Goldfish Mirror - Side Mirrors
 

Would there be any merit to increasing the body size of a side mirror so that it is elongated?

If this mirror were large enough, you could even sneak in some downforce for racing.

My better judgement tells me the smaller the mirror, the better. However if you look at some motorcycle mirrors they can get pretty long, even though the glass/mirror area is the same.

I drew such a mirror up, with Gurney flap like spoilers it looks just like a Goldfish. However, it might work better, if it works at all, without these vortex creators.

In fact you might want to view this as a mirror image Kammback mirror, if there ever was such a thing.

I get crazy ideas all the time. You won't hurt my feeling if you think this one fails to swim up river.

http://i184.photobucket.com/albums/x...ish-Mirror.jpg

Motorcycle example:...........fashion statement or science?
http://www.moto-works.jp/products/ca...o_mirrors.html
http://www.moto-works.jp/bikes/00_03...o_winker_f.jpg

You can get most if not all the same aero streamlining benefit, at ~1/10 the cost, via eBay motorcycle mirrors.

I guess I wanted to talk theory, not cost.

Smaller mirrors as found on motorcycles are going to be more aerodynamic than truck mirrors for towing, those are perhaps two extreme examples.

I guess if the side mirror housing were too long, it would impair the scope of vision around it. And maybe even hit the side of the car when you open the door. Those issues aside, I'm still wondering why we don't see mirrors like I've drawn everyday.

My current mirrors are large, square, and flat on the front. I have been considing the idea of designing a dome on the front and producing it on a 3d printer to add a bulett shape to the front. Since I have a canopy with no windows on the sides, I really do need my mirrors WITH cheaters to check my blind spots so reducing the size of the mirror is not really an option for me.

I like the fish fin idea to produce a raised low presure zone, however, I fear the flow disturbance my futher inturupt atached flow down the side of the car past the mirror. Hard to say without some testing. Maybe someone could provide some detailed data on mirror shapes and CD??

I know you said those issues aside, but IMHO it boils down to: cost and styling. Manufacturers provide the mirror that allows the driver to see well to the rear at the lowest possible manufacturing cost that complies with regulations. But it has to look good enough for consumers to buy it. So they put a slab of glass out there and wrap it in something that they think looks halfway decent. They're not going to spend 2, 5, or 10 times the money to get a .1 mpg increase with an aero mirror that the majority of consumers won't like the looks of.

Good point, and I bet we have at least a couple of people in this forum willing to experiment.

graydonengineering, I think after looking at several different types of Google images some observations can be made.

The length of the dome is typically no more than double the height. The motorcycle might be closer to 3-times.

The Goldfish, would be +4X's, which could get parade float like in a hurry.

My guess is the goldfish would be better off without the gurney flap.

http://ntrs.nasa.gov/archive/nasa/ca...1989004024.pdf

kach22i -

We have speculated that adding a clear "boat tail" would be the best way to make a mirror more aero. The problem is that the clear material often distorts the reflection off the mirror, and/or adding more reflactions, rendering the mirror useless.

I did a version of this by making an "Easter Egg" rear view mirror :

http://ecomodder.com/forum/member-cf...iew-mirror.jpg
http://img369.imageshack.us/img369/8...irror04sq7.jpg

I only tried it on the passenger side. In addition to the distortion it was pretty small. It may have worked better on the driver's side.

Imagine the bubble canopy of a P-51 Mustang. You could probably get one meant for an R/C plane. I think *that* would be the ideal shape.

CarloSW2

I've been experimenting a bit with mirrors on my Insight 1. I taped off all but 2x4.4" on the drivers side to simulate the small size available in racecar mirrors. It was pretty frightening to drive. I think that the reason that small mirrors work well in some applications, like bikes and race cars, is that the mirror can be close to the driver. As the mirror gets a ways away, the reverse image doesn't provide much coverage. I think that the inside "warp" mirror or the "wink" multipane, both used inside race cars, might be a better bet for good visibility. Of course, "good" will always be in the eye of the driver.

Re your idea of the Kamm back mirror, there was a similar picture offered up on this site around a year ago. Forget the manufacturer, but you can probably turn it up with a search. I think the idea has merit, assuming the mirror face isn't too small.

Hucho rates the delta Cd of mirrors at about .01 for the total of both sides. For "extreme" modders, it is probably worth the effort.

[QUOTE=cfg83;256313]kach22i -

We have speculated that adding a clear "boat tail" would be the best way to make a mirror more aero. The problem is that the clear material often distorts the reflection off the mirror, and/or adding more reflactions, rendering the mirror useless.


We have speculated about the optical distortion and light glare on different 'boattail' shapes.

http://i429.photobucket.com/albums/q...eflections.jpg

...and try to optimize it by having a flat plane parallel to the side glass.

http://i429.photobucket.com/albums/q...flections2.jpg

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.

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.

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
http://i184.photobucket.com/albums/x...ORD/WAT101.jpg

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.

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
http://www.gm-volt.com/images/volta.jpg

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.

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?

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
http://www.grc.nasa.gov/WWW/RT2001/i...ningham-f1.jpg

FanWing Pictures
http://www.fanwing.com/DSC07913.jpg

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

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

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
http://i28.photobucket.com/albums/c2...aeromirror.jpg
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
http://www.midlandwheels.com/Product...G/BIG/1556.jpg

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

We raced there several years. I believe arccosine still does.

kach22i -

Maybe instead of a goldfish mirror, you want a boxfish mirror :

Fish-inspired Mercedes bionic car: Most efficient 'This category' aerodynamic vehicle

http://www.instablogsimages.com/imag...ncept_car1.jpg
http://www.instablogsimages.com/imag...ncept_car5.jpg

CarloSW2

Here's another idea. Take a look at this link: Drag of a Sphere

If we make our mirror housing a 9" diameter sphere, it will drop into the low drag bucket (0.07 Cd) at about 66 mph.

