Are CF frames really safe?

On 5/22/2017 7:03 PM, John B. wrote:
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.


That's right. People expect a woven clothlike look or as a
Famous Designer used to call the stuff, "carbon wallpaper".

Structural carbon is usually fine-fiber sheet in a single
layer much like tubular tire sidewalls. Layers are aligned
in various directions and planes with a 2-part carrier then
pressure molded to remove most or at least some of the air
pockets and excess adhesive.

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

On Mon, 22 May 2017 08:38:18 -0700, Jeff Liebermann
wrote:

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.

This is what I mentioned in another post. My experience with
composites is that when built in a mold, as is a bicycle fame, the
first move is to spray the mold with a "gel coat" which provides the
visible outer surface of the structure. As this is "the easy way" to
produce a slick, shiny, outer surface I had assumed that bicycle
frames were likely the same.

The common visible "fabric" C.F. outer layer is usually simply a
cosmetic feature and provides very little to the strength of the
structure.


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.

But if the frame is built as a boat hull is, using a "gel coat", there
is no cracking of the outer surface with normal temperature induced
expansion and contraction. Again, from what I read a gel coat is
commonly used in bike frame manufacturer.

I also came across the following which does seem to agree with
articles I have read regarding strength of composite structures, that
fibers fail individually until the strength reaches a certain point
when the whole structure fails catastrophically.

http://www.gone.training/?p=111
"Additionally Carbon Fiber is highly susceptible to a phenomena called
Barely Visible Impact Damage (BVID). The Carbon Fiber looks fine on
the surface, however the structural integrity of the fibers below the
surface is less than satisfactory. The amount of damage below the
surface varies depending on the type and amount of force of the
impact. NDT is able to detect this damage using ultrasonic's, if they
have a suitable standard to compare the frame against. If not detected
or repaired this can lead to catastrophic failure. Could get really
ugly on a downhill run."


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.

Dyes would only work on cracks.
--
Cheers,

John B.

On Mon, 22 May 2017 12:10:40 -0700, 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.

But what is "CroMo"? One assumes you mean "Chrome Millennium Steel:
commonly called "chrome-moly" which simply identifies the basic
alloying elements. But SAE lists some 12 different chrome-moly steels
ranging from SAE 4118 with a yield strength of ~53,000 psi to SAE 4164
with a yield strength of ~80,000 psi.

--
Cheers,

John B.

On Mon, 22 May 2017 13:44:24 -0700 (PDT), Frank Krygowski
wrote:

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

Weighing might not have told you anything either as the fork crown is
usually the heaviest part of a fork and weights vary from about 300
Gr. down to arond 100 Gr. Steerer tubes also vary in weight for the
same diameter.
--
Cheers,

John B.

On 5/22/2017 8:38 AM, Jeff Liebermann wrote:
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.

The experts agree that the key thing is to have your CF frame inspected
periodically for damage. It's strong, but fragile. The wrong car
carrier, bumping it against a hard object, etc., can create flaws that
are not easy to see.

It's a good idea to strip all the components off once a year and have an
ultrasound done. See
http://carbonfibrerepair.com/ultrasound-inspection/. Probably
someplace similar in the U.S..

On 5/22/2017 5:58 PM, John B. wrote:

snip

But what is "CroMo"? One assumes you mean "Chrome Millennium Steel:
commonly called "chrome-moly" which simply identifies the basic
alloying elements. But SAE lists some 12 different chrome-moly steels
ranging from SAE 4118 with a yield strength of ~53,000 psi to SAE 4164
with a yield strength of ~80,000 psi.

Trek's catalog for that year says "Trek designed Tru-Temper tandem
Cro-Moly" for the frame tubes and "Tange Durango double-butted Cro-Moly
w/cast fork ends" for the fork. I don't know any more details.

On Monday, May 22, 2017 at 1:44:26 PM UTC-7, Frank Krygowski wrote:
On Monday, May 22, 2017 at 10:11:11 AM UTC-4, wrote:

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.

Well, the only point I was trying to make was that the builder may have had time constraints and assumed that a good single fork would be a descent tandem fork. We know what assumptions lead to.

On Monday, May 22, 2017 at 5:03:21 PM UTC-7, John B. wrote:
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.

My suspicion from looking at them is that there is an interior "balloon" mode and then after the entire outer surface is laid they put it in an exterior mold that squeezes it. The two halves of the outer mold squeeze a little of the resin between their halves which are then ground off. But it makes it look like there is a seam there when there isn't.

The frame is then painted.

On Monday, May 22, 2017 at 5:58:15 PM UTC-7, John B. wrote:
On Mon, 22 May 2017 12:10:40 -0700, 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.

But what is "CroMo"? One assumes you mean "Chrome Millennium Steel:
commonly called "chrome-moly" which simply identifies the basic
alloying elements. But SAE lists some 12 different chrome-moly steels
ranging from SAE 4118 with a yield strength of ~53,000 psi to SAE 4164
with a yield strength of ~80,000 psi.

Crappy spelling checker - Chrome Molybdenum Steel. These steels can have higher strengths with heat treating. But this is negated by welding so Columbus EL tubing used via Fillet Brazing is neither heat treated or butted if memory serves. This makes a very light frame but I don't know about their strength other than via hearsay.

On Monday, May 22, 2017 at 8:10:33 PM UTC-7, sms wrote:
On 5/22/2017 5:58 PM, John B. wrote:

snip

But what is "CroMo"? One assumes you mean "Chrome Millennium Steel:
commonly called "chrome-moly" which simply identifies the basic
alloying elements. But SAE lists some 12 different chrome-moly steels
ranging from SAE 4118 with a yield strength of ~53,000 psi to SAE 4164
with a yield strength of ~80,000 psi.

Trek's catalog for that year says "Trek designed Tru-Temper tandem
Cro-Moly" for the frame tubes and "Tange Durango double-butted Cro-Moly
w/cast fork ends" for the fork. I don't know any more details.

Double butting in forks sounds suspicious. Because fork legs can be used for very small or very large forks the butting would have to be pretty short.