lazy alternator belt

[rfbdorf]

It's tired of working, so a couple of times it decided to fly off its pulleys and sleep in the lower cowling of our 182P after 10-20 minutes of hard work. The engine was overhauled at Ly-Con about 35 hours ago. The belt itself appears OK. Due to misalignment? Has this happened to anyone here before?
- Richard

 

[Let'sgoflying!]

some IO520s will throw belts if there is misalignment.... had a viking-pal who repeatedly had this problem (they tried checking and tightening etc) til they took off the alternator and discovered a wallered out hole on a mounting lug somewhere. I guess they can get to wobbling/vibrating enough to toss a belt when the mounting system is not rock solid.

 

[Gary Sortor]

I guess they can get to wobbling/vibrating enough to toss a belt when the mounting system is not rock solid.

Found an alternator's mounting system juryrigged on my plane when an a/c system was removed by a previous owner. That caused the belt to be continually thrown. So, anything is possible. Once the new, factory bracket was installed, everything was fine.

 

[gismo]

First, once a belt has come off, it is much more prone to repeating the performance even if the belt looks fine visually. I think something breaks inside the belt which makes it wobble (BTDT). Second, misalignment can cause belt problems, but IME it takes a fair amount if the belt is new and the tension is correct. If you can lay a straight edge across both pulleys and there are no gaps, it should be good enough. Finally it doesn't take much vibration at the right frequency to get a belt to whip around and come off. I've read of cases where the belt problem was a symptom of a crankshaft counterweight problem (stuck). Try to watch the belt while the engine is running at various RPM to see if it starts to move up and down.