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Old 01-31-2013, 10:03 PM   #1 (permalink)
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Designing better side mirrors...

Hi all,

I have been looking at my huge F150 side mirrors, which are a square foot each, and I know I can do better.

I have decided to make some fiberglass replacements that meet the legal requirements for seeing 200 ft behind me, but which are far aerodynamically smaller, to reduce drag.

I've watched a lot of wind tunnel tests, re-watching again and again what happens with the air over the mirrors and it is a mess. I think I might be able to do better.

I'll make some models and post some photos and take ideas and feedback. I'll make more models...

The idea here is to work out what is more efficient, and doesn't create turbulence right against the glass where you can hear it.

Has anyone already done any work like this?

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Old 02-01-2013, 12:24 AM   #2 (permalink)
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Here is a link to one of the best aerodynamic (and pricey) mirror designs.

Racemirrors

The photos of these mirrors show several elements that could be modeled at home.
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Old 02-01-2013, 01:10 AM   #3 (permalink)
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Quote:
Originally Posted by plasticuser View Post
Has anyone already done any work like this?
Hi,
One ecomodder has done, but the video is gone.
I like the original, or maybe high-line version of the ELR

or www.rearviewsafety.com
or the Tesla X:

-mort
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Old 02-01-2013, 08:56 AM   #4 (permalink)
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I've had video mirrors for almost 4 years now.

http://ecomodder.com/forum/showthrea...tml#post106080
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Old 02-01-2013, 09:45 AM   #5 (permalink)
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Video mirrors are ideal, however they're just illegal in too many places. I do so much interstate travel (I'll be in Tennessee, Indiana and Pennsylvania just in the next two weeks) and I'm bound to pass through one of those areas where they write tickets for that, or having too dark tint, or etc.

On the upside, the work I'm planning to do, and what I have in mind would benefit those who can use video cameras as well as mirrors.

My idea came from watching the airflow in wind tunnel videos. Normally, the air that hits the window comes from over the hood, 1/4 of the way in to the center line. As it comes around the windshield, it drops down at a 10-15° angle. Since drag increases as a square of the speed, tuning the headlight for 50-70 mph seems far better than any lower speed where it has a near negligible effect, relatively speaking.

I have this notion of a triangle of fiberglass or carbon fiber or 3D printed ABS that picks up the air as it comes around the A pillar and lets it take a more gentle curve, coming just 3" or 4" out of the side of the vehicle. The curve would be optimal for the 10-15° airflow. This would give a nice 6" tall by 3-4" wide mirror in close to the vehicle that has about 1/2 to1/3 the frontal area, but to the wind has maybe 1/6 to 1/4 the area.

I need to do some testing on the idea because I know it will have some trailing turbulence and putting it that close to the window may create a comfort issue. That said, with my aerocap on, the most obvious wind noise is from my mirrors anyway.
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Old 02-01-2013, 10:05 AM   #6 (permalink)
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You want nice small mirror, but I don't recommend putting them right against your truck for obvious reasons:
1.) You will not have good visibility.
2.) You may possibly effect the attached flow of the vehicle.

You want the mirror to protrude about 6" (past attached flow in most cases). Maybe do a tuft test to see. Since your truck is not a race car, there may be turbulent air flowing past the mirror,in that case it would be better to put a small mirror really close to the truck, but then again you run into the visibility issue.

If you make a nice mold, don't forget to make it it reproducable!
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Old 02-01-2013, 10:22 AM   #7 (permalink)
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In the wind tunnel videos I saw, on the F150 it completely disrupts the airflow against the side of the truck about 8" high, reaching about 16" high by the back of the truck. I think I could stick a lego house there and it would be better.

That said, in most UCC states, the requirement is to be able to see 200 feet behind the vehicle, and a little math for my vehicle tells me I need a 4.5" extension to meet that requirement. For shorter vehicles, the distance will be less. Obviously, if towing, on a truck the mirrors need to be wider.

Design issues!

The second idea I have is a small pyramid inverted on a long or extendable stalk. Like the 2nd attachment above.

The third idea I have is for a slatted mirror that has many vertical elements. It would allow air to pass through the slats, but from the driver's view, the mirrors would be overlapping prisms and provide a single image. However, this would be a PITA to make or adjust.
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Old 02-01-2013, 10:27 AM   #8 (permalink)
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I will get my boattail mirrors in testing soon:



Those have better visibility than stock mirrors due to convex mirror. Frontal area is about 75mmx105mm=0,00788m2 vs regular Lupo 3L mirror (this is smaller than most mirrors already) 120mmx190mm=0,0228m2. That is 2,8 times smaller
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Old 02-01-2013, 10:53 AM   #9 (permalink)
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That is a nice design. How does the clear piece attach to the car?

I checked out your website and it looks like you're really onto something there

It would (sadly and wrongly) be illegal most UCC states in the USA. They require the driver's mirror be flat, and the passenger mirror be convex with "OBJECTS IN MIRROR MAY BE CLOSER THAN THEY APPEAR" etched into it. Anything else would not be DOT approved and can be ticketed.
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Old 02-01-2013, 11:20 AM   #10 (permalink)
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Clear piece can be glued or attached with double sided tape. Ofcourse those are illegal in europe also, but most polices arent interested if they look legimate and you can prove that visibility is better...

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