it kinda bugs me that car manufacturers have easy options like this to make cars more efficient, but don’t.

nice results.

but it sure is going to be surreal for the person who rear ends this thing…. and it literally folds like cardboard.

now let’s see someone do this mod to an actual car :P

Impressive that he did all the testing and didn’t just assumed, and interesting that the shape could have so much effect but so many cars still ignore it in their designs, and I mean designs of cars that are labeled green, not just the designs of your hummers and such, although, you can’t make a tail as long as this one since you can’t park in many many places then, and people like to be able to park their car :)

But why didn’t he use black straps to attach it? I mean why go through all that trouble and drop the ball like that?

@sasdface You do realize how light aluminum is right? And even if you dropped this thing from space the tubing would probably not penetrate the body of a car.

I don’t understand why attaching something to the back of the car would make it more aerodynamic? Wouldn’t moding the front of the car be more effective? Maybe I need to read up more on aerodynamics..

@nave
The problem is that most consumers would never buy aerodynamic cars. Manufacturers put a huge effort into convincing the public that you NEED an un-aerodynamic slab of an SUV to get to the mall and back in style. Most people were stupid enough to buy into it and now it’s hard to reverse that meme and suggest that goofy looking aerodynamic cars are cooler than goofy looking blocks with wheels. (Scion xB, anyone?)

What about ye olde futuristic waterdrop-shaped car designs? With blunt front and thin rear. I’m sure it’s possible to design one that doesn’t look too ugly and is still relatively compact.

I would be interested to see how this affects acceleration as well. Obviously it would make it faster, but I’m wondering if it scales in relation to fuel economy.

This, much like the Mythbusters test, is primarily a “proof of concept”. Neither is particularly practical using the tested methods. However, the concept is solid and can be scientifically proven and now (hopefully) the engineers will work on adapting them into practical solutions. (Retractable tail/fins? Adapted painting techniques to mask a dimpled exterior?) As far as high efficiency vehicle technology goes, the industry is in it’s infancy.
One would have better luck adding unsightly modifications to vehicles in Europe, where gas is much more expensive than here (not to mention they lack our American ego about cars).
That being said, offer me a 80 mpg hybrid with 5 star safety ratings and a reasonable amount of low-end torque and I would definitely own one, no matter how unsightly it may be. It would be fairly easy to repel any heckles with a response of, “It gets 80 miles per gallon and does 0-60 in 8.2…piss off”.

I agree with the “blocks on wheels” argument. I dont understand why when driving on the highway, i see tons of big ass SUV’s with only one person in them. Now i could possibly see if you had a crowd to carry around, but one person?? I also dont understand how the Scion XB is selling, its ugly as shit. Not to mention the newer designs of cars are ALL blocky and “retro”. They DO need to make them more aerodynamic. Its all likely a ploy to keep oil sales up…

im not 100% sure thats legal in most states …. atleast to park in a parking lot

pluss that tape on the windshield is not legal … in maryland atleast

…inflatable… silly pda kybd

I thought a “chopped tail” design was just as good for drag and had the benefit of not having the wright of the tail.

Manufacturers generally do these tests with their cars to make them as efficient as possible for the materials alloted. This is not likely true of a Geo Metro, which is like a sized-up matchbox car with a lawnmower engine.

If you do this to a modern ‘green’ vehicle, especially the electric ones, you will ruin the laminar flow and increase separation and turbulence more than improve it.

That said, good job with the thorough research.

@marshall plan
if you’re going to bring your shitty political trolling into the discussion, then gtfo. i don’t see you mentioning the countless number of people the US has killed, from its own citizens (lack of affordable healthcare, war on drugs, police brutality) to countless “non-wars” (China 1945-46 1950-53, Korea 1950-53, Guatemala 1954 1960 1967-69, Indonesia 1958, Cuba 1959-61, Congo 1964, Peru 1965, Laos 1964-73, Vietnam 1961-73, Cambodia 1969-70, Lebanon 1983-84, Grenada 1983, Libya 1986, El Salvador 1980s, Nicaragua 1980s
Panama 1989, Sudan 1998, Afghanistan, Iraq).

