A Brief Introduction to Carbon Fiber, with a brief excursus on metal, and butter.

This topic came up on an email list I'm on, so I thought I'd write up this little reliving of high-school organic chemistry as a blog post.

The virtue of carbon in particular is that stretch and bend can be very carefully controlled. Carbon atoms have four very strong bonding sites, which enable it to bond together into very controllable structures. You can make strings, sheets, or three-dimensional solids. You may have heard of these three-dimensional highly pure carbon lattices; they're called diamonds. That should give a sense of how strong carbon bonds are.

But for things like bicycle building, you can get your carbon atoms to bond together into a flat surface, and then you layer a bunch of these flat surfaces together, and it works like a truck's leaf spring: You have a very strong material and you can control the way that it will flex and bend by the way that you orient the fibers. (Laterally stiff yet vertically compliant, yes!)

And if you get more-or-less randomly oriented fibers, then they'll be in microscopic sheets bonded together by occasional cross-sheet single bonds--and the sheets will easily slide off. A great example of this is the graphite in pencils; it easily sheers off under friction into a grey powder--and the sticks of graphite break easily, where a piece of metal of the same thickness would bend.

If you look at the periodic table of the elements, you'll note that Silicon lies right under carbon. It has the same orientation of four bonding sites but for various reasons, those four bonds are less flexible than carbon's--you basically can't make silicon fibers like you can with carbon. But the properties of high-purity solid silicon--better known as glass--are familiar to us. Solid glass has a pretty random assortment of bonds, like pencil graphite, but most of them will be three-dimensional bonds (when you increase the number of three-d bonds, you make crystal glass), making glass a very strong material (stronger than wood, in fact). That's why you can build very tough things like boat hulls from glass fibers embedded in a flexible matrix.

That's the usual failure mode of carbon fiber as well; once it goes beyond (or in a different direction from) its designed flex, the whole thing can just explode (in a better scenario, some of the layers go and you have enough warning to stop the use before the whole object gives way.

But when it breaks, it breaks catastrophically: if some atom-to-atom bonds start breaking, the rest of the material isn't flexible enough to bend; the whole thing just gives way. Similarly, when you look at broken metal pieces, they're either twisted and stretched or they've parted suddenly and you can see the crystalline structures inside them, due to either bad metallurgy, or (if I understand correctly) in the case of alloys, flexing.

If you want to understand metallurgy, get your hands on a stick of butter. First, break it in half and note how it crumbles at the breaking point. Then knead it for a minute: you can use a knife in a dish, or you can do what pastry chefs do and work it under cold water (there's a reason you use ice water and butter to make pie crusts!). You'll find that the material becomes much more flexible and stretchy, much less likely to break and crumble. This is what you want if you're making puff pastry (very thin layers of butter and flour) and also what you want your metal to be like if you're making something like wire, that you want to be flexible and strong, or a bike frame. The real genius of metallurgy is making things that will be strong and tough and springy--something that butyrology has yet to master!

The Other Big Problem with composites, in my book, is their irrecyclability. The epoxy matrix in which they're embedded is very tough stuff, but it can't be melted down because it's made of big complex molecules; they have to break down chemically, and it's not practically feasible at this point to reverse the chemical reactions that it took to make epoxy. (If you've dealt with epoxy, you know hoe much heat it gives off as it cures; all that energy would have to go back into the epoxy in order to break it down, and heat alone doesn't do it.)

Once composites start getting soft; they can't be melted down and re-used but they also can't be trusted with your life and safety. That's the reason why many (most?) dumps have an express prohibition on boat hulls of any kind.

The Chicago way

I've told people before about Chicago's method of "fixing" potholes:
1) put barrier over pothole.
2) wait for car to smash barrier.
3) repeat 1 & 2 until pothole is filled with broken barriers.

Here's the method in practice.

Juxtaposition: University of Chicago Alumni opportunities

Today there came in the mail an offer for "Around the World by Private Jet: An exploration of the world's greatest treasures & legendary places"--a trip sponsored by the University of Chicago Alumni Association (I didn't get invited. They must target their advertising by graduation year).

