Why pop up headlights ?, Philosophic question ... Options

[blitZ]

Just get some Euro front turn signals and put some bright LED lights in the white section. I use these as my daytime running lights so the car is more visible.

[johannes]

In the sixties the "flush" headlights were forbidden. The only light that was allowed in the USA was the 7' round lamp.
So if you wanted to design a low car, you had not a lot of alternatives.
- Frog eyes like the 911
- Pop up like the 914 ...

Popup headlights are now forbidden on new cars because of the pedestrian protection regulation. It's a shame ! Popup headlamps are soooo coool ...

http://www.youtube.com/watch?v=1-dSISRUDq0

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[ericread]

The worst thing about the 914 was the air coming off the roof. The 911 had much cleaner air flow on the rear end.

Paul, I'm confused. I would have though "spoiling" the airflow over the rear end would be the best thing about a 914? (IMG:style_emoticons/default/confused24.gif)

By putting a duck tail "spoiler" on the back of my 911 it reduced the cleanliness by -113lbs. (of lift) per corner.

I know you're confused, but the drop off of the 914 roof line is a bad thing.

I respectfully disagree.it breaks up the drag surface..A golf ball flys farther with dimples then with out..thats a fact..we need someone to find it in a book and post it

You are correct. Dimples help a golf ball fly longer.

But cut a chunk out of a golf ball and how does it fly then???? Not so good.

The same with our cars. A slight dimpling or air disruption off the roof would be a good thing. The huge cavity behind the rear window is not so good.

Eric Read

[Todd Enlund]

I respectfully disagree.it breaks up the drag surface..A golf ball flys farther with dimples then with out..thats a fact..we need someone to find it in a book and post it

This is true, but the principle is different. The dimples on the golf ball cause boundary layer turbulence, which increases the Reynolds number, which minimizes flow separation, which minimizes base drag.

[roadster fan]

This is true, but the principle is different. The dimples on the golf ball cause boundary layer turbulence, which increases the Reynolds number, which minimizes flow separation, which minimizes base drag.

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uh..............yeah, what he said! (IMG:style_emoticons/default/laugh.gif)

[biggy72]

I respectfully disagree.it breaks up the drag surface..A golf ball flys farther with dimples then with out..thats a fact..we need someone to find it in a book and post it

This is true, but the principle is different. The dimples on the golf ball cause boundary layer turbulence, which increases the Reynolds number, which minimizes flow separation, which minimizes base drag.

I was thinking about this last night, but why are bonneville cars as smooth as possible? I would really like to build one at some point and I have been considering things I could do to be different to go faster. I was thinking about dimpling some of the car to do this especially in areas where I wanted the boundary layer to be as small as possible. You never see it done, but it seems like it should work in theory.

[Solo914]

I respectfully disagree.it breaks up the drag surface..A golf ball flys farther with dimples then with out..thats a fact..we need someone to find it in a book and post it

This is true, but the principle is different. The dimples on the golf ball cause boundary layer turbulence, which increases the Reynolds number, which minimizes flow separation, which minimizes base drag.

I was thinking about this last night, but why are bonneville cars as smooth as possible? I would really like to build one at some point and I have been considering things I could do to be different to go faster. I was thinking about dimpling some of the car to do this especially in areas where I wanted the boundary layer to be as small as possible. You never see it done, but it seems like it should work in theory.

Bonneville cars are not a round ball. Its the same reason they don't use dimple technology on F1 cars, they are able to make the drag coefficient lower by changing the shape with a golf ball you are kind of stuck (IMG:style_emoticons/default/wink.gif)

Now, you could do some interesting things on existing cars where you can't change their design. Say, dimple the leading front of a volkswagen Beetle or Audi tt etc.

Kyle

[Todd Enlund]

I was thinking about this last night, but why are bonneville cars as smooth as possible? I would really like to build one at some point and I have been considering things I could do to be different to go faster. I was thinking about dimpling some of the car to do this especially in areas where I wanted the boundary layer to be as small as possible. You never see it done, but it seems like it should work in theory.

