muffler fatigue

[pgkevet]

This is the rjx muffler for my YS56 engine. On sunday after an odd sound on startup I found a large jagged crack 1/3rd circumference about half way along the muffler. It looks like metal fatigue and vibration propagation.

It's four months old and uncrashed. The vendor has asked for return with likely replacement - excellent service as usual.

I'm just interested if anyone else has seen this and an obvious warning that it's another area to check in case of a lean run.

It can't have been visible long 'cos I've been good about cleaning heli after flight recently

[squeaky pete]

was a day for exhausts werent it

[pgkevet]

..at least I had a spare heli

[RafeyRJX]

Dont know about your exhaust but I spent most of last summer trying to cure a horrible vibration... changed every rotating part, never cured it. Ended in a total failure of the aileron linkage in flight, the metal actual just snapped clean off - Result, a totalled machine! Only one side of the airframe remained un damaged, smashed servos, broken rx, ......... a new kit and rebuild, I found the problem, the head block was slightly off centered. So what I'm saying is, whatever you do, if there's vibration causing fatigue, find it and cure it or you'll loose your heli to the sky gods! and dont rule out anything. Like i said, final inspection came down to poor tolerances on the headblock!

[pgkevet]

vibe hunting should be followed logically if it's not an obvious find and fix... blades off:still there?, bom off:still there?, boom back, head off etc..and a sounding rod held against different areas can help isolate it too.

I wrote a short 'diary of a vibe hunt'.. recently about my old 450 where I admit I wasn't particualrly logical but did get there in the end.

Was that head miss manufacturered or bent (more common). On e of the areas we're often lazy about (I'm guilty) is not balancing the head and/or tail block/grips

[RafeyRJX]

Absolutely right - methodical hunt is the only way. One which I followed. The only neglect was the head block as it was brand new. An up grade as it happens, official release to help cure a problem with the FB bearings coming loose.
My fault really, I checked everything carefully, one piece at a time but not the head block. I assumed it was ok as it was new. Just a miss manufactured part. Live and learn eh.

[Sesame]

Talking about the mufflers I had BOTH my outrage 55 mufflers baffles break free the weekend before last, both mufflers about 6-8 months old. to be fair they were swapped over for nice shiny new ones. but I expect the same thing will happen uness they have strengthened the welds