Are CF frames really safe?

On Mon, 22 May 2017 14:39:19 +0700, John B.
wrote:

Are C.F. frames painted?

Yes, unless you like the basket weave look.

Do the frames crack without disturbing the
coating, whatever it may be?

Good point. I don't know. I'm assuming that the bicycle paint is
like automotive paint, which flexes a little to prevent the thermal
expansion and contraction of the underlying car body from cracking the
paint. My guess(tm) is that if the underlying carbon fiber tube moves
a little, the paint will stretch to fit, rather than crack.

Why all the folderol with phosphorescent
stuff when the conventional "dye Check" kit will show cracks and you
can pay a couple of dollars more and get the set that shows up under
ultraviolet light.

Because a dye leakage test will show cracks in the paint, not cracks
in the underlying CF tubing. At best, it's a good way to test the
quality of the paint job. I don't think anyone has crashed riding a
bicycle with cracks in their paint job.

After all, it is used to inspect vehicles that thunder along 5 miles
up in the air while a bicycle runs along on the surface :-)

I'm not sure, but methinks some other method is used on painted
surfaces and that dyes are only used on parts with exposed surfaces.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 5/22/2017 7:11 AM, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

An inexperienced builder choosing the wrong type of fork for a tandem,
and then having it fail, doesn't mean much. On a tandem you want a
stronger fork and stronger wheels.

My Trek tandem has never had a fork failure, and it's got a CroMo fork.
Using Frank's statistical logic, my example of one proves that steel is
the best.

On Monday, May 22, 2017 at 12:14:06 PM UTC-7, sms wrote:
On 5/22/2017 7:11 AM, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure.. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

An inexperienced builder choosing the wrong type of fork for a tandem,
and then having it fail, doesn't mean much. On a tandem you want a
stronger fork and stronger wheels.

My Trek tandem has never had a fork failure, and it's got a CroMo fork.
Using Frank's statistical logic, my example of one proves that steel is
the best.

I didn't notice Frank saying that the builder was inexperienced.

On Monday, May 22, 2017 at 10:11:11 AM UTC-4, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure.. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

But of course viewing something from a historic perspective is easy.

I agree, that fork disqualified it as a "good" steel bike. Or more specifically,
it disqualified the fork.

It does make me wonder, if you're buying a custom frame, how do you know what
you're getting? The builder of this frame, a guy named Jim Bradford, had a
good reputation. I never thought to ask him "Did you perhaps use fork blades
intended for racing single bikes on velodromes?" And once they were in, the
only way to tell that the wall thickness was 1/3 of what it should have been
would be to weigh the fork and look up other fork weights for comparison. I
certainly never thought to do that.

- Frank Krygowski

On Monday, May 22, 2017 at 3:57:59 PM UTC-4, wrote:
On Monday, May 22, 2017 at 12:14:06 PM UTC-7, sms wrote:
On 5/22/2017 7:11 AM, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

An inexperienced builder choosing the wrong type of fork for a tandem,
and then having it fail, doesn't mean much. On a tandem you want a
stronger fork and stronger wheels.

My Trek tandem has never had a fork failure, and it's got a CroMo fork.
Using Frank's statistical logic, my example of one proves that steel is
the best.

I didn't notice Frank saying that the builder was inexperienced.

He was not. He was locally well known, and recommended by a couple different
sources. He'd built lots of bikes, including at least one other tandem, the
one he and his fiance rode.

I suspect the problem was he was way behind schedule and was cutting corners.
When I picked up the bike, it was painted the wrong color, and various other
details were not as ordered. He said "Look, I'm going to Europe for my
honeymoon in a couple weeks. Do you want the bike or not?"

- Frank Krygowski

On Monday, May 22, 2017 at 1:54:20 PM UTC-7, Frank Krygowski wrote:
On Monday, May 22, 2017 at 3:57:59 PM UTC-4, wrote:
On Monday, May 22, 2017 at 12:14:06 PM UTC-7, sms wrote:
On 5/22/2017 7:11 AM, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

An inexperienced builder choosing the wrong type of fork for a tandem,
and then having it fail, doesn't mean much. On a tandem you want a
stronger fork and stronger wheels.

My Trek tandem has never had a fork failure, and it's got a CroMo fork.
Using Frank's statistical logic, my example of one proves that steel is
the best.

I didn't notice Frank saying that the builder was inexperienced.

