Kawasaki Concours Forum
The C10, aka Kawasaki Concours - The Original => The Bike - C10 => Topic started by: LessPaul on December 06, 2013, 08:58:31 AM
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I've looked thru a bunch of threads, but still don't see an explanation for this that makes sense to me.
I'm just not getting the whole physics/aerodynamics things at work here.
I just bought a barely used Scorpion EXO 1000 helmet off craigslist, to use with my new (to me) 1986 Connie.
I took the bike out last weekend for a shakedown, and with the face shield down on the helmet, I was getting all sorts of wind noise. This is my first bike with a fairing and love the calm pocket of air I ride in. But I don't understand why so much wind noise? When I flip the face sheild up, the noise is basically non-existent. Flip it down and it roars.
Here's what I don't understand. When I owned a CB350 back in my 20s, I rode with an open face helmet, with a detachable windshield (common to the day). Without the face shield (and no fairing), my eyes would water furious (but with no wind noise). With the face shield, no watering eyes and no appreciable wind noise, even though I was still being battered by wind at highway speeds.
Also, when my son had his CB550 and 750, I'd ride them, borrowing his full face helmet with face shield, and rode with no wind noise (still without a fairing).
So why, when I'm sitting in this calm pocket or air behind the Connie's fairing, does wind noise become such a factor when I pull the helmet's face shield down?
Just not getting it. A lil' help?
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Your comparison to other bikes is meaningless.
It is like saying "Other dogs didn't bite...why this one?"
Obviously, opening the face shield makes a change where the air flow is strong,
so what you think of as a small change is meaningful.
Also, the change AT THE HELMET is going to be really noticeable at your ears.
Fluid dynamics is complicated. Empirically, it makes a big difference.
Get a modular helmet and ride with it open. That is what I do on the C10.
Mine is quieter that way too. Don't overthink it.
saxman
(a theoretical physicist by day)
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The reason I brought up the other bikes is that they were naked, with no wind protection. All that raging air produced no appreciable wind noise in the helmet, but riding in a calm pocket behind a protective fairing did.
That's what produced the incongruity in me.
And I'd prefer to ride with a closed face shield. Eye protection and all.
I don't think modulars were intended to be ridden in the open position, no?
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Wind noise, velocity at given points make for different perceived volume. Take a simple example, roll a car wind down a 1/4 inch, sounds different than all the way down.
The variances will always be there and as datsaxman said, fluid dynamics are complicated, doesn't take much to change the velocity and direction to make a noticeable difference.
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The exact same thing happens to me with my Shoei RF1000. Whether it's on my Connie or my Wee-Strom, with the visor down there is noticeable (but tolerable) wind noise. With the visor up, the noise level is very much reduced, almost to nothing. I ride that way all the time and wear safety-glasses for eye protection. The visor in the up position acts to help control the airflow over the top of the helmet, directing it more smoothly and eliminating some turbulence. It's called the boundary layer, the closest layer of air to the surface of the helmet. The smoother it is the quieter it is. I've always wandered what would happen if you tried to mount two visors, one in the open position, for the airflow control and one in the closed position. In theory you'd have the best of both worlds.
http://en.wikipedia.org/wiki/Boundary_layer (http://en.wikipedia.org/wiki/Boundary_layer)
http://en.wikipedia.org/wiki/Laminar_flow (http://en.wikipedia.org/wiki/Laminar_flow)
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I have a Scorpion EXO 1000 and it's quiet with the bike shield all the way up and noisy as :censored: with it down. The visor fits very poorly and doesn't seal well for one thing. It's actually more quiet with it up....at least to me. It's a :censored: helmet as far as noise goes, but I like the non-fogging visor and the shade built into the helmet.
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A few years ago i bought a Nolan modular to replace my aging Shoei. The Nolan is definitely nosier than the Shoei with the shields closed. I suppose the Shoei, not being a modular, is more aero.
I like that new Concours windshield assy but can't recall the name. It is very adjustable for rake and maybe height. I probably will not get it since my Connie is now my secondary bike and it's an 87, but wish it was available years ago before I bought my newer bike.
My newer bike is a Cruiser with no shield and the goofy Nolan still produces a surprising amount of wind noise though no buffeting is experienced because no windshield on the bike.
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Summit670...that windshield you speak of is a Madstad...makes all the difference in the world!
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+++ on the Madstad. I installed one on the Buell Ulysses, and it is much much much better.
I can usually find a reasonably quiet position.
The stock windshield on the Buell is not much good by itself...
saxman
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The Madstad is a pair of highly adjustable brackets that:
1) move the windshield forward an inch or so.
2) allow the height and rake to be adjusted.
Very happy with it.
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I usually ride with my face shield cracked open a notch. I also wear tinted safety glasses behind the visor, and my helmet also comes with it's own tinted visor. So, essentially, I have three layers of clear/tinted protection between my eyes and the road in the daytime, but only one layer at night, plus the windscreen of course.
Running with the visor cracked open seems to help reduce the noise a bit. HJC Symax II btw...
What seems to help more is getting a taller or shorter windscreen on the bike. The stock screen is notoriously noisy, and essentially channels turbulent air directly at your helmet visor. I changed it out for a 24" Cee Bailey (you may want a taller or shorter one depending on how tall you are from your butt to to the top of your helmet btw), which helped considerably.
Others have went the Rifle or other routes, but in pretty much all of the cases I've read the noise situation improved considerably when the stock windscreen was replaced. Something to consider.
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The wind-shield is pushing aside the air so when the air finally gets past the edge of the shield it is "concentrated" or higher pressure.
Because of this and the fact that some of the air is coming straight at you and some has been pushed sideways by the shield you get turbulence, as well as the turbulence caused by the lower pressure behind the shield interacting with the concentrated air at the edge.
The turbulence is the noise that you hear with the visor down.
With the visor up you are guiding the airflow over the helmet so it is quieter.
The solution depending on where you live and what kind of weather you ride in is a taller or shorter shield.
A shorter shield will put the concentrated air below your helmet so the lid only hits linear air and is smoother and quieter.
A taller shield pushes the concentrated air above your lid so again quieter.
Now I ride in all kinds of weather so I went for a taller screen (in my case a Rifle + home-made 22" screen).
On my C14 in the summer I fit the OEM shield and leave it in the down position.
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The most quiet helmet on the market today is Schuberth C3 Pro
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My RF-1100 is noisier sitting behind the stock 2011 shield than it is if I stand up on the pegs and lean forward where the helmet is in free-flowing air. It then gets fairly quiet.
As far a riding with the face shield up to change the airflow, what about using a dual sport helmet like the Arai XD-4 or Shoei Hornet or Icon Variant?