Exhaust mounting holes are getting worn on a 912

[fastfred]

My exhaust springs wearing the attachment holes. Does anyone one know of a fix to stop this before it wears through?

[Dave S]

Fred,

My DAR (also an EAA tech counselor) advised me that both the springs and holes will wear (if left to their own devices) due to high frequency vibration common to the engine.

His advice even before I fired the engine was to lay a bead of red RTV on both sides of each spring over the coils. A second piece of advice is to run a length of safety wire through the holes in the tabs and through the spring coming back on the outside (to keep the junk together if one breaks.

To date - neither the springs nor the holes have worn noticeably.

PS - disregard the spark gap note on the rocker arm cover - I have since changed to a smaller gap.

[fastfred]

Thanks I did that last year and it seems like that made it wear even more. I wondered I there was and insert that could be put in there. We might have to machine one for it.

[4Hummer]

Solid brass rivet than drill it out for the spring ! Worked on my Rotax 503 for my flex wing trike, I later switched to ball joint clamps

[KFWG]

I’ve got the same wear going on. I need to amend it since the wear is getting pretty advanced. Is there an alternative to getting it welded? Any hardware ideas? A flanged bushing insert? I see the rivet idea. Any others?

[Maverick]

If the wear is on the tabs, what about welding an A.N. washer to each side of the tab? Not sure if it would be all that easy but seems like it would strengthen the holes. There's not much can be done to the springs.

[KFWG]

If the wear is on the tabs, what about welding an A.N. washer to each side of the tab? Not sure if it would be all that easy but seems like it would strengthen the holes. There's not much can be done to the springs.

I thought about just that!
However, I pulled the exhaust and am having a welder replace the older style sheet steel flanges with the newer style rod loops. Problem solved but no plane to fly on nice weekend!

[avidflyer]

To late now that you have pulled the exhaust, but what about drilling another set of holes further down on the tabs, use longer springs, and then when or if they get worn down, put new tabs or doublers on the sides of the existing ones. That would probably double the time before you have to address the issue. JImChuk

[jrevens]

I wonder if periodically lubricating those wear points with a high-temp lubricant would make a difference. Perhaps working in a little anti-seize grease,.. or maybe a few drops of of a graphite or moly- containing lube like Loctite every so often. Has anyone tried that? Loctite might be better since it would probably attract less dirt after the carrier evaporates, leaving the graphite. Maybe some other dry-film lubricant such as Dow 321 would be even better.

[PapuaPilot]

To late now that you have pulled the exhaust, but what about drilling another set of holes further down on the tabs, use longer springs, and then when or if they get worn down, put new tabs or doublers on the sides of the existing ones. That would probably double the time before you have to address the issue. JImChuk

I think this is a great idea. We have done similar repairs on certified aircraft.

I don't think John's idea would make much of a difference.

[Maverick]

Phil,
How helpful is putting the red silicone on the springs? I've seen it both ways on different planes certified and armature built.
Fred

[PapuaPilot]

I don't have much personal experience, but I hear it helps.