September 11, 2012

"The shorter the vehicle, the more difficulty engineers have in making aerodynamics work in favor of fuel economy, as well as interior noise."

"Cars like the Spark create an expectation, because of their small size, that they have superhigh highway fuel economy. But in reality they have the aerodynamics of a brick."

42 comments:

rhhardin said...

Weight matters with starting and stopping, not cruising.

Everything else is wind resistance.

The Drill SGT said...

Like sailboats, overall waterline length helps :)

edutcher said...

I can believe it.

And then there's the safety factor; the Blonde calls them instant coffins.

Paul said...

No surprise here Ann. A canoe works same way. Longer ones take less energy once you get them to going.

So those 'engineers' finally figured that out?

Sounds like government engineers!

rhhardin said...

With boats, it's that longer waves travel faster (in deep water), and a longer boat sets up a longer wave.

So the boat can go faster without beginning to climb its own wake.

Speedboats get around it by explicitly climbing their own wake through power alone.

john said...

The real problem with those supersmall cars is the limited room for Obama bumper stickers.

This question has been bugging me for a while: Why do you see Obama bumper stickers on Toyota Pius's but never on Chevy Volts?

(Although I probably wouldn't recognize a Volt if I actually saw one.)

roesch/voltaire said...

My wife's Nissen Juke, which looks like a frog in our eyes, seem to slip through the air easily while sipping on the gas. Some smaller cars are getting better at the N.V.H. sources.

Alex said...

I don't bother with vehicles anymore. I have my own private copter and use NetJets for cross country travel.

campy said...

Obviously what is needed is a federal regulation requiring air to move out of the way of small cars.

Peter said...

The solution is to build it as a two-seater-- with tandem (that is, one behind the other) seats.

The body of the car would be narrow but not short, with a fastback cargo area in the back. And the wheels would stick out the sides (perhaps with fairings around the "sticking out" part).

Scott said...

Last year, while my Civic was in the shop for body work for a couple of weeks, I got to drive a rental Fiat 500.

The Fiat was fun to drive, albeit not as sure-footed as the Civic. It had a six speed auto transmission, and was very comfortable for two people. Gas mileage was good.

Bryan C said...

So pretty much what engineers have known since the 1920's, then. Marketability, functionality, and streamlining have always had a precarious relationship. I think the Chrysler Aiflow was a beautiful car, but the market was not interested.

"I have my own private copter and use NetJets for cross country travel."

How quaint. I prefer telepods, myself. And this new compound eye is really handy for detail work.

whoresoftheinternet said...

This just in:

NY Times attempting to push fuel efficient small cars as cool.

Much like vegetarianism and veganism, the only people who will think this is cool will not have testicles, brains, or the ability to build societies.

Film at 11.

Tyrone Slothrop said...

You can't beat physics. This is what a car is supposed to look like.

Michelle Dulak Thomson said...

Peter,

The solution is to build it as a two-seater-- with tandem (that is, one behind the other) seats.

The body of the car would be narrow but not short, with a fastback cargo area in the back. And the wheels would stick out the sides (perhaps with fairings around the "sticking out" part).


It sounds like you're describing the original Aptera. The company ran out of money before the initial launch date, but it seems two have been bought by a Chinese firm who are also launching a more ordinary-looking four-wheeled sedan version.

But the original design was, IIRC, based on a sailplane fuselage minus the wings (hence the name), and I think the first prototype was a tandem two-seater (though the ones in the linked article look as though there's standard-side-by-side seating), with two wheels in front sticking out the sides with fairings, and a third wheel at the rear. So it was very light, also skinny and long. There was some complicated arrangement allowing the wheels to bank while the car itself stayed more or less horizontal.

I'm glad to see that someone's continuing with this. I was bummed when the company folded the first time.

Michelle Dulak Thomson said...

" ... seems TO have been bought ..."

Damn middle-age-onset homophone typing disorder. Usually I catch those before hitting "publish."

Methadras said...

Smart car just put out a commercial showing how their little death trap can withstand the weight of an SUV sitting on top of it's roof. LOL, I understand that many people don't have a knowledge of statics, but rolling vehicle dynamics are a completely different animal and they will never show you their crash tests in that sardine can. Ever.

David-2 said...

Coincidentally, this was just posted at the (excellent) blog of Tim Blair's: Cars 4 Kids - I especially like the caption "car you walk through on your way to a real car"!

David-2 said...
This comment has been removed by the author.
Tim said...

I, for one, am gratified there are people who care more about their MPG than they do their lives.

Prospectively, I thank you, whoever you are, for increasing the odds my family and I survive any crash we might be so unfortunate to have.

Tyrone Slothrop said...

I'll bet you can fit a shitload of clowns in that there Spark.

Rusty said...


So those 'engineers' finally figured that out?


They've known it for a long time.
Remember the Cam back?


Methadras said...
Smart car just put out a commercial showing how their little death trap can withstand the weight of an SUV sitting on top of it's roof. LOL, I understand that many people don't have a knowledge of statics, but rolling vehicle dynamics are a completely different animal and they will never show you their crash tests in that sardine can. Ever.

The industry has just about reached the maximum thermal efficiency they can get out of a gallon of gas in an internal combustion engine. To meet CAFE standards requires a less powerful power plant and a less secure structure.


