MA2 rim cracking - what might be causing this?

jim beam writes:

forgive me for being so retarded gary - i mistakenly thought you had
an interest in the science. it appears not.

if at some point, you /do/ wish to get tech, then i'm happy to
oblige. in the mean time, thanks and goodbye.

Ah, yet another one of jim's hissy fits.

jim beam writes:

imo, you still need to address the effect on reliability of running
a rim at near yield, which is basically what you're recommending
below.

You still need to show that this is in fact "near yield."

"Mike S." mikeshaw2@coxDOTnet writes:

snip
Conincidentally, I saw the first turkey vulture of spring
today. (Robins are passé.)

Yeah, when you're laying on the side of the road recovering at the
top of a hill for long enough they start to thing you're road kill.

Heh. When I moved from Chicago to SE Minnesota and, for the first
time in my life, had decent sized hills to climb I used to be a trifle
worried about those vultures circling over me. I always wondered if
the knew something I didn't.

On 9 Mar 2004 00:00:30 -0800, (Carl Fogel)
wrote:
I'm ashamed to say that I missed your post (an argument for
one of those new-fangled threaded newsreaders).

Threadless newsreaders are lighter and stiffer.
--
Rick Onanian

In article ,
says...
"Mike S." mikeshaw2@coxDOTnet writes:

snip
Conincidentally, I saw the first turkey vulture of spring
today. (Robins are passé.)

Yeah, when you're laying on the side of the road recovering at the
top of a hill for long enough they start to thing you're road kill.

Heh. When I moved from Chicago to SE Minnesota and, for the first
time in my life, had decent sized hills to climb I used to be a trifle
worried about those vultures circling over me. I always wondered if
the knew something I didn't.

There is not much blacktop in Central Australia, but the big birds of
prey love the few main highways, especially the black kites. The
blacktop provides paradise, thermal lift and food via roadkill. So they
cruise down the road, rarely flapping. When they come to a cyclist, they
invariably do one turn to check you out before sailing down the road
ahead.. They have good eyes, so I figure they check the level in your
water bottle....

Rick Onanian writes:

On 9 Mar 2004 00:00:30 -0800, (Carl Fogel)
wrote:

I'm ashamed to say that I missed your post (an argument for one of
those new-fangled threaded newsreaders).

Threadless newsreaders are lighter and stiffer.

And butt-ass ugly. ;-)

On Tue, 09 Mar 2004 21:12:17 -0600, Tim McNamara
wrote:
Rick Onanian writes:
On 9 Mar 2004 00:00:30 -0800, (Carl Fogel)
wrote:
I'm ashamed to say that I missed your post (an argument for one of
those new-fangled threaded newsreaders).

Threadless newsreaders are lighter and stiffer.

And butt-ass ugly. ;-)

No, that's threaded newsreaders. Threadless are *ass-butt* ugly...
--
Rick Onanian

wrote:
jim beam / Johnnie Walker writes besottenly:


It appears to me that these sockets were too short for the depth of
the rim cross section and that when installed and their eyelets
crimped, the rim was locally close to yield. Addition of high
spoke tension caused the inner bed to fail, since this is an
additive load, and when it cracked, only the outer wall supported
most of the load. The small longitudinal cracks in the outer wall
are typical of rims without sockets that rely on the outer wall to
support spoke loads.


The reason I come to this conclusion is that I have spoked many
wheels close to the limit of compressive collapse and used them
until they wore out, never having developed cracks. Therefore, I
believe it takes more than high spoke tension to cause such a
failure. The scenario I offer is the only one that comes to mind
at the moment. This rim, as you say, is not a typical anodizing
failure, as has been previously mentioned.


does that account for drive side only failure - what has been
described in this case? rim sockets are stamped in a fixed die.
there is not sufficient variability in their manufacture to create a
batch of "short" sockets. the only possible way would be for a
socket for the "wrong" rim was used, and that's much more likely to
be a significant difference that would be detected before the rim
got out the door rather than what we see here.


I don't get it. Part of the time you pedagogically advise this
newsgroup on all aspects of materials and their failures, and then you
ask about obvious effects as though you had no understanding of it.

