Originally Posted by
DiabloScott
Sorry, I wasn't arguing with you, I was adding on. Bicycle design is hardly at all like airplane design. I don't think most bike manufacturers do any real engineering at all - they just use what's available and what's standard with occasional destructive testing for quality control; and for aluminum that means they're generally over-built. The more boutique and custom makers who do design closer to the edge have to spend more time with engineers.
Now... knowing what you do about how fatigue happens and with a general understanding of loads on a bike frame; how would you evaluate the OP's claim that his previously undamaged seat tube failed from fatigue, not near a weld?
Oh I didn't take it as that at all, I am a huge geek and love to talk about metal, structures etc. Being new to biking I really appreciate the discussion.
I would love to see a picture, closeup, of the failure. Considering fatigue failures are caused over millions of cycles I do not think it is a fatigue failure simply because I do not think the human butt has the endurance that would be required to cause a true fatigue failure.
I would like to add that I chose a steel bike because steel is more forgiving to damage and is much easier to fix for anyone with with even poor welding skills (me).