Metal fatigue
- Thread starter 531 pro
- Start date
torqueless
Senior Retro Guru
Where exactly was the break in the bar, 531pro? I have a morbid interest in this stuff, probably because just about every bit of bike I own is a candidate for similar failure. I treat such reports as "a word to the wise", and reading this thread has inspired me to clean some 20 year-old tape residue off a pair of Cinelli bars and inspect the assortment of scars. I doubt I'm the only person with zig-zag scars up the drops from trying to get those Campag. NR brake lever clamps into position. That would have been easier without the tape residue no doubt!
That's one reason I prefer the old (IIRC) Mafac lever clamps that you fold around the bars, in much the same way as you would the old steel band-on downtube gear-lever clip.
Apart from that, I've got a few scars further up the bars from trying to get a steel stem into position. The bar-clamp on the stem was too wide to go 'round the bends. Given that any one of these scars could be a 'stress-raiser', I'm reasoning that on the whole it may be safer to polish them out, even though that obviously means reducing the wall-thickness of the tube to the depth of the scars.... Well, I ain't gonna be doin' any sprinting...
I've had to do something similar to a 531 downtube. Somebody I trusted to replace my bottom-bracket shell left a scar nearly all the way around my downtube...the kind of scar that a pipe-cutter would make......... WTF? :evil: :cry: So I had to 'polish' that away.. It's three or four inches away from the bracket-shell so I'm hoping it's on the butted bit of the tube. That's what I call a 'stress raiser', both metallurgically and psychologically... :x That to me is the real value of 'original paint', which, if genuine, is the best guarantee you've got that nobody has been building future failure-sites into your tubes..
That's one reason I prefer the old (IIRC) Mafac lever clamps that you fold around the bars, in much the same way as you would the old steel band-on downtube gear-lever clip.
Apart from that, I've got a few scars further up the bars from trying to get a steel stem into position. The bar-clamp on the stem was too wide to go 'round the bends. Given that any one of these scars could be a 'stress-raiser', I'm reasoning that on the whole it may be safer to polish them out, even though that obviously means reducing the wall-thickness of the tube to the depth of the scars.... Well, I ain't gonna be doin' any sprinting...
I've had to do something similar to a 531 downtube. Somebody I trusted to replace my bottom-bracket shell left a scar nearly all the way around my downtube...the kind of scar that a pipe-cutter would make......... WTF? :evil: :cry: So I had to 'polish' that away.. It's three or four inches away from the bracket-shell so I'm hoping it's on the butted bit of the tube. That's what I call a 'stress raiser', both metallurgically and psychologically... :x That to me is the real value of 'original paint', which, if genuine, is the best guarantee you've got that nobody has been building future failure-sites into your tubes..
TimColnago
Dirt Disciple
I have quite a few Non Accident related faliures over the years…
Campagnolo C Record Wide Flange Track Hub. Spoke tension pulled hub apart!
Cinelli Bars. Sprinting away from traffic lights and bar snapped
653 Mercian Fillet brazed frame. Testing newly fitted dual pivot brakes. Frame fork clearance to close and front wheel touched frame resulting in front wheel touching frame and sending me over the bars and crumpled frame. Long dispute with Mercian who thought I had ridden into a stationary object. :twisted:
Ralegh Dyna Tech (Not Sure what Model) Climbing out of saddle and frame cracked where drilling is for down tube shifters.
Peugeot Aluminium Frame X2. Snapped on seat stays. Given replacement under warranty which also snapped.
Kirk Prescion frame. Dissolved; Front mech hanger separated from frame.
Bottom bracket - Axle snapped on winter Derbyshire training ride leaving me stranded the days before mobile phones.
Campagnolo C Record Wide Flange Track Hub. Spoke tension pulled hub apart!
Cinelli Bars. Sprinting away from traffic lights and bar snapped
653 Mercian Fillet brazed frame. Testing newly fitted dual pivot brakes. Frame fork clearance to close and front wheel touched frame resulting in front wheel touching frame and sending me over the bars and crumpled frame. Long dispute with Mercian who thought I had ridden into a stationary object. :twisted:
Ralegh Dyna Tech (Not Sure what Model) Climbing out of saddle and frame cracked where drilling is for down tube shifters.
Peugeot Aluminium Frame X2. Snapped on seat stays. Given replacement under warranty which also snapped.
Kirk Prescion frame. Dissolved; Front mech hanger separated from frame.
Bottom bracket - Axle snapped on winter Derbyshire training ride leaving me stranded the days before mobile phones.
It's only in recent years that apart from the aerospace industry, nobody did any real stress or fatigue testing - using empirical design standards you designed your parts, made a prototype for someone to test and if it didn't break that became the production standard. If it did break, you hoped no one got hurt and make the next ones a bit thicker! This has only changed in the last 15 years where modern CAD packages have built-in stress analysis combined with better quality production methods.
Consequently, many old parts are hugely over-engineered - the ones that weren't broke years ago!
Consequently, many old parts are hugely over-engineered - the ones that weren't broke years ago!
