Broken Heat Shield Bracket M20K

[Smroot]

I'm having issues with the exhaust heat shield on my M20K located in front of the engine below the prop.  At the PPI a year ago I was told that the bracket had broken and it wasn't attached when they removed the cowling.  That shop "fixed" it but I'm not sure how they repaired it.  When I changed the oil at about 35 hours, the heat shield fell to the floor when we removed the lower cowling.  At that time I had new brackets fabricated of a thicker gauge metal and reattached it.  Now at the annual, about 40 hours later it was still attached to the exhaust pipe but one of the brackets had broken again.  So it was hanging by one bracket and surely going to vibrate off in a short time.  Has anyone else had this issue and how do I confidently repair it this time?  I'm afraid of it coming loose and rattling around inside the cowling.  Unfortunately I don't have pictures.  

 

Tim

 

  

[carusoam]

What prop do you have there, Tim?

Any chance you have had it balanced?

I'm going on your avatar picture.

Best regards,

-a-

[Smroot]

MT prop. Has roughly 300 hrs, I've never balanced it. Thx.

[kortopates]

I'll bet the issue is due to tightening both clamps securely that hold the heat shield to the exhaust pipe. You'll note the two clamps for the heat shield go on different sections of exhaust pipe. The service manual, see section 77, is very clear with a big CAUTION not to tighten both sides so that their is some play for movement as the pipes heat up. Tightening them both prevents any movement causing the bracket to crack at the clamp till it breaks and as you must know heat shields aren't cheap. 

Kind of underlines the need to use and follow proper documentation.

[carusoam]

Sounds like something an MSC should know about, but an ordinary mechanic did not recognize the situation...

Best regards,

-a-

[Smroot]

Kortopates, 

Thanks, that sounds like the solution.  The heat shield I'm talking about is on the same section of exhaust but could be the same issue.  I'm having the annual done at Maxwell Aviation and have talked to Don about it.  I think he had a solution.  

 

My last annual was done at a MSC too but I was never very happy with the work.  Several attention to detail issues but I won't name or dis the shop on a public forum.   

 

Cheers!

[kortopates]

Tim,

Perhaps Don will fabricate a new bracket for it and rivet it on.

I see you have an SB. I assure you though the front cross over exhaust section is two separate pipes. You'd have look closely though as the junction is covered up by the heat shield and not really evident with the shield on.

Regardless though, the fact is the front heat shield takes a lot of abuse being where it is across two sections of pipe and is unlikely to  last the lifetime of the engine even when properly installed.