Wildguzzi.com
General Category => General Discussion => Topic started by: toaster404 on May 27, 2016, 07:54:36 AM
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Individuals here appear to be among the most thoughtful and educated on the various fora I frequent. So perhaps someone here has a pointer to research or some ideas that are based on physics and aerodynamics rather than on TV or magic.
I am going to make a windshield for (at least) my wife's 2009 Versys 650.
Description: http://www.visordown.com/reviews/motorcycles/adventure/kawasaki-kle650-versys-2006---2014/361.html (http://www.visordown.com/reviews/motorcycles/adventure/kawasaki-kle650-versys-2006---2014/361.html)
The stock windscreen is minimalist. See, e.g. http://www.totalmotorcycle.com/photos/2009models/2009-Kawasaki-Versysa.jpg (http://www.totalmotorcycle.com/photos/2009models/2009-Kawasaki-Versysa.jpg) She likes this for the lower speed work, but became tired on the Interstate earlier this week after only an hour. On the big Guzzi, I was just relaxing! So we need a suitable screen.
The Versys fora have a variety of solutions and numerous nicely hyped commercial products exist. However, any suggestion that there might exist wind tunnel tests or real-world evaluations without bias brings the usual cries of "heretic" - cries I am well used to!!
The aftermarket screens seem fairly pedestrian.
Puig example: http://www.puig.tv/tuning-bikes/kawasaki-versys-650-2009/touring-screen/c171en/f213-r19-m2183/ (http://www.puig.tv/tuning-bikes/kawasaki-versys-650-2009/touring-screen/c171en/f213-r19-m2183/)
Givi example: http://www.revzilla.com/motorcycle/givi-d405st-windscreen-kawasaki-versys-650-2006-2009 (http://www.revzilla.com/motorcycle/givi-d405st-windscreen-kawasaki-versys-650-2006-2009)
There are examples from similar bikes, e.g., the VStrom. See, e.g. http://www.calsci.com/motorcycleinfo/VStrom1.html#Windshield (http://www.calsci.com/motorcycleinfo/VStrom1.html#Windshield)
I have a VStrom with the stock screen and a laminar lip (came that way). It's pretty tall overall, and surprisingly vertical, but I can see over the lip fine and ride at reckless driving jail time speed with my visor open.
I can cut a screen without any issues at all. I'm just trying to figure out how to get the Karman vortex stream minimized and controlled. Ideally, I'd have a screen that puts a fairly clean flow into her chest (stock is fair at this) and a screen that puts a fairly thin and steady stream of eddies just over the top of her helmet at speed. That's what the VStrom screen does.
One aspect I don't understand is the use of tapering upward screens. Flow on a curved screen is up and out, with these edges being oblique to that flow. The minimal and probably dangerous testing I've done by waving a stick with yarn on it around at speed (I have not yet been committed or arrested for these antics) suggests that a fairly regular, possibly spiraling vortex forms and then breaks up. There's always some odd complex flow at the upper "corner" - at best, this just clears my shoulder. The worst examples put some kind of mini-jackhammer into my shoulder / ear area. I am not at all convinced that this taper does more than look good. Were I tapering a windshield, I would put the wide at the top to minimize the amount of air moving up the windshield.
So, what departure angle to the edge of the screen is best?
Another aspect is the rake backwards. I can see this rake can help avoid drag lift of the front wheel. The Versys actually has some built in ramps I suspect are there to keep the front wheel loaded at speed. But is there some magic rake angle?
A further consideration is control of vortex generation. The laminar lip is one clunky method. That's what I have on my Guzzi. Hideous but effective enough. Considering just making an adjustable wing, or an entirely new shield or three. Another method is the adjustable wing, available in several incarnations. These all work through redirection and through flow smoothing by injection of a band of air up behind the upper edge.
I have not seen the use of simple vortex control systems. The most obvious would be a serrated edge. This works well - I did a test on a cruiser some time ago. The problem is that nice row of shark teeth pointed at one's face and neck. Another more-promising system is the Wheeler vortex generator. See http://patentimages.storage.googleapis.com/pages/US5058837-1.png (http://patentimages.storage.googleapis.com/pages/US5058837-1.png) Even small ones make a surprising difference in some turbulent spots, but I haven't worked up the edge of a windshield. Would be interesting.
There's also the simple vane vortex generators.
So I'm all in a muddle. Considering a shield that is, as much as feasible, a wing just below eye level of about shoulder width with vortex generators spaced along it. A separate wing is impractical, but a heavily cut out shield with reinforcement on the verticals would do.
Another alternative could be a widening upward curved shield with a stepped edge allowing flow directly off a the steps whose edge is at right angles to flow. Heavily ventilated in the middle, of course. I'm used to having a bike that has good ventilation in the summer and a fair amount of gorilla tape covering vents in the winter!! Tempted sometimes to fit aircraft window vents.
Anyone who has made it this far has probably gone down this rathole before. Any ideas?
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(http://www.thisoldtractor.com/mg_images/quota_parabellum_3.jpg)
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Don't underestimate the design of the helmet in reducing buffeting. Some newer designs of helmets feature anti-buffeting features, the Kabuto helmet I wear greatly reduces buffeting.
Relying on windscreen design is difficult because a small change in rider position as you move around on the seat or simply sitting up straighter can impact the benefits of windscreen effects. The helmet remains the constant factor.
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Here is what I think I know about air management .
Mostly a nice still pocket of air is dependent on equalizing pressure . Proper venting seems to be the key , I experimented with airflow on a BMW airhead RT fairing , winglets , foils , lips , etc . In the end it came down to venting the windshield , had the same results with a police style windshield used on a naked beemer and a Jackal . Take a look at the Pacifica Aerofoil/Swanee/H&H fairing which is the best handlebar mount design ... EVER . The body is vented , as is the shield .
Dusty
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www.calsci.com
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This design worked on a Triumph 800 I had. Last time I checked they did not have one for a V7.
http://www.madstad.com/
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This design worked on a Triumph 800 I had. Last time I checked they did not have one for a V7.
http://www.madstad.com/
Decent design , but the "unprecedented" stuff is silly .
