[email protected] wrote: <snip>
> What are you talking about. I have never mentioned dye penetration. What's more, you ignore that
> cracked rims were brought to us primarily on the day Mavic offered the MA-40, a version of rim
> that not anodized precursor (MA-2) is still performing well with no cracks and no fear of
> cracking. You may not have ridden bicycles in the days before anodized rims and the greater
> durability claimed for them. Those of us who recall that day also remember how cracked rims were
> everywhere after that. Reducing the anodizing thickness has ameliorated that a little.
"I have never mentioned dye penetration." well, it's certainly what you were referring to here:
http://groups.google.com/groups?selm=9%25x_a.11466%24dk4.433979%40typhoon.sonic.net&oe=UTF-
8&output=gplain
either you have done dye penetrant testing for cracks in rims or you haven't. which is it?
in addition, you assert that the ma2 is not anodized. it most definitely was available in clear
anodized. i have one. in fact, i've even taken the trouble to specifically look for ma2's since we
first started this little love-fest, and guess what? only 1 of the 30-odd silver ma2's i have
inspected has been unanodized, [and that had corrosion issues]. so, while you may be the guy that
managed to stockpile the last of the small number of unanodized ma2's that were ever imported, the
poor unsuspecting masses have had to put up with clear anodized ma2's, so kindly adjust your
rhetoric. and if you still don't believe me, take a look at the old mavic catalog for confirmation
of the silver anodized ma2's existence.
<snip>
> OK, so why do we have, as you seem to imply, poorer alloys today than in the 1950's when none of
> these failures occurred even though average roads were rougher in those days? So you are claiming
> that rims crack not because they are anodized but rather that they are made of less suitable
> alloys... even though the MA-2 and MA-40 were the same extrusion to begin with.
your implication, not mine. modern alloys have much better yield &
u.t.s. with better weldability. "suitability" depends on the overall objective. if you want a rim
that is strong enough to deal with ultra-dished wheels and lower spoke counts, than yes,
modern alloys are better. as a component whose predominant failure mode [outside of sunny
california] is braking surface wear, i see no problem with having a rim have a higher chance
of cracking at higher mileage if physical wear predominates and the other primary design
criteria are better met.
<snip>
> You're dodging. With experience in rims, you could readily make an accurate assessment of this
> failure, knowing that such events were unknown before anodizing. Besides, claiming that it
> couldn't be caused by anodizing because it was worn off, as some have opined, misses the point
> that the crack opens in tension, inside the profile, not from the outside (brake surface) that
> failed last in forced rupture.
dodging what? those pics are inconclusive. unless you are telling us that you've had an identical
failure and that it's been properly analyzed by an appropriate specialist, then you can't feed us
what then amounts to conjecture and guesswork. your assertion that "such events were unknown before
anodizing" makes absolutely no account of changes in alloy, heat treatment, eyelet design, etc. etc.
it's just a wildly emotive statement.
snip>
> OH? You also don't recall the days of failed parts on older cars where axles often broke to expose
> intergranular failure from which mechanics of the day were led to say, "your axle was too old, it
> crystallized" which they went on to show by the surface of the fracture. Forced ruptures are
> smeared and fine in texture, fatigue failures are rough and crystalline in aluminum used here.
since when did a hot [or cold] forged carbon steel axle have the same microstructure as an extruded
alloy rim? what effect does carbon diffusion have on this extruded alloy rim? how about sulfides?
this is a complete red herring.
<snip>
> Scraping a knife over either kind of anodizing without penetrating force, you will find a hard
> crust that resists scratching. You can also inspect such surfaces under grazing incidence light
> and see cracks in both hard anodizing and cosmetic anodizing. Your method of attacking straw men
> does not do much convincing for those who are aware of these techniques of argumentation. I
> haven't seen you point out why these rims crack other than saying that it isn't anodizing.
what you are saying jobst, yet again, is that there is only one element in this failure equation,
anodizing, and i am telling you, yet again, that it's not as simple as that. there are many
elements, which do include anodizing, but also include alloy composition, heat treatment, hot & cold
work history, mechanical design and chemical environment. to make a blanket statement essentially
saying "it's anodizing - end of story" is as accurate as your mechanic saying "your axle was too
old, it crystallized".
