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Exhaust Spring Cut-Thru…

Piper J3

Well Known Member
While doing Annual Condition Inspection I found a crack in the exhaust exit end of the muffler. I advertised on VAF classified thread for a used muffler and got several responses. I ended up buying a complete exhaust system with only 70TT and decided to replace the muffler and also the exhaust stacks. Several of my exhaust stacks exhibited extreme wear on the spring hooks. This condition is not easily noticed because a bead of high-temp RTV is placed over the spring loops to prevent vibration. I installed Stainless Steel springs early-on when the original springs started breaking. The springs themselves don’t show much wear. My guess is the springs are harder material than the muffler hooks. My exhaust has 750TT.
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Thanks for the heads up Jim. I put RTV on mine at the hook and 2 stripes down the opposing sides. I have not had a broken spring in 600 hours. I do have a dynamic balancer and check the prop balance at every conditional, don’t know if that is making a difference. The next conditional is coming up in August and I will strip all the RTV and do a close inspection on the springs and hooks.
 
Is everyone pulling the springs (and applying anti-sieze, where required), then reapplying RTV to the springs every condition inspection? I've noticed more wear on the exhaust loops v. the springs, also.
 
I forgot to mention in my post #1 above.... On this new installation, I bent the hooks on all the exhaust stacks and the muffler so the springs would have more stretch. The thinking is with more stretch, the springs won't move as much in the loops and wear might be reduced. Time will tell.....
 
I've had lots of OEM springs get rusty early on (50 hrs) .. and two or three broken springs so far (180hrs). I started replacing them with (apparently) better quality ones available on Aircraft Spruce and haven't had those issues anymore.

Whether these new springs wear out those hooks and fast or slower.. I'm not sure yet.. can't say I noticed any wear so far anywhere.
 
I pull my exhaust every 5 years when I do the hose replacement. I cut off the old springs with a moto-tool because they seem to harden from the heat up/cooldown cycles. I use Spark plug anti-seize compound from Auto Zone. No leaks and no wear in 10 years and over 1200 hrs service.
 
Hi all,
Having used a Rotax 2 stroke engine for 15 years or so, with the same springs and hooks, and never having a spring/hook failure I believe RTV silicon applied to the springs is a must as it controls vibration of the spring. But I have always wrapped the hooks with thin copper sheet (a bit of a pain) which acts as a bearing and prevents wear of the hook.....worked for me.
Cheers
Mike
 
I remove the muffler every year, and reapply RTV, and anti-seize. No broken springs but wear and cracking around the ball joints requiring weld work after 700 hours. The springs appear to have stretched so I, too, have bent the hooks to increase the tension. Maybe time to replace the springs, but stainless or otherwise...?
 
I pull the muffler every year and apply anti-sieze but always leave the springs hanging from the silicone glob so I can't see the wear. Today I removed all the springs and soaked them in gasoline to remove all the RTV. They were all worn like this, I'm replacing all 8.

spring.jpg
 
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