Main gear rubbing on tension bar.

[Will.iam]

After replacing my worn out donuts on the main gear, i have noticed my left gear has wear marks on the front. Crawling up under the gearwell i see marks on my tension rod. I don’t think the gear has shifted but maybe my rod has? This is frustrating as i had a MSC do the donut replacement and check the gear tension. What could be causing them to contact each other? And more importantly how do i get it fixed to not keep rubbing?

[PT20J]

Does the logbook entry show they did a retract test after completing the work?

[Will.iam]

It was when it was in annual i know they checked the gear at annual but ill double check for the statement. 

[PT20J]

I would take it back to the shop. If they did something incorrectly, they should fix it and learn from the situation. 

[Will.iam]

  On 2/11/2022 at 3:44 PM, JohnZ said:

@Will.iam I had a similar issue with my 76’ F. I don’t remember what the part is called, but essentially it is just a spacer. Mooney makes these spacers in various sizes… the taller ones push the gear further back in the wheel well. The shorter ones bring it forward. Call Dan at Lasar. I bought 2 from them and kept the one that worked best, returned the other. 

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Thanks for the info. where does said spacer go in the picture? Maybe they left mine out altogether? 

[EricJ]

That spacer looks like a good way to fix it, but I'd try to figure out what changed to make it need a different spacer.

 

[Will.iam]

  On 2/11/2022 at 11:54 PM, EricJ said:

That spacer looks like a good way to fix it, but I'd try to figure out what changed to make it need a different spacer.

 

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I’m thinking i might not have the spacer will have to go and double check maybe they left it out by accident. I hate when i have left over parts from reassembling something. 

[1964-M20E]

I don't think the spacer would cause this.  The main part of the gear showing wear is not affected by the spacer on top of the shock disc link.

I would look at the main gear retraction truss.  With the gear half retracted see how much play there is at the main retract tension bar and the retract truss.

[1980Mooney]

  On 2/10/2022 at 10:51 PM, Will.iam said:

After replacing my worn out donuts on the main gear, i have noticed my left gear has wear marks on the front. Crawling up under the gearwell i see marks on my tension rod. I don’t think the gear has shifted but maybe my rod has? This is frustrating as i had a MSC do the donut replacement and check the gear tension. What could be causing them to contact each other? And more importantly how do i get it fixed to not keep rubbing?

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I agree with @PT20J and @EricJ but I WOULD NOT FLY THE PLANE.  THERE IS NO NORMAL WAY THAT THE RETRACTION TUBE SHOULD BE ABLE TO CONTACT THE MAIN GEAR ASSEMBLY. Something is seriously wrong. I would fear a main gear collapse which would be incredibly expensive. The geometric arc of the swing of the main landing gear assembly (2 below in yellow diamond) and the movement of the retraction tube truss holding the retraction tube (16 below in green box) is defined, fixed and should remain stable and repeatable through its operation and life.  @1964-M20E is right - It does not vary with shock disk load or compression and has nothing to do with the shock dics.  (see the first video below - no way should it contact).  I would jack it up and conduct a retraction test carefully looking at the reason for contact.( Like in second video.)  I am not an A&P but have worked on my plane a lot over 23 years. 

• The main gear assembly (2 in yellow diamond) is a solid fixture.  You are contacting at the point of the red circle.  Compression of the shock disks has nothing to do with the geometry of the main gear assembly.
• The only way it could contact is if 
  • The main gear assembly (2 yellow diamond) is bent or flexing because of a broken weld or corrosion.
  • The main gear assembly brackets (4, 6 and on the other end purple pentagon) are broken, loose or excessively worn allowing the main gear assembly to shift.
  • The retraction truss (green box) is cracked or broken and flexing towards the landing gear as pressure is applied in the retracted position.
  • The bushing in the hinge of the retraction truss is missing (on bolt 19 in blue star - part number 914020-143) allowing it to twist and flex toward the landing gear as pressure is applied in the retracted position.
  • The bolt holding the retraction truss or threaded backer (19 in green box) is loose, cracked, or bent allowing it to flex toward the landing gear as pressure is applied in the retracted position.

Do you have a parts manual and also a service manual?

Also look at these 2 Mooney gear retraction videos.  The first one clearly shows your gear retraction geometry.

 

Also this video shows it but not as clearly.

Mooney M20J 201 Gear Swing and Emergency Retraction Test - YouTube

 

 

Edited February 12, 2022 by 1980Mooney

[1980Mooney]

Interestingly here is a parallel current discussion on pre-J Mooney's landing gear.  The gear is basically the same.

 

Edited February 12, 2022 by 1980Mooney

[67 m20F chump]

The tube it’s rubbing against isn’t exactly thick.  This could get ugly.

[1980Mooney]

  On 2/14/2022 at 11:48 AM, 67 m20F chump said:

The tube it’s rubbing against isn’t exactly thick.  This could get ugly.

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And expensive. Only Mooney sells that.  I had to replace one about 8 years ago due to corrosion. 
And even more if breaks…the gear will collapse. 

Edited February 14, 2022 by 1980Mooney

[IvanP]

Resurrecting an old topic. I just found similar marks on my Bravo after having the shock discs changed. 

@Will.iam how did you resolve your issue? 

Regards,

Ivan 

[Joshua Blackh4t]

  On 2/11/2022 at 3:34 PM, PT20J said:

I would take it back to the shop. If they did something incorrectly, they should fix it and learn from the situation. 

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Maybe some people think like that.

Personally, I look at it this way: had they picked up the problem at the gear swing test, then they would spend another x hours getting it right and then charge for that time.

Since they weren't paid for the extra work in the first place, they shouldn't do if for free now.

So by all means take it back, I would hope they help out by fitting you straight in and maybe a reduced price, but certainly not free.

People are not perfect, troubleshooting faults is part of every job. 

[kortopates]

Couldn't agree more. I had that happen to me noticed it immediately doing the retract test  and I tracked it down to small change in length in the new shock disk link tower from Lasar. I couldn't get Dan at Lasar to exchange with another so I ended up purchasing a second one and gave him his old one back. The second shock disk tower link solved the issue but it cost me. LASAR sells a PMA's version of the shock disc link tower which is what I used - I've used them before from them but that was the only one that gave me a problem. 

As these are hand made airplanes I couldn't see asking a mechanic for a discount because new parts didn't fit as well as the prior ones.

Bigger tires can cause this issue too, but this of course wasn't from a change in tires. But I am using the thickest tire treads with minimal clearance here - Goodyear Custom III's.

[PT20J]

  On 9/4/2023 at 8:28 PM, Joshua Blackh4t said:

Maybe some people think like that.

Personally, I look at it this way: had they picked up the problem at the gear swing test, then they would spend another x hours getting it right and then charge for that time.

Since they weren't paid for the extra work in the first place, they shouldn't do if for free now.

So by all means take it back, I would hope they help out by fitting you straight in and maybe a reduced price, but certainly not free.

People are not perfect, troubleshooting faults is part of every job. 

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You completely missed my point. I never mentioned who should pay for anything. That's entirely beside the point. I simply said that I would take it back to the shop that worked on it. They are in the best position to review what was done and why there is a problem. And, in solving the problem, they will learn something that they can apply perhaps in the future. That's how maintainers become experienced.