Cusco & Machu Picchu! Easter Island! Samoa! Great Barrier Reef!...you get the idea. Oh, and at each leg of the journey, there are alternate options, seeing Xi'an, China, instead of Tibet, for example, in case you've BTDT. All this for the mere pittance of $56,950 per person.

Are you free November 1-24, 2009?

It was the dates that caught my eye, and made me immediately think of the email that I'd received from a graduating (class of '09, having finished his physics major and also learnt a fistful of languages in three years) student the previous day:
Yesterday I received my official nomination to serve in the
Peace Corps in the republic of Turkmenistan as a teacher,
from September 29, 2009 to December 11, 2011. Tomorrow I
will accept this invitation, which is a binding commitment.

Bravo, MSK!

Someone should write an opera...

In brief: the Fausto Coppi-Gino Bartali rivalry of the pre- and post-WWII years was defining for a generation of Italians, probably for a generation of Europeans, and certainly for a generation of racing bicyclists. You were a coppiano or a bartaliano, and it was as much an urban/rural or class division as a sporting one. The fact that those two were so often so much better than others, and so often only challenged by each other, reflected and provided an opportunity to sublimate serious social differences.

Jeff MacGregor said it well: "So in a time when the very words have been debased by overuse, a truly great sporting rivalry -- an "epic rivalry" -- is a rare and precious thing. One made possible only by athletes or teams who define and then expand not just each others' limits, but the limits of the age in which they compete. Opponents at the very peak of their powers, equals, who transform one another. Always at great cost. Which is why "Ali/Frazier" remains the standard measure of a modern American epic, and speaks to the needs of our culture as fully as "Gilgamesh" or "Beowulf" spoke to the needs of theirs." (Hat tip to LC for the quote.)

Coppi didn't stop cycling until his death at the age of 41; Bartali, the conservative and (relatively) clean-living of the duo, lived to be 85. But, and here is my service to you, readers (are there any librettists and composers amongst you?), shortly after Coppi's death, Bartali wrote a brief memoir, "Coppi and me," for the French Magazine Le Miroir des sports. Belgium Knee Warmers has now published the article in four parts: Here is a link to the first.

It's heartbreaking to read, and so easy to translate Bartali into a mirror of Peter Shaffer's Salieri, knowing greatness--and trying so hard to best it, to destroy it, even. And to be sentenced to live long enough to see greatness achieve immortality, and one's own near-greatness forgotten.

Wildlife is God's way of getting rid of drunken tourists

This just in. Well, only three weeks ago.

But can't you picture the pandas sitting around talking: "You know, dude, I'm a vegetarian. Even if they come in, I'm not biting 'em. . . . I mean, look at them, so helpless, and almost intelligent." "No way, I'm chowing down. If God didn't intend for us to eat them, then why would he marinate them in beer before sending them?"

Worlks for grades 13-16, too.

Cartoon by xkcd.com

Oh, one other ingredient: Wool

Yes, I am an enthusiastic person, willing to try lotsa things, and say "yes" to many many requests. Like, for example: "Sure, I'll bike 100 miles for Susan Nelson's fight against cancer." But I do believe in a certain level of preparedness for things, and like a well-trained mom, 90% of the preparation involves wearing wool.

Why was I so joyous on Sunday? I was wearing my three, no, four favorite garments: an incredibly soft and warm lambswool sweater (turtle-ish neck, 1/4 zip, from Brooks Brothers, believe it or not), my 1952 (manufacture date is on the label!) Australian Army wool pants (5-pocket; I often roll them into knickers for bike riding), and Smartwool knee socks.

Also knicker tights under the pants, an Under Armor undershirt under the sweater, my team jersey over it, glove liners and fleece mittens, and, what the smart people do: plastic bags twixt my socks and shoes, adding warmth without cutting off circulation. All the people who snickered beforehand were the ones seeking out a warm engine block to put their toes on afterwards.