As I said, the stresses are additive and the right side spokes are
tighter than the left... and pull to the right at the bottom of the
sockets putting a high load on the left side of the upper end to
rapidly take the cross section to fatigue failure at that area.

that's nearer the mark! not sure that explains where the "short
sockets" come from though.



imo, you still need to address the effect on reliability of running
a rim at near yield, which is basically what you're recommending
below.


Your mix of top and bottom response confuses the issues even more.
Can you get some help in writing to a newsgroup? Of course you could
glean some of that from reading postings for their format as well.


if my local garage torqued the lug nuts on my car wheels at double
manufacturer spec because they thought they knew better than honda
did, and they failed because of subsequent fatigue, and i had an
accident, i'd have a winning law suit. over-tightening spokes
because "i think it works best" is not very scientific. you need to
produce something in support of your argument as to why this /won't/
accelerate rim failure if you want to make this over-tension
recommendation.



The yield in this case is compressive buckling of the hoop, not stress
at spoke attachments. This is a fairly static load that cannot
initiate cracks and probably even makes up for some of the tensile
loads around spoke attachments. So who ever said "i think it works
best"? Besides, you throw in "over-tightening spokes" as though
anyone suggested doing so. Spokes in the wheels I describe are
running less than half of yield stress as I just reiterated in this
thread. I see you read these things selectively. The reason for
tight spoking is that the strength of the wheel is dependent on spoke
tension, its strength being given by that tension. I've written about
this in the book and here hundreds of times. I'm sure you could
Google to some of those postings is you were interested.

thanks for clarifying that you're advocating less than half yield
stress, because, with respect, when you make a statement like "I have
spoked many wheels close to the limit of compressive collapse" [1] one
is inclined to think you're advocating something substantially more.

[1] -
http://groups.google.com/groups?selm...output=gplain]


Now stop whining! ...and find the shift key on your KBD.

Jobst Brandt

Bruce Graham wrote in message .au...
In article ,
says...
"Mike S." mikeshaw2@coxDOTnet writes:

snip
Conincidentally, I saw the first turkey vulture of spring
today. (Robins are passé.)

Yeah, when you're laying on the side of the road recovering at the
top of a hill for long enough they start to thing you're road kill.

Heh. When I moved from Chicago to SE Minnesota and, for the first
time in my life, had decent sized hills to climb I used to be a trifle
worried about those vultures circling over me. I always wondered if
the knew something I didn't.

There is not much blacktop in Central Australia, but the big birds of
prey love the few main highways, especially the black kites. The
blacktop provides paradise, thermal lift and food via roadkill. So they
cruise down the road, rarely flapping. When they come to a cyclist, they
invariably do one turn to check you out before sailing down the road
ahead.. They have good eyes, so I figure they check the level in your
water bottle....

Dear Mike, Tim, and Bruce,

Here, the turkey vultures seem to commute up and down the
Arkansas River valley between opposing bluffs. About two
dozen roost every year in a fifty-foot blue spruce a few
blocks away, probably because it sticks up above the
rest of the trees in the neighborhood. Every evening in
the summer, dozens of other vultures can be seen flying
west over my house to other roosts. Occasionally they
settle in the trees on my block. They're rather graceful
birds, once they're aloft, and seem to enjoy aerobatics.

Here's one that I knew slightly:

http://www.chieftain.com/display/1023688800/lifestyle/1

I met Hurlly several times on my daily ride and found
him to be a perfect gentleman, willing to move out of
the way. He was eventually re-captured and placed in the
zoo, having proved that he was going to keep pestering
people on the nature trail for treats instead of joining
the other vultures.

The bald eagles do the same thing further west, fishing
during the day at the reservoir and then flying even
further up the river to distant roosts. They have
a rather grim, dogged air as they fly past in a dead
straight line.

Carl Fogel

Rick Onanian wrote in message . ..
On Tue, 09 Mar 2004 21:12:17 -0600, Tim McNamara
wrote:
Rick Onanian writes:
On 9 Mar 2004 00:00:30 -0800, (Carl Fogel)
wrote:
I'm ashamed to say that I missed your post (an argument for one of
those new-fangled threaded newsreaders).

Threadless newsreaders are lighter and stiffer.

And butt-ass ugly. ;-)

No, that's threaded newsreaders. Threadless are *ass-butt* ugly...

Dear Rick and Tim,

Your comments have convinced me--no threaded newsreader.

Think of it as fixed-gear simplicity.

Carl Fogel