Trim indicator cable broke

[Greg Ellis]

I have a 63 C model.  As you can see in the photos, the trim indicator cable broke at the threaded part near the stop block (left side of the block).  Anyone have a creative way to fix this?  I called an MSC but I don’t think they understood what happened.  They said just pull out the wire and thread in new wire.  They gave me a Mooney part number but said it was just piano wire.  That does not look like piano wire to me.  Any thoughts?  Thanks.  I looked in the parts catalog and the maintenance manual but could not see this cable in there anywhere.

[PT20J]

Later models had a piano wire. It looks like the bracket and the moveable part on the trim screw don't line up and this put a side load on the threaded portion which eventually caused a stress fracture. Since there are threads left on both ends of the broken part, I would try to find a female threaded barrel with the same thread dimensions and use it to reconnect the two ends after bending the bracket slightly to align them. You should probably use a die to clean up the threads before trying to screw on the barrel.

[Greg Ellis]

2 minutes ago, PT20J said:

Later models had a piano wire. It looks like the bracket and the moveable part on the trim screw don't line up and this put a side load on the threaded portion which eventually caused a stress fracture. Since there are threads left on both ends of the broken part, I would try to find a female threaded barrel with the same thread dimensions and use it to reconnect the two ends after bending the bracket slightly to align them. You should probably use a die to clean up the threads before trying to screw on the barrel.

Thanks for that.  I thought about it as well and found some at McMaster Carr but I am unsure of the thread size.  Any easy way to measure that?  Also, there is not an alignment problem. The stop block has some play in it and can be move slightly side to side to realign the cable pieces.

[N201MKTurbo]

The easiest way to figure out the thread size is to remove one of the jamb nuts and find the screw that fits it. Take it to the ACE hardware store. They will help you out. They may have the threaded spacer you need too.

[Greg Ellis]

2 minutes ago, N201MKTurbo said:

The easiest way to figure out the thread size is to remove one of the jamb nuts and find the screw that fits it. Take it to the ACE hardware store. They will help you out. They may have the threaded spacer you need too.

Thank you.

[47U]

2 hours ago, Greg Ellis said:

I looked in the parts catalog and the maintenance manual but could not see this cable in there anywhere.

The 1965-1967 IPC shows the pn as 740019.  I’m pretty sure it’s the same part as the ‘63C.  As far as fixing it… LASAR used to have the capability to rework Bowden cables, they made up a new flap retract cable for me 10 or 12 years ago.  Or, you could call your favorite MSC and get a quote for the price for a new one.  I’m sure the factory could make one up, with a few weeks lead time.  I’m sure McFarland could make you a new cable under the Owner Produced Parts program if you wanted to go that route.  Or, search for a used one from the salvage yards.      

You’ve got quite a bit of threaded rod aft of the lock nuts.  You might effect a (temproary?) repair by splicing the two broken ends together using a threaded ferrule (like the one in the pic below, from McMaster Carr).  That would generate excess wire at the other and require readjustment of the piano wire under the indicator cover housing.  Which, if it’s like mine, has a ring terminal on the end of the piano wire.  You’d have to cut the wire and put on a new ring terminal.  

One last observation, (if permitted, I’m not sure whose correct here, the IPC graphic is inconclusive) but you have both jam nuts on one side of the block, whereas I have one jam nut each on either side of the block.  (The block isn’t threaded, is it?)  

Anyway, let us know how it turns out… good luck!

Here’s mine…

[Greg Ellis]

10 minutes ago, 47U said:

The 1965-1967 IPC shows the pn as 740019.  I’m pretty sure it’s the same part as the ‘63C.  As far as fixing it… LASAR used to have the capability to rework Bowden cables, they made up a new flap retract cable for me 10 or 12 years ago.  Or, you could call your favorite MSC and get a quote for the price for a new one.  I’m sure the factory could make one up, with a few weeks lead time.  I’m sure McFarland could make you a new cable under the Owner Produced Parts program if you wanted to go that route.  Or, search for a used one from the salvage yards.      

You’ve got quite a bit of threaded rod aft of the lock nuts.  You might effect a (temproary?) repair by splicing the two broken ends together using a threaded ferrule (like the one in the pic below, from McMaster Carr).  That would generate excess wire at the other and require readjustment of the piano wire under the indicator cover housing.  Which, if it’s like mine, has a ring terminal on the end of the piano wire.  You’d have to cut the wire and put on a new ring terminal.  

One last observation, (if permitted, I’m not sure whose correct here, the IPC graphic is inconclusive) but you have both jam nuts on one side of the block, whereas I have one jam nut each on either side of the block.  (The block isn’t threaded, is it?)  

Anyway, let us know how it turns out… good luck!

Here’s mine…

Thanks for the response.  There is a jam nut in the other side.  I removed it to get the photo since it broke right at the nut.  I had two on one side and one on the other.  Thanks again.

[EricJ]

A piece of threaded standoff nut (basically a long nut) would make an easy temporary fix (maybe even a permanent one).

 

[MikeOH]

I'm still curious about what caused the fracture in the first place.  I mean, how much load can the trim INDICATOR put on that rod??

I'm with @PT20J, when I first looked at the photo I saw the misalignment and thought that side-load, over time, caused a stress fracture.  How worn is the side of that block?

[N201MKTurbo]

6 minutes ago, MikeOH said:

I'm still curious about what caused the fracture in the first place.  I mean, how much load can the trim INDICATOR put on that rod??

I'm with @PT20J, when I first looked at the photo I saw the misalignment and thought that side-load, over time, caused a stress fracture.  How worn is the side of that block?

