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Great article. Now if Snave was still a member, this could get interesting. He used to have some interesting theories on this subject. It was always entertaining. :D http://canadamotoguide.com/2016/05/04/motorcycle-aerodynamics/

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MOTORCYCLE AERODYNAMICS

MAY 4, 2016 MICHAEL UHLARIK 22 COMMENTS

Motorcycle aerodynamics is a misunderstood subject and often comes with many misconceptions. Unlike cars, motorcycles are inherently awful at slicing through the air, no matter what shape they are. This is why so little progress has been made to improve their aerodynamic efficiency over the past 130 years. But with exponential advances made in computer simulation and the recent arrival of some wild new solutions on racing motorcycles, could that all be about to change?
Chris
 

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Sure aerodynamics are important, but for touring folks like me the point is moot.

With the Burgman's big fairing, a large windscreen and side cases that are more like barge-boards sticking out in the airflow it's all quite academic. I have the aerodynamics of a brick, a large concrete block at that! :eek

I've actually looked into a single wheel eggshell type trailer like the Uni-go or one from Third Wheel Trailers as a possible solution to get the luggage out of the airflow. The only problem is finding a suitable hitch for the 2014 Burgman 650.

https://www.unigotrailers.com/

https://thirdwheeltrailers.com/

Here's how wide I am (shot last week in Tennessee), the bank angle of a brick!

 

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Discussion Starter · #3 ·
If you're a brick, I'm a barn door. :)



That's probably the configuration that reaches 140 mph. :eek

Mine though has two 37-liter SW-Motech Trax aluminum cases sticking out the side. Nice and useful...and square. Like a barn door in the wind.



Chris
 

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If you put that BMW naked next to my Suzuki naked I bet the Suzuki is about half again as wide. If not, it may just look that way.

Though I do not try to bust the TON much since my last crash, with my two 22 liter Givi side cases and top box it will go past 105 MPH with ease.

I know back in 2007 my first 2003 Burgman 650 was clocked at 122 MPH on Lidar in Wyoming. It had a GIVI screen I had cut down 3 inches and shimmed the bottom out 3/8s an inch. I folded the mirrors in and was crouched down behind the shield. And I had a full dressed 1500cc Goldwing Aspencade 20 feet in front of me. The Goldwing and I started 1.5 miles back, side by side from the trooper and I kept up with it almost.
 

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There's having the aerodynamics of a barn door; then there's having the aerodynamics of the barn, the silo, the farm house, and a herd of cows.
Man, you described Chris's (Bikes) BUTT to the T!!! :grin Having spent a lot of miles behind him on Mountain roads his bike is PHAT. :wink
 
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Sure aerodynamics are important, but for touring folks like me the point is moot.

With the Burgman's big fairing, a large windscreen and side cases that are more like barge-boards sticking out in the airflow it's all quite academic. I have the aerodynamics of a brick, a large concrete block at that! :eek

I've actually looked into a single wheel eggshell type trailer like the Uni-go or one from Third Wheel Trailers as a possible solution to get the luggage out of the airflow. The only problem is finding a suitable hitch for the 2014 Burgman 650.

https://www.unigotrailers.com/

https://thirdwheeltrailers.com/

Here's how wide I am (shot last week in Tennessee), the bank angle of a brick!
Steve, if you were closer and could bring a trailer over we could cobble up a hitch in about a day. Then WE could copy and sell them. I could make some for the 2002-2012 Burgmans using my bike as a model but I would need a 2013 or newer Burgman to make one fit for the newer ones. Same with the Burgman 400's, I'd need one for a week to cobble up something
 
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Discussion Starter · #8 · (Edited)
... :grin Having spent a lot of miles behind him on Mountain roads his bike is PHAT. :wink
Maybe I should quit slowing down so you can catch up???

Chris
 

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If you're a brick, I'm a barn door. :)



That's probably the configuration that reaches 140 mph. :eek

Mine though has two 37-liter SW-Motech Trax aluminum cases sticking out the side. Nice and useful...and square. Like a barn door in the wind.



Chris
My God, I haven’t seen steamer trunks like that since the bon voyage scenes of Titanic. :D
 

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I consider Craig Vetter a friend. If you ever get a chance to meet him do so. He and Carol have a small Ranch in Carmel CA. Visitors are welcome most times. Just after my accident in April 2015 I would email Craig and we called each other a few times. Then in June that year he hit a DEER and suffered a head injury. While he is doing better I do not think Craig will ever be on two wheels again.

His leadership in aerodynamics has helped but still most manufactures are blind to function. The Aero treatment on modern bikes is all about fashion and nothing to do with real function.

If you were to take Chris's BMW and strip it down and then put what is called a "Dustbin" fairing on it I'd bet it would hit 160 MPH if geared right.
I'd go as far to say a Burgman 400 stripped down and put a total Dustbin and tapered tail fairing on it, put some 21 Gram sliders in the CVT and went to a Speed event like Bonniville LSR youd hit 120 MPH or more. Its all about Aero BABY.
 

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Might need to be up-geared a little, but that's a reasonable estimate of top speed with the bike's aerodynamics cleaned up.

Top speed is a function of available* horsepower and drag. Drag reduction is linear (10% less drag gets you 10% more top speed), horsepower is square-root (10% more power gets you about 5% more top speed).

And drag-reduction can be cheap :)

*without up-gearing, you may find that you run off the far side of the power curve before you hit the drag-limited top speed for your peak HP.
 