If you want to talk about arms dealing, why not discuss how the US is directly responsible for creating and financing what is the modern-day Taliban?

@jeditalian
seems like a fair price
my friend’s geo metro would stall if you tried to go up a steep hill and then turned the air conditioning on

3 cylinders of pure muscle! it can sometimes outrun a motorcycle! it’s almost guaranteed to be faster than a bicycle! GEO METRO!

@ML Sounds like you need some opposite sex lovin?

@zhanx: Yes.

Never really seen the Geo Metro or the Scion XB before and I have to say; what the bloody hell? people actually thought “hey that looks like a nice car” and bought one with their own money? I’d rather have a Morris Minor than one of those two cars!

Extendable tail, how about using fabric for the cover with movable struts so the tail can extend/retract at will, like this BMW concept:

When I see this I think of the Dymaxion Car.

http://en.wikipedia.org/wiki/Dymaxion_car

http://farm2.static.flickr.com/1340/1481273227_0f7aa0576a.jpg

http://www.washedashore.com/projects/dymax/dworld/e44.jpg

Really a shame it was basically destroyed by Detroit. Could’ve revolutionized the industry. Buckminster Fuller is still one of the greatest minds of all time.

@marshall-

@octel wants you to gtfo with your political trolling because it’s inconsistent with HIS political trolling.

The results of this augmentation is interesting, but unfortunately the whole thing looks hideous. One of the biggest selling points of any car is aesthetics, which often comes at a cost aerodynamics.

On a side note, what really bugs me with “futuristic” concept cars, particularly the ones that are meant to be fuel efficient, environmentally friendly, etc, is that they are fucking ugly. Surely, if an industry wants to break free from petrol dependence, at least try making it look attractive as well.

This is all well and good, but the question is how much of an increase will there be once you cover all of the state and federal regulations to make it street legal? There are bumper laws and other considerations such as location of lights. It might work just as well, but without following all the rules, it makes this more of a test run than anything conclusive.

@Whatnot “You do realize how light aluminum is right? And even if you dropped this thing from space the tubing would probably not penetrate the body of a car.”

Motorcyclists and bicyclists might take issue with your line of thinking.

@Andy, surface area has nothing to do with gravity

@Kevin, you can make a dune buggy legal, it’s mostly about lights, horns, and plates. That being said, you can register a car as a kit car and get away with crazy mods. I’m not sure what your point was about motorcyclists and bicyclists though.

@TheFinn and other people objecting to this test, this is clearly a proof of concept

So, can this be made inflatable, or at least retractable like a convertible? Nobody would need or want this thing in city driving, but if you could pop it out while on the interstate…

eric: I think you’ve missed the point. The mod may reduce traction a little (probably insignificant, it will be ~1% of the weight), but that’s only because it’s a custom mod. Putting shopping in the trunk would have a larger effect.

The demonstration is showing the application of rear end tails in improving the aerodynamics, the weight distribution (/wheelbase) of the car is irrelevant and could be changed and compensated for easily by a manufacture.

omg… What has happened to the hackaday commenting crowd? Normally nice people interested in hacks… motors seem to bring out the freaks…
Yes car might look odd, but great idea, 15% is great. I reckon someone needs to do a eco-kitcar. Something like the banham spider, light weight, streamlined, easily repairable (composite pieces to replace what you need) and cheap (fits of a common cheap car body)

@kevin “Motorcyclists and bicyclists might take issue with your line of thinking”

Yeah think of all the cardrivers impaled when they hit cyclists with aluminum bicycles… oh wait.

@Andy
Time for some Newtonian physics!
Andy, the gravitational pull on an object is relational ONLY to the mass of the body (Ie. The earth), the distance between the two, and the mass of the object (ie. the “Mod”). Surface area has bupkiss to do gravitational pull. If I have a 1x1x2 (length x width x height) foot object that has 1KG of mass, and a 2x1x1 object of the same mass… they both weigh 1KG on Earth!

“Of course it does you hold a big square peice of wood flat – then hold it on its side | see which is the lightest (Y)”
Your example is flawed. All you are doing is changing the pressure, but the mass (and thus weight) is the same. A 1KG paving slab weighs the same on its face or on its edge. It just means that it is not evenly distributing its weight across the face of the slab, but instead is distributing it’s weight across a smaller area.

