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
+++++++++++++++++ Earlier posts +++++++++++++++++++++
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I would point out that this test assumes all the loads are applied as if
climbing out of the saddle. And then you need to assume the test actually
simulates those loads. I suppose if you want a bike optimized for riding out
of the saddle all the time- this is your test.
As for me I'm not much concerned about head tube failures in steel frames.
Joe Bender-Zanoni
Great Notch, NJ
>> In a message dated 11/6/2004 2:41:45 PM Eastern Standard Time,
>> gillies@cs.ubc.ca writes:
>>
>> << http://www.damonrinard.com/
>>
>> Quite possibly - after all, the DeRosa in this fatigue-limit test
>> performed the worst out of 20 bikes !! And will we be stuck with TREK
>> OCLV frames for a long, long, long time because apparently they are
>> balanced in a way that allows them to survive many fatigue cycles ?? >>
>>
>> Talking about most of these bikes is off topic but this test is at least
>> questionable and at worst bologna.
>> It is ironic that in real world use, Trek OCLV, Cannondale and Principia
>
>
are
>> KNOWN to break! Of all the makes listed, these guys have an acknowledged
>> history!
>> And then the DeRosa and other lugged bike broke in the exact same place...
>
>
A
>> place I have never seen a bike break in over 30 years in the biz! That
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>
really
>> seems strange. I see that they don't show how they held the front end of
>
>
the
>> frames in their stress testing machine. Hmmmm.
>> I urge anyone concerned about their DeRosas to abandon use immediately and
>> send them to me.
>>
>> Dale Brown
>> Greensboro, NC