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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Odd failure
Date: Wed, 10 Jul 2024 07:48:07 -0500
Organization: Yellow Jersey, Ltd.
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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? I've seen 
them split on both sides at once, the pieces falling away. A 
crack on one side is a very good failure since the wheel 
didn't come out!

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.
-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971