Exhaust spring failures - ROTAX 503

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Tuneturkey

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10113, Hyde Park Ct., Baton Rouge, LA 70816
In less then 8 hours of running time, 4 out of 6 springs have failed. These are the stock, CS, 66mm springs. Piping is strait forward, one 90deg elbow and strait pipe to muffler. clips on elbow to muffler are almost 3 inches so springs are stretched pretty far, so 66mm springs are too short. assembly hangs on the exhaust manifold and a spring holding the muffler against the side of the fuse. Engine runs smoothly with minimal vibration even at idle.
Can anyone suggest alternate springs.
Engine is on a High-Max, tractor config. with muffler hort. extending aft on side of fuse.
 

Daleandee

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JBM sells stainless steel 6.2 mm springs that they claim will stretch to 4"


You may already know this but don't pull the spring by gripping with pliers as that will put stress risers in it causing early failure. I used to wrap a small piece of safety wire around the end and use that to pull the spring open with.

Dunno if this helps ...
 

TFF

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I started putting the stainless ones on a friend’s 912s on his AirCam. I probably have put 20 regular ones on over the years and not a lot of hours. Pretty much fixed it.
 

TiPi

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The springs also need to be coated with high-temp silicon. Apply a 6-8mm worm along the outside of the spring (away from the exhaust) and lightly press it into the spring coils. This reduces or stops the movement of the spring from harmonic oscillations and prolongs the spring life.
On my 912, without silicon, the springs lasted 25-50h, with silicon I now have 500h on the current set.
 
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MadProfessor8138

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The springs also need to be coated with high-temp silicon. Apply a 6-8mm worm along the outside of the spring (away from the exhaust) and lightly press it into the spring coils. This reduces or stops the movement of the spring from harmonic oscillations and prolongs the spring life.
On my 912, without silicon, the springs lasted 25-50h, with silicon I now have 500h on the current set.
Before using the high temp rtv sealer.....run safety wire through the clips and spring....then apply the rtv.
If a spring ever does break....the safety wire will hold it in place.


You may already know this but don't pull the spring by gripping with pliers as that will put stress risers in it causing early failure. I used to wrap a small piece of safety wire around the end and use that to pull the spring open with.
The tool used to work on automotive drum brakes is handy for installing exhaust springs.
You get good leverage and the spring isn't stressed .

Kevin
 

TrikeTrash

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Feb 8, 2014
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Kingston, TN (12TN)
I just use a loop of heavy string to put my springs on. That way if I get it on the wrong side I can just cut it off. The springs are whatever Ace Hardware have and since they have a selection of lengths I'm not that choosy if they're galvanized, plated or whatever. They'll all rust or break if left alone, so best practice is to replace all of them ever 2 years or so. Also at that time I'll give the whole exhaust several coats of BBQ paint. When I put them back on I use a loose safety wire wrap and may or may not add the silicon.

I modified the positions of the spring attachments early on, so that the original zig-zag spring pattern was replaced with a parallel arrangement. I also dropped back from the original six springs to three. The wire between joints in the pic below is for RF suppression, I read somewhere that any moving or rattling juncture between metal can create RF, so I ground them.

DSC05926.JPG
 

TFF

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You have to run the safety wire through the springs on an Aircam. Spring breaks it will go through the prop. All break muffler goes through the prop.
 
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