Harvey: Just like digital watches aren't necessarily accurate just because they are digital, junk science does not necessarily have any value just because it looks like science...... Again, I say: "Just say no to junk science." Cheers, Greg Parker Ann Arbor, Michigan Date: Sun, 07 Nov 2004 07:29:46 -0500 From: HM & SS Sachs <sachs@erols.com> To: classicrendezvous@bikelist.org, gillies@cs.ubc.ca, joebz@optonline.net, OROBOYZ@aol.com, bikengr@netnet.net Subject: Testing, was [CR]No more DeRosas : they all broke ?!?!
Gentlepeople:
I'm a bit conconcerned about our instinct to jump on and denigrate the test
results (and methods) shown at
http://www.damonrinard.com/
First, it is devilishly hard to build a test protocol that mimics "real life." The guys at Engineering for Bicycles have at least tried. Maybe we don't know enough about how the head tube was anchored, but why should the results otherwise surprise.
Second, I found the test approach rather interesting, in assuming that climbing out of the saddle is the extreme load, and angling the force to simulate that. The second test I might have wanted in an ideal world would have had an impulse applied near-vertically to the rear drops, to simulate hitting something ugly.
Third, Wilson and Papadopoulos (Bicycling Science) have given the properties of materials some thought and expressed things pretty well. If I understand them correctly, there is an evolving and influential school of thought that extrapolating from megacycles at low strain is less relevant for failure prediction than testing with extreme loads/strains. This is exactly what these folks have done.
Fourth, I didn't find much to be surprised about. Yes, it probably missed some failure modes at the back end (see above), but overall it seemed to fit what we all think we know about notches, welding, holes in cylinders, and the likely effects of joining very heavy stuff to very light stuff.
Finally, and I don't want to put words into others' mouths, I don't see this as affecting our love for lugged steel frames. We all know that it is possible to consistently manufacture lighter frames that are relatively reliable from other materials. But we also know that for some inexplicable reason we like lugged steel, and ride it confidently, knowing that our bikes are incredibly unlikely to fail in service -- even though we've all seen lugged steel frames that have failed.
So, I'm thrilled that someone has found time and funding to do this work, and to expose the results to public scrutiny. Can you at least clap with one hand? :-)
thanks
harvey sachs
mcLean VA