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Manual Gear Rigging Annual Time


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Doing our first annual on new to us 63 M20C. All for cylinders compression 79, so I should be happy about that.  Starting the gear rigging process over the weekend. If anyone knows of more than just service manual information, videos or advice on the gear rigging process it would be greatly appreciated. I’m assuming some chafing on the tail fairing is inevitable?  The A&P/IA and I are practicing “Social Distancing”, making sure the Mooney is not within 15’ of Cessna or Piper.  

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+1 on proper aircraft spacing in such critical times... :)

All the other planes are jealous of the Mooney’s foldable legs...
 

1) There may be some chafe tape that can be put on the underside of the sheet metal piece that is messing up the fancy paint...

2) Also check for some rubber spacers that may supposed to be between the cover Sheet metal and the fuselage...

3) The sheet metal cover may have some shape to it that indicates that the little rubber spacers belong there...

Some parts go missing over the decades...

I think I remember the spacers being stuck to my M20C’s paint...

PP thoughts only, not a mechanic...

best regards,

-a-

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Gear rigging is actually fairly straightforward, and is easier done than described.  Once you and your mechanic get going on it, you'll most likely get the understanding of the process quickly.  I will add a few observations/comments below picked up over the years.

- a "click" type torque wrench isn't as useful as the old style "needle" ones.  The problem is that the click will happen and pop the overcenter lock open.  It's difficult to tell if it's right or not. Not impossible, but more difficult.

- make sure you're using the proper values.  There was an AD and Service Bulletin that changed some of the components and also the torque values.  You can't just go with the service manual, although that does describe the methods well.  I've attached a copy of the Service Instruction below as a photo.

- the torque measurement is taken just as the overcenter begins to move.  There is an actual measurement value given in the book, and you can definitely use a feeler gauge for the exact measurement. The only problem is you'll destroy that feeler gauge by the overcenter link crushing it.  Just cut apart a beer or coke can and use that instead.  After doing a few, your fingertip gets 'calibrated' to the feel.

- if you have to adjust one of the gear, expect to have to adjust all of them.  As one gear is tightened or loosened, it will affect the other gear values.

- perhaps most importantly: realize that the gear is probably already rigged correctly.  These things have very little wear and generally don't change one year to the next.  If your torque readings are incorrect, your first assumption should be that you took the readings wrong.  Go back and double check, ask other people to help check it also, and don't adjust the rigging until you're all in agreement that the torque values need to be adjusted.  There are stories here on MooneySpace where an M20C went to a new shop, they adjusted the gear rigging, and the gear collapsed.

- too tight is as bad as being too loose.  If the nose gear is rigged too tight, it can break the retraction truss at the welds and the nose gear will collapse.  Again, there are stories and pictures here on MooneySpace. 

- I have seen a mechanic want to change the gear settings in order to get the gear doors to close fully.  This is especially possible pre-1964 models- in 64 they changed the gear door attach fittings and/or pushrods.  This is wrong, dangerous, sloppy, and lazy.  Use the service manual exactly as written, except the torque values- use the Service Bulletin/Instruction for that.

Good luck, let us know how it goes.

Andy (A&P/IA)

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B201MKTurbo. I apologize for perhaps using the wrong phrase. We are about to check the rigging or preload. We do not intend to change the rigging unless clearly out of spec. My understanding is this gear is very robust and the “if it ain’t broke don’t fix it” principle definitely applies. 

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One item to look at are the two pushrods for the nose gear. You have two solid rods with no springs in them IIRC . The later electric gear models have springs in them and one only measures the torque on the main gear over centers and then the squish of the springs for the nose gear.

With you having the two solid rods getting BOTH to have similar "pressures" can be a challenge if you do wind up having to go all the way to a rerig. I check them just by trying to twist the rods on the Heim joints (with the gear down) to see if they are about the same force. Usually one is real loose and one is tight. Done correctly they both have some pressure on them (resistance to twisting the Heim joint) but maybe not perfectly the same. 

If after you get the rigging correct and you need to adjust the nose gear doors  more than the rods allow then you will have to reset the eccentric bushings in the gear truss and then go through the entire rigging exercise again. The eccentrics adjust how far the nose tire goes into the nose well and by connection, how far the nose gear doors close. They are a b^&*( to adjust). 

It would sure be nice if we could just use the later spring rods on the early models. It would make setting the rigging way easier. 

