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Old 09-06-2010, 08:21 PM
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Default RE: Magnum XLS .52A

I love my Magnum 52, but can't say the same for the muffler. The engine is on the Gt. Planes Ultra Sport 40 that they did a limited run of kits on a couple of years ago. With retracts, the plane flies like my old piped pattern planes. But....the factory muffler rear cone insisted on twisting in flight, with the "stinger" scorching the fuselage paint job. I cleaned it all up, JB Welded the seams, and for good measure, drilled and tapped the seams for 2/56 Allyn head bolts.
After a few flights, it sheared the bolts off. So I tried a Tower 46 muffler. Engine was probably even faster. But I had many of the same problems. Finally, I had an OS 50SX that I was using with a Pitts style muffler, so I tried the OS muffler, and lo and behold, the bolt pattern is the same. This lowered the rpm a little, but my problems went away.

Why do I think this problem may be occurring? I wonder if it isn't a difference in heat, between the cast front part, the thin shiny part in the middle, and the cast part in the rear, with a variance in expansion under heat when running?
I'm no engineer, but I suspect this may have something to do with it. Any comments will be interesting.

Clair Sieverling