Goldfish Mirror - Side Mirrors

[jime57]

Here is a link to Longacre mirrors which are of the warp type used in racecars. I've raced with these and find they provide very good coverage and since the distortion is in only one dimension, the brain seems to handle the reverse image well:

Longacre Racing - Online Catalog: Electronic Wheel Scales, Gauges, Pyrometers, Chassis Setup and More!

The "replacement" mirror avoids the cost of the brackets, which are probably useless in a street car.

Here is a link to the multipannel "Wink" mirror:

G-Force 5 Panel Wink Mirror Kit - SafeRacer

It has no distortion of the wide angle view. Disadvantage is that it is large and blocks a lot of forward/upward visibility like signal lights.

Some folks use convex mirrors, but I find the distortion troubling.

[graydonengineering]

Has anyone experimented with a fiber-optic mirror? The thought is, the end of the fiber-optic cable could point backward off the side of the car and go through the door to the inside. The image could then be magnified with a lense for viewing at a reasonable distance. Then you would simply have a small cable outside instead of a large mirror. Maybe it could even be integrated into the back of the car to eliminate drag all together. Image illumination could be an issue.. Not sure but it seems like it could work.

[winkosmosis]

Originally Posted by graydonengineering

Has anyone experimented with a fiber-optic mirror? The thought is, the end of the fiber-optic cable could point backward off the side of the car and go through the door to the inside. The image could then be magnified with a lense for viewing at a reasonable distance. Then you would simply have a small cable outside instead of a large mirror. Maybe it could even be integrated into the back of the car to eliminate drag all together. Image illumination could be an issue.. Not sure but it seems like it could work.

That wouldn't work. The fiber optic cables aren't going to just funnel the image to your eyes.


Maybe if you had lenses projecting the image onto a screen, then fiber optic cables at the back of that screen sending pixels of light to another screen on the inside. But that would be a thick bundle of cables. A camera makes moer sense.

[kach22i]

Originally Posted by jimepting

Here is a link to the multipannel "Wink" mirror:

I saw a few extra wide rear view mirrors out at the Michigan Classic Vintage Races event at Waterford Hills a few weeks ago.

Photo album:
2011 Michigan Classics Vintage Races - WATERFORD pictures by kach22i - Photobucket

[Frank Lee]

Once again the gains are at the rear. I don't know why mirrors would be any different than any other body being pushed through the wind- except that they are usually located in an accelerated air flow zone from the greenhouse. Anyway if an object is too blunt for the air flow's liking, the air takes care of it itself by forming a largely stagnant bubble. Thus I wouldn't predict any sizable gains, if anything at all, from elongating or rounding the front of the mirror housing. We know how awful the flow can be coming off the rear though- it's a major source of wind noise.

[kach22i]

Originally Posted by Frank Lee

Once again the gains are at the rear. I don't know why mirrors would be any different than any other body being pushed through the wind

No one is saying they are different, in fact I'm saying or asking if they can be the same. A Kamm-back mirror would be not different than a Kamm-back car body, except for the lack of ground plane and the air wash off the windshield, right?

Imagine this is your mirror: the mirror part would be to the far left
Production Chevy Volt to Have a Kammback, Round Front, and Tapered Corners


Frank Lee, I don't know why I always seem to read your comments in the negative. If negative is not your goal, then I will just have to do my best to read more carefully.

[Frank Lee]

The difference with a Kamm body is they are able to make a wake zone that has smaller area than the frontal area and the frontal area is determined by the size of the interior they desire. With a mirror housing, you have x size for the mirror and I think making the housing larger in frontal area so that you can taper it back down to the size of the mirror at it's trailing edge would result in greater CdA simply due to the greater frontal area even though the Cd itself might be better. Or if I'm wrong about that maybe nobody does it- not even racers- because they don't like the looks?

I'd think there's an optimum fore-aft length for mirror housings though. Thinking about the mirrors on my '60s Chevy cars and the big mirrors on my '76 Chevy Camper truck that are just about plain flat planes- I'd expect more turbulence off them than mirrors with housings with enough length to have a place for flow to be attached or reasonably linear before it separates off the back, like the ones on my Tempo or Sable.

The clear trailing fairings might have some merit if they can be shaped to not interfere with the mirror's image. Then too there are probably issues with fogging and icing and how do you clear it without scratching it up, etc.

I'd say the best bet is minimizing the size of the mirror if you can do it. Or eliminating the mirror if you can do that. Or locating the mirror in a less accelerated flow region. Maybe pressurized air can be fed to the mirrors for air curtains?

[kach22i]

Originally Posted by Frank Lee

Maybe pressurized air can be fed to the mirrors for air curtains?

All good observations, and logical.

The quote above does remind me of a few other things.

Engineering and Fabrication Techniques for Low-Noise-Research Fan Blades


FanWing Pictures


Like others have observed, a lot of work-around for just a little gain.

CdA,:
Automobile drag coefficient - Wikipedia, the free encyclopedia

The combination of drag coefficient and area - drag area - is represented as CdA (or CxA), a multiplication of the Cd value by the area.

I guess this is the crux; how much larger can you make the mirror body for the sake of smooth flow before the surface area drag undoes the gain?

[Patrick]

I think there may be some gains available on the front. Take a look at this: Shape Effects on Drag

The rounded-front bullet shape has about 1/4 the drag of a flat plate.

[kach22i]

Originally Posted by Patrick

I think there may be some gains available on the front. Take a look at this: Shape Effects on Drag

The rounded-front bullet shape has about 1/4 the drag of a flat plate.

Good link.

Another crazy idea, gold ball dimples?

In addition to the Goldfish or truncated teardrop shape?

EDIT.....did some more searching, and found a similar thread.

http://www.gassavers.org/showthread.php?t=6054

The gray semi-circle at the right end represents a 2" convex mirror. The gray triangle in the background is the mount on the car.

However at the trailing edge, a taper to a thin tip or edge is a good thing. It encourages the airflow to rejoin itself smoothly. An airplane wing is a good example of both the rounded blunt leading edge and a tapered trailing edge.

I really should edit that wikipedia article that seems to be responsible for perpetuating the bs that a Kamm back can create some sort of virtual and equivalent teardrop shape. It can't. It's an engineering trade-off. You cut it sharply at the point of diminishing returns. Most of the drag of a truncated teardrop will be in proportion to the cross sectional area of the truncation.

Back in about 1980 I put some bullet mirrors on my 1966 Mustang similar to this.
http://www.midlandwheels.com/Shop/P-...et-Mirror.html


I'm now looking at these with a new insight.