 

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On 2/24/2020 at 6:52 AM, M20Doc said:

From Mooney.com , under the support tab there is a manual revision check list.

Clarence

 

On 4/3/2020 at 7:21 AM, N201MKTurbo said:

I always get nervous when I hear someone is rigging the gear. If it is out of rig, It is probably because someone else rigged the gear...

 

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Cliffy, thanks for the info and help. However my nose gear retract rods are not solid they have the springs, see attached picture. The plane is a 63 D models that the factor converted to C with retractable gear in the late 60s. So I guess the question is, do we follow the manual gear procedure for the mains and the electric gear for the nose?  I do not see in the logs where these rods were changed since the factory conversion.   Thanks

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Sorry to beat this to death.  I went through the logs and some really old documents that came with the plane.  Found the itemized invoice and documentation that came right from the Mooney factory that did the conversion in 1966.  Apparently it was a program for D owners to take their factory new plane back and have them converted for about $1800, was a lot of $ back then.  At any rate both retract tubes part numbers on the documents traces back to the Service Manual and Part Catalog to be with ones with the springs not the solids.  So confirmed, the factory did it so it is original equipment.  The owner declined the electric gear option, but "actuator bracket installed" as well as some other electric components.  I assume if to be later modified. (No thank you)  LOL

The fun part of the Service Manual is it doesn't say much of what to do with the springs, other than 0.060".  The older style 62,63,64 years have 0.060" space between the spring and a collar.  The 65 and later (what I have) there is not that space, so not sure what/where to measure or if 0.050" is unacceptable. 

It was funny how we figured out this difference.  The mains once we learned how little the over center moves and should read the torque were all well within the acceptable range.  Went to the nose gear and it was WAY off.  Those springs on the tubes must make a big difference.  It appears they compress as you put the gear into over center lock and unload a little once in OC.  Start to raise gear and they compress, load just before the OC moves.  Had four A&P's in the shop today all had their comments none had Mooney experience, but plenty to say.  The A&P I use who has some but not a ton of Mooney experience ignored them and said the system is working smooth and nice, mains in spec, the springs on nose tubes a good thing and we are not going to start chasing our tails into a problem that doesn't exist and result in a bigger problem.  He was more interested in carefully and methodically inspecting the entire retract system for corrosion, weld cracks and proper lubrication per the manual.

I have a lot of cleaning to do.   LOL  Thank you everyone for your help.  hopefully I made sense?

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You're not beating anything to death. Its all fun for some of us to try and help. 

One thing to remember is that with the springs you don't need to check the nose gear over center torque. The over centers are held in place by the compression of the springs on the push rods. That is why the spring compression is measured to make sure enough "pressure" is applied to the over center mechanism to keep it over center   when the gear is down,  just like the pressure from the solid rods do.

The spring rods have been engineered in such a way the Mooney knew how much  pressure they would exert at the required compression distance, thereby providing enough over center locking to keep the nose gear down. (We are disregarding any age related lowering of the compression pressure due to being constantly compressed for 50+ years)

All you need to do is measure how far the springs are compressed between gear unlocked and down and locked.  If you watch it carefully as it goes over center you will see where you can put a pair of calipers and measure the compression when fully down ans locked.  To increase the compression just lengthen the rods at the Heim joint ends. 

Your records are an eye opener as far as the spring rods go. That tells me even Mooney had no issue with them being used. Anyway, they have been in for so many years that any issues would have shown up by now I'm sure. Like I said mine had it done also but they used the solid rods,

You might have found a reasonably good A&P Someone with some common sense.

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Cliffy, thank you for your kindness and patience. I too enjoy learning all I can but don’t want to annoy the group. The process you described is exactly what the A&P did measuring with calipers. I appreciate that he doesn’t get in a just get it done attitude but says let’s do some research I would rather take time to do it right than get it done wrong. He usually doesn’t charge for at least half his time.  He admits he is particular slower likes to research and explain so doesn’t charge for that. 
 

I had an old taylorcraft in great shape. I went to several shops in the area and they messed stuff up for a lot of money. I learned of Ed who was chief for museum and restored a B17 several others and his latest is a flying MiG 17. No one wanted to work on the Mooney, he was happy to. He loves how it’s made engineering and says it’s spacious to work on compared to the MiG. Lol

we will keep plugging away at it.  Thanks again

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