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Just snapped 20-yr-old crank arm...
I've been riding an Exel crank on my commuter for 20 years now.
Actually, it was on my first racing bike. Today it snapped. My foot hit the ground on a bumpy dirt road uphill, with the pedal still clipped to it. No crash. Man, that was a first. I suppose it's something you don't want to happen too often. I wonder if this kind of thing is going to start happening with all this 20-year-old alloy stuff I'm using right now... Oh well! I must have another crank in a box around here somewhere... --JP |
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Just snapped 20-yr-old crank arm...
Jeff Potter writes:
I've been riding an Exel crank on my commuter for 20 years now. Was it standing in your garage that long or did it get any mileage? How much? Where did it break and how does the break look? If it was bad material, the fracture will be uniformly colored. If it broke gradually from a crack initiation it will show waves from the clean (last failure) to the initiation point. Actually, it was on my first racing bike. Today it snapped. My foot hit the ground on a bumpy dirt road uphill, with the pedal still clipped to it. No crash. Man, that was a first. I suppose it's something you don't want to happen too often. I wonder if this kind of thing is going to start happening with all this 20-year-old alloy stuff I'm using right now... Oh well! I must have another crank in a box around here somewhere... As I have related often, failures at the pedal eye occurred on my bicycle about every 10,000 miles on the average for more than 25 years. That's a lot of cranks and they were mostly Campagnolo and later Shimano. Since then I modified the pedal end of the cranks so they no longer fret, cause crack initiation, and break off through the pedal eye. So where did your crank break? Jobst Brandt |
#3
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Just snapped 20-yr-old crank arm...
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#4
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Just snapped 20-yr-old crank arm...
wrote
... Since then I modified the pedal end of the cranks so they no longer fret, cause crack initiation, and break off through the pedal eye. Can you kindly point to where you have described the modifications. I recall you writing about similar design issues with lug nuts on auto wheels, but I must have missed your description of the actual mods. Cheers, Shawn |
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Just snapped 20-yr-old crank arm...
On Tue, 25 May 2004 22:17:17 GMT, "Shawn Amir"
wrote: wrote ... Since then I modified the pedal end of the cranks so they no longer fret, cause crack initiation, and break off through the pedal eye. Can you kindly point to where you have described the modifications. I recall you writing about similar design issues with lug nuts on auto wheels, but I must have missed your description of the actual mods. Cheers, Shawn Dear Shawn, Here's one of Jobst's posts on his lug-nut pedal modification: http://groups.google.com/groups?selm...&output=gplain David Damerell has done us all a favor by taking the time and trouble to host a 700kb picture of Jobst's modified pedal and crank: http://www.chiark.greenend.org.uk/~d...ndt-cranks.jpg At full size, the picture clearly shows the split in the conical washer around the threaded pedal shaft and corresponding conical depression in the pedal eye. You can find more details by searching for "jobst lug" at: http://groups.google.com/groups?hl=e....bicycles.tech While google groups is slow to include new posts (up to a day's delay), it's easily accessible (no newsreader needed), offers a simple search, and goes back to the crack of doom for rec.bicycles.tech. Carl Fogel |
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Just snapped 20-yr-old crank arm...
David Reuteler writes:
As I have related often, failures at the pedal eye occurred on my bicycle about every 10,000 miles on the average for more than 25 years. That's a lot of cranks and they were mostly Campagnolo and later Shimano. Good lord, that scares the crap out of me. Would you venture a guess at the standard deviation of those failures? (Not that I'm worried with 16,000 miles on my current crank and memories of a catastrophic failure behind me). I don't know but that was more than one per year and the last Campagnolo Cranks were C-Record that failed in less than 3000 miles. That's when I switched to Dura Ace and finally modified these to put an end to crank inspections before every ride. Although others had failures, I had more than average occurrences. These my be affected by the gears I ride and the terrain. I weight 180 lbs. http://tinyurl.com/adls As you can see, there are a lot of tours in between 1960 and 1990 whose reports were lost but they were much like the ones described. Anyone who is good at searching the web for old postings and can find those reports (that appeared on REC.BICYCLE) would be greatly appreciated. I have not been able to find them and the people I rode with and are mentioned in them would love to have copies. Jobst Brandt |
#8
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Just snapped 20-yr-old crank arm...
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#9
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Just snapped 20-yr-old crank arm...
On 26 May 2004, Evan Evans wrote:
Old bikes are nice to look at but you are taking your chances riding them. Even the best components ore subject to fatigue. If you ride much a new bike every once & awile is cheep insurance. One trip to the emergancy room will go along way on that new bike. You are taking your chances every time you ride what you know nothing about. Better be well acquainted with your equipment, whether old or new. Sergio Pisa |
#10
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Just snapped 20-yr-old crank arm...
Old bikes are nice to look at but you are taking your chances riding
them. Even the best components ore subject to fatigue. If you ride much a new bike every once & awile is cheep insurance. One trip to the emergancy room will go along way on that new bike. |
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