Can we design better cars? You need to demand a look at Nature.

Nature is Pretty Cool

Let me start off with saying I'm a engine designer for a major automobile brand.

Recently, we were studying the impact of a minor front fascia change between two mostly identical vehicles. One has one less row of seats, is lighter and has somewhat more aggressive "male" styling. We're trying to appeal to young male entrepreneurs with this one. The other is more of a family vehicle, for a well-to-do soccer mom.

It shares the exact same engine as the larger model, but with the new aggressive styling it gets worse gas mileage. But wait, doesn't the fact that it has less cargo room, less cabin room, and lighter help? Of course, but these are all sacrifices made so it can look cooler.

This got me thinking about the state of automotive design. Everyone is trying to make the most powerful car, the coolest car, the most luxurious car, and the most efficient car… but are they really?

People regard the Toyota Prius as today's current "efficient car" but…

Ok, let's look at nature for a minute.

Let's assume there's an object that is malleable, has the best possible aerodynamic shape for the path that it follows.

That's a raindrop. (More specifically, the teardrop shape that rain is assumed to be)

As a quick note, rain, due to the surface tension always ends up spheroid shaped object. Of course it would benefit from the tail that a teardrop has, but the force keeping the shape together is greater than the drag being enacted on it, therefore it keeps itself in a sphere shape.

Let's for a second examine Cd values. Cd is the coefficient of drag. This is how efficiently the shape "cuts" through the air. The goal for the shape is to disrupt the air as little as possible while equally distributing the disturbing that is does do.

As you can see, the airfoil (teardrop) shape has the best aerodynamic efficiency by kind of a large margin.

This is because the rounded front edge minimized skin friction and more equally distributes it whereas a cone front end would grow in friction as it reached the end. Basically the "flatness" of the circle in front slows the air down enough so it doesn't compound frictional force as it progresses. Cutting through air is different than cutting through skin, we're only considering speed here. Swords and knives work by focusing the greatest amount of force to the smallest possible point. 

Now, lets bring all this aerodynamic knowledge to car design.

First, we have nearly flat bottom sides. All that area between the tires is flat. The best possible shape we can compare our vehicles to is the bullet. This is obviously being very optimistic, because there is a lot of flat area on the front of the vehicles and sharp angles throughout the design.

If automobile manufacturers were all people, I'd be smacking their hands and telling them they've each been a bad boy.

Of course automobile design has gotten much better over the years, but we KNOW what is a better design and yet we're not doing anything about it.

The closest thing we have on the horizon is the Elio Motors 3 wheeled vehicle. There's also the currently produced Volkswagen XL1 that achieves a Cd of 0.19. Then if you're comparing the two, the CdA (drag area) the Elio has 0.26m^2 and the XL1 has 0.271m^1. We can extrapolate that the Elio should be much better by comparison especially with the taper on the back end (additionally, for 1/20th the cost). For reference, the 2001 Honda Civic has a Cd of 0.36 and a CdA of 0.682m^2.

So, even our absolute best vehicles are performing as well as a bullet.

What's preventing us from doing this?

Short answer, the consumers.

People like sexy, powerful, and utility. A majority of our time is spent driving to and from work each day. The average commute is 25 minutes each way and the average person drives 101 minutes per day. About half your time driving is driving to and from work, which is done alone 90% of the time.

Why do you need a sexy, powerful, utility-ready car when most of your driving is done to and from work by yourself with minimal cargo? Who knows.

I think we as consumers should expect better from our car manufacturers. Increasing our efficiency means reducing our waste.

This way, in a few years we'll still have a nature to observe to give us ideas on how to be better engineers.

-Zack

Zack KellyComment