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Exhaust Spring Clearance and Radiator Hose

Tacco

Well Known Member
I was really uncomfortable with the clearance of this exhaust spring and the lower radiator hose. So I put on a heat shield consisting of a cork and aluminum sheet. About 3/32 thick. This is how it looked at my 100 hour inspection. The spring is definitely contacting the shield and look at the heat discoloration on the aluminum. Thinking about replacing spring with the tip ground down a bit to increase clearance. What do you think? BTW turning it around so the curved radius is facing the radiator hose is worse, i.e. closer.

Second question, what is your experience with stainless steel springs?
 

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Swap those awful springs out straight away and buy some stainless replacements from Spruce.

Our 2 12's had multiple spring failures to the point I have submitted a safety report to Rotax. They failed within the first 10 hours of operation and had all the silicone support as required.
 
At about 275 hours I lost an exhaust spring somewhere between Osh and Idaho. Checked the remaining springs and they were ok except one that showed a lot of wear on the hook that attaches to the exhaust. All the springs that looked good had lots and lots of red RTV. The one bad spring had very little red goop. My guess is that vibration is the enemy of the springs. Solved by lots of red goop. And, I added this as an item to check at annual.
 
Also, check the "stretch" of the springs. I installed stainless steel springs three years ago and had to bend the welded loops on the exhaust tubes in order to achieve a decent amount of tension being developed by the springs. Never lost a spring...
 
OK folks, here is more and what I did. The spring was rubbing on the exhaust tube as well as hitting the radiator shield. It was destined to fail. In addition, the exhaust ball joint was leaking, note carbon jet from the joint and on the spring, radiator shield, and welded hooks. So....

I bent out the hooks a bit. Replaced the spring and plan to wrap the radiator hose in insulating foil. Check out the clearance now. Adequate? Also re-lubed the joint with more Heavy Duty Anti-Seize. Will watch for leaking on next flight.
 

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Fixed this problem with the help of Van’s Engineering guys. Note how fuel line is behind radiator hose. This forces the radiator hose forward. Rerouted the fuel line forward of the radiator hose. Both clear the exhaust pipe and spring fine. :)
 
OK folks, here is more and what I did. The spring was rubbing on the exhaust tube as well as hitting the radiator shield. It was destined to fail. In addition, the exhaust ball joint was leaking, note carbon jet from the joint and on the spring, radiator shield, and welded hooks. So....

I bent out the hooks a bit. Replaced the spring and plan to wrap the radiator hose in insulating foil. Check out the clearance now. Adequate? Also re-lubed the joint with more Heavy Duty Anti-Seize. Will watch for leaking on next flight.


Is that Permatex high temp red RTV silicone gasket maker #81160 on the springs, or something else?
 
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