why does my belt flap?

[n8brown]

So i've gone through several belts now on my alternator. The last two have ripped completely off. I don't know whats cuasing that but i do know that when i have the belt tightened down the top side is looks smoothe but the side from the crank pully is flapping like crazy. Whats going on?

 

[mechted]

are you properly tensioning the belt? sounds like it could be a touch loose
should only deflect about 3/8" under a fairly firm finger push on the longest section of belt

 

[reptilianman]

Could be a bent pully,or a crack in a bracket.

 

[Blue85]

why does my belt flap?

Have you lost a lot of weight lately?