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Sunday, November 25, 2007


Why cars still use 19th century technology

One question I've sometimes seen is "Why do cars in the early 21st century still rely on technology invented in the 19th century?" Behind this question is an assumption that surely someone in the 20th century would have come up with a better operating principle for an engine. The trouble is, that isn't necessarily the case - while engineers can refine engines based on 19th century designs, most of the discoveries in the 20th century didn't provide useful ways to design a new engine. The biggest one, nuclear power, wasn't exactly a good power source for cars (and nuclear power plants still incorporate devices that would be recognizable to a 19th century engineer, as they're fundementally steam engines).

19th century engineers had at least a working knowledge of the types of science used to build motors - thermodynamics, kinematics, and electricity. Just about everything that's been talked about as an alternative to the internal combustion engine also, in fact, dates back to the 19th century or earlier. Steam engines existed before the 19th century, as did piston-cylinder devices and crankshafts. And the following devices were all available to a 19th century inventor, at least by the end of the century:

Trying to come up with a list of engine types that are entirely 20th century designs isn't easy. There were a few designs that you could argue are 20th century. The first gas turbine engine didn't appear until the 20th century, but it built on turbines that had been designed in the 19th. Felix Wankel came up with his magical spinning triangles in the 20th century, but there were steam powered rotary engines in the 19th century. Interestingly, there have been cars built that used both of these technologies - and neither one has proven to be so much better than four stroke piston engines to have replaced them or even picked up a large market share.

Of course, put a 21st century gasoline engine next to a 19th century one, and you'll notice huge differences. A modern gasoline engine will be made from much more advanced materials, spin at RPM ranges that Otto would have thought impossible, and make far more power while burning less gas. But it is still something Otto would have recognized as his four stroke engine.

So there's three reasons we still have 19th century technology in 21st century cars. One is that when you've got a design that works well, engineers don't usually scrap it as much as just make a lot of improvements. Second, there aren't really any new operating principles that 21st century scientists have for cars at the moment- it's either burn fuel to get heat, use a fuel cell, or store electricity in batteries, all of which could be done over a hundred years ago too. Third, the engineers in the 19th century weren't stupid.

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