Oxygen knob/wire failure

[DaveMC]

so I just had my oxygen knob fail today. the wire inside is presumed to be broken.  

 it looks like I have to remove the entire PORT side plastic panel to get to the mechanism and that panel goes up ender the instrument panel and all the way back to the baggage compartment.  

I have a 94 Bravo TLS. 

 

any suggestion or advice?

 

[larryb]

There are numerous threads on this topic. IMO, it's a weak point in the Mooney design. If you need a new wire, you do not need to remove the entire interior front to back. Just the seats and the pilot side panel. Get a new wire and feed it through the existing casing. Add some tri-flow as you feed it in. The wire typically breaks at the knob where it is wound around a pin. There may well be enough slack at the tank end to pull some through and not need to replace the wire core. But I figured why go to all that trouble and still have the old brittle wire when for just a few $ more I can have a nice new wire that I hopefully won't have to deal with again. 

https://www.mcmaster.com/catalog/9495K92

[carusoam]

Looks like we lose one connection every few months....

Sometimes it is lost at the cabin end...

Sometimes it is at the bottle end...

The bottle end is pretty easy to check.

The search function will probably reveal a few pics of what needs to get done...

Best regards,

-a-

[DaveMC]

yeah. its the pilot end.... the bottle is intact....ugh.  guess im gonna need a few hours on this one.  

[DaveMC]

11 hours ago, larryb said:

There are numerous threads on this topic. IMO, it's a weak point in the Mooney design. If you need a new wire, you do not need to remove the entire interior front to back. Just the seats and the pilot side panel. Get a new wire and feed it through the existing casing. Add some tri-flow as you feed it in. The wire typically breaks at the knob where it is wound around a pin. There may well be enough slack at the tank end to pull some through and not need to replace the wire core. But I figured why go to all that trouble and still have the old brittle wire when for just a few $ more I can have a nice new wire that I hopefully won't have to deal with again. 

https://www.mcmaster.com/catalog/9495K92

Thanks Larry. and thank you for the link.  but which wire is it?

[DaveMC]

sorry Larry looks like you laid it out for me on the link

 

thank you

[DaveMC]

20 hours ago, larryb said:

There are numerous threads on this topic. IMO, it's a weak point in the Mooney design. If you need a new wire, you do not need to remove the entire interior front to back. Just the seats and the pilot side panel. Get a new wire and feed it through the existing casing. Add some tri-flow as you feed it in. The wire typically breaks at the knob where it is wound around a pin. There may well be enough slack at the tank end to pull some through and not need to replace the wire core. But I figured why go to all that trouble and still have the old brittle wire when for just a few $ more I can have a nice new wire that I hopefully won't have to deal with again. 

https://www.mcmaster.com/catalog/9495K92

Hey Larry I’m going to upload a picture of the panel. I removed the seats and removed all of the surface screws for this panel but it appears to be held in inside behind the armrest. I took a picture. I gave it a little bit of a tug but did not want to keep pulling. How do I get it off when it appears to be attached at the armrest?

 

 

[larryb]

Mine is a 97. It has been 3 years since I did it but I don’t recall it being bolted at the arm rest. First I’d remove the lower vertical carpet piece. Also remove the rear seat shoulder harness bolt. I recall a few screws in the rear that are hidden behind plastic plugs. Once all the screws out I am pretty sure it just lifted out. It wedges in by with side window glass so it definitely needs to be lifted out. Finding all the screws was my biggest problem.

[DaveMC]

Sooooooo.  I did it all got it out switched out the wire and coiled it around a nail. attached it and put it all back k together and it was going fine. ...  now it isn't ,  I think the coil slipped off the peg. any sage words of advice as I pull it all back off and start over?

 

 

[carusoam]

Bummer...

There may be a better method of making the loop at the end of the hardened wire...

If it’s a hardened wire....

Did you have any difficulty making the loop?  
 

If it broke or wouldn’t hold its shape... signs of hardened wire...

Push/pull controls are often hard wires...

Annealing the end will allow for making a good loop...

I learned this from watching a guy repair a lawnmower throttle when I was about 10...

So... if this is at all helpful... that guy is about 80+ now I can always call him for more detail...  

 

There is probably a safety wire technique that holds your loop in place...

Best regards,

-a-

[DaveMC]

I made a good loop using a small caliber screwdriver. I think it just slipped of.  I was honestly wondering how in the heck it was inns stay on in the first place.   there is nothing there to prevent it from slipping off. 

[carusoam]

Dave,

Did you see Mark’s thread?

He May have better pics...(?)

The system is too critical to not have connected in a known way...

Another resource for info would be the company that supplies the O2 system... or the Mooney parts and MMs...

Might invite @M20Doc to see if he has insight... (O2 system control wire connection...)

-a-

 

[DaveMC]

Yeah it liked justice that and I thought I did a really good job of making a tight coil.  I was worried it might slip off just because of the angle of twist in the cable.  Ill be pulling it all back out tomorrow   just wonder if anybody. had any tricks about getting it yo stay on.  

[larryb]

I wrapped my cable around a nail clamped in a vise. I did it pretty tight, and it's tight enough that it took a pair of pliers to snap it on the knob. I have not had a problem with it coming off. I did have problems with keeping the gears meshing and had to stake the rivet that holds the gears to the backplate to tighten it up. Somebody here made a nifty clamp, but I don't have the appropriate tooling for that. 

