Aero Device on Windscreen Wiper Questions?

[blake]

It's not money-saving, it's just aerodynamics!

If you were to put your vehicle in an air tunnel, you would see that the laminar air flows "bend" to the left and right when meeting your windscreen. The "passenger" side wiper points with the flow while the "driver" side is pointing aginst the flow, therefore the driver's side needs something to counteract the tendency for the air flows to lift the wiper up.

[GordonD]

I think that windshield wiper "technology" is the one thing that car manufacturers have totally ignored and we are essentially using the same stuff as Henry Ford did - just electric motors rather than vaccuum ones.

if you have one of the modern minivans or other vehicle with very long slopped wind windshe3ilds you will find that the blades aer parked on a part of the screen which tends to get very cold and is 'in front' of the heated portion so melted snow etc runs down onto the cold blades and forms a nice ball of ice.

Why couldn't windshield wipers be mounted on the roof and then they would be easy to keep clean when not in use. I don't believe the roof redesign would be that hard and - now I think of it - didn't the old cars have it there? What happened ? Is it aesthetics or a valid reason?

[chughes163]

dont talk to me about windscreen wipers! this week has been a complete PITA with regard to them - I had to replace them on our ford fiesta so i went down to halfords. I told the guy with the poor complexion behind the counter it was a 1999 Ford Fiesta...he spends roughly 10 mins going through his book finding the correct ones and eventually supplies whats needed....i get home and attempt to put them on the car and discover he has given us completely the wrong sizes...considering halfords is 8 miles away from home it was a bit annoying....

so off i trot back to halfords with the original wiper blades in tact - I couldnt bring them the first time round as the car was in use. I show the guy whats needed and he says their out of stock..great...

so i go to the next nearest halfords where im met by another spotty bloke behind the counter - he then says that they have 1 of the blades in stock and another similar one which is 1 inch bigger that 'should' fit...anyway luckily it did....but what a load of hassle!

I asked him about the spoilers on the wiper blades and for some reason the manufacturers only suggest you put 1 spoilered wiper on the drivers side...he didnt know the reason behind this...(what a surprise!)

[GordonD]

chughes163

this sounds like a trip to our eqivalent of Halfords Canadian (or as it's affectionately known Crappy) Tire. It appears that they are not allowed to hire anyone who knows anything or knowns how to find out.

I try to avoid it but sometimes I have no choice. I usualy sit in the parking lot for a few minutes before going in doing a Tantric Mantra which - if I'm not held up in the checkout line for more than 5 minutes - will get me out of the store with blood pressure this side of congestive heart failure.

My motto - if you want to talk to a car guy go to a car place - screw the money. And I'm Scottish

[Dark Silver S]

Quote:

Originally posted by blake
It's not money-saving, it's just aerodynamics!

If you were to put your vehicle in an air tunnel, you would see that the laminar air flows "bend" to the left and right when meeting your windscreen. The "passenger" side wiper points with the flow while the "driver" side is pointing aginst the flow, therefore the driver's side needs something to counteract the tendency for the air flows to lift the wiper up.

That's interesting. I would have thought that the laminar flow went "up" the windscreen rather than left or right. In fact, as I think about it....

Using my windscreen as an example - the aero device is placed so that the air flow, if going straight back (creating a high pressure zone at the surface of the windscreen), presses the wiper into the screen WHEN THE WIPER IS PARKED. AT the end of the wiper sweep, the aero device would cause the wiper to go to the left, if that was the direction of the laminar flow. And the passenger wiper should see some lift at the end of it's sweep.

I guess I'm going to have to find the nearest wind tunnel or the nearest wind tunnel simulator and check this out.

[blake]

SCooperS,

Note that I said the flow would "bend" not turn a 90 and rush across the windscreen. Unless your windscreen is completely flat and not curved like mine, I would agree that most of the flow would be perpendicular to the blades at rest.

[Dark Silver S]

Blake, I suspect that the actual flow is much more complicated than either of us realize, and is probably further complicated by the high pressure zone at the base of the windscreen. It would be interesting to see a flow diagram.

Edit: I got my wish. Nicey dreary rainy day here, and I went for a ride in the rain. The flow pattern actually radiates from a center about where the speedo is. So the driver's side wiper is almost always perpendicular to the flow, and the passenger's side wiper is almost always parallel. Thus the answer to my question.