Shear stress ...
Nick Kew
Just past the top of the route, something strange happened, and I felt
myself going over the bars. A strange and interesting experience, as
I fell I could see in slow motion exactly what was happening, and I
was able to control my fall rather well, avoiding any injury beyond
a bump and a couple of light grazes. I strongly suspect that I wouldn't
have had that level of control if my head had been constrained in an
eggshell.
Getting up, I discovered the reason for my fall. My left handlebar was
hanging loose, having snapped through sheering, presumably at the moment
of maximum stress as the front wheel (intentionally) hit the slab of rock
that was the far side of a dip I was traversing. The bars had bent
round, and the brakes were rubbing due to that. I unhitched the brakes
and started out to walk the seven or eight rocky - but mostly downhill -
miles home.
Anyway, I'm well, and not sure how much I'm going to have to replace
this time. But I'm wondering how often this kind of thing happens and,
given that there were no visible signs of deterioration in the handlebars,
how I should avoid this kind if thing happening in future, perhaps with
much nastier consequences. Perhaps one should stick to nice heavy steel
bars? And for similar reasons, forks. And ....
(oh, and, er, the subject line is intentional :-)
--
Nick Kew
A.Lee
> Getting up, I discovered the reason for my fall. My left handlebar was
> hanging loose, having snapped through sheering,
Someone on rec.bikes.tech recommended that bikes used off-road should have
their bars replaced every year without fail.
Alan.
--
To reply by e-mail, change the ' + ' to 'plus'.
http://www.dvatc.co.uk - Off-road cycling in the North Midlands.
David Martin
<ni...@hugin.webthing.com> wrote:
> But I'm wondering how often this kind of thing happens and,
> given that there were no visible signs of deterioration in the handlebars,
> how I should avoid this kind if thing happening in future, perhaps with
> much nastier consequences.
Many years ago (about 16) in a land far south from here (Maidenhead) I was
riding up to a roundabout on the Asomethingorother (308?) and my left hand
handlebar[1] came off in my hands. (an SR something or other)
being in my pre-clipless days I had tightly done up toestraps and cleated
shoes. And a handlebar in each hand. And a major roundabout coming up.
Fortunately a piece of road furniture came to my aid as I was able to stop
and make a lunge for the railing.
It does happen. It is worth checking your kit frequently, especially if you
put the bars under any level of stress. And it is a lot easier to do now
with multi bolt front loading stems. If you are really paranoid you could do
a dye penetrant test.
I'll be checking mine when I dismantle the road bike for respraying and
upgrading. The MTB is steel so should give a bit more warning of imminent
failure.
..d
[1] until that point it was my left and right handlebar
Simon Brooke
('ni...@hugin.webthing.com') wrote:
> Well, I went for a quick spin on the moors this afternoon.
>
> Just past the top of the route, something strange happened, and I felt
> myself going over the bars. A strange and interesting experience, as
> I fell I could see in slow motion exactly what was happening, and I
> was able to control my fall rather well, avoiding any injury beyond
> a bump and a couple of light grazes. I strongly suspect that I
> wouldn't have had that level of control if my head had been
> constrained in an eggshell.
Ouch! Glad it's no worse!
> Getting up, I discovered the reason for my fall. My left handlebar
> was hanging loose, having snapped through sheering, presumably at the
> moment of maximum stress as the front wheel (intentionally) hit the
> slab of rock
> that was the far side of a dip I was traversing.
More detail, please: aluminium or carbon bars? How old? Rigid or
suspension forks? With bar-ends or without (and if 'with' were you
using them?). Seeing it's you I'm guessing 'aluminium', 'quite',
'rigid', 'without' and 'no'...
> Anyway, I'm well, and not sure how much I'm going to have to replace
> this time. But I'm wondering how often this kind of thing happens
> and, given that there were no visible signs of deterioration in the
> handlebars, how I should avoid this kind if thing happening in future,
> perhaps with
> much nastier consequences. Perhaps one should stick to nice heavy
> steel bars? And for similar reasons, forks. And ....
