Re: [CR] Frame Weight and Stiffness - and Failure Analysis of Bike Components

From: "Jon M. Crate" <Jon@FAI.US>
To: 'Hugh Thornton' <hughwthornton@yahoo.co.uk>, 'Classic Rendezvous' <classicrendezvous@bikelist.org>
References: <293972.91054.qm@web25902.mail.ukl.yahoo.com>
Date: Thu, 29 Oct 2009 14:06:54 -0400
Organization: FAI Materials Testing Laboratory
Thread-Index: AcpYoukZX5+jjbQ2T2ij/oxh34eLxgAHWrhg
In-Reply-To: <293972.91054.qm@web25902.mail.ukl.yahoo.com>
Subject: Re: [CR] Frame Weight and Stiffness - and Failure Analysis of Bike Components

Hugh, I loved this reference, thank you.

I noted on their site a series of analyses of bike component failures: http://materials.open.ac.uk/mem/mem_ccf.htm

Most are fatigue related, especially several made of aluminum or fasteners. It reminded me of the fact that I am riding a 40 year old machine. Yesterday I came within about 12 inches of an oncoming bus.

Safety requires us to take precautions when on two wheels, but there is an additional concept we need riding vintage bikes concerning hidden (or hard to see) fatigue cracks. At the bottom of this analysis of the failure of an aluminum crank arm: http://materials.open.ac.uk/mem/mem_ccf4.htm the author gives the excellent advice: "This unfortunate incident may have been prevented only by very close visual inspection or dye penetrant testing on the component during the relatively short crack propagation phase."

On these pages, they cite several failures initiated by galvanic corrosion caused by dissimilar metals left wet: http://materials.open.ac.uk/mem/mem_ccf7.htm http://materials.open.ac.uk/mem/mem_ccf_rims.htm

So the take home lesson is to not only keep an eye on the road, keep a close one on your gear.

Jon M. Crate FAI Materials Testing Laboratory Marietta, Georgia 30066 http://www.FAI.US

-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Hugh Thornton Sent: Thursday, October 29, 2009 10:20 AM To: Classic Rendezvous Subject: [CR] Frame Weight and Stiffness

I have a mid-fifties 24" fillet-brazed Gillott frame with oversized top tube that I thought felt rather light when I lifted it, so I weighed it complete with front fork and Stronglight alloy needle bearing headset (quite light) and the total was 2.85kg. Not bad for a 24" 531 butted frameset with Campagnolo dropouts, but not outstanding. Looking on the internet for comparisons, I came across this web page which has some information on frame weights and stiffness:

http://materials.open.ac.uk/bikeframes/bikeframe.htm

What is so interesting is how well the 531 butted frame compares in stiffness, though not in weight, to more modern frames. It is not surprising that this material was THE standard in racing frames for so long. It probably held the top spot in all European countries with the exception of Italy where Columbus seemed to be the tubing of choice for most top-end frames. I remember some time ago that Reynolds advertised that 531 had won so many out of the last so many Tours de France (almost all, if not all, of them). Does anybody remember when that was, or what the numbers were, or even have a copy of that advertisement? Must have been in the late seventies or more likely sometime in the eighties when they had notched up a few more victories. They really had an impressive record until aluminum and carbon took over. Hugh Thornton Cheshire, England