Dusty
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Parabellum supposedly uses a wind tunnel for design,
http://parabellum.com/Search.aspx?k=%20Versys
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This design worked on a Triumph 800 I had. Last time I checked they did not have one for a V7.
http://www.madstad.com/
Wish I'd had a Madstad for my Quota!
http://www.madstad.com/s.nl/sc.7/category.2335/.f
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Don't underestimate the design of the helmet in reducing buffeting. Some newer designs of helmets feature anti-buffeting features, the Kabuto helmet I wear greatly reduces buffeting.
Relying on windscreen design is difficult because a small change in rider position as you move around on the seat or simply sitting up straighter can impact the benefits of windscreen effects. The helmet remains the constant factor.
I have been looking into this. She requires inexpensive helmets because they are sort of disposable on her head. There's one in the trash right now! However, once she stops depositing herself on the ground next to her tipped over bike, we will shop helmets. And will look at that brand. Thank you.
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Here is what I think I know about air management .
Mostly a nice still pocket of air is dependent on equalizing pressure . Proper venting seems to be the key , I experimented with airflow on a BMW airhead RT fairing , winglets , foils , lips , etc . In the end it came down to venting the windshield , had the same results with a police style windshield used on a naked beemer and a Jackal . Take a look at the Pacifica Aerofoil/Swanee/H&H fairing which is the best handlebar mount design ... EVER . The body is vented , as is the shield .
Dusty
This one? http://www.harpermoto.com/h-and-h-fairing-for-cali-1400.html (http://www.harpermoto.com/h-and-h-fairing-for-cali-1400.html) I really wish the 1400 touring had a quick release system allowing swap from winter shelter to summer flyscreen!
Venting in large measure is in my sketches. I am also likely to put a couple of aircraft window vents into my 1400 windshield, for cooling and pressure equalization.
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This design worked on a Triumph 800 I had. Last time I checked they did not have one for a V7.
http://www.madstad.com/
This resembles my flying wing sketch a good deal. Up and down take extra holes. I can make holes. Changing tilt takes some longer machine screws and perhaps some wedged sleeves, if necessary. The angle on the Versys is fairly decent already.
I'll take this one for inspiration. Still unconvinced on overall shape and wish I understood stalled trailing edge vortex generation better. I know that my addition of vortex generators on one of my cars gave surprising slipperiness increase at Interstate speeds - obviously more quiet and mileage increased something like 5%. Not so much at lower speeds - only at the magic 75 mph careful cop-watch speed!
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I also do not understand the narrow windscreens. They do really well....IF...there is no cross wind at all, which around here is a very small amount of time. One reason I like the SPIII fairing and windscreen is how wide it is. I suppose mfgs do it because then they can get a higher top speed out of it, and maybe because it makes the bike look 'sleeker'?
The efficiency of the screen at deflecting air is a balance. 90% of the newer bike screens are now spaced away from any fairing to allow a flow behind the windscreen as well as in front. This relieves a lot of the pressure differential and you get a cleaner departure from the top and edges of the screen. Think slotted or Fowler flaps. As shown above you can do the same if your screen does not have any venting. I use an MRA X deflector to help smooth the flow at the top of the screen. Makes it less turbulent and can be adjusted to flow the air a little higher or lower as desired.
For an 'extreme' view of venting look at some of JB's solutions. Two of his turned the screen into swiss cheese and one was just expanded metal screen material. This is a solution that does not really deflect much of the air, but, it acts like a mass of turbulators for the air that is directed at the rider.
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Parabellum supposedly uses a wind tunnel for design,
http://parabellum.com/Search.aspx?k=%20Versys
Looking at http://parabellum.com/PARABELLUM-Replacement-Windshield-for-the-Kawasaki-Versys-2007-09-P73.aspx (http://parabellum.com/PARABELLUM-Replacement-Windshield-for-the-Kawasaki-Versys-2007-09-P73.aspx)
The mirror cutouts are rather interesting. Flow likely rolls over into a nice vortex at the cutout, forming a bit of a hole for the wash from the mirror. I have noticed the mirrors really give much of the noise on my VStrom, and are a source of turbulence on Versys. I suspect the original Versys mirrors are only good for a few more spills, then I'll replace them with something a bit lower and wider.
Charlie B's post is very interesting. I thought of using some of the mesh around here, but it turned out to be steel. Not friendly to riders and rather hefty!!! I keep thinking a wider wing or highly ventilated system should work. Of course, the obvious thing to do is an inverted version of the 727 or 747 flap system! See, e.g., https://upload.wikimedia.org/wikipedia/commons/7/72/Undercarriage.b747.arp.jpg (https://upload.wikimedia.org/wikipedia/commons/7/72/Undercarriage.b747.arp.jpg)
Thank you all very much for your thoughts. This is a very interesting subject. I really wish I had access to time, equipment, and a wind tunnel. The only wind tunnel work I ever did was documentation on a hypersonic hot shot tunnel. I don't believe we need to worry about Mach 21!!
I will document the trials.
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Airflow isn't always what you think. Airplanes are "tufted" to see what is happening. It's nothing more than pieces of yarn about 3 inches long stuck down with tape. I'm headed out to lunch, but a google search should show it.
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Airflow isn't always what you think. Airplanes are "tufted" to see what is happening. It's nothing more than pieces of yarn about 3 inches long stuck down with tape. I'm headed out to lunch, but a google search should show it.
I did this on my Quota when chasing wind noise and turbulence. Worked like a charm.
String, tape, and go for a ride!
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As you know, the windshield acts like a wing through the relative wind. The idea is to get the flow to "stall or burble" at a point higher than your head. You can do this by adding a shield or stubwing on the outside, or by venting, or both. Once you have created the neutral space in the area you want, you must then decide if you want to look over or through the screen. I once added a second, taller windshield in front of an SP1000 fairing. I left an angled gap open at the bottom. It looked like crap, but it was very effective. I have seen photos of windshield on bikes in Europe where they add a second section of windshield above the original, leaving an open viewing area. The top screen looked to be adjustible in angle and height. Good luck and show us what you end up with.
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www.calsci.com
Don't miss that calsci post from the King of Fleece! Especially this page:
http://www.calsci.com/motorcycleinfo/Fairing.html (http://www.calsci.com/motorcycleinfo/Fairing.html)
It's about as physics-riddled as you could ask. Everything from the Wright brothers through 5th derivative fairing to Einstein's esthetics of the curvature of space.
They also make sensible-looking windscreens including one for your wife's Versys.
Way to go, King! Great post.
