Single front wiper crx?
 

Do you think the gains of a single front wiper on a crx are worth much, if anything at all?
Obviously one wiper will be half the drag of both - but do they actually make much drag at all ?

(At higher speed my wipers start to get pushed up the screen - almost as far as half way lol . It seems a common problem, a few people from crx uk raise the bonnet, making the air flow over the wiper. Some other members move their wipers as far down as possible... so they are sitting on the black plastic trim.
The other members just buy new wiper arms lol ;) )

However it does say there must be some wind resistance acting on the blade/ arm - put it this way even pushing the wipers up with your arm is almost impossible.

But that would be a different topic ( infact i might make one about the bonnet raising mod )



So back to the single wiper :

Im not talking about removing one wiper and using the other , i mean a proper conversion that gives full sweep from one wiper....

Could run it to the side
similar to this crx

http://img404.imageshack.us/img404/6...2008066it5.jpg

Or even more sleek ( but blocking a little vision ) straight up :
Sorry for poor pic
http://home.online.no/~kseland/s_wiper.gif

I think the best thing to do would be to make a lip that directs air up over the wipers. That way you aren't compromising safety or going through the trouble of modding them. Remember, any energy you save will be cancelled out if you get into an accident and have to send your CRX to the junkyard.

The first picture is a proper kit, and gives the full sweep of the screen...
Just like some of the mercedes and lamborghini's have single wipers

My benz used a very strange setup where it looked like one wiper, but it was really two that rested flat, and one wiper covered the whole winshield while the other traveled at half the speed to cover just the passenger side. Didn't seem to have any advantages over conventional wipers. But sure was cool

re91sit: I remember seeing those! Weird.

chipX, my ranking, best to worst (considering aero, practicality & safety):

- sheilded wipers
- 1 exposed wiper parked vertically in the center
- 1 exposed wiper parked normally
- no wipers (safety)

the opel eco speedster had a single vertical wiper and an 0.20 Cd...
not that there's a direct connection, but i'm sure they would have gone for something else if it added more drag than standard wipers

http://i77.photobucket.com/albums/j5...pt2002-001.jpg

wiper
 

During development of their PNGV Car,GM noticed during windtunnel evaluations,that the windshield wiper had virtually no impact on drag.-------- I eliminated the wipers on my CRX at Bonneville and it had no effect on top speed.It's possible that the high-pressure bubble just ahead of the windshield "shields" the wipers from the outer flow.

^Yes the evidence suggests to me the flow in that region is really quite stagnant on my car and probably the CRX- or any "3-box" design too. As the new stuff approaches a "1-box" design (having a very sloped hood and almost the same angle to the windshield) I suppose it probably would be a different situation via the lack of that stagnant "bubble".

And, not that I have links or anything to back it up, but I would think the vertically parked wiper would be the WORST. For one it's up out of the "bubble", for two vehicles out in the world are for all practical purposes always in yaw. So imagine crossflow across that windshield.

I can think of a reason northerners might like a vert wiper: probably would have a much less tendency to freeze into that big pile of snow and ice we always have at the base of the windshield.

"Do you think the gains of a single front wiper on a crx are worth much, if anything at all?" No.

Frank, what's up with you and yaw, yaw, yaw? If you are traveling down the highway at 70, and you have say a 5mph crosswind at 45 degrees, the resulting yaw vector is so small as to be negligible.

If you have hurricane force winds at exactly 90 degrees to the road, yaw might be a concern, but most of the time around here, any breeze is so slow that you can barely feel it.

Just look at all the tuft testing pics posted on this forum. Generally the tufts are pointed straight back.

Thanks, Frank - I stand corrected! I fell into the same trap I occasionally remind others about: forgetting about yaw, or apparent flow direction when saying there's no need to remove the fore/aft roof rack rails/mounts because they present little projected area.

So I correct my list: the vertically parked, centrally located single wiper is best only when used with a wind direction indicator.

:p

No effect, or no significant effect? I thought you mentioned somewhere that shielding the wipers netted a small improvement.

Yes, here it is:

Ah, OK! .28 mph. Could have been a passing bird farting. Never mind!

Not trying to be contrary, but they shielded the wipers anyway on the Precept. Likely just for styling reasons.

1. Only 55 mph roads here.

2. 5 mph in the plains? LOL! A CALM day is 15 mph and it isn't uncommon to have 30-35 mph winds.

3. And those winds~ are they EVER lined up with where you are going? Seems like I go East-West a lot and of course the predominant wind is from the North.

So... 15 mph x-wind 90 deg. to the road; travelling 60 mph = 11 deg yaw- right?

