Things that make you go, "Hmmmm"

[Guitarmaster]

Well, the pre-buy went pretty well with only one squawk; the trim torque tube.  See attached photos....

Best guess is someone did the bushing AD, but didn't replace the shaft(s) since there were plastic bushings in all the bulkheads where it passes through.  So, guess what I get to do! 

When your plane goes to annual, probably not a bad idea to check this.  The shaft is thin .035 aluminum and it looks like it was cut with a pipe cutter in three places.

Cheers!
 

[carusoam]

Great pirep, Matt

And pics too.

Best regards,

-a-

[Guest]

Reference S/B M20-185 for wear limits.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-185-1.pdf?t=1540312073554

Clarence

[Guitarmaster]

Reference S/B M20-185 for wear limits.
https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-185-1.pdf?t=1540312073554
Clarence

Thank you Clarence. The deepest groove measured with a pin gauge was .005 so we caught it in time. Presently in the process of completing SB M20-185.

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[Ragsf15e]

It’s fun if you need a new one.  Ask me how I know... had to have it replaced at annual at Top Gun.  Expensive, took very long time to get a new one from the factory, expensive.  That about covers it.

well, that and previous annual was at a different msc and they didn’t mention it... did it get that bad in 1 year?

Edited October 25, 2018 by Ragsf15e

[Igor_U]

My 67F has no grommets but phenolic blocks in place and not affected by this SB.

Nevertheless, one of the tubes got worn and my IA asked to be replaced few years ago... As you mentioned not readily available due to different rod ends (I think it was unique p/n for that ne year) but LASAR came with their replacement -  expensive for sure but cheaper then ordering new from factory.

[pilot_jb]

Grease grooves.   

[Ragsf15e]

This discussion and the PTSD from getting a new trim tube from the factory inspired me to look at mine today (it’s in annual anyway).  Is the only wear place where it goes through a bulkhead just aft of the battery/avionics bay door?  Mine seems to have black blocks installed on the bulkhead that support the trim tube just above the bulkhead instead of it setting on the bulkhead.  My IA said “sacrificial material”.  It still has black lines on it from rubbing against this material but is not “cut” into like the op pictures.  Is that just how they wear?  Wear on sacrafial blocks until those wear down and then wear on the bulkhead if you don’t catch it?

[carusoam]

Rags, for more detail see the use of phenolic blocks in the posts above...

There were a few ways Mooney did this.

The blocks are definitely heavier...

Best regards,

-a-

[Browncbr1]

I’m glad I decided to pull my trim shafts this year.  The middle and rear phenolic blocks were ok, well away from aluminum.  However, the front one was clearly letting the shaft rub the bulkhead.  Luckily, the wear is about half of the allowable limit, so I’m good to go with new grommets and tape.  

 

[DXB]

On 10/25/2018 at 12:33 PM, M20Doc said:

Reference S/B M20-185 for wear limits.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-185-1.pdf?t=1540312073554

Clarence

Hmm - I originally thought this AD didnt apply to me - it starts at 6800079 for the C models, and I have 680002.  Then I noticed the comment in to check older models to see if they have the nylon grommets rather than the older mica bearing blocks.  So I did that.  Hmmm. The rear bulkhead passthrough has no grommet whatsoever - I don’t know what a “mica bearing block” is supposed to look like BTW.   Can it break and fall off?  I also see zero wear on the tube- like it’s never been in contact- luckily.   So I need to install grommets and tape? Am I missing something?  

[BigD]

Hmm - I originally thought this AD didnt apply to me - it starts at 6800079 for the C models, and I have 680002.  Then I noticed the comment in to check older models to see if they have the nylon grommets rather than the older mica bearing blocks.  So I did that.  Hmmm. The rear bulkhead passthrough has no grommet whatsoever - I don’t know what a “mica bearing block” is supposed to look like BTW.   Can it break and fall off?  I also see zero wear on the tube- like it’s never been in contact- luckily.   So I need to install grommets and tape? Am I missing something?  

I’d like to know as well!


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[Browncbr1]

One thing I’ve come to believe while doing this project is that all the wear on my trim tubes actually are a result of dirt and grit that was mixed into a thick paste where someone had been lubricating the phenolic blocks.   If anything is to be used, it should be dry like graphite powder.   Otherwise and dirt or dust will stick and wear it down like sand paper.   

Secondly, if you are taking it apart, make clear note of trim position at both ends of the system.  Otherwise, you may put it back together out of original travel stop positions.   Secondly, the universal joints and bushings were drilled by hand, so they only go back together in one orientation for the pins to fit correctly.   Mark everything with sharpie to help orient when putting back together.  

Edited July 23, 2019 by Browncbr1

[Browncbr1]

On 7/21/2019 at 8:59 AM, DXB said:

Hmm - I originally thought this AD didnt apply to me - it starts at 6800079 for the C models, and I have 680002.  Then I noticed the comment in to check older models to see if they have the nylon grommets rather than the older mica bearing blocks.  So I did that.  Hmmm. The rear bulkhead passthrough has no grommet whatsoever - I don’t know what a “mica bearing block” is supposed to look like BTW.   Can it break and fall off?  I also see zero wear on the tube- like it’s never been in contact- luckily.   So I need to install grommets and tape? Am I missing something?  

There is a bulkhead that is the aft wall of the luggage compartment (forward most wall of eppenage).  There is nothing on that bulkhead.   The aft bulkhead is located to the right as you look into the tail inspection panel.  It is right infront of the universal joint.

[DXB]

2 hours ago, Browncbr1 said:

There is a bulkhead that is the aft wall of the luggage compartment (forward most wall of eppenage).  There is nothing on that bulkhead.   The aft bulkhead is located to the right as you look into the tail inspection panel.  It is right infront of the universal joint.

Ah thanks - solves my confusion.