Moto
P.S. The page is not without fault, though. It specifies both "2 cups = 400ml" and "2 cups = 500ml" within a few lines of each other. Could be a quantum thing I guess.
M.
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As you know, the windshield acts like a wing through the relative wind. The idea is to get the flow to "stall or burble" at a point higher than your head.....
The other alternative (fly screens, etal,) is to keep your helmet in clear air to avoid buffering, but having the screen break most of the wind hitting your chest. The result is less fatigue riding at speed. You usually still end up with a fair amount of noise, and as stated before, the helmet really comes into play here.
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Calsci:
"Wind tunnels are made to measure lift and drag, not noise and turbulence." Incorrect. I've seen them used to measure much much more. A hollow sniffer will let one find the edge of turbulent flow. Holes in surfaces can allow one to monitor detailed pressure changes which I was told can allow determination of laminar flow break away. There are other things I've seen done, but these were not civilian tunnels.
"When outside air spills into the rider area, it almost always falls in a curved path, causing spinning vortices of air" - Part of my work on windshields has focused on reducing the size and increasing the number of vortices. Vortex generators such as the Wheeler design interrupt the formation of large powerful vortices through the development of longitudinal vortices. Really quite striking. Hideous in practice, of course! I have a spray painted plywood shield with beer can vortex generators around here somewhere. Worked great!!!
"to eliminate all Von Karman vortices" - this is a bit of a stretch, I would imagine!! I just want a relatively thin controlled zone of mixed up flow, rather than the bang band of big whorls.
I'll pick up some material tomorrow, or maybe I have some. Almost anything works for prototyping.
Another thing not generally worked on is the aft end of things. I get better mileage and less buffeting with a big bag directly behind me. I've thought of designing front throw over bags that tie into the bike's shape a bit and come back to my knees, and rear throw over bags tapering aft that follow on the lines of the front bags and come close to my legs. Expect there would be a reduction in drag.
Wonder whether a tall bag close behind the rider would lift the turbulent layer a bit over the rider's head. Not fun in cross winds, though!
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My Buell had a madstad, it was very effective and quiet
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From the CalSci website:
"Of course the quietest possible ride is when you're looking through the windshield, but only about 1% of our customers are interested in looking through a windshield."
That has been my experience, too. (The first part, not the second part.)
I have several windscreens for my Vespa and my Norge. By far, the quietest, least turbulence-causing windscreens are those that I look through, not over.
The next best option is no windscreen whatsoever. There is more wind pressure on my chest, of course, but my full-face helmet is quiet and serene as it slices through clean air.
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(http://thumb.ibb.co/hFNQrF/image.jpg) (http://ibb.co/hFNQrF)
Don't know if this image will come through, but if it does, it shows the shield on my Beemer, which is the best I've used. It causes very little buffeting. The combination of about 45 degree rake, slight lift at the top, and relativel narrowness provides significant protection while smoothing the windflow around my helmet.
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There is no one fits all solution nor a single solution that can simply be moved around to adjust for buffeting in the various riding positions someone experiences.
It's a lot of marketing.
No two riders sit with the same exact posture nor are their bodies the same (length of neck,torso etc) and all those play a significant role in where the wind or turbulence hits the helmet or head. Then consider that moat of us tend to shift our positions, sometimes leaning a bit forward, sometimes sitting up straighter and that small pocket of still air we try to create just isn't big enough to cover all those variables.
Graig Vetter (for those old enough to remember) came up with a standard in fairings and windscreen design but most of them were large. He too figured out that cutting holes in the lower part of the windscreen alleviated pressure and helped with buffeting and also the tendency for the pressure behind the windscreen to pull the rider forward. Holes in the windscreen are hardly new or something recently discovered. Might be a good read- Vetters story about hiw he created his designs. Smart guy.
When you get to smaller windscreens ala the ADV or ST styles expecting to create some still air pocket for all riding positions, even for the same rider is asking a bit much.
It is possible because some have done it to get to the happy place that reduces buffeting, usually either by cutting down the windscreen so that your head is in clean air or with a windscreen that starts to get rather large.
Once the windscreen gets so big you are looking through it, might as well get in the car because you've just taken your soul and character adorned motorcycle and created...
An appliance.
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What made the Vetter windscreens work is that the pressure-relief holes were "capped" with adjustable vents. You could seal them off or open them fully or partially. That made it pretty easy to get the smooth flow you wanted without letting in the rain.
Adjustable venting is not rocket science.
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My former brother in law actually worked for Vetter as a test driver, until the accident!
We're more looking for a reduction in buffeting and improvement in comfort, not some magic thing. The closest to magic is my VStrom, which I feel like mega-tufting so I can see what's going on!
I will likely get one or more aircraft vents to have around. Drill a hole, implant the vent, and there's your adjustable air flow. Unlike a plane, the side windows are always open!
I anticipate being able to scrounge around the property in a bit, maybe I have some stuff. I need stuff for saddle bag supports, too, so it's about time I scrounge. Outside entities have also been suggesting that my valuable raw material storage heaps are unsightly and a nuisance, so maybe I'll root around and triage some!
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(http://i273.photobucket.com/albums/jj221/ratguzzi/2016%20loop%20frame/loop4_zpsmekz8e26.jpg) (http://s273.photobucket.com/user/ratguzzi/media/2016%20loop%20frame/loop4_zpsmekz8e26.jpg.html)
:grin:
Dean
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gaffer tape, cardboard and chicken wire can make excellent prototype bits of fairing, taping bits of yarn is also very useful. The best way is to go out and experiment, I spent a whole summer trying various things on my cali. Ended up with a slightly modded swannee and its absolutely brilliant.... good luck
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Given that Moto Guzzi has a perfectly good wind tunnel it is amazing to me that the standard screen on the EVT is so bad at producing turbulence and back draft.
The back draft is such that riding in the rain with my open face helmet is almost a no go. Spray etc is blown back in such a way that I end up with water on both sides of my visor and on both sides of my glasses. Four layers of water to try to look through makes it very difficult to see!
I tried the bike without the screen altogether but found the riding position completely wrong for an unfaired bike. I was feeling the strain at as little as 50 mph.
Modification is on the "get around to it" list but in the meantime I guess I'll need to give Rainex a try.
Interesting thread! I look forward to seeing where it goes.