30 mph wind = 22 deg yaw?

Imagine 10 to 20 deg yaw flowing over your vehicle on a regular basis.

Or when I'm putzing around at 50 mph or less... even more.

That would really screw up boattailing in the plan view wouldn't it?

I get a visual of it whenever I'm in the rain and snow- the drops/flakes go up and off the windshield at an angle, and the behavior of the drops can sometimes be seen to be different on the side glass.

I guess flying C150s and riding motorcycles and bicycles has also made me acutely aware of x-winds. Try lining a C150 up to the runway in a crosswind and YOU WILL APPRECIATE YAW. :p

P.S. Tufts straight back: I suppose tuft testing is more fruitful on calm days?

Yes I did the no wiper/ cowl fillet thing for quite a while. All it demonstrated to me was that my testing wasn't good enough to pick up a change that small, if in fact there was any change. It also demonstrated that getting caught in the rain or getting splashed on with no wipers is a greater inconvenience than the .0000000000001 mpg gain.

BTW, look into the Bosch and RainX single piece blades. They are much slimmer than normal wipers, and the top surface is like a wing, so rather than lift off the windshield they are pushed down.

I don't live in the plains, on a calm day there is no detectable air movement on the ground, 35 is a hella storm, the speed limit is 75, half the people go 80. And the snowflakes go straight up the middle of the windshield.

What state do you live in?

Also, even in high yaw conditions, it is the forces applied parallel to the vehicle axis which have the most effect on fuel economy. The yaw will cause turbulence to the side of the vehicle, but not cause much impedance to the forward direction.

I also ride bicycles. Crosswinds make me wobble back and forth sideways, but they don't slow me down. And if you turn your body like a sail, you can actually get a boost!

ND SD MN WI IA all pretty much the same RE: wind as far as I know.

"The yaw will cause turbulence to the side of the vehicle, but not cause much impedance to the forward direction."

That's debatable. Turbulence pretty much wrecks aero.

P.S. Wind resource data: http://www.ncdc.noaa.gov/oa/climate/...d/avgwind.html

and

http://i146.photobucket.com/albums/r...her/gfwind.png

My area: 10-13mph ave/yr
Yours: 5-8mph ave/yr

My first guess was high. Well, seems the weatherman is always talking about 15-30mph winds!

Yeah, you have sorta half of what I have. That thar is our difference in perception re: yaw.

Well... a lot of us live here!

I have been thinking about this on my Honda Insight as it would be easy to remove the left side mounted wiper and just slightly extend the range of the center mounted one and have a set up just like my Jaguar XJ40. I don't know what it would entail but probably just a redesigned bell crank for the wiper....if I could only get to it....#8-) Also I would remove the wiper on the rear window as it does virtually no good anyway and I cant see out of the window even when its clean.

Re crosswinds:

source

I think weathermen here are usually spouting, '15mph winds with gusts to 25 & 30 mph'.

As to the average wind speed, you're probably mostly driving during the day.
Here in N. Central SD, wind speed at night is usually 3-8 miles less than afternoon wind speed.

You are right- gusting. Well that's still wind ya gotta cut through even if periodically.

Metro: good find! :thumbup:

I thought this was interesting: "Fadler said: “Zero to 180 degrees is oncoming wind, and anything from 180 to 360 degrees is going to help you.” I'd think that the 90 deg xwinds and tailwinds close to that would hurt and not help. I mean- to pull numbers from the air to illustrate- I'd think it would be "Zero to 180 degrees is oncoming wind, and anything from 200 to 340 degrees is going to help you.”

Guess I'll keep yammering about yaw when it comes up.

Hmmmm.....
most of the 90's british touring cars had single wipers, parked in the central position. I guess since then rules have changed?

Perhaps the difference varies car to car?

http://ll.speedhunters.com/u/f/eagam...cc_95_grid.jpg

Infact on that picture i cant see one with standard 2 piece wipers
Ok so a few of those are in use as it's raining, but you can see.....

cool, my car is in the lead :)
http://i77.photobucket.com/albums/j5...Fr_299242g.jpg
here's another one, the extensively greenpeace ecomodded twingo... but this is a one box design, with virtually no break between the window and the hood... on the speedster i think the windshield is much more bubble shaped, so a great portion of the air goes round the sides... this curve may make it difficult to install normal wipers.

what i do notice is that on modern cars the A pillars sometimes extend before the window, especially at the base... now this could be to trap rain, but on some cars it looks a bit much... perhaps this is to contain a high pressure bubble to shield the wipers, feed the air intake for cabin cooling etc, but in a controlled manner so the bubble becomes part of the cars "ideal" aero profile

the benefit of a single wiper will greatly depend on the size and pressure of the bubble and what goes on at the sides near the A pillars

Aye,
Or a place to put the wipers (at the sides of the screen )
http://upload.wikimedia.org/wikipedi...6_black_vl.jpg

The wipers are so low profile on those cars ^
Also i dont really know if it needs to have the wipers sat there, as the trailing edge of the bonnet is already raised and there is a big step from bonnet to screen , height wise.


