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M20J exhaust strap


n5756k

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The aviation aisle of your local auto parts store sells muffler hangers. You won't need the metal parts but the kit is probably about $10.

http://www.autozone.com/emission-control-and-exhaust/exhaust-system-hanger/walker-exhaust-system-hanger/277502_810150_19329

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There is one of my old airplane tires in the hanger that is missing part of the sidewall.  It is square cut out.  It may or may not match the muffler hanger on the aeroplane.  So technically it is a certified part on the certified airplane.

Edited by Yetti
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The sidewall from the tire is much more rigid than baffle material.   It is pretty hard to work with.  Sharp utility knife to cut it.  Drill bit to presize the holes. Hanger is a wrong term to use since it does not just hang like a car exhaust does.  Based on the airflow across it and the amount the engine moves.  It needs some down force to keep it in place.

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Cutting a piece from an old tire is a common practice but I would recommend going by the NAPA or AutoZone or equivalent. The hanger kits there should be much stronger than repurposed tire rubber. I had to have an emergency repair done last year out of town - thanks @ Lee Fox - but the stress of the 90 deg twist that my plane has caused a failure in a few months. I redid it and I was able to engineer out the twist and double up the strap. Happy camper.

IMG_20161201_122038875[1].jpg

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3 hours ago, Bob_Belville said:

Cutting a piece from an old tire is a common practice but I would recommend going by the NAPA or AutoZone or equivalent. The hanger kits there should be much stronger than repurposed tire rubber. I had to have an emergency repair done last year out of town - thanks @ Lee Fox - but the stress of the 90 deg twist that my plane has caused a failure in a few months. I redid it and I was able to engineer out the twist and double up the strap. Happy camper.

IMG_20161201_122038875[1].jpg

You are kind of missing a whole bracket.  There is a multi swivel stainless bracket that bolts to the firewall the rubber piece goes between and then another stainless part that bolts to the stainless clamp.

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1 minute ago, Yetti said:

You are kind of missing a whole bracket.  There is a multi swivel stainless bracket that bolts to the firewall the rubber piece goes between and then another stainless part that bolts to the stainless clamp.

Not on all models apparently. I sent several done both ways.

I am very happy with what I have now.

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8 minutes ago, Yetti said:

I would get the hanger hardware if you can.  There is no heat sink between the clamp around the tail pipe and the rubber.  That method has a pretty short self life with the 1400 degree exhaust pipe..

Yetti, I think you exaggerate. 1400 deg is the EGT in the header 6" from the exhaust valve. The tailpipe is considerably downstream of that point and in my installation downstream of the PFS muffler. While the original pipe clamp has a short tab that the rubber clamps to, the heat dissipation cannot be great.  

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I may be a bit high on temp..... but I do know the stainless tail pipe has been colored from heat.   And why did the OP strap fail?  Seems like there could be an improvement in design.   And do you have the hanger further back on the tail pipe?

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55 minutes ago, Yetti said:

I may be a bit high on temp..... but I do know the stainless tail pipe has been colored from heat.   And why did the OP strap fail?  Seems like there could be an improvement in design.   And do you have the hanger further back on the tail pipe?

I think the 2 failures I've experienced were due to the stress of the twist. I suspect mine and a good many vintage Mooneys lost the pivoting bracket.

With the PFS tailpipe there are 2 "hangers', the one in my pic and another one near the tail end. I think the J model pic in the OP would be in a similar position to the 2nd one which is hung from the bottom of the fuselage at the rear of the cowl flaps. The one I picture with the doubled up strap is hung from the lower firewall.

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Please try a piece of engine baffling.  You can probably get a scrap piece for free from your local mechanic.  It is exactly the right consistency to work with and is designed for a high temperature environment.  I used this to replace my strap a few years ago and it is still perfectly intact.

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32 minutes ago, Wistarmo said:

Please try a piece of engine baffling.  You can probably get a scrap piece for free from your local mechanic.  It is exactly the right consistency to work with and is designed for a high temperature environment.  I used this to replace my strap a few years ago and it is still perfectly intact.

The baffle is the metal. the "rubber" is baffle seal. But I suppose the temps that the baffle seal sees are much lower than the tailpipe. More importantly, the baffle seal is not typically reinforced with fiber. I'm pretty sure the seal would not last 50 hours on my plane.

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The one on my C was found broken at annual. It looked like a piece of tire sidewall. A new piece was fabricated, holes were drilled (it looks like Bob's except it has 2 screws) and installed. Should last a good, long time. Net cost, zero. For the curious, it's on the firewall, and there is nothing beyond it. Different models, different  details. And no, with it broken there won't be a fire, it will just wiggle around more (maybe 2").

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On March 17, 2017 at 11:38 AM, Hyett6420 said:

I read lots of "normal practice" etc lines in this thread, but no-one has posted what the FAA approved practice is.  I CANNOT believe for one moment that you are "allowed" to go down to the local scrap dealer, cut out an old tyre and use it as a strap.  The strap in the photo also looks over tightened at some point in its life which has cut the retaining fabric, or put excessive pressure on it.   This is a safety item chaps. $70 is NOT that much, its not even a $100 hamburger.

Andrew

 

Andrew,

The North American tire, is made to a much higher standard then a British tyre and is therefore an approved replacement.

Clarence

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On March 17, 2017 at 1:01 PM, Yetti said:

I would get the hanger hardware if you can.  There is no heat sink between the clamp around the tail pipe and the rubber.  That method has a pretty short self life with the 1400 degree exhaust pipe..

Not endorsing any specific material other than that approved (and yes, I've seen tire sidewall used countless times), but if your exhaust pipe hits 1400 degrees, you've got much bigger problems than an exhaust hangar.  

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Not endorsing any specific material other than that approved (and yes, I've seen tire sidewall used countless times), but if your exhaust pipe hits 1400 degrees, you've got much bigger problems than an exhaust hangar.  

+1
At that temperature your exhaust pipe would be glowing cherry red.
And that's after the exhaust gases pass through a few feet of pipe and heat exchanger.
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Here are pictures of "Reinforced Baffle Seal" that I have used.  It has a fabric/fiber middle layer for reinforcement, as demonstrated by the white line down the middle of the two orange layers.  The last picture is of an orange piece on the left that I put on my M20J five years ago.  The black piece on the right is original to the aircraft.  My mechanic gave me a short piece for free.

IMG_0787.JPG

IMG_0785.JPG

IMG_0788.JPG

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