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I read quickly and maybe missed this, but something I'd consider re buffeting:
The majority of buffeting comes from airflow rising under the windshield and fairing, wrapping around the tank and upwards towards the rider's head. Three places to look to reduce it are:
- Letting air through or under the screen using ducts/holes in the screen, space between the screen and the fairing, etc.
- Filling the 'pocket' over the tank to change the airflow shape - most easily done with a tank bag
- Changing the shape of the lower airflow as it starts to head upwards - this can be done with airfoils or winglets (like the Stelvio, or add-ons for the Gold Wing), with tank pannier bags (a favorite of adventure riders), lowers on the fairing, etc.
Helmet shape, windshield, and other factors are all there, but it's surprising how much can be done with these three areas.
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(http://i273.photobucket.com/albums/jj221/ratguzzi/2016%20loop%20frame/loop4_zpsmekz8e26.jpg) (http://s273.photobucket.com/user/ratguzzi/media/2016%20loop%20frame/loop4_zpsmekz8e26.jpg.html)
:grin:
Dean
Yep, that's the one! I didn't know JB finished 'farkling' his new rat.
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Moto Guzzi put that wind tunnel to good use with the Norge. The 8Vs fairing is very good. The heat management is outstanding to the point that few bikes do it as well.
The windscreen? There is no way to make one that suits everyone. With riders from 5'4 to 6'4" and probably more at both ends they had to find some design that hit most of the points and they accomplished that IMHO.
I rarely bother to adjust it, leaving it in the low position and I get next to nil buffeting. There is no vacuum effect to pull you forward and it doesn't act like a noise tunnel either.
The Norge fairing and windscreen? Tops in the class of STs.
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The "Laminar Lip" added to my '03 Stone Touring's OEM Sport windshield has been very effective in reducing buffeting almost to nil. Windshield "rake" experimentation also helps. I found a more upright position worked better than more laid back, which struck me as odd, but it clearly is better upright.
Ralph
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The lip on my 1400 and on my DL1000 VStrom are very effective. Unfortunately, the stock screen on the Versys does not lend itself to any kind of lip, being small and pointed.
However, the earlier Versys has a small screen. I notice the next generation has a differently shaped screen more like the Norge. These are similar to the Mastad. The Versys also has a swell and notch aspect to the area below the windscreen, which may help generate a low pressure zone pulling side wash off the screen downwards.
I will make up a large, medium, and small outline based up the Calsci, Mastad, Norge, and newer Versys screens. I will also make a rake control system. I actually want to make the screen on my 1400 slightly more vertical. Getting a bit more up and less out flow than I want, based on minimalist tuft experimentation.
Thank you all for your suggestions.
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Fairly certain the wind tunnel hasn't been used in years . Yeah , I know about the Norge photo , probably staged for effect .
Dusty
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For what it is worth from Wiki:
It is unknown to what extent the wind tunnel is used currently. The December 2005 press release for the Norge 1200 states that the bike was "thoroughly tested" in the Mandello wind tunnel.[4] Aprilia, a company in the same group as Moto Guzzi, maintains a relationship with the aerodynamics program at the University of Perugia, where computer simulations combined with practical tests (done in smaller tunnels using scale models) can more effectively and economically provide accurate testing and feedback.
GliderJohn
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Everyone laughs but the expanded metal with house screen works amazingly well. No buffeting of any sort and I can go 70mph with a baseball cap on and sipping a pepsi. All you feel is a slight little breeze through it.
Now see the EV in the background? It has the classic barndoor on it. The WORST windshield I ever sat behind as far as super severe buffeting and weird handling if you go over 80mph. I did the same thing on a few different windshields, pump it full of holes. It drastically changes it into a great windshield like my screen. Virtually no buffeting and very quiet. I guess I am diffusing the air stream and not trying to deflect it.
JB
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you might try one of these; MRA x-screen
http://www.twistedthrottle.com/mra-x-creen-windshield-for-suzuki-dl650-04-11
The link is to one for a vstrom, but they make them for a variety of bikes and they just clamp on. They are highly adjustable. I have used them and they work well.
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I just put a national cycle street shield EX on my 850T adjusted about nose height. It works extremely well. It has a 2 inch gap at the bottom which curves in toward the bike. I don't know if that has anything to do with cancelling the buffeting/stability but works great. Looks ok ish. I have only ran about 65mph. $150 free shipping from Revzilla
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I have had good luck with Longride shields on the Harley it has a reverse curve that kicks the air up and over my helmet.
http://www.longrideshields.com/category_s/1822.htm
It still is not as good as my original Swanee Pacifico Aero Foil on my 98 V11 EV which you can still get as a reproduction from Harpers.
http://www.harpermoto.com/h-and-h-handlebar-mount-fairing.html
Longride also makes a universal shield that I have no experience with but if you were to call them I am sure they would be of help.
http://www.longrideshields.com/category_s/1826.htm
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I found with the standard MG screen on my B11 that if I had it down and only just clearing the headlight I got buffeting but if I gave it 1/2" - 3/4" clearance I didn't
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Here's a side view of my SPIII fairing and the MRA X visor. The MRA X smooths the departure from the screen and moves the flow up about 2" so it just clears my helmet. Without it the airflow 'hit' my helmet just above the visor. The visor is adjustable for angle and also has two arms so it can be placed further up or further away from the windscreen.
I do not have any pressure reducing holes and don't feel I need any. I think the airflow from under the fairing through the forks and such compensates for the pressure difference.
(http://i1083.photobucket.com/albums/j384/portablevcb/guzzi/20160528_142403.jpg)
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PS if you get the airflow to go over your helmet completely then the venting properties of your helmet are greatly reduced. Also, rain drops do not get 'blown' off your visor. Things to consider :)
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Everyone laughs but the expanded metal with house screen works amazingly well. No buffeting of any sort and I can go 70mph with a baseball cap on and sipping a pepsi. All you feel is a slight little breeze through it.
Now see the EV in the background? It has the classic barndoor on it. The WORST windshield I ever sat behind as far as super severe buffeting and weird handling if you go over 80mph. I did the same thing on a few different windshields, pump it full of holes. It drastically changes it into a great windshield like my screen. Virtually no buffeting and very quiet. I guess I am diffusing the air stream and not trying to deflect it.
