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My thought was to write companion articles that talk a bit about what goes on inside the frame (stuff you can't see) and behind the scenes. One is written, and you'll find a link to it (Beauty on the Inside) appending to this article, just below it.
This is the other, and it flowed from visits to the bowels of Felt's headquarters, as I have done on numerous occasions, to talk to its director of engineering Jeff Soucek. I like asking him about their product testing, and not just wind tunnel or Alphamantis testing but the kind that keeps my bike and its parts from failing (a slow bike ride means a kinda bad day, a failed bike underneath me means a really bad day).
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But this isn't QC, and sometime I'd like to write about that in depth. Felt employs a number of full-time employees in Asia who travel from factory to factory, and every reputable brand has these. Most companies like Felt have their carbon bikes manufactured and assembled in the Orient.
There are typically three kinds of factories over there used by these companies. One specializes in making the bike frames themselves, and it works very closely with its American customers on the frame molds and lay-up schedules (see Beauty on the Inside). A second factory is simply for complete bike assembly. Finally, there are factories all over Asia that make sub-assemblies: that forge, extrude, machine, mold; who draw and bend tubes; and who make all sort of parts from saddles to aerobar armrests.
A quality control agent won't stand over every part made by every employee, but will spend a significant number of time at each factory making sure that the go, no-go standards the company sets up in advance are adhered to by the factory. It's not in the interest of the factory to skirt these guidelines, because if a product is rejected that QC agent will start looking at every part. The factory won't get paid on rejects. It's important to have the QC agents there, not stateside.
Felt tests some of its frame and fork products at its headquarters in Irvine, California. It will test both its own and its competitors' products, and some companies (Cannondale notably) are famous for its lab that also tests the components that go on its bikes (for things like cable fatigue failure, saline corrosion, and so forth).
The image above tests frame deflection when weights are applied to certain areas and the frame is fixtured in different ways. A frame maker might want to know how much a frame deflects, and maybe where it deflects, i.e., where the bending occurs in the down tube. What would you do as a response? Wrap the downtube with carbon, test it again. Once you like the way your frame adapts to the change you made in the lab you'd translate this into a change in the lay-up schedule. Then the frame is manufactured with the change in the schedule, it comes stateside, you test it again. Then, of course, you ride it. And you test the entire bike for both fatigue and ballistic stresses.
When I was a bike maker we tested our frames much the same way as the image above, but not quite. We had a piece of 4-inch square stock coming up from the slab, with a fixture atop it that accepted a frame's bottom bracket shell. Our frame was perched upright for this test. We affixed a stem and a straight tube through the stem, and the fork dropouts were allowed to flow back and forth as a torsional force was applied. That force was in the form of a weight hung from one end of the "handlebar," and measured the deflection of the head tube relative to a vertical line. This is how we came upon the shape and the lay-up of the carbon gussets we stuck into our otherwise aluminum Kilo Private Reserve frames (a bike that might be remember by those who've been in the sport for 20-plus years).
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The image above is of a 10 kilogram weight dropped on a fork, testing the ability of that fork to withstand a frontal impact (like a curb or a pothole). The operative metrics are the height above the fork from which the weight is dropped as well as the number of times the weight is dropped onto the fork before the amount of deflection demonstrates that the fork is failing.
This is one of a number of tests a fork will undergo, including fatigue testing, which might be a fraction of the energy applied to the fork in this ballistic test, but such force applied over a period of time, maybe 100,000 cycles. You might start such a fatigue test on Friday, show up Monday morning and see how many cycles your fork withstood before deflection that signifies failure.
In my factory we built a structure we called The Guillotine, much like this test machine above, except we tested front-end failure of our frames. We put a fork-like structure into the frame, but it had one "fork blade" protruding from the crown and a metal strike plate on it. We dropped the weight from a specified height, and noted how many times it took before the frame began to buckle. We were interested not only in how the frame withstood the failure, but how the frame failed (not all at once, and not in pieces).
How did we know what was acceptable, 25 or so years ago? We didn't, in terms of an agreed-upon protocol. We were cheap (because we were broke). We had written in our athlete contracts that the athlete "traded" our bikes for the most recent bicycle the athlete raced on prior to entering into a contract with us. We tested all these bikes to failure. We didn't know how durable our frames should be, but we reckoned that if they were as or more durable than the best of our competitors' bikes, it would place us on sound footing. Again, the carbon gussets we placed in our frames added notable frame strength, as this test proved to us. This is why, even up to today, I love to see frames that are deep from the leading to edge of the head tube to the trailing edge of that head/top/down tube complex.