Well, of course, one can break things. Particularly if one rides bikes
with silly-light components. But I never have and I'm a big guy and
ride a lot of fairly silly stuff. If you'd been putting bar ends on
silly-light carbon bars I'd call that asking for it, but otherwise I'd
say it's a pretty unusual accident - no less serious for that, of
course.
--
si...@jasmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/
Das Internet is nicht fuer gefingerclicken und giffengrabben... Ist
nicht fuer gewerken bei das dumpkopfen. Das mausklicken sichtseeren
keepen das bandwit-spewin hans in das pockets muss; relaxen und
watchen das cursorblinken. -- quoted from the jargon file
Nick Kew
Simon Brooke <si...@jasmine.org.uk> writes:
>> Getting up, I discovered the reason for my fall. My left handlebar
>> was hanging loose, having snapped through sheering, presumably at the
>> moment of maximum stress as the front wheel (intentionally) hit the
>> slab of rock
>> that was the far side of a dip I was traversing.
>
> More detail, please: aluminium or carbon bars? How old? Rigid or
> suspension forks? With bar-ends or without (and if 'with' were you
> using them?). Seeing it's you I'm guessing 'aluminium', 'quite',
> 'rigid', 'without' and 'no'...
Hehe, right on every count (I'm impressed; we've only met twice and
never in a cycling context).
The bars say aluminium alloy. The idea of Al actually bothers me a
bit precisely because I know it's weak against sheering, but I kind-of
assumed bike manufacturers would know about that, and the kind of alloy
used in bars would be different. The frame is a cr-mo, fwiw.
--
Nick Kew
Simon Brooke
('ni...@hugin.webthing.com') wrote:
Well, I bet at least 70% of the bars out there are aluminium alloys of
one sort or another, and failures are pretty rare. Nasty when it
happens of course. Carbon composite is possibly a better material for
bars but most CC bars are silly-light so also fragile, and, of course,
carbon composite suffers from the problem that weakening due to damage
is not always evident. Steel bars are still available, if rare.
You might consider a set of 'downhill' bars, on the basis that the
downhill boys value strength over weight.
--
si...@jasmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Madness takes its toll. Please have exact change.
Pete Biggs
> Someone on rec.bikes.tech recommended that bikes used off-road should
> have their bars replaced every year without fail.
Manufacturers of road bars recommend replacing the bars regularly as well.
I've never bothered to do that myself but should rethink about it now,
especially as mine have (light) score marks either side of the stem!
~PB
Just zis Guy, you know?
> Manufacturers of road bars recommend replacing the bars regularly as
> well.
Mine failed after about 18 years IIRC.
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk
88% of helmet statistics are made up, 65% of them at Washington
University
Nick Kew
"Just zis Guy, you know?" <outloo...@microsoft.com> writes:
>> Manufacturers of road bars recommend replacing the bars regularly as
>> well.
>
> Mine failed after about 18 years IIRC.
Mine lasted a little less than half that, in mixed on/off road use.
--
Nick Kew
taywood
>Just past the top of the route, something strange happened, and I felt
> myself going over the bars. A strange and interesting experience, as
> I fell I could see in slow motion exactly what was happening, and I
> was able to control my fall rather well, avoiding any injury beyond
> a bump and a couple of light grazes. I strongly suspect that I wouldn't
> have had that level of control if my head had been constrained in an
> eggshell.
Sounds like you've never fallen before, lucky sod.
Around 55 years ago we had a schoolfriend who was a goalie and
used to practise taking dives on the schoolfield.
We thought this would be great practise for falling off our bikes
and devised ways of rolling over the bars onto the grass and stepping
off a sliding bike. We didnt have spd's in those days.
Over the years I've put my shoulders out in falls but never, thankfully,
put my arm out to break the fall. Thats a learned skill.
And we didnt have 'eggshells' !