JB
This may be related. On the calsci website it is claimed that louvres below a certain size don't pass air above a certain speed:
"Why don't we put louvers on our vents? Air sticks to any surface; immediately at the surface the air is not moving. As you move away from the surface the air speed picks up with distance. The curve of airspeed vs. distance from the surface is called a Poisson curve. As you go to higher and higher speeds the Poisson curves from adjacent surfaces on the louvers move outwards until they touch. When they touch, that's the maximum air flow speed for that gap. Typical 1/2" louvers will choke off air flow to a maximum speed around 40 mph or so; above that speed you need more and more air flow to compensate for the growing vacuum behind the windshield, but the louvers have maxed out. So the louvered vent becomes less and less effective as your speed increases to 80 mph or beyond, and the windshield becomes more noisy and has more turbulence as you pick up speed."
In effect, your screened windscreen is made of thousands of louver openings, all operating well beyond the speed at which they can pass an air flow undisturbed. Exactly how that works out collectively for the set of them is not obvious to me.
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Everyone laughs but the expanded metal with house screen works amazingly well. No buffeting of any sort and I can go 70mph with a baseball cap on and sipping a pepsi. All you feel is a slight little breeze through it.
Now see the EV in the background? It has the classic barndoor on it. The WORST windshield I ever sat behind as far as super severe buffeting and weird handling if you go over 80mph. I did the same thing on a few different windshields, pump it full of holes. It drastically changes it into a great windshield like my screen. Virtually no buffeting and very quiet. I guess I am diffusing the air stream and not trying to deflect it.
JB
I'm curious JB. Do you think the orientation of the expanded metal mesh makes any difference. That is to say, which way the little metal edges are pointing. The 'RAT' by the way looks more like 'UTE' to me.
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Here's a side view of my SPIII fairing and the MRA X visor. The MRA X smooths the departure from the screen and moves the flow up about 2" so it just clears my helmet. Without it the airflow 'hit' my helmet just above the visor. The visor is adjustable for angle and also has two arms so it can be placed further up or further away from the windscreen.
I do not have any pressure reducing holes and don't feel I need any. I think the airflow from under the fairing through the forks and such compensates for the pressure difference.
(http://i1083.photobucket.com/albums/j384/portablevcb/guzzi/20160528_142403.jpg)
Charlie , doesn't the gap between the laminar lip and the main shield create a pressure
equalizer ?
Dusty
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(http://i273.photobucket.com/albums/jj221/ratguzzi/2016%20loop%20frame/loop4_zpsmekz8e26.jpg) (http://s273.photobucket.com/user/ratguzzi/media/2016%20loop%20frame/loop4_zpsmekz8e26.jpg.html)
:grin:
Dean
Hey Dean....
What type of fairing is on that California Titanium in the back ground????
Much thanks...
Rich
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Charlie , doesn't the gap between the laminar lip and the main shield create a pressure
equalizer ?
Dusty
Only near the lip. That's the reason it works is it lets the air flow over lip of the stock windscreen without turbulence. There is still a vacuum lower behind the shield. I can feel some of it from the air pushing me from behind. That part is countered by the flow up under the fairing to some extent.
PS If I was really interested, I'd either put some vents low on the windscreeen, or space the windscreen out away from the fairing by a bit less than an inch.
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I have an old Shoei FM5 fairing -- it looks like a smaller version of the SP fairing. Just transferred it from the T to the Mille. Solved the pressure differential problem by removing the rubber ring that seals the headlamp rim to the fairing. That leaves about a 5mm gap all around the headlamp to equalize pressure behind the fairing and windscreen. Oddly, rain has never come through that gap.
(http://thumb.ibb.co/mthGWF/2upcropped.jpg) (http://ibb.co/mthGWF)
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Given that Moto Guzzi has a perfectly good wind tunnel it is amazing to me that the standard screen on the EVT is so bad at producing turbulence and back draft.
John,
The wind tunnel in Mandello hasn't been used for developing bikes since the late '80s or early '90s.
It wasn't used to develop the EVT fairing/windscreen of the '00s.
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John,
The wind tunnel in Mandello hasn't been used for developing bikes since the late '80s or early '90s.
It wasn't used to develop the EVT fairing/windscreen of the '00s.
Yes I knew it wasn't in use. That much is obvious by my standard handlebar fairing. It's there though, so one has to wonder why not.
Think about how having an actual wind tunnel tested and developed handlebar fairing would have enhanced reputation/sales.
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I just fitted an X-creen to my Nevada Adventure Project bike and tested it over two days.
The original screen directed the air at my chest and my head was buffeted.
Last night when I rode the first time with the X-creen fitted it was a wind-free period and even on the freeway at 75mph the air was quite smooth.
Tonight there was a gusty wind blowing so I tried again, and sure enough, there was some buffeting but quite bearable. It's a winner for me.
(http://thumb.ibb.co/fruPJv/IMG_20160527_202422.jpg) (http://ibb.co/fruPJv)
(http://thumb.ibb.co/eggRWF/IMG_20160527_202517.jpg) (http://ibb.co/eggRWF)
Other people in other situations describe it as useless, but I think its effectiveness will depend on how high the original screen is. I still have some more positions to try the X-creen in but I sometimes find that there is not a lot of difference in the changes.
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Interesting, the large wing. I'm trying to keep things very simple, but might well end up with a wing. A shield that puts turbulent band into chest without wing and over head with wing might be ideal - I can make a clamp on wing without any particular trouble.
Regardless, I made a shield that is a composite of many designs. Will be fitting up and mounting fairly soon. Will make a wind tunnel and tuft it, too. Take some pictures. Depending on how the flow works, I might fit Wheeler Y vortex generators, make mirror notches, and/or ventilate the shield in various places.
On the 1400, I mocked up a system to put the stock shield parallel to the fork rather than raked back. If this works, I'll make some metal mount shims that look better and are more stable. Ended up making my lowers ineffective, so they're off.
Next is to try figuring out why only my right shin gets fried. I get turbulent buffeting and lots of heat only on the right side!!! Doesn't make any sense to me. Will put that bike into the processor (fan and a yarn stick sniffer), see whether I can tell what's what.
Will also see what I can do to get the updraft under my helmet fixed on the Versys, 1400, and VStrom. None are bad, but while I'm making aero-mods, might as well.
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Yes I knew it wasn't in use. That much is obvious by my standard handlebar fairing. It's there though, so one has to wonder why not.