If you watch that mechanism work, the block that the indicator rod screws into, is on a lead screw. It is kept from rotating by the sheet metal slot. You can see that there is some clearance. when you turn the trim wheel one way, the block goes to one side of the slot. When you turn the trim wheel the other way, the block moves to the other side of the slot. This puts a slight bending moment on the cable. After 61 years of this slight bending back and forth, it suffered a stress fracture.

[Greg Ellis]

An update….was able to get a coupling nut and make a fix for my issue.  These are yet another Mooney part that no longer exists.  Fortunately MacFarlane may be able to make a new one. But at least things are working again.  Thanks for all advice.

[N201MKTurbo]

I wouldn’t be in a rush to replace that cable. That fix looks stronger than stock.

[EricJ]

Yes, that's the way to fix that.    That's the same thing as the "standoff" nut I mentioned.     My only potential suggestion would be to put a thin jam nut on the end of it to keep the cable from turning in it, or maybe some loctite or something.

[N201MKTurbo]

I hate to be a smart ass. (Well, maybe not), but you have the same grease globs before the repair and after. You would think you could wiped it down and maybe put some new grease on it. 

[47U]

11 hours ago, N201MKTurbo said:

I hate to be a smart ass. (Well, maybe not), but you have the same grease globs before the repair and after. You would think you could wiped it down and maybe put some new grease on it. 

First step in lubrication is cleaning the parts involved.  My first annual (over 10 years ago)… picture of (one of the) nose gear retraction rods, aircraft was on a hangared on grass farm strip.  No excuses for this condition.

Cleaning/lubrication is something any owner can perform, as long as disassembly of the parts is not required.

[Yetti]

While we are on lube,    Clean and lube the chain, and lube all those universal joints in the trim tubes.    Makes your trim smooth as butter.

[N201MKTurbo]

7 minutes ago, Yetti said:

While we are on lube,    Clean and lube the chain, and lube all those universal joints in the trim tubes.    Makes your trim smooth as butter.

Last time I had my chain off, I cleaned it and re-lubed it with a high quality bicycle paraffin lube. It is smooth as silk and not all yucked up with grease.

[Yetti]

7 minutes ago, N201MKTurbo said:

Last time I had my chain off, I cleaned it and re-lubed it with a high quality bicycle paraffin lube. It is smooth as silk and not all yucked up with grease.

My grease was hard as a rock after 40 years.  The cheap fix is some silicone spray on the old rock hard grease.  or some TriFlow.   Either seems to loosen it up for awhile.

[N201MKTurbo]

23 minutes ago, Yetti said:

My grease was hard as a rock after 40 years.  The cheap fix is some silicone spray on the old rock hard grease.  or some TriFlow.   Either seems to loosen it up for awhile.

It should get some attention at every annual.

[PT20J]

1 hour ago, N201MKTurbo said:

Last time I had my chain off, I cleaned it and re-lubed it with a high quality bicycle paraffin lube. It is smooth as silk and not all yucked up with grease.

I cannot for the life of me understand why Mooney says to lube the chain with grease. A chain needs a less viscous lube that gets into the rollers. On mine, I had to replace the hardened brass bushing for the trim wheel shaft that had worn from never being lubed.  Also, there was some eccentricity between the top and bottom sprockets so the chain tension had to be adjusted as a compromise between too loose at one point and too tight 180 deg opposite.

[Yetti]

1 hour ago, N201MKTurbo said:

It should get some attention at every annual.

Agreed.   did not own it then.

[N201MKTurbo]

1 hour ago, PT20J said:

I cannot for the life of me understand why Mooney says to lube the chain with grease. A chain needs a less viscous lube that gets into the rollers. On mine, I had to replace the hardened brass bushing for the trim wheel shaft that had worn from never being lubed.  Also, there was some eccentricity between the top and bottom sprockets so the chain tension had to be adjusted as a compromise between too loose at one point and too tight 180 deg opposite.

I’ve never wrapped my head around that either. Grease seems dumb. 
 

l stuck the cleaned chain in a can and hosed it down with paraffin chain lube, worked it in then hung it up to dry. After it was dry, I wiped the paraffin off the surface. The chain looks brand new and is super limber.

BTW, that chain is standard chain, you can buy it for cheap on line.

[FlyingDude]

On 7/18/2024 at 10:29 AM, Greg Ellis said:

An update….

I guess you checked that but the coupling barrel does not get in the way when it moves all the way to the "right" on your picture, right?

[47U]

6 hours ago, PT20J said:

I cannot for the life of me understand why Mooney says to lube the chain with grease.

The vintage series lubrication chart specs triflow for the chain and worm gear.  My gears are not enclosed like later models, see pics in previous posts.  Could it be that when Mooney enclosed the gears that’s when they switched to grease?  Even so, the chain is not enclosed in the housing, so it makes no sense to use grease on the chain.

[N201MKTurbo]

20 hours ago, PT20J said:

I cannot for the life of me understand why Mooney says to lube the chain with grease. A chain needs a less viscous lube that gets into the rollers. On mine, I had to replace the hardened brass bushing for the trim wheel shaft that had worn from never being lubed.  Also, there was some eccentricity between the top and bottom sprockets so the chain tension had to be adjusted as a compromise between too loose at one point and too tight 180 deg opposite.

I was thinking about the grease some more. While lubing the chain with a good chain lube is better for the chain, grease is probably better for the sprockets. So adding a few dabs of grease to the inside of the chain would reduce ware on the sprockets.