On Mon, 29 May 2017 11:39:33 -0700 (PDT), "
wrote:

On Monday, May 29, 2017 at 10:40:18 AM UTC-5, wrote:
Quality control for metal bikes is relatively easy - especially for steel since all of the important connection can be seen on the workmanship.


Quality control for metal bikes is easy? With brazing and lugs, no longer used, you cannot see or tell if the brass/silver has covered the entire inside surface of the lugs. Just have to hope. And with welding, TIG, the surface weld is not the only story. You have to look at the inside too. This will tell if the penetration is correct. The surface can be nice and neat but if the weld does not penetrate the correct amount, then its just appearance and its a poor weld. Do you think every frame company takes a microscope or camera and looks at the inside of every weld? Or more likely the guy taking the frame off the welding rack just glances at the welds and says looks good.

When "sweating" pipe joints it is fairly easy to see whether he joint
is fully brazed by watching the inside while applying the brazing
material from the outside. You can actually see the brazing material
arrive at the other end of the joint... assuming of course that you
can see the other end.

The usual method of inspecting welds made in structures that you
really don't want to break like gas pipelines and probably bicycles is
to X-ray them. Then the films are inspected using a light table to
ensure that the weld is within specifications.

Having said that a competent welder can usually pretty well tell
whether he is getting 100% penetration using stick or TIG but I doubt
many production bike frames are welded that way. From looking at the
usual bike welding I'd say that it is MIG.




Now my experience has shown me that CF is not reliable.

So what we need is more information on the percentages of CF bikes that are having quality control problems.



I assume others have asked, but please enlighten us about all the experience with carbon fiber you claim to have. I'm guessing the experts have chemical engineering degrees and have observed hundreds or thousands of controlled experiments involving carbon fiber. Have you owned thousands of carbon frames and thousands of carbon handlebars and thousands of carbon cranksets and thousands of carbon rims from many, many makers? That must cost you millions and millions of dollars to buy these test samples. And the time to test all these samples must be enormous.

I suspect the percentage of carbon frame bikes having problems is the same percentage of aluminum or steel frames having problems.



Question - are the pro level bikes that are breaking so often custom built in their company's racing labs so that the quality control is much lower than the assembly lines in China or Taiwan?


Pro bikes break often? Now I have seem a few frames break on TV races. When there is a big crash at 35 mph and ten riders and frames all go flipping into the air and sliding on the pavement, some of the bikes break. But usually you see a rider with half his clothes ripped off and blood running down his legs, arms, and face try to get back on his still operating bike and ride down the road. Sometimes someone will come off the sidelines and grab him and make him stop because he is wobbly and has a concussion. But the bike still works after the crash. Pro teams may retire/scrap the frame that night because after the crash it is just not trusted anymore. And does not look good either.
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Cheers,

John B.