Think about how having an actual wind tunnel tested and developed handlebar fairing would have enhanced reputation/sales.
It's not used because it's too small for the modern behemoths.
The modern bikes are big and don't have enough clearance with the inside surface of the tunnel for good/accurate results.
That's what they say...
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It's not used because it's too small for the modern behemoths.
The modern bikes are big and don't have enough clearance with the inside surface of the tunnel for good/accurate results.
That's what they say...
Rumor has it that when the gigantic electric motor that drive the fan are started it causes a brown out in Mandello :laugh: Maybe they should go back to the Fiat aircraft engine .
Dusty
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I just fitted an X-creen to my Nevada Adventure Project bike and tested it over two days.
The original screen directed the air at my chest and my head was buffeted.
Last night when I rode the first time with the X-creen fitted it was a wind-free period and even on the freeway at 75mph the air was quite smooth.
Tonight there was a gusty wind blowing so I tried again, and sure enough, there was some buffeting but quite bearable. It's a winner for me.
Other people in other situations describe it as useless, but I think its effectiveness will depend on how high the original screen is. I still have some more positions to try the X-creen in but I sometimes find that there is not a lot of difference in the changes.
I put an X-creen on my Stelvio. It helped lift the "rumbling" wind noise a bit over my helmet.
Sadly, my passenger gets more wind coming up from below.
I'm still play with the positioning.
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It's not used because it's too small for the modern behemoths.
The modern bikes are big and don't have enough clearance with the inside surface of the tunnel for good/accurate results.
That's what they say...
Makes sense. The Guzzi GP bikes were quite small in frontal area, even compared to other racers of the time, IIRC.
Thanks for posting this.
Who said it, by the way? Guzzi?
Moto
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Rule of thumb for wind tunnel design: In order to avoid the effects of wall and ceiling boundary layers, the clearance has to be at least twice the dimension of the model. So if a motorcycle is 1 meter wide and 1.5 meters high, the tunnel has to be at least 5 meters wide and 4.5 meters high. The Guzzi tunnel is less than 3 meters in diameter and I don't think this would fit, for instance, a Norge or Stelvio:
(http://thumb.ibb.co/dbpryv/galleria_vento.jpg) (http://ibb.co/dbpryv)
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Quote from Testarossa:
The Guzzi tunnel is less than 3 meters in diameter and I don't think this would fit, for instance, a Norge or Stelvio:
Is there a possibility they used scaled down models, at least to test the basics?
GliderJohn
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I just fitted an X-creen to my Nevada Adventure Project bike and tested it over two days.
The original screen directed the air at my chest and my head was buffeted.
Last night when I rode the first time with the X-creen fitted it was a wind-free period and even on the freeway at 75mph the air was quite smooth.
Tonight there was a gusty wind blowing so I tried again, and sure enough, there was some buffeting but quite bearable. It's a winner for me.
Other people in other situations describe it as useless, but I think its effectiveness will depend on how high the original screen is. I still have some more positions to try the X-creen in but I sometimes find that there is not a lot of difference in the changes.
I mounted mine without the 'arms'. Moved the X closer to the stock screen and seemed to work a bit better that way. I kept the arms in case I wanted to extend the X further up, but, have not needed to do that.
PS when trying to decide what to do about my screen I fabbed up a 'visor' type shield with some brass sheet. Made 'Z' brackets to mount to the existing screen. It seemed to work so I bought the MRA version. FWIW, MRA sells clamp on mounts for the X so you don't have to drill holes in your screen for mounting.
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Who said it, by the way? Guzzi?
Moto
This question came up about ten years ago when the Norge was being shown. People wondered if it had been done in the Guzzi wind tunnel. I don't recall who, but someone associated with Guzzi said the tunnel was too small for the modern bikes for the reasons Seth mentioned above.
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A previous thread on the wind tunnel: http://wildguzzi.com/forum/index.php?topic=60862.0
A Norge on static display inside:
(http://farm1.static.flickr.com/86/258867691_259750cf1e_b.jpg)
V11 LeMans in the tunnel.
(https://c1.staticflickr.com/3/2157/2107307642_bdb43e69e8_z.jpg?zz=1)
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Is there a possibility they used scaled down models, at least to test the basics?
GliderJohn
You could use a scale model, with a scale model rider, to get basic drag and stability data. But the scale model rider couldn't report on the subjective experience of buffeting behind the windscreen, and I can't imagine what instrumentation you'd need to measure the turbulence between the screen and the mini-rider's chest.
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Quote from Testarossa:
Is there a possibility they used scaled down models, at least to test the basics?
GliderJohn
Or they didn't need to put the whole bike in, just the fairings mounted on a front end. Whatever is behind that is just for looks.
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It's not used because it's too small for the modern behemoths.
The modern bikes are big and don't have enough clearance with the inside surface of the tunnel for good/accurate results.
That's what they say...
They say that do they? Last time I heard they didn't use full sized ships for tank testing....
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Rumor has it that when the gigantic electric motor that drive the fan are started it causes a brown out in Mandello :laugh: Maybe they should go back to the Fiat aircraft engine .
Dusty
Ah! That would imply expense! You might be onto something there Dusty.
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Cut a shield in rough for the Versys. Will be interesting to see.
After all this windshield looking, raised the angle on my Cal 1400 and took off the lowers. Terrible! Modified the lowers to put air behind the raised angle shield, but haven't been out.
Also on Cal 1400, screen now looks way too wide and big for summer riding. Will make a narrower screen. Might pull it off for summer and get handlebar mount drag fairing or fly screen to keep pressure off. Really a lot of junk bolted onto the touring model!!
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Motorcycles are not like airplanes and ships. On a motorcycle, the rider is part of the shape affecting airflow. You can't get accurate data on any shape -- including a fairing -- without both its upstream and downstream components (that is, the fork and wheel, and the rider/tank/radiator/engine). It may be counterintuitive, but the downstream shape affects what happens further forward. For instance a choke point builds a high-pressure zone ahead of itself, and by eliminating the turbulent zone behind a plate (by filling with a rider, for instance) you reduce drag (and accelerate flow) over the whole body. Moreover, the rider's movements affect airflow over the whole system. Finally, a chief goal of wind-tunnel testing is to improve rider comfort -- which you can't measure with miniature dummies.
Thus scale model testing of motorcycles isn't a valid process.
