Owner produced heat shield

[wpbarnar]

Does anyone know what series stainless steel the heat shields are manufactured from?   The attachment bracket/ standoff portion of exhaust heat shield on my K model is broken beyond repair.  The shield portion is in good shape.   The bracket should be straightforward to fabricate as an owner produced part if I can determine the correct material.

The broken bracket made a nasty gouge in the exhaust tube.  The remaining metal was paper thin.  Great catch by my IA. The movement was not obvious and damage not visible until the shield was removed.  Not long from having a hole with hot impending gases and the nasty consequences associated  them.  Forward heat shield on the x-over tube.  

Thanks

Bill

 

[thinwing]

I use online metals...they will have sheet stainless ,also strap shaped and will precut metal to your dimension..than its just a matter of bending the strap to shape.I recommend high nickel content stainless

[carusoam]

Bill,

Got any pictures you can share?

It might also get you a better answer...?

Best regards,

-a-

[Hank]

Check your current one with a magnet. 400-series is magnetic, 300-series isn't. My bet would be 440 stainless.

Edited November 14, 2016 by Hank

[N601RX]

321 is a common alloy used for aircraft exhaust . 

[wpbarnar]

Photos of the shield mounted on x over tube, back side of shield  and broken bracket, damage to tube from chafing.

The heat shield material is not magnetic.

Found out today that just the brackets were available from Mooney without having to purchase the whole assembly.   I ordered those instead of going the owner produced route but still would like to know the metallurgy for future reference.

Bill

[Guest]

5 hours ago, wpbarnar said:

Photos of the shield mounted on x over tube, back side of shield  and broken bracket, damage to tube from chafing.

The heat shield material is not magnetic.

Found out today that just the brackets were available from Mooney without having to purchase the whole assembly.   I ordered those instead of going the owner produced route but still would like to know the metallurgy for future reference.

Bill

It looks like you'll need an exhaust pipe repair as well.

Clarence

[wpbarnar]

The exhaust pipe has already been sent out for repair.   The remaining wall thickness of the tube was scary thin.   

Nothing obvious when first visually inspected with heat shield in place.   Just a tiny  bit of movement on the shield which prompted the IA to look deeper.

Bill

[kortopates]

I popular option near me for exhaust repair work is http://www.customaircraft.com/  But they are not an FAA repair station, so you will not get a 337 form back with the repair. They actually used to be years ago, but the FAA requirements to separate their experimental work from certified work made it too difficult for them and they dropped their FAA status. So you would have to rely on your A&P's approval of the work. I will add they do a lot of repairs for certified aircraft including even the military. Plus they have made the very repair you need now a number of times - unfortunately its very common. Make sure the installer follows the maintenance manual on re-installing the heat shield not to tighten both fasteners tightly; one side needs to have some play as the exhaust pipe expands with heat.

Edited November 15, 2016 by kortopates

[Bryan]

My bracket has the same break and since you said it was a Mooney part available I called LASAR. Their part lookup showed it as part number 630-122-501. They said the bracket was $600+.

I will be exploring other options.

Any word on the metallurgy?  It does not appear magnetic. Maybe stainless?

[kortopates]

My bracket has the same break and since you said it was a Mooney part available I called LASAR. Their part lookup showed it as part number 630-122-501. They said the bracket was $600+.
I will be exploring other options.
Any word on the metallurgy?  It does not appear magnetic. Maybe stainless?

Common problem. It's stainless. Send your broken one to the above shop for duplication. Install it as a owner produced part. Probably cost you a third of the new cost and will be identical. But obviously send them some pictures first for an estimate.


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[Bryan]

Thanks @kortopates. I will give them a shout.

I got my Tempest Fine Wire plugs installed yesterday and during preflight found the bracket broke.  As soon as I get this fixed, I will do another Savvy test flight.

[larryb]

Resurrecting an old thread here. This has been a constant problem for me. The bracket was found cracked at the pre-buy when I bought 15 months ago. It was replaced by new at that time. A year later at the first annual it was cracked again, and my shop welded it. And I found it is cracked again today. Does anybody have a good solution for this? Has anybody actually gone the owner-produced route with a more robust material?

[carusoam]

@larryb,

Sounds like something can be done better... Something related to vibration...

See if @M20Doc has any insight to vibration of the exhaust pipe on the M20K, or it’s vibration absorbing mounts?

Larry, got any pics of the pipe and anything that touches that section of pipe?

Check how old the engine mounts are. They may be aged or sagging and no longer at work?