He was not. He was locally well known, and recommended by a couple different
sources. He'd built lots of bikes, including at least one other tandem, the
one he and his fiance rode.

I suspect the problem was he was way behind schedule and was cutting corners.
When I picked up the bike, it was painted the wrong color, and various other
details were not as ordered. He said "Look, I'm going to Europe for my
honeymoon in a couple weeks. Do you want the bike or not?"

I've mentioned this before, but I had a friend who lost a fork blade on a Rodriguez tandem -- another well-respected tandem builder. I think it was incompletely brazed. He suffered serious injuries, as did his girlfriend/stoker. I recall more than one story of a tack brazed fork that mistakenly went into the paint queue during the Italiano bike craze in the late '70s. Apparently someone didn't finish it up when it came around on the carousel.

-- Jay Beattie.

On 5/22/2017 4:51 PM, jbeattie wrote:
On Monday, May 22, 2017 at 1:54:20 PM UTC-7, Frank Krygowski wrote:
On Monday, May 22, 2017 at 3:57:59 PM UTC-4, wrote:
On Monday, May 22, 2017 at 12:14:06 PM UTC-7, sms wrote:
On 5/22/2017 7:11 AM, wrote:
On Sunday, May 21, 2017 at 6:59:58 PM UTC-7, Frank Krygowski wrote:
On 5/21/2017 5:16 PM, wrote:
There is no reason for people to not buy CF except because they have a higher rate of failure than other materials. I have been riding for 40 years and have never heard of a good steel bike having a catastrophic failure. And I haven't heard of ANY aluminum bikes having catastrophic failures.

Well, our good steel fork on our custom Reynolds 531 tandem failed
catastrophically. Fortunately, we were going very slow (less than 10
mph) so our bodies didn't suffer catastrophic failure. We just got
banged up a bit.

It turned out to be a case of very badly chosen fork blades, by a
builder in a hurry. I think he just used what he had on hand, rather
than proper tandem fork blades.

Then this would hardly qualify as a "good" steel bike. Tandems in particular absolutely must have proper construction as you discovered. A fork designed (especially with Reynolds tubing) for a single would hardly be appropriate for a tandem.

An inexperienced builder choosing the wrong type of fork for a tandem,
and then having it fail, doesn't mean much. On a tandem you want a
stronger fork and stronger wheels.

My Trek tandem has never had a fork failure, and it's got a CroMo fork.
Using Frank's statistical logic, my example of one proves that steel is
the best.

I didn't notice Frank saying that the builder was inexperienced.

He was not. He was locally well known, and recommended by a couple different
sources. He'd built lots of bikes, including at least one other tandem, the
one he and his fiance rode.

I suspect the problem was he was way behind schedule and was cutting corners.
When I picked up the bike, it was painted the wrong color, and various other
details were not as ordered. He said "Look, I'm going to Europe for my
honeymoon in a couple weeks. Do you want the bike or not?"

I've mentioned this before, but I had a friend who lost a fork blade on a Rodriguez tandem -- another well-respected tandem builder. I think it was incompletely brazed. He suffered serious injuries, as did his girlfriend/stoker. I recall more than one story of a tack brazed fork that mistakenly went into the paint queue during the Italiano bike craze in the late '70s. Apparently someone didn't finish it up when it came around on the carousel.

Nothing's changed regarding humans or Murphy's Law:

http://www.yellowjersey.org/photosfromthepast/mt17f.jpg

I pulled those darned-near-brazed ends out of a fork last
Monday morning. They were 'brazed' in April, crooked, but
the joints cracked when it came here for alignment.

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

On Sunday, May 21, 2017 at 5:57:07 PM UTC-7, John B. wrote:
On Sun, 21 May 2017 13:45:44 -0700, sms
wrote:

On 5/21/2017 12:58 PM, Duane wrote:

Why would I buy expensive equipment to test my frame? And I back up my
hard drives weekly.

Good idea.

A month ago my daughter's Thinkpad's drive crashed. Yesterday my son's
Thinkpad's drive crashed. I think I need to start replacing drives every
three years.

I just read a Seagate announcement that they do not rate their hard
disks in MTBF as they say that doesn't present a true picture. Now
they use Annualized Failure Rate (AFR) which hey say presents a more
accurate assessment of potential drive life.

