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Air-barrier Convertible Roof

Inspired by doctorremulac's "Wiperless Dry Windshield"
  (+11)(+11)
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On an episode of Mythbusters they tested the theory that there is a speed at which the flow of air over an open convertible will divert rain and allow the occupants to stay completely dry. I seem to remember it was ~30mph. Problem is, though you may stay dry while driving 30 and above, most driving does require occasional stopping. At which point you're soaked.

After being intrigued by [doctorremulac3]'s Wiperless Dry Windshield idea, I did some digging and found that commercial "air doors" are widely used as an effective barrier in many applications. Even decently large units don't seem to draw a whole lot of power (the largest unit on the linked website spanning 66" consumes 300W).

Recognizing the difference between using one of these vertically as a "door" vs horizontally and taking into account gravity, I still think that this could be a feasable way to block rain from entering the cabin of a convertible when it is moving under 30mph. I envision either one or two electric air compressors in the trunk sending air to a pop-up unit mounted behind the seats blowing air forward, or air ducts through the windshield pillars that would duct the air backwards out of a slot where the windshield ends; the latter would seem the most intuitive since the airflow would be consistant with vehicle motion. The system would sense when the windshield wipers were on, and would turn on instantly when vehicle speed falls below a certain threshold. Once the vehicle accelerates to above the threshold, the system automatically turns off to conserve power.

This idea would also be useful as an "air-door" for open cabin windows in any non-convertible as well.

acurafan07, Jun 22 2012

Air-Doors http://www.ceconpol...com/air-curtain.htm
[acurafan07, Jun 22 2012]

Wiper-less Dry Windshield Wiper-less_20Dry_20Windshield
Inspiring idea [acurafan07, Jun 22 2012]

NASA studied something similar http://ntrs.nasa.go...8716_1981068716.pdf
(dupe from Wiper-less Dry Windshield) "Preliminary data on rain deflection from aircraft windshields by means of high-velocity jet-air blast" [cajunfj40, Jun 27 2012]

[link]






       Sounds workable. But how often will people want to drive in the rain with the top down, airroof or no?
MaxwellBuchanan, Jun 22 2012
  

       Provided it's a reasonable temperature, why not? I almost feel it'd be worth it for the looks on people's faces alone; watching the rain magically divert from the cabin.
acurafan07, Jun 22 2012
  

       Fair point. [+]
MaxwellBuchanan, Jun 22 2012
  

       Sounds workable.   

       On a non-convertible, it might bear considering fitting one of these at the side, over the doors, so when it's raining it's possible to get out and put on a coat or open an umbrella without getting wet.   

       That would probably only work on a 4x4 where the roof level was above the head height of the occupant standing on the ground.
8th of 7, Jun 22 2012
  

       [8th] great addition. To make it work on a short car, have the air roof start at the centerline of the car and slope at a 45 degree angle. Making that work on a convertible may be more difficult.   

       One potential problem with the idea in general: What happens when passing or being passed by a large truck that slashes though a puddle. Diverting a few raindrops sounds a lot eaiser than diverting a large splash.
scad mientist, Jun 22 2012
  

       I'm sure the size and speed of the raindrops makes a large difference
Voice, Jun 23 2012
  

       hmmm, could airflow alone create an entire canopy, or even a capsule depending on the shape of the nose-cone and the tail section of a craft to re-direct vortices? If it, You coul... and it wou... I... hmmmMmm...   

       .   

       ow   

       I went to the Air door link supplied by [acurafan] and see that this company also supplies Ultrasonic Rat Repellers. This sounds like a pretty good product to me as I couldn't stand being overrun by Ultrasonic Rats. Sounds like the enemies of Ninja Turtles.
AusCan531, Jun 23 2012
  

       I went to the Air door link supplied by [acurafan] and see that this company also supplies Ultrasonic Rat Repellers. This sounds like a pretty good product to me as I couldn't stand being overrun by Ultrasonic Rats. Sounds like they would be the enemies of the Ninja Turtles.
AusCan531, Jun 23 2012
  

       This implies that the Air Door is not in itself a sufficient barrier to prevent the ingress of ultrasonic rats.
pocmloc, Jun 23 2012
  

       No, only the super deluxe model has that feature.   

       It also includes two ultrasonic cats for added measure.
acurafan07, Jun 23 2012
  

       I hear their ultrasonic hedgehog repeller runs rings around the competition.   

       I'm wondering if you can keep it quiet by having two layers of air, the fast outside layer facing the rain and the quiet inside buffer or sound insulation layer facing the passenger compartment. Same concept as a turbofan.   

       Bun of course.
doctorremulac3, Jun 24 2012
  

       See linky.   

       Anyone know about the "Sucker Cars" from various motor-racing events? Usually ran one season, then banned because they worked too well. Big fan sucked all the air out from under the chassis, creating mondo downforce without all the drag-inducing wings.   

       Combine these ideas - get your high-volume high-velocity air from under the vehicle, duct it out to where needed - door openings, roof openings, low pressure drag-inducing areas, etc.   

       Me likey.   

       I also wonder how good an aerodynamic envelope one could "create" by judiciously aiming these high-velocity air curtains, creating a smoother "surface" for the turbulent flow layer to "adhere" to, away from the less aerodynamic bits of the vehicle/occupants in question.
cajunfj40, Jun 27 2012
  
      
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