I think the a much better case can be made for 2 cycle turbo diesel engines and body panels made from foam filled graphite.





ampersand said...

The body of the car would be narrow but not short, with a fastback cargo area in the back. And the wheels would stick out the sides (perhaps with fairings around the "sticking out" part).

Been there. Done that

Eric said...

The solution is to build it as a two-seater-- with tandem (that is, one behind the other) seats.

You'll never get something like that through crash tests without putting in a lot of extra steel. It would weigh quite a bit for its size, and the narrow wheel base would make it easy to roll.

Eric said...

You can't beat physics. This is what a car is supposed to look like.

Hahahahaha. The typewriter by the steering wheel is a nice touch.

kentuckyliz said...

Where the f*** is my jetpack?"

NSFW...no asterisks in the song.

kentuckyliz said...

Long and thin and stuff to the side for stability...sounds familiar.

Does this boat make my butt look big?

ricpic said...

Big cars are "hulking,"
Small cars are the brick,
So quit your sulking
And love Big Bro's trick.

kentuckyliz said...

I was sitting at a red light behind a Nissan Cube today, thinking, gosh, that's unaerodynamic.

Didn't realize until today that the Nissan Juke has suicide doors.

With a name like suicide doors, who thought it would be a good idea to bring them back?

Isn't Ralph Nader having a fit?

Frankns said...

Anyone who's ever owned a two door Jeep knows the problems of "a small boxy shape" intimately.

And they've known it for 20+ years without benefit of government engineers

traditionalguy said...

An option heavy Pontiac Grand Prix circa 2000 had near perfect size, handling, a cadillac's otions and great fuel economy. The car got 32 mpg on a v8 with front end drive.

So who outlawed that success story? I smell the Feds CAFE standards at work.

traditionalguy said...

An option heavy Pontiac Grand Prix circa 2000 had near perfect size, handling, a cadillac's otions and great fuel economy. The car got 32 mpg on a v8 with front end drive.

So who outlawed that success story? I smell the Feds CAFE standards at work.

kcom said...

"This is what a car is supposed to look like."

I've always wanted a car with dual file cabinets.

I can also picture the intercom buzzing and the secretary saying, "I'm sorry, Mr. Williams, I just hit your 3 o'clock."

Joe said...

Another problem with light cars is the turbulence of nearby vehicle affect you more.

Road noise is the big reason I'm thinking of going to a Camry Hybrid over a Civic for next car.

Smilin' Jack said...

On the bright side, if you drive one of those things on the highway you're quite likely to die. And dying is the greenest thing you can do.

_Jim said...


Methadras said...

" Smart car just put out a commercial ... LOL, I understand that many people don't have a knowledge of statics, but rolling vehicle dynamics are a completely different animal and they will never show you their crash tests in that sardine can. Ever.
9/11/12 1:04 PM"

This is why one should NEVER EVER take the word of a blog poster as the LAST word ... crash testing the SMART car (or "Who needs manufacturer's commercials?"):

http://www.youtube.com/watch?v=ju6t-yyoU8s

_Jim

Skyler said...

Just to be clear, it's not that the car is short that creates inefficiencies, it's the way it is shortened. An abrupt cut in the profile can cause greater low pressure behind the car, which decreases fuel efficiency.

Trashhauler said...

Back about four decades ago when I was half-sleeping through the required courses in aerodynamics, I learned of something called the "fineness ratio," wherein drag was proportional to how long a fuselage was in relation to its width. Apparently, some physical relationships don't change much.

holdfast said...

If you like Smart Car crash vids, try this one, where the Smart has a head-on, offset crash with a Mercedes C Class, the smallest normal car sold by Mercedes in North America (Merc also makes the Smart).

Although the Smart's steel crash cage more or less survives, the brains of any occupants would be turned into watery jello by the delta-V of this crash. The Smart has no crumple-zone to absorb the kinetic energy - instead it is all transmitted to the rigid steel cage. Even if the occupants' necks aren't snapped, their brains will be pulped.

I'll stick with my SUV, thanks.

http://www.youtube.com/watch?v=IIsP8ulBwfg

_Jim said...


holdfast said...
"...
I'll stick with my SUV, thanks."

Bigger car ALWAYS wins.

Duh.

I never enjoyed the sheer SIZE of a car so much as my +4000 lbs '86 (Police-package-equipped; bought at city auction) 4-dr Caprice after having had a motor-cycle accident (where the other party, an older female, never saw me at dusk and pulled out from a parking lot into my roadway). I felt safe in that car as it took me a couple months to get over the expectation that any given party was going to 'pull' in front of me again at any moment (it took awhile to shake that fear, that expectation).


(I'd actually like to know more about the 'protective cages' on the SMART car ... I believe I could have used one in that M/C accident even though my injuries *were* minor.)

_Jim

Don't Tread 2012 said...

I generally eschew the 'coffin-on-wheels' car if I can help it. I am stunned by the number of the curiously-named 'Smart' cars I used to see on the road...now, not so many...

My regular driver is a newer Camry, my wife a Pilot. Also have a Stang convertible.

I still maintain that the best winter car I ever had was a '74 Dodge Dart with the Slant Six engine. That thing would start and run when others' brand new cars would not turn over due to extreme cold.

That was one reliable 'buzzin' half-dozen'.

Phil 3:14 said...

So just to be clear, we're saying

size does matter.