 

The good news is now that you've taken it apart once it'll go twice as fast next time.

 

Larry

[FoxMike]

You might consider some lube ( triflow) on the cable to cut the friction.  I had the bottle outs the cable ws loose.  Put a liberal amount of triflow down the cable twice.  Worked much better when I got done.

[DaveMC]

20 hours ago, larryb said:

I wrapped my cable around a nail clamped in a vise. I did it pretty tight, and it's tight enough that it took a pair of pliers to snap it on the knob. I have not had a problem with it coming off. I did have problems with keeping the gears meshing and had to stake the rivet that holds the gears to the backplate to tighten it up. Somebody here made a nifty clamp, but I don't have the appropriate tooling for that. 

 

The good news is now that you've taken it apart once it'll go twice as fast next time.

 

Larry

So I got her all apart AGAIN    It did slip off.  so I recut it and made a very tight coil.  reassembled it and worked it back and forth a few times and this is what it looks like.  the coil is un-tightening as you move it back and forth.

This is such a bad design. Anybody do anything different to keep the coil from doing this. 

 

[larryb]

How much resistance is there? My knob moves easily, not nearly enough pressure to unwind the loop.

[carusoam]

What retains the wire on the post?

Is there a clip to go with that, or a hole?

Something has to act as a retainer... to keep ordinary vibration from making it fall off...

PP thoughts only, not a mechanic...

Best regards,

-a-

[DaveMC]

1 hour ago, larryb said:

How much resistance is there? My knob moves easily, not nearly enough pressure to unwind the loop.

There is some pressure on it particularly when I am threading the inner wire.  I need to get lubricant further aft so I am going to try and use some triflow further aft.  other than that I have no clue

[DaveMC]

50 minutes ago, carusoam said:

What retains the wire on the post?

Is there a clip to go with that, or a hole?

Something has to act as a retainer... to keep ordinary vibration from making it fall off...

PP thoughts only, not a mechanic...

Best regards,

-a-

Thats what I thought. But nope no retainer and no hole

[carusoam]

Dave,

I spent some time just looking for the tank’s valve, and how it gets controlled...

These parts are standard in the aviation industry...   they should have all the details nicely documented around the net somewhere...

Best regards,

-a-

[larryb]

With the inner wire removed try to blow compressed air into the casing from both ends. Then spray tri flow into the empty casing from both ends. Then as you feed the wire spray some tri flow on it every foot. Verify the tank valve moves easily. There is no retainer for the wire at the knob end.

[DaveMC]

Thank you all for your help and suggestions.  I thought I would post a detailed account of my experience and chalanges and what I did in case it might help someone else.  

I have a 1994 Bravo TLS

First,  taking the side panel off was a lot easer than I thought once I did two things. remove the pilots side rear seat and remove the retaining nut on the oxygen knob.  Obviously the pilots sent needs to be removed. I took out both front seats to make the job easier.  

On the arm rest electronics I marked one with a sharpie and took pictures of their current positions to speed the reassembly. 

The coiled wire that the solid wire moves in is porous so spraying triflow in one end or the other only gets the lubricant about a foot or so down the line. so I sprayed any exposed coil wire along the length with a bit of triflow. reasoning that it would penetrate into the hollow core.  It worked. I held a cloth behind the wire to prevent oil overspray from getting all over.  I also sprayed  the wire during insertion.  

The core wire: Comes pretty tightly coiled and I used the link Larryb provided (Thank you Larry).  I used the old wire to measure the approximate length and cut it about a foot longer to have plenty to work with.  I made the tight small end coil using a small gauge screwdriver in a bench vice and a pair of pliers , and it made a very nice coil.

I drilled a hole, just ever so slightly bigger that the core wire, in a piece of 2x4 in a bench vice.  I then ran the new wire through the hole working it back and forth to get the majority of the shipping coil out of it. In affect straightening it. 

Then insert the core wire and thread it to the tank.  At the tank end I used a pair of pliers to pull it and guide it into then tank switch clamp.  and did not tighten the clamp yet so the wire would slide back and forth while I was adjusting the pilot end of the wire.  Then back in the airplane to push it the rest of the way in.  

On my first try I put the coil over the post with the running end toward the inside and on the bottom,(see pic below) thinking that this was the best way  to avoid it "popping " off.  I was wrong. see pic.  All this did was to create a binding effect, that both opened the loop and produced torque moving the loop off of the post. 

So I reversed, putting the coil towards the inside and the running end over the top and BINGO!!

 and 

 

 

 

As you can see in the video there was quite a bit of motion at the peg so I twerked the end a little inboard and it was fixed!! 

 

 

The videos are taken with the  mechnisum  screwed back in place in its normal position.  I hope this is helpful to anyone else who has to go through this.  I got really good at getting access and after doing it several times was able to get it completely apart in under and hour and about the same getting it cack together.   

 

PS:

I also tightened the valve end too tight once severing the wire to be carful on that end.

 

Tailwinds

 

Dave

 

 

 

 

 

 

 

 

[carusoam]

Great videos Dave!

Thanks for sharing the details.

Best regards,

-a-

[Fritz1]

Dave, your coil looks pretty good now, it has to be wound tight enough so it snaps onto the peg, the peg has a little groove that can hold a small retaining clip, cut the coil short enough with Dremel disk so retaining clip goes on. Figured this one out together with Brian Kendrick when he did my annual in January, has been working like a charm ever since. -Fritz