Best regards,

-a-

[larryb]

Aside from the legality of it all, anybody see an issue with using something like this instead of the expensive and crack-prone metal heat shield?

https://www.amazon.com/gp/product/B01BAOW4KI/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

[N201MKTurbo]

11 minutes ago, larryb said:

Aside from the legality of it all, anybody see an issue with using something like this instead of the expensive and crack-prone metal heat shield?

https://www.amazon.com/gp/product/B01BAOW4KI/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

I actually used this for a while on my system on advice from the engineer (Mr. Sandman) of my system.

Don't do it!

It works but after a couple of years the pipe under the header wrap rotted out and had to be replaced.

I tried a number of home brew attempts to build a better heat shield. They are scattered all over the deserts of Arizona along with a few certified($) heat shields.. 

I finally just glued high temp insulating heat shield matting to the cowl and haven't had any problems sense.

http://www.aircraftspruce.com/catalog/eppages/alumheatbarrierstops.php?gclid=EAIaIQobChMIvb_B-fH03AIVkKDsCh2JSQVVEAYYASABEgIB7fD_BwE

 

Edited August 17, 2018 by N201MKTurbo

[wpbarnar]

On 8/16/2018 at 9:49 PM, larryb said:

Resurrecting an old thread here. This has been a constant problem for me. The bracket was found cracked at the pre-buy when I bought 15 months ago. It was replaced by new at that time. A year later at the first annual it was cracked again, and my shop welded it. And I found it is cracked again today. Does anybody have a good solution for this? Has anybody actually gone the owner-produced route with a more robust material?

My experience is similar. I started this post and have had experienced another failure after my initial repair with parts purchased from Mooney.   

I am thinking about trying something like below.   The heat shield is not rigid which should eliminate the potential to crack.

Additionally,  most of the respondents in this thread are Encore owners.  Is this  problem unique to the Encore or do other K models experience similar failures.

Bill

6E645805-140B-4D13-9F18-6A420CE46CE3.jp2

[RLCarter]

a common issue with exhaust systems is how they are installed, if the system is just bolted down as it goes together it will be in a bind and as it heats up and expands it generally gets worse and parts distort and/or fail. I generally install the complete system before evenly tightening things up, then do the same with the heat shields

[larryb]

In this application, the heat shield spans a slip joint. Therefore one must tighten one clamp securely and leave the other clamp slightly loose. 

I have already added the adhesive backed Thermo-Tek barrier to my cowl in front of the exhaust because I was not confident in the Mooney heat shield. I am not sure if this is sufficient if there were no Mooney heat shield though.

I am also curious if other K models don't even have a heat shield. It looks like the shield was added via SB in 1987. 

Larry

 

 

[kortopates]

11 hours ago, wpbarnar said:

My experience is similar. I started this post and have had experienced another failure after my initial repair with parts purchased from Mooney.   

I am thinking about trying something like below.   The heat shield is not rigid which should eliminate the potential to crack.

Additionally,  most of the respondents in this thread are Encore owners.  Is this  problem unique to the Encore or do other K models experience similar failures.

Bill

6E645805-140B-4D13-9F18-6A420CE46CE3.jp2

 

10 hours ago, RLCarter said:

a common issue with exhaust systems is how they are installed, if the system is just bolted down as it goes together it will be in a bind and as it heats up and expands it generally gets worse and parts distort and/or fail. I generally install the complete system before evenly tightening things up, then do the same with the heat shields

Robert is absolutely right. Although this particular heat shield is prone to breaking due to where its sits, its improper installation that leads to premature cracking of the bracket.

The cracking of the bracket is due to the thermal expansion of both sides of the junction. The maintenance manual provides very specific instructions on not to clamp both sides of the shield down tightly to allow for this. But that's obvious what was done in the picture above that shows how the clamp damaged the crossover pipe. Mine last for years with proper installation. If anything I err on installing too loose and have to periodically tighten one of the clamps when I do an oil change. be sure to read the maintenance manual on installation. 

[kortopates]

In this application, the heat shield spans a slip joint. Therefore one must tighten one clamp securely and leave the other clamp slightly loose. 
I have already added the adhesive backed Thermo-Tek barrier to my cowl in front of the exhaust because I was not confident in the Mooney heat shield. I am not sure if this is sufficient if there were no Mooney heat shield though.
I am also curious if other K models don't even have a heat shield. It looks like the shield was added via SB in 1987. 
Larry
 
 

Must have been typing at the same time.
I also added the Thermo-Tek barrier - over time without it, it drys out the fiber glass layers requiring periodic repair.


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