Example: The Barracuda ES.2 Near-Line Serial ATA drive:
"The product shall achieve an Annualized Failure Rate - AFR - of 0.73%
(Mean Time Between Failures - MTBF - of 1.2 Million hrs) when operated
in an environment that ensures the HDA case temperatures do not exceed
40°C"

LOL Well they had to say -something- !! They are still smarting from the 3TB 43% failure debacle 2 yrs ago.

https://www.eteknix.com/3tb-seagate-...-constant-use/
http://www.pcworld.com/article/30289...ure-rates.html

On Mon, 22 May 2017 07:37:19 -0500, AMuzi wrote:

On 5/22/2017 2:39 AM, John B. wrote:
On Sun, 21 May 2017 21:54:47 -0700, Jeff Liebermann
wrote:

On Mon, 22 May 2017 07:26:23 +0700, John B.
wrote:

I've always wondered whether a simple "dye check" could not be used.

It can, if the paint doesn't get in the way. I've seen tubing filled
with oil or water with a phosphorescent dye added. Apply pressure and
the fluid will try to squeeze through any holes in the tubing. A UV
light might show the leak (if the paint doesn't get in the way). Don't
suggest transparent coatings instead of paint. Most clear coats block
UV but not all of them. This formulation is clear, but apparently
passes UV:
http://www.frozencpu.com/products/3854/uvp-01/Clearneon_UV_Reactive_Clear_Coat_Paint_-_Blue.html
https://www.clearneon.com


Are C.F. frames painted? Do the frames crack without disturbing the
coating, whatever it may be? Why all the folderol with phosphorescent
stuff when the conventional "dye Check" kit will show cracks and you
can pay a couple of dollars more and get the set that shows up under
ultraviolet light.

After all, it is used to inspect vehicles that thunder along 5 miles
up in the air while a bicycle runs along on the surface :-)


They are generally painted or at least coated in UV block
clear just like aircraft components.

I probably should have specified "paint" a bit more diligently as I
think that the outer layer may be some sort of UV proof resin rather
then a "paint". At least that is how a boat is built. The mold is
first sprayed with a "Gel Coat" which is a colored resin coating that
provides the smooth, slick, colored (usually white in a boat), U.V.
proof, visible surface of the structure.

Given that modern C.F. bike frames are built in a mold it would seem
likely that somewhat the same technique would be used. The outer,
visible, layer of C.F. cloth on most fanes, for example, is normally
cosmetic not structural.

--
Cheers,

John B.

On Mon, 22 May 2017 07:51:32 -0400, Frank Krygowski
wrote:

On 5/21/2017 11:54 PM, John B. wrote:
On Sun, 21 May 2017 21:56:39 -0400, Frank Krygowski wrote:


About failures like those shown in the links: It occurs to me that with
failed metal parts, one can often examine the fracture and get clues as
to whether the failure was sudden overload vs. long term fatigue, about
the direction of loads, etc. But AFAIK those techniques can't be used
on composite parts. Can anyone confirm that?

I can't quantify this but I believe that the inspection of composite
structures is basically an inspection of, essentially, fiber
condition, condition of the resin-fiber bonds and condition of the
resin bond - water content, etc.

I would believe that direction and severity of stress can be
determined and/or calculated but as a break in a composite is largely
a failure of the fibers I wonder whether long term fatigue figures
could be determined.

For example, a golf club shaft would be tested by flexing the shaft a
large number of times but I don't believe that there would be a change
in the material itself although it is likely that C.F. fiber might be
progressive rather then catatonic.

Common inspection methods include Ultrasonic (several different
methods), X-ray, Moisture detection, Thermography and Neutron
Radiography, all of which seem to measure density rather than
strength.

I haven't studied laminates strengths in depth but what I have read
talks about essentially fiber strengths. there are calculations that
show that once a sufficient amount of fiber breakage that breakage
then accelerates but I've seen nothing about determining degree of
broken fiber within a structure.

I have no idea whether, other then fiber breakage, repeated stress is
damaging to a composite structure. Whether "work hardening", per se,
is a property of composites.

With long term fatigue failures of metal, one can often see "beach
marks" which are sort of ripples in the fractured surface. They
generally show the direction of the fracture's gradual progression.
Sudden impact failures have a different appearance of the fracture
surface. But I'm not aware of any similar features of a CF break.

I don't believe that composites work that way as the metal structure
basically changes its nature with stress while a composite structure
looses strength as individual fibers inside the cured resin are
broken. Ultimately, of course, the composite structure fails but from
what I read there isn't any visual change on the surface.
--
Cheers,

John B.