Tue Mar 6 20:27:23 EST 2012

not to mention road salt's going to kill it after a decade

So CarTalk recently featured a question from a guy who wanted a diesel car that would last 60 years, and 500,000 miles. (804,000 kilometres) The Tappet Brothers said he was crazy, that it was a dumb idea, but didn't actually answer the question.

Now, it is a dumb question, but I'd like to try a stab at it.

First of all, forget diesel. In fact, forget anything fueled by hydrocarbons. If you've glanced at the television in the last decade, you'd know that fossil fuels are a real bad long-term bet.

This means going electric, and (in 2012), paying a fairly steep price premium. Electric cars are also a mixture of good and bad news, from a maintenance standpoint.

The good: Many, many fewer moving parts. An internal combustion engine is an unholy pile of camshafts, crankshafts, pistons, gears, and fans; many of which run at high speeds, close tolerances, and very high temperatures. Maintenance is ongoing, and nontrivial.

In comparison, an induction motor has one moving part: the rotor. Over the course of 804,000 kilometres, you'll be going through a bunch of shaft bearings, but that's more or less it, for the motor. Plus, the extremely wide torque bands of electric motors mean that the gearboxes only need one or two gears, and if you use hub motors, and are willing to sacrifice high speed, you can run direct drive. This means the only consumable items on an electric car are the tires, the windshield wipers, and:

The bad: The battery.

We've been trying to figure out a good way to store electricity for the last century, and so far, haven't made a whole lot of progress. The best of the best, lithium-ion, is both heavier, and more expensive, per joule than gasoline. They're prone to bursting into extremely vigorous lithium-metal fires when abused, slowly discharge themselves when left alone, and have surprisingly short lifetimes when heavily used. (Say, in a car) Deep discharges also burn battery lifetime, say, if you bought an electric car that advertised a hundred kilometre range, and tried to actually drive a hundred kilometres.

Replacement costs are ball-punchingly steep: most of the cost of an electric car is in the battery pack, so replacing it is like buying most of a brand new car. If you drive it very, very gently, and never let it get below 50% charge, you'll probably be buying a new battery every 150,000 kilometres. At ~US$30,000 a pop, that adds up.

There's a degree of amortization here: over time, battery technology will get better, but it's anybody's guess as to how much better it will get.

In the article, Tom and Ray list off about a dozen features in today's cars that didn't exist 60 years ago. Power/ABS brakes, fuel injection, modern suspension technologies, etc etc. This is a bit disingenuous: there's very little room left for improvement, the gasoline car of 2012 is about as good as gasoline cars will ever be, except for one thing.

Autonomous cars.

The self driving car has been a staple of science fiction for the last, well, 60 years, but we're getting close. Real close. My wild-ass guess is that between DARPA and Google, the technology for driverless cars will be ready for prime time in five years.

The wildcard here is the legal side. We could have cars that drive themselves flawlessly, but without laws that let them operate on the street, they'll be useless.

Assuming we leap that hurdle, the big driver (ah ha ha) for autonomous car adoption will be insurance companies. And after driverless vehicles become common, we'll see laws that ban manual operation of vehicles anyplace where an out-of-control car could injure someone else.

So, no, buying a car today that would be useful for 60 years is not going to be easy.