Tubing Failure?

Check this out: http://tinyurl.com/273vtaq

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.

I've got three of these things: one old (like 5 years) and two
relatively new. This is one of the new ones.

The give me 3" of saddle setback as in http://tinyurl.com/2apxre6

The old one has seen quite a few hours on my full-rigid
POS/utility/errand bike with no problems.

The steel tubing whose wall pulled out is quite thin: less than
1mm... maybe .8mm.

Could it be that the welding or brazing process on this one
somehow weakened the tubing but did not on the older one?

Does 27.2mm ID tubing maybe come in different wall thickness and
maybe the failed unit had thinner-walled tubing?

I don't have a tool to measure the wall thickness of a non-failed
assembly - just a micrometer, that I was able to fit within the
hole on the failed one.
--
PeteCresswell

On Jul 2, 7:07*pm, "(PeteCresswell)" wrote:

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.

That would seem to be a matter of interpretation

The give me 3" of saddle setback as inhttp://tinyurl.com/2apxre6

Wow! No wonder.

DR

On Jul 2, 6:07 pm, "(PeteCresswell)" wrote:
Check this out:http://tinyurl.com/273vtaq

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.


Isn't that the usual failure mode for welded joints?

I've got three of these things: one old (like 5 years) and two
relatively new. This is one of the new ones.


Bad weld? Improperly cooled? Design limitation? (Is that rust in
there? Interesting pattern.)

On 3 July, 02:07, "(PeteCresswell)" wrote:
Check this out:http://tinyurl.com/273vtaq

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.

No apparent stretching makes it a weld failure.


I've got three of these things: one old (like 5 years) and two
relatively new. * This is one of the new ones.

The give me 3" of saddle setback as inhttp://tinyurl.com/2apxre6

The old one has seen quite a few hours on my full-rigid
POS/utility/errand bike with no problems.

The steel tubing whose wall pulled out is quite thin: less than
1mm... maybe .8mm.

Could it be that the welding or brazing process on this one
somehow weakened the tubing but did not on the older one?

Yes.


Does 27.2mm ID tubing maybe come in different wall thickness and
maybe the failed unit had thinner-walled tubing?

Still looks like a weld failure.

I don't have a tool to measure the wall thickness of a non-failed
assembly - just a micrometer, that I was able to fit within the
hole on the failed one.


Use the micrometer in conjunction with a rod(inside the tubing).
Still looks like a weld failure. There is not enough detail available
in in the pictures to make anything further thaan guesses. Could be
lack of weld penetration, could be granulation of the steel caused by
overheating.

(PeteCresswell) wrote:
Check this out: http://tinyurl.com/273vtaq

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.

I've got three of these things: one old (like 5 years) and two
relatively new. This is one of the new ones.

The give me 3" of saddle setback as in http://tinyurl.com/2apxre6

The old one has seen quite a few hours on my full-rigid
POS/utility/errand bike with no problems.

The steel tubing whose wall pulled out is quite thin: less than
1mm... maybe .8mm.

Could it be that the welding or brazing process on this one
somehow weakened the tubing but did not on the older one?

Does 27.2mm ID tubing maybe come in different wall thickness and
maybe the failed unit had thinner-walled tubing?

I don't have a tool to measure the wall thickness of a non-failed
assembly - just a micrometer, that I was able to fit within the
hole on the failed one.

OMG what a design.
The weld itself "didn't fail" but the separation next to the
weld (normal varied hardness zone) indicates a design
failure. Wrong material thickness for the application IMHO.

For a guy your size, 1.0 butted tube in a closed figure is
about as light as I'd use. 1.0 steel hanging in midair by a
weld and levered by your full weight seems, well, risky.

Sure hope you're OK.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

(PeteCresswell) wrote:
Check this out: http://tinyurl.com/273vtaq

The weld did not fail.

Instead the wall of the tubing around the weld just pulled out.

I've got three of these things: one old (like 5 years) and two
relatively new. This is one of the new ones.

The give me 3" of saddle setback as in http://tinyurl.com/2apxre6

Why do you have so much setback? If you need more cockpit length why use
such a short stem? You wind up with a wheelie bike with slack angles
like a beach cruiser. Is that what you want?

On Jul 2, 8:07*pm, "(PeteCresswell)" wrote:

Could it be that the welding or brazing process on this one
somehow weakened the tubing but did not on the older one?

