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Safety wire exhaust springs?

JwWright57

Well Known Member
Hey I’m reading the Rotax install manual and they specify safety wiring the exhaust springs. I don’t recall seeing that in the plans
 

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I do not recall if it was mentioned in my plans (several years ago now), but it is fairly common and prudent to safety wire the springs in some suitable manner -- the safety wire serves to keep a broken spring from impacting some poor ground-based soul's noggin. I ran a loop of safety wire longitudinally through each spring and around the exhaust pipe clip -- it doesn't (and shouldn't) need to be too tight. Our pusher-prop aviator friends also do this to keep spring shards from impacting their expensive pusher props.
 
And as a side note this year at condition inspection I took my muffler off so had to remove the springs and safety wire. I found several of the safety wires broken and wouldn’t have noticed on a visual inspection. I know better next year to really check those safety wires that I use to retain the springs in the event one would break.
 
In addition o the safety wire, we always filled the sprin/safety wire area with red rtv to keep the saftey wire from vibrating the spring to failure and loss the pieces in the engine compartment.
 
The factory supplied springs are about as much use as a chocolate fireguard.

We built 2 RV12's and during the initial fly off testing 6 springs failed !

We replaced all of them with after market stainless ones and have not had problems since.

This was flagged under a maintenance MOR to Rotax and as at this time, a year later - no reply.

I would junk the factory supplied ones, replace with stainless ones from your usual supplier and squirt a stripe of RTV along the length of them to stop harmonic vibration.
 
As a data point: My eight original Rotax OEM exhaust springs have lasted for over 1,000 hours and appear to be still going strong (I know, I just jinxed myself). Don't know if its a factor but I ran two strips of RTV down the side of each spring rather than filling the interior of each spring with RTV.
 
I’m 7 for 8 being good using the same method as David above. But only a 130 hrs so far. Carb balance that vibration out
 
It’s really important on pusher configurations where everything that comes loose goes through the prop. I used to have a Searey.
 
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