Now, surface area and aerodynamics.. you might say they’re linked ;)
/Rant

Oh, and these cars sold under the Suzuki name (“Swift) were built a bit better, with nicer lights, trim, and a 1.3 DOHC 4 cyl. with front+rear antisway bars… fun pocket rocket!
The 3cyl is gutless stock though, but with a little work you can get more than 90 BHP without a turbo. With a car that only weighs 1500 pounds, you can have some good fun in a cheap runabout.

also I am VERY happy with the 3cyl in my 94 metro. Plenty of acceleration plenty of passing power. I drive 54 miles one way to work almost every day with 4 people crammed inside my little metro. No problem (except people whining about the cramped quarters which stopped the moment I put my hand out for the $24 in gas it would cost to take the van hehe)

I am surprised just how much power that tiny little engine has.

@Chris Taylor: I agree w/ you totally.

This is a great hack.

I’d really like to try something similar for my pickup. Regular careless driving nets me ~24mpg, while I can achieve 28 mpg easily by slowing down and driving conservatively, and occasionally >30mpg being really careful w/ the throttle.

I’d bet I could find >%25 better mileage by building a boat-tail to bridge from the cab to a dropped tailgate, tied into a smooth under-body panel. It is so noisy driving on the freeway, I’m sure there are huge improvements to be found. The original aerocivic modder guy said that the sound of the wind was nearly silent in his car when he was on the freeway from lack of turbulence.

Sheet metal and dzus clips > duct tape and bailing wire.

I just think this mod could be dangerous, I mean imagine all the people going off the road because they’re laughing their asses off!

@Chris Taylor

Your argument about lift creating drag makes sense, but I feel you are too hastily brushing aside the traction of the wheel. Surely traction involves losses to friction. I’m probably arguing for arguments sake here, but it just seems like both of you could be correct.
Perhaps it is possible that the mod creates some lift, and with it some drag. But this lift would decrease the normal force on the tires, thus redusing the frictional losses here.

how many hacks on hackaday are ‘stylish’? How many are built to be functional? To test a theory? To prove something is doable?

Why are people so obsessed with the cars looks?

Also, about the comments on euro cars… Have you seen the cars most men and women drive in europe?

anyway, great mod, great idea, good post and please someone banhammer offensive homophobes and general losers above. Shocked mainly at how awful their grasp of physics and basic aerodynamics are… A banable offense in commenting if ever there was one (JOKE!!!)

@le’chef: Downforce also creates drag, but not because of tire friction; it increases drag because it’s the same force as lift, just in the opposite direction. Any time you create lift you’re creating drag. In aircraft this is called “induced drag.” In simple terms, the energy to create the lift force has to come from somewhere.

Decreasing weight on the tires could in theory increase fuel economy by reducing sidewall flex, but I doubt this mod is creating enough lift to even cancel out its own weight.

@Orv

What in the hell are you talking about? Drag is the resistance in opposition of thrust. The engine used to move an object through any medium(air for aircrafts, water for submersiable crafts, both for floating vessels) must take into account the energy to displace( push around the vehicle) the medium itself. The more streamlined the vehicle, the easier it is to push through and less energy is needed for displacement. This energy can then be used for thrust.

Induced drag is an intended effect used by aifcrafts to slow them down( air breaks). The wings normally open up flaps to reduced the lifting effect of the wings so that the plane can slowly land without crashing into anything on the runway( else we would need longer runways).

In conclusion,lift works in opposition of gravity. Downforce works in opposition of lift( good for race cars, dangerous for aircrafts). Drag is in opposition of thrust( in the opposing direction of travel). Lastly, thrust is the application of locomotive force to any object to make it move in any direction( engines generate, drives translate, and I’m always late regardless. lol)

In the old days (VW beetle) they though easing up on the flow like this was aerodynamic, but now they know it is best to cut off abruptly (hence the name, spoiler).

I wonder if he could put some Fiber Optic cable from the original Tail lights leading to the new Tails’ tail light, so no modification is needed when he attaches or removes the tail.