Regarding the greenpeace twingo :

I wonder how well the twingo's wiper works? surely it leaves the bottom corners un-wiped? Thats more hazardous than the top corners...
Also does where the wiper drive attach , not look like it may increasing the frontal area slightly above the car( might just be photo angle )

I would like to direct you back to my first post on this thread and the raising bonnet thread....

Quoting myself now :
"At higher speed my wipers start to get pushed up the screen - almost as far as half way lol . It seems a common problem, a few people from crx uk raise the bonnet, making the air flow over the wiper. Some other members move their wipers as far down as possible... so they are sitting on the black plastic trim.
The other members just buy new wiper arms lol "


Before i " fixed " the wipers, they would get pushed to about 45* , then the wiper sensor/motor would kick in and make them do their full sweep. At high speed i had no option but to have the wipers ON lol.

I would say that the airflow is hitting the wipers to pull them from their original resting place.

The way i got around that was sitting the wipers so that they point downwards, slightly towards the bonnet, which forces any force to be taken away from the tip of the wiper.....

I guess if you speed tested the crx, then 0.78mph is not worth much on a road car.

I would also like to say that this problem seems to affect the phase 2 mark 2 crx. I have not heard of ph1 mk2 owners having the problem with their wipers being pushed up the screen.

For your info : the american ( and uk D series ) crx's which i refer to as phase 1, have a totally different front end ( headlights ,bumper, hood ...and suspension, track dimensions, wheel offset, crossmember etc etc - which makes my phase2 harder to get aftermarket parts for ! My phase2 was only available in the uk for 2 years)

American / d series / "normal " crx front end :

http://i10.photobucket.com/albums/a1...front_qrtr.jpg

My " phase2 " front end :

http://i10.photobucket.com/albums/a1...k/ef8_pins.jpg

http://img290.imageshack.us/img290/1...erences4fo.jpg

Note the difference between headlights, center raised bonnet ( i think this is the wiper problem - although you would expect it to be the other way around ?!?! ) , bumper etc.

Many people dont realise the differences until they see the cars side by side :)

yawn- more yaw!
 

the following two examples demonstrate the generic trends, but are not necessarily accurate for any particular vehicle.

http://i146.photobucket.com/albums/r...encher/yaw.jpg

For the first example, let us examine a generic sports sedan. Its top view is shown in Fig. 6.14 (this data is for a 20% scale model, at Re L = 3.0 x 10 6 , with smooth underbody). The graph depicts the effect of wind side-slip angle ß W on the aerodynamic coefficients. In order to explain the source of these aerodynamic loads let us observe the generic flow field depicted in Fig. 6.15. Basically, for the small, near-zero side-slip conditions the flow is attached on the vehicle’s sides, and the pressure distribution (from a top view) resembles the pressure distribution on a thick airfoil.

http://i146.photobucket.com/albums/r...ncher/yaw2.jpg

The pressure distribution data of Fig. 6.16 (after SAE paper 73-0232) reinforces this comparison. This analogy to the airfoil case explains the almost linear increase of side force, C Y , with side-slip angle ß W , which eventually stalls at about ß W ~ 25° (see also Fig. 5.16).

Returning to Fig. 6.15, you can see that at the larger side-slip angles the flow separates at the side of the vehicle, and when combined with the separation at the back, creates a much larger separation bubble. Because of the low pressure inside this separated zone, and the increase of the frontal area with increasing ß W , the drag coefficient increases sharply, as shown in Fig. 6.14. Usually, the larger separation bubble created by the side slip increases the velocity above the vehicle, resulting in a smaller increase in the lift. At very large side-slip angles (of over 35°), the separated area behind the rear window is reduced by the momentum of the side flow, causing a reversal of this trend in the lift (e.g., a local reduction in the lift).

Race Car Aerodynamics - Designing for Speed *-* Bentley Publishers - Repair Manuals and Automotive Books

Relevant even at lower speeds...

my XT was single from the factory. I don't think they considered styling much at all so there must have been a reason for it.. (it IS very flashy though!)

wiper
 

I can tell you categorically that below 100 mph they make no difference whatsoever.I suggest you put your energy elsewhere.Really,it's a dead end.