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If I strongly shrug my shoulders my helmet becomes very quiet. Otherwise I get a lot of noise that appears to be coming form the sides of the helmet (HJC, Bell and Bilt, all do the same, I using molded ear plugs). Noise is as bad as it was on the Quota but the helmet is not buffeted around like it was on the Quota.
Same noise with the MRA screen, or the Givi A770 (and on the other bikes).
I've used my hand to try and block air flow near the collar but nothing works like shrugging. Wondering if I should resort to wearing football pads! Or maybe a foam neck brace collar.
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Fixing the air management on my Vintage took a little time, but I have it just right. The original windshield was all wrong height-wise, so I approached Rifle about something better. I sent them my mounts and they made a taller and wider version that looks and fits like the stocker (this windshield is now part of their catalog). Leaning the shield back as far as the mounts allowed improved things a great deal, but I still experienced buffeting. I think the differential pressure between the front and back of the shield created poor laminar flow so I ordered a couple of Vetter Pop Vents to balance things a bit. The result worked very well. The vents can be rotated, opened, or closed creating lots of options. In the bargain, I have a bit more comfort in the summer. The vent's cost was very affordable (around forty bucks). This is an inexpensive, fairly stock-looking solution to correct buffeting.
http://www.craigvetter.com/pages/Online_Store/Online_Store_main.html
(http://i28.photobucket.com/albums/c229/JamesBagley/d90d1d7d.jpg)[/i][/i][/i][/i]
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Motorcycles are not like airplanes and ships. On a motorcycle, the rider is part of the shape affecting airflow. You can't get accurate data on any shape -- including a fairing -- without both its upstream and downstream components (that is, the fork and wheel, and the rider/tank/radiator/engine). It may be counterintuitive, but the downstream shape affects what happens further forward. For instance a choke point builds a high-pressure zone ahead of itself, and by eliminating the turbulent zone behind a plate (by filling with a rider, for instance) you reduce drag (and accelerate flow) over the whole body. Moreover, the rider's movements affect airflow over the whole system. Finally, a chief goal of wind-tunnel testing is to improve rider comfort -- which you can't measure with miniature dummies.
Thus scale model testing of motorcycles isn't a valid process.
True that. One of the main uses of the Guzzi wind tunnel was to have the actual GP riders experiment to find their own most aerodynamic riding positions. Aerodynamics was Guzzi's big advantage.
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And speaking of finding the most aerodynamic riding position -- wind tunnel training has become a necessary component of top-level ski racing. This is Olympic champ Daron Rahlves in the Calspan wind tunnel in Buffalo:
(http://mms.businesswire.com/bwapps/mediaserver/ViewMedia?mgid=54615&vid=5)
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Okaaaaay... so motorcycles need to be tested full size with rider, and the Guzzi wind tunnel is too small? Answer is obvious. Replace it with a bigger one! The advantages would be huge and seeing as how they have done it before, why not?
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I think Guzzi did an amazin job in the wind tunnel with the Norge.. I can smoke at 50mph.. and the wind tunnel is plenty big..
(http://www.motoguzzi.com/mediaObject/images/Museum/galleria_vento/original/galleria_vento.jpg)
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Okaaaaay... so motorcycles need to be tested full size with rider, and the Guzzi wind tunnel is too small? Answer is obvious. Replace it with a bigger one! The advantages would be huge and seeing as how they have done it before, why not?
Well here is the problem . It would cost a lot of money and be of limited use . Computer sims have become the norm John , I don't believe even Honda uses a real wind tunnel .
Dusty
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Well here is the problem . It would cost a lot of money and be of limited use . Computer sims have become the norm John , I don't believe even Honda uses a real wind tunnel .
Dusty
Well that's sort of the point I think Dusty. No one is actually using a wind tunnel and here we all are complaining about turbulent and ineffective screens and fairings.
But here Guzzi has an actual wind tunnel and can do real world practical testing if they wish. It couldn't hurt their sales if they were to become known for having the best wind protection in the world could it?
The one above certainly looks big enough to me, but what would I know about that.
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Well that's sort of the point I think Dusty. No one is actually using a wind tunnel and here we all are complaining about turbulent and ineffective screens and fairings.
But here Guzzi has an actual wind tunnel and can do real world practical testing if they wish. It couldn't hurt their sales if they were to become known for having the best wind protection in the world could it?
The one above certainly looks big enough to me, but what would I know about that.
All true John , the problem is aero is actually fairly well understood . Shape it like any creature than can swim fast , salmon , dolphins , Michael Phelps ,(OK maybe not him :rolleyes:) , then watch as they sit on showroom floors unsold . HD spent a small fortune to develop fairings and screens that were more than just turbulence generators , and made a big production out of having done so . Problem is , all they really did was vent their screens , something Honda , BMW , and some aftermarket companies have been doing for years :rolleyes: MV Agusta racing fairings from the 1960's were about as low drag, low turbulence as could be W/O a full enclosure , their helicopter experience coming into play . Honda basically copied them on their gp bikes of that era , so we know what works . Hannigan built what amounted to a giant racing fairing , all round surfaces , no turbulence , and they wouldn't sell . I rode behind one on an airhead , dead calm . Problem was , everyone at that beemer gathering talked about how ugly it was . Unfortunately style trumps effectiveness .
Dusty
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It is my understanding the tunnel is no longer useable and it was damn expensive to use in the first place. I "think" I heard they used it on a project after the Quota - but they really really should have used it on the Quota.
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Kind of insane. I like the wind tunnel designed things. I will eventually get around to faking a tunnel here. Calm day, stacked fans, yarn. Really helped before on a cruiser. Wave a piece of cardboard around until the yarn at the bad spot stops fluttering!!!!
Personally, I'd ride a trashcan if I didn't fry. If fabbing stuff up wasn't such a pain I might be there already.
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If I strongly shrug my shoulders my helmet becomes very quiet. Otherwise I get a lot of noise that appears to be coming form the sides of the helmet (HJC, Bell and Bilt, all do the same, I using molded ear plugs). Noise is as bad as it was on the Quota but the helmet is not buffeted around like it was on the Quota.
Same noise with the MRA screen, or the Givi A770 (and on the other bikes).
I've used my hand to try and block air flow near the collar but nothing works like shrugging. Wondering if I should resort to wearing football pads! Or maybe a foam neck brace collar.
