Aluminum will work harden - stressing and pushing it out of shape makes it stiffer, but more brittle. Forging aluminum is a controlled process to impart the desired stiffness and strength to a specific aluminum alloy through work hardening. Think about bending the straight part of a hanger (steel, but the principle is the same) - it is harder to straighten the curve back out because the curve is stiffer once you have bent it than the straight, and if you do it a couple of times - it will break. All metals have this property (cycle fatigue life), but only two (steel and titanium) have an infinite cycle life* if* you keep the stress below a certain level (% of maximum). Thus if properly engineered, and properly used, steel and titanium can last basically forever. Aluminum will always eventually fail, and lower stress = longer life, but the lifespan is always finite. This is why you don't want to ride certain well used French aluminum handlebars and stems - they weren't always of the finest materials, manufacture or design. This is also why you need to inspect old aluminum parts if you still use them in highly stressed applications (steel and titanium too if they are highly stressed). An old cottered steel crank, even a cheap one can last a very, very long time, but that 50 year old Campagnolo Nuovo Record or Stronglight Model 93 crank may need to be retired to the bike hung on the wall if it has seen a hard life. I still ride bikes and parts that are approaching 50 years old, but I do not jump curbs, etc. - my parts have seen a fairly easy life.
Laing Cocoa, FL On Friday, October 26, 2018 at 8:07:00 AM UTC-4, Steve Palincsar wrote: > Cranks don't break because you were so strong you snapped them, like > breaking a stick over your knee. I've had *four* cranks break on me, > three through the pedal eye and one straight across the middle, and one > other that had a crack originating at the pedal eye that I found before > it progressed far enough to actually break. It's not like it doesn't > happen, believe me. > > On 10/26/18 1:11 AM, Bill Schairer wrote: > > I know that people do break cranks but I have never ever understood how? > It just seems like there lots of other things that should fail before the > crank would assuming everything is operating at all less than totally > frozen. In any case, I’m pretty darn sure that I don’t have the strenght > to break a crank under any circumstances so it is not something I worry > about. Handlebars I can imagine but I’m still riding with 40 year old > bars. > > > -- > Steve Palincsar > Alexandria, Virginia > USA > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
