Re: Odd failure

On 7/10/2024 2:59 PM, Roger Merriman wrote:

Frank Krygowski <frkrygow@sbcglobal.net> wrote:

On 7/10/2024 8:48 AM, AMuzi wrote:

On 7/9/2024 9:23 PM, Frank Krygowski wrote:

At the start of yesterday's club ride, a good friend had taken her
bike out of her hatchback as usual, slipped the front wheel into the
forks as usual, and tightened the quick release. She said she heard a
"ping." Then her quick release felt funny, in that it had lost it's
"over center" clamp action.
>
Several guys fussed with it, trying to determine what had gone wrong.
The fundamental clamp action still worked, just not the over-center
action. We pulled the skewer out and saw no visible problem.
>
Ultimately, we clamped it, pounded as hard as we could on the top of
the tire as she held up the front wheel, pushed as hard as possible
side to side on the wheel, and proclaimed it rideable.
>
She completed the 35+ mile ride just fine with the wheel still tight
in the forks. But I suggested she follow me home so I could donate a
spare skewer, plus take hers apart to see what might have happened in
there.
>
When I disassembled the skewer's lever action, here's what I found:
The left or lever end of the skewer features a steel cylinder maybe
1/2" diameter and ~1/2" long, drilled with a transverse hole ~3/8"
diameter. The circular eccentric surface of the lever operates inside
that hole, applying leftward force to put the skewer in tension. (Most
of us probably knew all that.)
>
In her case, the metal between the side wall of the transverse hole
and the outer surface of the 1/2" cylinder failed in tension,
doubtlessly due to fatigue. That caused enough deformation to remove
the over-center action. The other side wall held and provided clamping
tension. I think it was important that the cylindrical end piece is a
pretty close fit in the thick chrome "nut" in which the lever pivots,
so serious bending action on the remaining metal wasn't possible.
>
I'd never seen that sort of failure before, and neither had my bike
mechanic buddies. I wonder if others here (especially Andrew) had.
>

>
I have, just not commonly.
>
I think you said the bell cracked on one side. Those are hardenable
steel and hardened, then chromed. The crack is probably parallel to the
axle's centerline, yes?

>
If I understand you correctly: No, it wasn't the chromed external "bell"
that failed. It was the skewer itself, within the bell. But not the
small diameter shaft; instead, the larger diameter integral end of the
skewer.
>
Here, I just tried for a photo:
https://www.flickr.com/photos/16972296@N08/53846893247/in/dateposted-public/

>
Speaking of failure, yesterday I replaced a left arm on a 1993
Campagnolo equipped Bianchi which was otherwise well maintained with
plenty of miles:
>
http://www.yellowjersey.org/photosfromthepast/failfcmi.jpg
>
It split on the outside corner, parallel to the BB axis. I cut a slice
as opposite as possible to open the crank and show the metal's grain.
It made noise but didn't fall off the spindle.

>
I love and ride old bicycles, but I wonder how many components are
approaching their fatigue life.
>

I found that various bolts had reached theirs when i converted the old MTB
to the commute beast, ie put panniers on, mudguards and more road focused
tires, plus lights.
 But various QR stuff just gave up the ghost in terms of not tightening
correctly or needing excessive force to do so.
 The wheels or rather the front one continued to do so until I replaced with
a bolt late last year.
 Mind you also had a rear mech come apart.
 Can’t say the frame or bars or indeed bolts have given me any concern, the
Frame/stem/bar are all original the seat post failed or rather started to
rotate the saddle until a month or so.
 Bike is 19 years old at this point or close enough, so an old bike not
obsolete but certainly dated though MTB have gone through much more change
this century than road bikes arguably.
 Roger Merriman
 

QR cams, open or closed style, all brands and models, work best with some lubricant. Old, encrusted, sticky and/or rusted cams will not, as you report, close and lock properly.
Next time, oil your cam, work the lever until the black crud runs out and try it once more.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971