Try one of those cooling towels they sell at home improvement stores. What I use. In summer or real warm temps I soak it, wring it slightly and use it like a scarf, tucking the ends inside my shirt.
That does what you're talking about and really keeps you cool too.
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Thanks!
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Wow, I feel like a neanderthal by just sticking a DART flyscreen on and calling it good. I put them on all my bikes. The work great and make riding a pleasure, look good too.
I don't want the antiseptic feeling of perfect dead air in front of me while riding.
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Wow, I feel like a neanderthal by just sticking a DART flyscreen on and calling it good. I put them on all my bikes. The work great and make riding a pleasure, look good too.
I don't want the antiseptic feeling of perfect dead air in front of me while riding.
Which screen classic or Marlin?
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Which screen classic or Marlin?
All classic. I tried the Marlin once on my CB1100 with horrific results, so put the classic on and all is well.
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For ordinary riding, I like the small screens. Interstate just beats me up. Winter is COLD. Those are the issues I have.
Wife has just this tiny screen and tires at over 50 mph. That's my main issue.
My VStrom gives a noisy flutter up by the bottom of my helmet. That's another issue.
Ideal summer would be a small screen and some under chin flutter aero mods.
Really, so few bikes have good aero. Explanation of no wind tunnel testing except for race positions makes sense!! A nice thorough simple study of a few bikes in a tunnel would be wonderful. There are tunnels near hear, but they're being used by the air force, so I can't just show up. Also big. Very big. Some supersonic! Loud.
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There are more bikes than you think with good aero.
FJR's, Beemer RT's, ST1300 from what I hear from owners, Gold Wings. Then there are the sport bikes that are good when you are tucked (which is what they are designed for). For some the Norge is good and a few even like the Stelvio.
Some do better with an aftermarket screen, especially if you want a 'bubble' around your helmet. Even the Honda Deauville was nice with an aftermarket screen, but, was pretty good with the stock screen.
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Forgot.
If your screen is directing the airflow where you want it and it is just a little buffeting to get rid of.....try putting a split hose around the edge of the screen, about 3/8" dia should do the trick. It acts as a turbulator, breaking up the eddies into smaller eddies.
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Cut a shield in rough for the Versys. Will be interesting to see.
After all this windshield looking, raised the angle on my Cal 1400 and took off the lowers. Terrible! Modified the lowers to put air behind the raised angle shield, but haven't been out.
Also on Cal 1400, screen now looks way too wide and big for summer riding. Will make a narrower screen. Might pull it off for summer and get handlebar mount drag fairing or fly screen to keep pressure off. Really a lot of junk bolted onto the touring model!!
I hate looking through a windshield, or having the top right in my line of vision, which was the case with my Touring windshield on the Custom. So, a couple of days ago I had two inches cut from the highest portion of the shield, while preserving the original shape as much as possible. HUGE improvement, and it doesn't look much different. Remains to be seen if it changes the buffeting I get over about 60 mph....
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Tubulator ???????
Dusty
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Tubulator ???????
Dusty
usually attached at right angles to the encabulator.
You'll learn all about it here.
https://www.youtube.com/watch?v=W9LXG7rPQfE
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usually attached at right angles to the encabulator.
You'll learn all about it here.
https://www.youtube.com/watch?v=W9LXG7rPQfE
Love that video John :laugh:
Guessing a tubulator is somehow involved in the embedding of nano-tags in modern oils that investigators use to determine if customers are using the proper brand and weight of oil . You know , for warranty claims and such :rolleyes:
Dusty
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Intstead of putting on turbulators I just put the whole thing in the turbulatron, then it's good forever!
The Wheeler vortex generators are actually very effective. I have a corner turbulence control concept using them I have to work on.
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Has anyone tried to apply vortex generators to a motorcycle fairing?
(http://thumb.ibb.co/h2DFrF/n2miad.jpg) (http://ibb.co/h2DFrF)
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Righto. Gary Wheeler.
http://www.ducati.ms/forums/44-multistrada/138752-vortex-generators-windscreen.html (http://www.ducati.ms/forums/44-multistrada/138752-vortex-generators-windscreen.html)
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Exactly, although they do a bit better with tails. Create counter-rotating double vortex systems, so thinking about how those will help tame bubble generators is important. On my cruiser, I rode along on the Interstate using a grease pencil to mark the airflow lines all over the place, and feeling where the bubbles were worst. That information guided my placement. I didn't crash or get stopped by law enforcement for a mental checkup!
I even put a line on a helmet once, which were very effective.
Next, I'll hammer golfball dents into the bodywork!
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Here is what I think I know about air management .
Mostly a nice still pocket of air is dependent on equalizing pressure . Proper venting seems to be the key , I experimented with airflow on a BMW airhead RT fairing , winglets , foils , lips , etc . In the end it came down to venting the windshield , had the same results with a police style windshield used on a naked beemer and a Jackal . Take a look at the Pacifica Aerofoil/Swanee/H&H fairing which is the best handlebar mount design ... EVER . The body is vented , as is the shield .
Dusty
Go with Dusty ... made one prototype and two practical wind shields from 3mm acrylic. The turbulence around the head comes from air pressure differences behind the shield compared to the front .. varies with wind speed and ambient pressure - continually.
The best design will incorporate an adjustable sized opening that seks to minimize the differential pressure. Once you achieve that then the strakes, if used will come into effect.
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usually attached at right angles to the encabulator.
You'll learn all about it here.
https://www.youtube.com/watch?v=W9LXG7rPQfE
You are a bad man JohnR, I can't wait to show that to the guys at work.
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Has anyone tried to apply vortex generators to a motorcycle fairing?
(http://thumb.ibb.co/h2DFrF/n2miad.jpg) (http://ibb.co/h2DFrF)
I had them stuck on my Memphis Shades batwing. Ended up only being useful at the corner where the the hand protection lumps swing up to the windshield and along the edge of the windshield. I had a summer low barrier with them all along the top edge - made for a distinctly less turbulent and narrower band of disturbed air between the sheltered air and the full slipstream. They need not be large, so long as they're in a nicely moving part of the laminar boundary layer. Want them oriented along the air flow. Cross winds change the air flow and their effect changes, but I don't know how, can just reach out and feel things working differently. Having to watch the road and ride interferes with careful testing!!