Snapping handle bars

"Bob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It seems like a lot of handle bars are snapping this year. That sort of
thing scares the heck out of me. I had a carbon fork that developed cracks
on both sides. I hate to think what could have happened on a fast descent

if

Quoted message said:

they snapped. Similar fear would apply to handle bars.

Are these carbon bars that are failing?

When you put stupid light parts on your bike you can expect stupid things to
happen.

I have personally experienced a stem failure at 33 MPH. It was a welded
stem and nearly new, never gave the slightest warning. I will guarantee
you that it is not a great thing to experience. I ended up in the hospital
with a broken collar bone, several broken ribs, one of which penetrated my
lung. I will never use a welded stem again nor will I switch to carbon or
other light front end components. Front end failures, even at slow speed
can be catastrophic.

Ken

"Bob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It seems like a lot of handle bars are snapping this year. That sort of
thing scares the heck out of me. I had a carbon fork that developed cracks
on both sides. I hate to think what could have happened on a fast descent

if

Quoted message said:

they snapped. Similar fear would apply to handle bars.

Are these carbon bars that are failing?

-Bob

in article [email hidden], IMKen at
[email hidden] wrote on 7/17/04 5:32 PM:

Quoted message said:

I have personally experienced a stem failure at 33 MPH. It was a welded
stem and nearly new, never gave the slightest warning. I will guarantee
you that it is not a great thing to experience. I ended up in the hospital
with a broken collar bone, several broken ribs, one of which penetrated my
lung. I will never use a welded stem again nor will I switch to carbon or
other light front end components. Front end failures, even at slow speed
can be catastrophic.

How did it fail? Did it fail at a weld? Care to name the stem?

Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, IL
http://www.heronbicycles.com/
http://www.tullios.com/

As far as welded stems- aren't almost all stems welded?
Which ones AREN'T? are some CNC?
thanks

remove the polite word to reply said:

As far as welded stems- aren't almost all stems welded?
Which ones AREN'T? are some CNC?

Lots of stems are forged. Some cheaper ones are cast.
None of these are guarantees of breaking or not breaking.
I think CNC may be the worst way to make a stem - many
parts broke during the stupid-light CNC parts craze.
Salsa steel stems have a good reputation, and they're welded,
for example. Further discussion of this probably belongs
on rec.bicycles.tech.

On 17 Jul 2004 20:36:09 -0700, [email hidden] (remove

the polite word to reply) said:

As far as welded stems- aren't almost all stems welded?

Many or most are forged.

JT

Personally, I've long prefered to use the welded chromoly stem from
Cineli- I've always feared a sudden breakage from my stems, and after
finding fracturing developing in my aluminum stems ( Syncros ) I
switched to cromoly and haven't looked back. You don't get the super
light weight of exotic materials but a few extra grams won't kill me
while a sudden failure could. I prefer cromoly because it bends,
twists and tears before failing and the welding process is much
simpler than the tig welding aluminum needs.
Benjamin Weiner is correct about bewaring of CNC parts because you
have to realize those parts are made by removing material from a
single solid block, a process that introduces considerable energies
and forces into the form - those very same energies and forces can
induce fracturing in the very same process. Furthermore, while CNC is
used for areospace components, a bike parts manufacturer will have a
lower margin, meaning lesser quality CNC machines, operators,
tolerances and finally quality control.

John Forrest Tomlinson <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On 17 Jul 2004 20:36:09 -0700, [email hidden] (remove

the polite word to reply) said:

As far as welded stems- aren't almost all stems welded?

Many or most are forged.

JT

In article <[email hidden]>,

(Laz) said:

Personally, I've long prefered to use the welded chromoly stem from
Cineli- I've always feared a sudden breakage from my stems, and after
finding fracturing developing in my aluminum stems ( Syncros ) I
switched to cromoly and haven't looked back. You don't get the super
light weight of exotic materials but a few extra grams won't kill me
while a sudden failure could. I prefer cromoly because it bends,
twists and tears before failing and the welding process is much
simpler than the tig welding aluminum needs.
Benjamin Weiner is correct about bewaring of CNC parts because you
have to realize those parts are made by removing material from a
single solid block, a process that introduces considerable energies
and forces into the form - those very same energies and forces can
induce fracturing in the very same process. Furthermore, while CNC is
used for areospace components, a bike parts manufacturer will have a
lower margin, meaning lesser quality CNC machines, operators,
tolerances and finally quality control.

I think you'd be surprised to find out that many of the shops that make
CNCed stems and other components also are doing aerospace or semiconductor
work. Some of those shops went looking for work like bike components (among
other things) when there was a turndown in the amount of work in the aero
and semicon fields. As for lesser quality machinery, well, the main
difference that really counts would be that less expensive machines have
lower horsepower ratings, hence can't take as heavy of a cut or go as fast.
Cheaper machines are frequently not as rigid as the expensive stuff, so
that can lead to finish and accuracy problems, but a competent
programmer/set-up guy knows how to work around that limitation. The
accuracy of the movement is all fairly close.

Metal has grain, similar to wood, so when one takes a piece of aluminum
bar stock (the grain runs lengthwise on this) and turn it on a lathe to
make a stem, it cuts through the grain out on the ends where the bars and
steerer tube go. A forging takes a piece of stock and, under massive
pressure, pushes the stock into a shape very close to the finished part.
The advantage is that the grain follows the shape of the part, hence it is
going to be stronger. Making forging dies is not cheap.

--
tanx,
Howard

So far, so good, so what?

remove YOUR SHOES to reply, ok?

Many are CNC. I spent 36 years of my life in metal working. I gave in
one time and it cost me hospital time. I will never use any stem that is not
forged by a reliable manufacture.

"remove the polite word to reply" <[email hidden]> wrote in
message news:[email hidden]...

Quoted message said:

As far as welded stems- aren't almost all stems welded?
Which ones AREN'T? are some CNC?
thanks

I am truely sorry to hear of your mishap, IMKen. That's pretty much
what I was getting at with my earlier post. Being in the business,
you've probabally seen how some of these el-cheapo machine shops are
run; that's why I wouldn't want to trust myself to parts that might
come from those types of places. From a design stand-point the
geometry/ stress-analysis might look good; but that fails to take into
account some of the realities of low-ball machine-shops.

Laz

"IMKen" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Many are CNC. I spent 36 years of my life in metal working. I gave in
one time and it cost me hospital time. I will never use any stem that is not
forged by a reliable manufacture.

"remove the polite word to reply" <[email hidden]> wrote in
message news:[email hidden]...

Quoted message said:

As far as welded stems- aren't almost all stems welded?
Which ones AREN'T? are some CNC?
thanks