There should be enough room inside to place a nicely sized mirror and electric adjustment mechanism. But you still have the problems of image distortion and cleaning the clear part so you can see through it.

botsapper,
Great graphics there.

Which programme did you use for those?

Peter.

The flat plate is obviously the worst-case scenario.
Beyond a bullet-shaped front, what most car mirrors approximate anyway, the gains are made at the back.

A carefully designed mirror-car body blending (Opel Vectra / Vauxhall Cavalier ? can help reduce drag and noise, while being ahead of the mirror plane.

If you look at mirror housings, some are tapered at the rear - at least on the C30/S40/V50 range Volvo used this trick.

I have looked up all the models listed and do not see that.

Maybe the black lip curls in a little at the end, hard to tell.

Sample: 2011 Volvo S40
2011 Volvo S40 T5 Sedan Mirror Photo | Automotive.com
http://image.automotive.com/f/2011_v...500/mirror.jpg

I suppose the last 1/2 inch does taper in, I'm sort of looking for an example where the last 2/3 rds of the housing/body tapers inward. Thanks for the short list of prospects in any case.

Maybe for the owners of cars and the makers of cars, keeping the mirror clean is the more important issue. If negative air pressure sucks water back onto the mirror face, it would be a "fail", and on the customer complaint list for sure.

Which programme did you use for those?

Peter.[/QUOTE]

Quick visualizations with Autodesk 3ds Max.

Very nice.

It would have to be vented to prevent fogging, right?

One thought I have had is what if you had a flat plate mirror on a shaft that could pivot to horizontal to the wind so they could slice through it like a knife on the fly when not needed, thuse reducing frontal area down to just a few square inches. You could have 2 switches on your steeing wheel to conect to little motors to flip them when needed. You would probably want to keep them perpendicular to the wind like a standar mirror unless driving on the highway.

A little nuts I know but just thinking outside the box here.

Two anti-fog alternatives; an hermetically sealed unit or an inducted draft anti-fog system...even heated during winter conditions.

Geez, lets use camera/sensor/display systems already.

...remember a time when car designers couldn't use aero-conformal headlights because of round/rectangular seal-beam lamp requirements.

I think that arguement against the round sealed-beams is largely bogus. Take most of the front-ends of vehicles with so-called aero lighting and if you wanted to, you could fit the round sealed beams in.

I for one am sad the round sealed beams went away. They didn't fog, haze, or yellow. They cost $5 to replace (why do dinky headlight bulbs cost more than an entire sealed beam assembly?) and they were easy to replace- no tearing the entire front fascia off to get at them. They put out a nice beam. And they were practically a universal fit. You could buy them at virtually any store in America.

Not nuts at all, this is how idea are born.

Yesterday I sketched up a mirror which is perforated, allowing built up front face pressure to flow though. Might work, but somehow just not very sexy, and deterioration of the mirror surface would always be an issue.

I can just imagine droplets of water resting in the tiny holes, waiting for night fall when they can freeze, expand and do destruction.

I say this is true for a good 50%.

The rule of no headlight covers over the old round headlights is the one which irked me. The European sports cars, and even some Japanese sports cars just were not the same.

Headlamp - Wikipedia, the free encyclopedia
http://upload.wikimedia.org/wikipedi...Euro_vs_US.jpg

I think Volvo had a segmented mirror on a concept car a few years back, but my google-foo is failing me right now. It was several mirror-slits behind each other, correctly paced and angled to give a single image.

It would behave just like screens, which at speed act like solids re: air flow.

Yes, the key here would be to make the holes large enough that the flow through would exist throughout the intended use velocity. I have considered making a mirror my polishing some perforated steel. It would be very labor intensive to get it up to mirror shine. It would give you a "flies eye view". Your brain would need to fill in the blanks.

http://www.mcmaster.com/param/images...ed9255t941.gif

Here is my thoughts. Mirror drag savings can be in the range of CD 0.01 or even more if your current mirrors are bad. To reach this with your own mirrors you should avoid few things and try to do what you can to make as sleek as possible.

1. Size is bad. So try to make mirrors as small as possible. I will use wideview mirrors in my Lupo. Smaller mirrors also reduce the frontal area. My Lupos mirros have about 1/3 of the original mirrors size and the original ones were already pretty small.
2. Shape. Mirrors should have the teardrop shape, because that is optimal. If you can build there the sharp teardrop end its even better. There might be even better shapes for mirrors if you study them at wind tunnel but best quess is teardrop shape.
3. Position is also important. Now this is my own thinking here. I think they should be as low as possible if you attach them to doors apillar corner. Reason is simple all the flow will come to that "mirror" corner from the hood and windshield so you dont want to disturb it more than you have to. In almost all modern cars the "leg" of the mirrors is as low as possible. If you dont care about the visual looks so much you can build it even lower.

Few pictures of the current state of my mirror project, scroll to the right for more mirror images. Tomorrow the story will continue with more images.
https://www.facebook.com/media/set/?...type=1&theater

Vekke -

If I were starting from scratch I would get some of these snowmobile mirrors :

http://ecomodder.com/forum/member-cf...-would-try.jpg

They are small, 2.5"x4", but they are *convex*, so I think they would have a good field of view.

CarloSW2

Mirrors I use are convex motorcycle "wheelie" mirrors ment to be attached to the handlebar. Square mirrors wont work what I have planned to try. So target is to build that boattail behind the mirror on round mirror is easier to cover.

CarloSW, that is what we call "out of the box".:thumbup: