Song wrote:
> I recently bought a front wheel with a radially-laced, straight-pull 24h Aerohead rim on ebay, and
> when it arrived, to my dismay, there were hairline cracks in the anodized layer - perhaps the rim
> itself? - on at least one side of every spoke hole on the rim.
>
> http://www.stanford.edu/~weisong/aerohead.htm
>
> The wheel itself is very true, no hops, does not appear to have been abused. If you're an
> experienced aerohead user or experienced with heat-treated rims in general, please tell me whether
> this damage is strictly cosmetic, or is an omen of catastrophic things to come.

If I still had it I would send you an "after" picture of an Aerohead (DT 14, 3X, 32) with a nice
line of three distorted spoke holes, spoke on the center one cracked clear out of the rim. This was
in theory a well-built wheel though it was one heck of a pothole-smack that did it in. You should
have heard the "Tonnnnnnnnnggggg", who dropped the piano?

Visible cracks on rims strike me as the kind of thing where you just don't bother to guess if
it'll work.

-Tad "what is all the fuss about Aeroheads?" (0 for 3)

Tad Borek writes:

>> I recently bought a front wheel with a radially-laced, straight-pull 24h Aerohead rim on eBay,
>> and when it arrived, to my dismay, there were hairline cracks in the anodized layer - perhaps the
>> rim itself? - on at least one side of every spoke hole on the rim.

http://www.stanford.edu/~weisong/aerohead.htm

>> The wheel itself is very true, no hops, does not appear to have been abused. If you're an
>> experienced Aerohead user or experienced with heat-treated rims in general, please tell me
>> whether this damage is strictly cosmetic, or is an omen of catastrophic things to come.

> If I still had it I would send you an "after" picture of an Aerohead (DT 14, 3X, 32) with a nice
> line of three distorted spoke holes, spoke on the center one cracked clear out of the rim. This
> was in theory a well-built wheel though it was one heck of a pothole-smack that did it in. You
> should have heard the "Tonnnnnnnnnggggg", who dropped the piano?

Are you suggesting that striking a pot hole ripped the spokes out? There must have been something
else at work because radial overloads only slacken spokes and do not significantly increase tension
in any spokes unless the arc of the rim is severely flattened (permanent large dent).

> Visible cracks on rims strike me as the kind of thing where you just don't bother to guess if
> it'll work.

I think such failures can be observed and carefully ridden home if suitable care is taken. Let's not
forget that the highest tension is in spokes not in the load affected zone (about six inches at the
ground contact point) and that it is the lower tension as spokes pass the ground contact zone that
causes fatigue failures, the ones in question here. This is not a forced failure condition as you
imply by the paragraph above. Failures that occur at such bumps in the road do so as the last straw,
so to speak, in stress cycles when the wheel becomes unloaded after the shock.

Jobst Brandt jobst.brandt@stanfordalumni.org

don't you think it interesting to see cracks perpendicular to maximum compressive stress?

jobst.brandt@stanfordalumni.org wrote:
> Wei Song writes:
>
>
>>I recently bought a front wheel with a radially-laced, straight-pull 24h Aerohead rim on eBay,
>>and when it arrived, to my dismay, there were hairline cracks in the anodized layer - perhaps the
>>rim itself?
>> - on at least one side of every spoke hole on the rim.
>
>
>>The seller has kindly offered compensation, but in order to reach agreement we agree on how
>>extensive it should be, he asked me to get a second opinion. So here I humbly seek all your second
>>opinions. If you have some time, check out the link below:
>
>
> http://www.stanford.edu/~weisong/aerohead.htm
>
>
>>The wheel itself is very true, no hops, does not appear to have been abused. If you're an
>>experienced Aerohead user or experienced with heat-treated rims in general, please tell me whether
>>this damage is strictly cosmetic, or is an omen of catastrophic things to come.
>
>
>>Note: blue Aerohead rims are supposed to be powder-coated, but this seems to be an older model and
>> sure looks like anodiztion to me. But perhaps you can tell?
>
>
> This rim is anodized and the crack is IN the aluminum, anodized coatings seldom being more than
> 0.001" thick. This problem cannot be solved with washers, there being no space to fit a washer
> inside this rim. It is possible that the inside of the rim has a counterbore that is too small for
> the spoke nipple head and that it has wedged itself into a splitting position but that doesn't
> hold much hope because such a nipple could not be readily turned to tension spokes. Therefore, I
> believe the cracks are on the way to getting larger with use.
>
> One should wonder why sockets and eyelets were used with success on 300g rims of old. The claim is
> that we have better materials today but the cracks don't support that claim.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org

Jim Beam / Jack Daniels writes:

> Don't you think it interesting to see cracks perpendicular to maximum compressive stress?

You are making an unwarranted assumption, especially in light of the opening crack. Instead of
posing rhetorical questions, you might add some perspective to this subject.

No, I don't find that interesting because that shows that the principal stress at this location
is tension from nipple outward bending force. As others have reported, star-burst failures have
also occurred.

Jobst Brandt jobst.brandt@stanfordalumni.org

jobst.brandt@stanfordalumni.org wrote:
> Tad Borek writes:
>>If I still had it I would send you an "after" picture of an Aerohead (DT 14, 3X, 32) with a nice
>>line of three distorted spoke holes, spoke on the center one cracked clear out of the rim. This
>>was in theory a well-built wheel though it was one heck of a pothole-smack that did it in. You
>>should have heard the "Tonnnnnnnnnggggg", who dropped the piano?
>
> Are you suggesting that striking a pot hole ripped the spokes out? There must have been something
> else at work because radial overloads only slacken spokes and do not significantly increase
> tension in any spokes unless the arc of the rim is severely flattened (permanent large dent).

Ya, there was a lot going on really. I've pondered the exact dynamics of that failure. Modeling the
pothole edge as a right angle that is struck by a wheel ~2" sunk into it wouldn't be too far off.
The tire (Vred) was well-inflated but very likely not at 145 psi or whatever the sidewall says.
Wheel almost new, my guess is the tension was a bit low. I was on the drops at ~high 20's mph and
unfortunately focused on the bumper in front rather than the pavement below.

The rim indeed ended up heart-shaped, w/a crisp indendation where the edge hit. The largest spoke
hole crack looked like someone had taken tin shears, cut a 1/8" gash, then needle-nose pliers, and
bent one of the resulting "corners" outward. I don't recall that spoke's relationship to the
flattened point on the rim.

>>Visible cracks on rims strike me as the kind of thing where you just don't bother to guess if
>>it'll work.
>
> I think such failures can be observed and carefully ridden home if suitable care is taken.

Yes though I rode carefully, and was missing the old brake QR of Campy SR. Who came up with those
buttons anyway?

I wouldn't push that though, that was my point about this ebayed wheel. Send it back, wheels
are cheap!

Let's not forget that the highest tension is
> in spokes not in the load affected zone (about six inches at the ground contact point) and that it
> is the lower tension as spokes pass the ground contact zone that causes fatigue failures, the ones
> in question here. This is not a forced failure condition as you imply by the paragraph above.
> Failures that occur at such bumps in the road do so as the last straw, so to speak, in stress
> cycles when the wheel becomes unloaded after the shock.

I had dismissed it as a wheel that was just poorly built. But seeing the OP's photos makes me
reconsider whether the shock brought out a rim defect, or whether the load exceeded the capabilities
of the materials for that particular rim. Despite the generally good reviews I haven't had good luck
with that rim.

-Tad

what's my assumption? why is it [whatever "it" may be] unwarranted?

i merely raise a point of interest because istr being lectured about how perpendicular cracking
modes are not seen because of a rim's compressive hoop stress.

jobst.brandt@stanfordalumni.org wrote:
> Jim Beam / Jack Daniels writes:
>
>
>>Don't you think it interesting to see cracks perpendicular to maximum compressive stress?
>
>
> You are making an unwarranted assumption, especially in light of the opening crack. Instead of
> posing rhetorical questions, you might add some perspective to this subject.
>
> No, I don't find that interesting because that shows that the principal stress at this location is
> tension from nipple outward bending force. As others have reported, star-burst failures have also
> occurred.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org

Jim Beam / Jack Daniels / Cutty Sark writes:

>>> Don't you think it interesting to see cracks perpendicular to maximum compressive stress?

>> You are making an unwarranted assumption, especially in light of the opening crack. Instead of
>> posing rhetorical questions, you might add some perspective to this subject.

> what's my assumption? why is it [whatever "it" may be] unwarranted?

Your assumption about "maximum compressive stress" is incorrect because otherwise the crack wouldn't
separate (tension) as shown.

> i merely raise a point of interest because istr being lectured about how perpendicular cracking
> modes are not seen because of a rim's compressive hoop stress.

I think you'll have to put all that in context if you want your thinking to be apparent in this
thread. I certainly did not say that and I don't know who did. Why don't you explain how you think
it occurs instead of these insinuations by rhetorical questions.

>> No, I don't find that interesting because that shows that the principal stress at this location
>> is tension from nipple outward bending force. As others have reported, star-burst failures have
>> also occurred.

Jobst Brandt jobst.brandt@stanfordalumni.org

jobst.brandt@stanfordalumni.org wrote in message news:<Od_Yb.2164$_3.35288@typhoon.sonic.net>...

> Why don't you explain how you think it occurs instead of these insinuations by rhetorical
> questions.
>

Dear Jobst,

You forgot the question mark on your own insinuating rhetorical question.

Carl Fogel

Carl Fogel wrote:

> Dear Jobst,
>
> You forgot the question mark on your own insinuating rhetorical question.

Carl, please don't taunt the curmudgeon. That sort of thing never ends well.
--
terry morse Palo Alto, CA http://www.terrymorse.com/bike/

On Thu, 19 Feb 2004 10:50:33 -0800, Terry Morse <tmorse@spamcop.net>
wrote:

>Carl, please don't taunt the curmudgeon. That sort of thing never ends well.

And in this case, that particular curmudgeon has a long track record of being right !

jobst.brandt@stanfordalumni.org wrote:

> Jim Beam / Jack Daniels / Cutty Sark writes:...

It is actually Johnny Walker.

Tom Sherman - Quad Cities (Illinois Side)