Years ago, I read a prediction, that by the 1990’s, most Detroit-built cars would have aluminum bodies. This was proposed because an all-aluminum car would be lighter (saves gasoline) non-rusting, and easier to recycle.
Well, like a lot of futurist predictions, it never happened. In fact, there are just two all-aluminum body cars in the world (the AUDI S8? and the NISSAN NSX). Land Rover used to build a model with an Al body, but it is not sold here anymore.
So what went wrong? Is Aluminum too expensive or difficult to work with? Hell, there is plenty of it around (I’m looking at the beer cans littering the floor in front of my chair).
Any automotive engineers care to comment?
Some thoughts and opinions…
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There was a minor revolution in auto body design in the late 80’s/early 90’s, where heavy use of FEA and other design programs were able to yield lighter, stronger designs using traditional metals (steel).
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The “kiddie centric movement” of the late 80’s, which started much of the safety craze in automobiles, cast doubts on use of lighter materials in many areas. This is both on a practical, and a perception standpoint. After all, what soccer mom would trust HER sweet, sweet treasures to an aluminum minivan?
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Increased focus on safety in crash tests, and modifications of the types of tests performed, have greatly favored steel cars.
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The current SUV craze does not lend itself to SUV’s made of aluminium.
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Like the case of stainless steel cars, there is no consumer demand at all for aluminium cars. (and yes, I know SS is very expensive too…)
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Fastening and welding techniques with aluminum cars are quite a bit more complicated and less fool-proof than with aluminum cars. IIRC, the Acura NSX had some serious problems with welds that were coming apart for the first few years.
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IIRC, the insurance industry has come out strongly against significant aluminum use in cars, both due to safety concerns and significantly higher repair costs.
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Lighter cars have an advantage in fuel economy, and that concern has disappeared off the radar scope for most average people.
Aluminum is also harder to shape into body panels than steel is, at least with automated methods. It’s been done, so it can be done, but I don’t think the results are as precise and consistent. All the aluminum cars I know of are kind of special cases.
Old Land Rovers were aluminum, but their body panels only had simple curves and they were expected to see pretty extreme operating conditions so rust resistance would have been important. The current Land Rover Defender is a continuation of the old design, so I’d guess it’s still aluminum.
Porsche 928s had an aluminum body, but they were low volume production and very expensive, so they could put in the hand labor to get the body panels just right.
My MGB has an aluminum hood (or bonnet, should I use the English term for and English car?), but that doesn’t exactly push the engineering envelope. It wobbles a bit and the fit ain’t exactly like the stones in the Pyramids. At least when it got towed I could laugh at the guy trying to put the magnetic lights on it.
Car factories aren’t the only place where you have to worry about the bodies, either. Audi had to set up a network of body shops that could do work on the A8 before it came out. But like the Porsche it’s very expensive, and the company can afford the extra effort.
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- Aluminum was once thought to be the next auto material because it’s price was falling rapidly and it could be engineered lighter and stiffer than steel in many situations. The main problem (that they then thought would be overcome, but never has been) is that car body parts are stamped in large pieces but aluminum isn’t nearly as easy to stamp as steel is; aluminum tends to tear instead of stretch. To prevent it from tearing it’s necessary to use thicker aluminum than steel, and that means re-tooling your production line. By and large, the advantages have not been thought enough to offset the cost, especially since the price of both steel and aluminum have fallen steadily. (Aluminum is recyclable, but it requires more energy to make and form at the outset and the intitial manufacturer isn’t the one to benefit much from recycling).
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- I have heard of a few high-end [basically hand-built] cars with aluminum bodies (Lamborghini, Ferrari, etc.) and I think there was some Land Rovers or Toyotas a couple decades back made of aluminum. Nothing recent though.
- By the by, the reason that soda cans are made of aluminum is that there’s a relatively easy method for doing so; spinning. Which as it sounds, involves among other things rotating the piece to be formed symmetrically about an axis, which isn’t useful for making non-round shapes like car fenders. - MC
Plastics
Another Al-bodied car:
Shelby Cobra
Most of what needed to be said has been, but I’ll add my two cents, anyway.
Aluminum is very, very costly compared to the steel typically used in traditional body stampings, and that’s not just the cost of the material. I work for a prototype metal stamper and when we do tryouts on Al parts it is nearly impossible to duplicate production with our smaller, lighter presses. Steel, on the other hand, is much more predictable.
Let’s say you want to put a 15 degree angle on a piece of steel. The steel has a spring action when you bend it where it tries to retain some of its original shape. You would need to bend the steel about twenty degrees for it to “springback” to the fifteen degrees you required. When you bend a piece of steel you can rely on 4 or 5 millimeters of springback. Not so with Al. Because of inconsistancies in the material itself you may see anywhere from 5 to 15 degrees of springback. Add that to the splitting/cracking mentioned before and you have a nightmare for body engineers.
That being said, Jaguar has a car in planning that will consist of nearly 60% aluminum panels. It can be done, but at a much, much lager cost than steel.