I can't plainly see the weld zone in your pic but I have seen lots of
supposedly good MIG welds (again, what that looks like from here)
where there is undercutting (material loss) right where the base
material ends and the weld begins. Basically, a misuse of a MIG
welder, where a wire feed adds material so the parts (base metal)
don't have to make up the bulk of the weld bead. Instead, the weld
bead should appear to rise from undisturbed base material, no dip or
valley at all, although base material certainly is melted into the
bead "mix", so to speak, by about half a material thickness according
to my learning.

(Stating the Obvious Dept.): Sometimes (commonly, in production
parts), the base material is thick enough to get away with a "bad",
undercut weld. Sometimes it isn't.
IOW this might be a manufacturing defect that should be warrantied.
Assuming you didn't fall: Maybe a cash refund would be best g ("we
laugh when no one gets hurt").

I guess you might be able to go through a pile of those seatposts and
pick out good ones (if any).
--D-y

AMuzi wrote:
PeteCresswell) wrote:
: Check this out: http://tinyurl.com/273vtaq
:
: The weld did not fail.
:
: Instead the wall of the tubing around the weld just pulled out.
:
: I've got three of these things: one old (like 5 years) and two
: relatively new. This is one of the new ones.
:
: The give me 3" of saddle setback as in http://tinyurl.com/2apxre6
:
: The old one has seen quite a few hours on my full-rigid
: POS/utility/errand bike with no problems.
:
: The steel tubing whose wall pulled out is quite thin: less than
: 1mm... maybe .8mm.
:
: Could it be that the welding or brazing process on this one
: somehow weakened the tubing but did not on the older one?
:
: Does 27.2mm ID tubing maybe come in different wall thickness and
: maybe the failed unit had thinner-walled tubing?
:
: I don't have a tool to measure the wall thickness of a non-failed
: assembly - just a micrometer, that I was able to fit within the
: hole on the failed one.

:OMG what a design.
:The weld itself "didn't fail" but the separation next to the
:weld (normal varied hardness zone) indicates a design
:failure. Wrong material thickness for the application IMHO.

Could be. I think it's a weld failure. Either way, pete needs to get
in touch with the people who make it. That could be deadly.


--
sig 116

Per David Scheidt:
Could be. I think it's a weld failure. Either way, pete needs to get
in touch with the people who make it. That could be deadly.

This one wasn't so bad - since it failed as I was returning
weight to the saddle after jumping a curb - I hadn't gone back to
spinning yet and still had a good bit of the control in my legs
rather than my butt.

The really nasty one was a ThudBuster that just went "Bang!"
while I was riding along on smooth pavement. Somehow I got
through that one - although I got to know the top tube a little
better than I wanted and had a sudden love affair with the
handlebars.

Another guy who had the same failure rounding the corner down the
block from his house wasn't so lucky. He missed multiple years
of work, lost his job, and underwent multiple back operations.
Last I heard he had won the law suite against the maker, but I
doubt if any amount of money could have made him whole.
--
PeteCresswell

Per Peter Cole:
Why do you have so much setback? If you need more cockpit length why use
such a short stem? You wind up with a wheelie bike with slack angles
like a beach cruiser. Is that what you want?

It's not cockpit length.

Imagine you're spinning along.

Now imagine some rough ground ahead.

You up shift a couple of gears and pedal hard enough that your
butt just sort of floats above the saddle and your legs take the
brunt of the bumps.

Once the rough spot has passed, you downshift to start spinning
again. As your butt settles back down on the saddle, it will
naturally settle in a certain spot.

Without all that setback, that spot for me is right on the
rivets/rear edge of the saddle: half on the saddle, half off.

Sure, I can consciously pull forward and hit usable saddle....
but after about five minutes of pedaling, my sit bones are back
to hanging off the edge of the saddle.

Handlebar placement is not a factor. I have MTB bars with those
hooked bar ends on them - canted slightly downwards. This gives
me almost six horizontal inches of variance in the cockpit length
and a good two inches variance in bar height just by changing my
grip on the bars. All grips in all positions give the above
result.

Next time around, if I have a choice; I'm coming back exactly the
same size as Wallmart's "medium" men's clothing dummy.
--
PeteCresswell