[CR]broken cranks

(Example: Framebuilders:Bernard Carré)

From: "brian blum" <brianblum@hotmail.com>
To: classicrendezvous@bikelist.org
Date: Fri, 13 Apr 2001 00:02:16
Subject: [CR]broken cranks

I was the proud breaker on a Raleigh Sports BB axle in around 1974. The SA hub held up but the daily cranking up the short 20% grade by my house with a load of newspapers got the best of the axle with a nice spiral torsion failure in the center of the axle and I weighed 103-125 lbs at the time. That bike still has twisted steel crank arms obviously Raleigh did not use the strongest carbon steel or the best finish on these parts. I broke an Avocet crank through the pedal eye on my favorite Colnago I bought from Mike Kone(WARNING ;) just kidding ). I was 0.25 miles out jamming up a hill on the way to work, my right foot skidded along the road into the red painted curve as demonstrated by the paint left on the pedal. I lucky kept it up right or I might have been under the car just to my left. That bike had tons of miles and I broke or wore out almost everything else on that bike except the brake calipers, handlebars and seat post.

Basically all your aluminum parts will eventually fail so beware of old parts especially if they are grooved or otherwise visually damaged. As the parts shown on the webpages demonstrates, most of the cracks were probably not noticeable before failure without dye penetrate or very close inspection so be very careful with high mile aluminum parts. Steel also fails but aluminum is much more suseptable. Remember that that Boeing 747 you are flying on is loaded with cracks, maintenance crews keep a log of observed cracks and just monitor there progression toward failure and usually replace parts before they lose too much strength. They miss once in a while such as the 1988 convertible Hawaiian airlines 737.