There are two ways to make an object faster... increase thrust or reduce drag. Thrust applied to a golf ball, for a given golfer, is fairly constant (if the golfer is any good). A golf ball MUST be round(ish). Round is not a very streamlined shape. Dimpling reduces the drag on a high drag object. Drag increases dramatically when the boundary layer separates, and the dimples delay the separation... a Bonneville car can be VERY streamlined, almost to the point of no boundary layer separation at all, so dimples would increase the drag.

Laminar flow, baby.

[Solo914]

Fun stuff.


http://www.eng-tips.com/viewthread.cfm?qid...764&page=10

Kyle

[JeffBowlsby]

Someone say '914' and 'Bonneville' in the same sentence? (IMG:style_emoticons/default/biggrin.gif)

[biggy72]

I found another picture of a red 914 at bonneville too awhile back, but I don't know anything about either of the cars. Does anyone have any info about them?

And thanks for that engtips article. Pretty good stuff to consider.

[bandjoey]

There was a show on Myth Busters a year ago about Pickup owners driving with their tail gates down, thinking it would reduce drag and increase gas mileage. Results of the tests showed the tail gate up was better because...my memory being almost gone...or so my wife says...airflow off the cab was dumping into the bed of the truck with the gate up, causing a swirling effect that enabled additional air to flow smoothly off the top of the air bubble, and over the tailgate. Actual results showed better gas mileage and lower drag. Could this same effect hapen on the 914? Go figure. Might find that old show on utube. Bill (IMG:style_emoticons/default/laugh.gif)

[Spoke]

No dimples on this vehicle & lots of thrust.

[RiqueMar]

Off topic from Aerodynamics, but what about theft or vandalism?

[orthobiz]

I read somewere:

AK, AL, AR, AZ, DC, DE, FL, GA, HI, ID, IN, KS, LA, MD, MI, ND, NH, NJ, NV, SC, TX, WA, WI - Height of headlamps must be at least 24 inches from the ground
CA, CT, ME, MT, OK - Height of headlamps must be at least 22 inches from the ground
NM - Height of headlamps must be at least 20 inches from the ground



Taillights

AL, AR, CO, DE, GA, IA, ID, IN, MD, NH, NJ, NM, RI, SC, WI - Taillights must be at least 20 inches off the ground
AZ, CT, DC, KS, MT, NV, OK, SD, TX, WA - Taillights must be at least 15 inches off the ground
CA - Taillights for post-'69 vehicles must be at a height of at least 15 inches

Wow! For a guy who read it somewhere, you have the BEST information retention ever!!!!

Paul

[biggy72]

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

[Eric_Shea]

I know you're confused, but the drop off of the 914 roof line is a bad thing.

Grumpy today aren't we?

Seriously, wouldn't disrupting the airflow over that long, flat surface like our rear lid help reduce lift? I would think it would make it so we wouldn't need a big goofy wings on our cars! (IMG:style_emoticons/default/poke.gif)

(serves ya right for being mean to me) (IMG:style_emoticons/default/tongue.gif)

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[URY914]

E, I wasn't being mean, just being a smart ass. Sorry.

Look at the shape of a rain drop. Now turn it on it's side. Does it look more like a 911 or a 914?

[Eric_Shea]

I know... I'm just (IMG:style_emoticons/default/poke.gif) ing at ya.

The problem I had with my 911 was, it got all squirelly on the back straight at Las Vegas as I was hauling ass coming into the infield 90 degree lefty.

My duck tail has made some serious differences in the way that car handles. I did a bit of reading on it (hence the 113lb. reduced lift figure) and it all made sense to "spoil" that airflow, which we all know is why they call them spoilers.

I get the teardrop thing, I also get the airfoil thing. My 911 looks more like an airplane wing than my 914 as well... I'd love to learn more because I honestly thought the 914 shape would perform better at speed with that feature.

[6freak]

No dimples on this vehicle & lots of thrust.

They are look`n for lift here not less drag