Re: [CR]How steel fails


Example: Component Manufacturers:Avocet

To: davebohm@home.com
Cc: gp@rivendellbicycles.com, classicrendezvous@bikelist.org
Date: Wed, 16 Jan 2002 11:15:23 -0500
Subject: Re: [CR]How steel fails
From: Richard M Sachs <richardsachs@juno.com>


<<I am with Grant on the super thin .5.38.5 ultrafoco tubes (is that even butted?). I don't see them having the same reliability that standard tubing has.>>

i kinda' agree too... but i am very pleased that the team's cross frames used main tubes on the light side of 7/4/7 and there hasn't been a single 'issue'. these were lugged frames that weighed 3.6-3.7lbs. some frames are in their 4th season. galli! e-RICHIE

On Wed, 16 Jan 2002 08:45:30 -0700 "dave bohm" <davebohm@home.com> writes:
> I would like to add a little to this
> : Super thin tubes are more likely to break than thick
> tubes, almost regardless of the quality of the steel. In other
> words, a
> frame made with 0.55mm butts (the tubes are out there), even if
> it's
> Jetson-age tubing with wonderful metallurgical scores, is closer
> to death
> than is a frame made with Hi-Ten steel that's 1.2mm at the butts.
> (My
> opinion, just from what I've seen in the past 20 years.)
>
>
> This is generally true, but not for the reasons most might think.
> If we make a comparison between a 1 1/8'' .9.6.9 downtube like SL or
> the like and a modern 1.25'' .7.4.7 True Temper Platinum tube we
> will find that they have nearly identical stiffness or (moment of
> inertia) and therefore have a similar stress level. Theoretically
> they should have similar durability.
> The upside is that the Platinum tube weighs 70 grams less than the
> older, thicker one. The downside, in my opinion is that the
> Platinum tube has a larger ratio of thickness to diameter and
> therefore is more prone to buckling failure if it is dented. So I
> would say that some modern tubing is just as durable it just that
> you cant ride around with a big ol dent in it like you might have
> been able to in the past.
> I am with Grant on the super thin .5.38.5 ultrafoco tubes (is that
> even butted?). I don't see them having the same reliability that
> standard tubing has.
>
> Dave Bohm
> Bohemian Bicycles
> Tucson Arizona