Service Bulletin M20-202

Per the above SB, the spacer is suggested if your nose gear geometry is off. Note that it will raise the height of the wheel in the wheel house when the gear is retracted (possibly causing contact with the wheel house?), and that it will drop the nose a bit, reducing your prop to ground clearance. I forget the measurements that I took, but a small spacer in that location does lower the nose more than you might think.

If you don’t have issues with steering/tracking on takeoff or landing, it might be best to skip the spacer. See article by Don Maxwell on “the 8 second ride”.

[M20F-1968]

As with most things regarding aviation, and particularly if you expect to own the plane for many years, but the proper tools to avoid injury to yourself and damage to the plane.

John Breda

[carusoam]

Seeing if @KLudwick is wandering by... a question that came up recently...

 

+1 on proper jacking techniques... lifting the plane by the engine, makes no sense...  it looks right, but can’t possibly be right...

if you have ever seen pics of engine case cracks... You know the case is already stressed to the max under ordinary conditions... why go with something that only looks right..?

PP thoughts only, there are threads around here that cover jacking techniques... and pics of the failures...

Best regards,

-a-

[carusoam]

5 hours ago, FlyingDude said:

How do you make sure that the gear won't lock at landing?

Thanks again

Following the Maintenance Manual is the best way to go...

The docs are simple, easy to follow, and keep you from making a bunch of easy mistakes...

Some assumptions are made, like the mechanic has been trained and has experience... and some of the basics have been superseded...

PP thoughts only, not a mechanic...

Best regards,

-a-

[FlyingDude]

Yeah guys, I appreciate the legal advice and the "don't try this at home" warnings... The official maintenance manual is 50+ years old. That very document calls for lifting by the prop, which the prop company later forbade! The MM has been superceded by SBs that call for lifting by the engine (which some of you call nonsensical... So it's not just about finding printed papers and following them...

As for the "leave it to the professionals" calls... I've seen some monkey business performed by "trained and certificated mechanics"... So I trust very few mechanics. Mine is at the top of the list  

Anyway guys. When an engine is removed, the plane squats on its tail. So, lifting the engine by the engine hook or mounts only lifts the weight of the engine. I just talked to my mechanic and he says that the tail-down method is pretty safe but if I wish so, lift-by-engine-mounts is also viable. That's what we're going with...

Thank you all for your input. This was very educational for me.

 

[carusoam]

There is also advice of not pulling or pushing on the prop... while moving the plane... 

Some engine mounts got fancy Jack points on them... (IO550s)

It really comes down to what could possibly go wrong when things slip or fail or get hit too hard...

The engine is kind of an expensive thing to use for pulling, pushing, or lifting...

Cheap lifting devices can slip out of their jacking points... or accidentally lower themselves...

+1 for not trusting anything... sort of... expect and plan for something to go awry... 

Then celebrate when the job is completed properly, at an affordable price!

PP thoughts only...

Best regards,

-a-

[Mooneymite]

5 hours ago, FlyingDude said:

 I don't know if I have the spacer. I'll look into that. Do you have a picture/link to the SB at hand? I'll Google it but you know...

Here's a picture of the spacer....

Edited January 9, 2021 by Mooneymite

[Mooneymite]

[FlyingDude]

Thanks. Could you post a pic of the spacer's height as well? 

[Hank]

6 hours ago, FlyingDude said:

Thanks. Could you post a pic of the spacer's height as well? 

My calibrated eyeball says it looks to be 1/8" -- 3/16". 

[M20F-1968]

16 hours ago, FlyingDude said:

Yeah guys, I appreciate the legal advice and the "don't try this at home" warnings... The official maintenance manual is 50+ years old. That very document calls for lifting by the prop, which the prop company later forbade! The MM has been superceded by SBs that call for lifting by the engine (which some of you call nonsensical... So it's not just about finding printed papers and following them...

As for the "leave it to the professionals" calls... I've seen some monkey business performed by "trained and certificated mechanics"... So I trust very few mechanics. Mine is at the top of the list  

Anyway guys. When an engine is removed, the plane squats on its tail. So, lifting the engine by the engine hook or mounts only lifts the weight of the engine. I just talked to my mechanic and he says that the tail-down method is pretty safe but if I wish so, lift-by-engine-mounts is also viable. That's what we're going with...

Thank you all for your input. This was very educational for me.

 

When I place my plane on jacks, it is always on 4 points.  Two Meyers jacks with locking pins on each, a hydraulic engine hoist with a locking collar and a cement tail weight on wheels made for the aircraft.  In that configuration it is quite stable.

John Breda

[RobertGary1]

It was also suggested to me to purchase all New hardware before starting as the bolts etc may come out well seasoned in rust. 

[FlyingDude]

Thanks, that's a good tip. Are original part numbers available? Did you get equivalent hardware from spruce or hardware store?

[Super Phreek]

The original part numbers are available through aircraft spruce.