The unreasonable strategic importance of ball bearings
It takes balls to win a war. It takes balls of steel.
I hear you. “Ball bearings aren’t that interesting,” you say. “You wrote an entire article to justify that subtitle,” you say. You caught me on the latter. As to the former, though, you’re wrong.
Background
Most machines move. Most machines are made of metal. This presents some logistical challenges. Just ask your local tribologist. According to Wikipedia, tribology is the study of “science and engineering of interacting surfaces in relative motion.”
Here’s the rub, surfaces in relative motion… well… rub. The result is friction. As a consequence, you lose a whole bunch of energy to heat. Also, the components start to wear. The friction of two surfaces sliding against each other is, reasonably enough, called sliding friction. Slap some spheres between two surfaces in relative motion, though, and the rolling motion reduces the friction. Spheres are also invaluable to constrain motion in the context of spheroid joints, think of a ball and socket like your shoulder.
Three fascinating ball bearing case studies
Unsurprisingly, people have been rolling stuff around for a long time. Basic bearings have been in use since antiquity. Some historians have theorized that illustrations on the tomb of Djehutihotep (pronounced “Djehutihotep”) indicate that ancient Egyptians rolled around construction material for pyramids and statues.
After a couple millennia of use, it turns out some interesting applications crop up….
1. In WWII, the Allies tried to strategically bomb German ball bearing factories
War involves a lot of machines. Trucks, planes, guns, tanks, and sundry other implements of destruction require bearings. In WWII, rapid mechanization increased the dependence on efficient, precise ball bearing production.
[Ball bearings] are at the heart of any mechanical device. Tiny metal balls covered in grease and encased in a steel ring. Inside the axle of a bicycle, for example, there are perhaps a dozen ball bearings, acting as mini steel rollers that allow the bicycle wheel to turn freely. A good road bicycle can cost thousands of dollars and include some extraordinarily sophisticated space-age materials. But without two or three dollars’ worth of quarter-inch diameter ball bearings, the bike won’t work. It literally won’t move. Same is true for the engine in your car. Or virtually any mechanical object that involves a rotating part.
— The Bomber Mafia, p. 81
The Allies attempted strategic bombing of German industrial centers to knock out ball bearing production.
“If you took out [Schweinfurt], it could have the potential to take down the entire German war economy. This is what the Americans were looking for, and they thought ball bearings might be that target.
It’s sort of like taking the key card out of a house of cards and having the whole thing collapse, or pulling on the thread of a spiderweb and having the whole thing unravel. That’s what the Americans thought they were going to do.”
— The Bomber Mafia, p. 83
In a war characterized by horrific new “Vengeance weapons” and the development of the nuclear bomb, ball bearings were still center stage.
2. China couldn’t make ballpoint pens until 2017
Honest to goodness. It could assemble a ballpoint pen, but, believe it or not, China — with a GDP of ~$12,000,000,000,000, a population of ~1,400,000,000, and ~350 nuclear weapons — couldn’t manufacture the tips for ballpoint pens.
It became headline news when Premier Li Keqiang complained about it on national TV. The “world’s factory,” which churns out smartphones, stealth fighters and WeChat, couldn’t manufacture a tiny metal ball.
The problem was two-fold. China simply didn’t have a machine with the precision to cut a tiny ball-bearing accurately. While it supplied the world with 80% of its ballpoint pens, all the balls came from Switzerland. The steel, according to Xinhua, must be “easy to cut but not liable to crack.” It also doesn’t produce steel of high enough quality to make the casing that surrounds the ball. It all comes from Germany or Japan.
— After years of research, China has finally figured out how to make ballpoint pens (Business Insider)
3. There is currently a ball bearing shortage 🇺🇦
The war in Ukraine has been a war of sophisticated technology — drones and anti-drone weapons, Javelin missiles — yet ball bearings remain a strategic resource in short supply.
The U.S. is sending billions of dollars in powerful weapons to Ukraine so it can fight off the Russian invasion. But that effort is leading to some shortages - not only in the weapons themselves, but also in the parts that they need - among them, ball bearings.
“And a Pentagon official I spoke with said, listen, these are not the kind of ball bearings you find at a local hardware store. These are precision ball bearings built to higher standards. And ball bearings are used in all sorts of military hardware — things like guidance systems, artillery, armored vehicles. The ball bearings help facilitate motion. They reduce friction and position moving machine parts. Now, the Pentagon says it’s meeting all its current contracts, and all are with U.S. companies, so it’s not like they’re running out. But clearly, you know, it’s an issue for them. And military officials tell me now they’re talking with industry about how we can create more ball bearings and move faster.”
— Can the U.S. keep up with Ukraine’s demand for weaponry? (NPR)
Despite the decades of technological innovation since WWII, the humble ball bearing is still vital to the effective prosecution of war.
Usually, I write data science-y Python explainers, but I hope you enjoyed reading something a little different. Next time you find yourself poking around a machine, try counting the bearings!
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