Over the last couple of years, my CKT exhaust system fitted to a Europa with
Rotax
912ULS has broken a few springs and not in the same location each time. I
never seem to be able to fly for more than about 30 hours before I find another
broken spring, each time with a short 1/2" straight piece remaining after the
hook has disappeared. The coils never break.
As per CKT instructions, I never use metal tools like vice grips and only use a
plastic cable tie for pulling the spring onto the welded anchors. The last time
when I replaced a spring, I cut lengths of old metal brake hydraulic tube to
fit inside the spring coils before passing locking wire through for safety.
This attempt at vibration damping obviously didn't prevent another breakage.
The aircraft carburettors are well balanced using Carbmate and the Airmaster
propeller
is also well balanced, so my aircraft runs "sewing machine" smoothly.
The replacement springs from CKT were bought as a packet of 8, if I recall
correctly
and are the simple type with a hook at each end. I would prefer the more
complicated type which act differently and have closed 'U' loops at each end,
but don't know where to find them.
I'm also considering to copy the 2-stroke microlight flyers, by wiping a thick
bead of high temperature silicone rubber sealant along the length of the spring
coils on the side furthest from the exhaust header tubes, which after setting
will hopefully act as a vibration damper. Dow Corning Momentive RTV106 red
silicone
sealant is what I have in mind and works at a temperature of up to 260C
( 500F ).
However if I could obtain the more complicated exhaust springs, I'd try those
first
before experimenting with RTV106. Your advice please, thanks.
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