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Deer Whistle - useful accessory

in June that year he hit a DEER and suffered a head injury. While he is doing better I do not think Craig will ever be on two wheels again.
I have been considering adding a deer whistle to my Burgman 650 but haven't gotten around to it. I almost hit a deer last week. I was in a 35 mph zone and some wind activated whistles don't work below 40 mph.



Cost: about $7 for a pair of wind activated AUDIBLE deer whistles.
They emits a high pitch whistle that Wildlife can definitely hear.
The whistle projects approx 200 yds in front and to the sides of the vehicle.


Bell 22-1-01000-8 Black Deer Warning
4.2 out of 5 stars 662
$6.36 Checkout Amazon or Walmart.
 

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Don't waste your money. I've read of too many deer/bike and deer/car collisions with deer whistles included to consider them anywhere close to effective. I also know a lot of riders in Wisconsin where deer could be the state rodent (ever hear of forest rats?) and most won't bother with that accessory knowing they don't do as advertised. If they did you could also just sound your horn to get the deer to move but I've BTDT and they don't move. What I do find that seems to work in my experience is to flash the headlights on/off. They do notice that and run.

Of course I just must include here about the "smart" doe I passed on a small highway in Wisconsin who I really hope had LOTS of babies and taught them about traffic. I came out of a curve looking at a mile long straight section (unusual on this road) and saw a car come around the curve coming the other way. Exactly half way between us this doe came out of the trees (trees very close to the road) and just stood on the gravel shoulder on my side. It looked at me, then the car, then back at me, then back at the car. This continued as I and the car slowed down expecting the doe to run across just as we both arrived at that spot. But the doe just stood there looking back and forth at us until we passed each other just in front of it. After we were past the doe trotted across the road! I really hope that one has lots of smart little babies.

On subject now... my current CTX1300 surprised me on my maiden ride from the dealer 145 miles to home. I really do believe aerodynamics has come a long way on motorcycles. It may not be as good as other vehicles but still a long way from where it was in the past. The body of my CTX was designed in a wind tunnel. This is the first and only bike I've been on that really does ignore the wind as to handling. I do notice the usual drop in mpg with a good headwind. But handling the bike in turbulence and constant winds, from any direction, behind big trucks on the super slab to wind storms on remote areas. This bike handles as if in a dead calm. *I* feel the wind and sometimes get pushed around as usual when riding a bike, but the bike stays settled as if there was no wind or turbulence. And even though looking at the bike you wouldn't think there is much wind/weather protection from an apparent lack of fairing in the lower half up front, you'd be wrong. There is a lot of protection, almost as much as my old Gold Wing. Of course, the Burgman, and most scooters, are known for weather protection. Especially below the handlebars. As to my thoughts on aerodynamics... The more protection there is, the more drag you can expect in most cases. YMMV
 
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Agreed, with one minor quibble -- going from no protection to a little will reduce drag (my little Vespa gained a few MPH of top speed by adding a small windscreen).

Your comments on the CTX remind me of the crosswind handling characteristics of the Honda Pacific Coast (PC800, '89-'98 ). Bike tilted a bit when hit by gusts -- sometimes quite a bit -- but always tracked straight. Kind of disconcerting at first, because you expect to have to counter crosswinds and it's weird when the bike's already doing it for you. The bike's mythical "autolean" system was a running joke on the PC800 mailing list (any bit of hard-to-understand wiring or tubing or whatever was presumed to be part of the autolean device). No such device was actually needed, just well-balanced interaction between the bike's aerodynamics and its steering-head geometry.

It's nice to see Honda didn't just do this on the PC.
 

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When I first got my 1978 Suzuki GS750N it was naked and mostly stock. Top speed was about 112 MPH on the German Autobahn. I then added hotter cams, a Jardine headder and some bigger carbs from a KZ1000. Top speed went up to about 120. I then bought a Full Cafe faring made in England and with a few mod's mounted it on the bike and top speed went up to over 140 MPH after I went up two teeth on the front sprocket for Redline RPM issues. Before the fairing I tried the bigger sprocket and lost 5 MPH.

It was sort of like this one only a bit smoother and longer to the rear and leg areas. Had to cut and clear the handelbar area.
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I have been considering adding a deer whistle to my Burgman 650 but haven't gotten around to it. I almost hit a deer last week. I was in a 35 mph zone and some wind activated whistles don't work below 40 mph.
If you can actually personally hear them, they MIGHT discourage deer. IIRC, deer hearing is more sensitive but within a narrower range than ours (20 Hz--20 000 Hz).



Many whistles are marketed as "ultrasonic" which is above 20 000 Hz. Most species are attuned to hear each other first (territorial, mating, offspring) or long-term predators. Deer need to hear bears, wolves and cougars skulking through the bush, not rodents. Smaller canines and felines can hear ultrasound since they prey on rodents, which DO communicate partly in the +20 000 Hz range.



:winkFun fact: Dolphins can "hear" and communicate in frequencies up to 150 000 Hz! This is even better than bats.
 

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If you can actually personally hear them, they MIGHT discourage deer. IIRC, deer hearing is more sensitive but within a narrower range than ours (20 Hz--20 000 Hz).



Many whistles are marketed as "ultrasonic" which is above 20 000 Hz. Most species are attuned to hear each other first (territorial, mating, offspring) or long-term predators. Deer need to hear bears, wolves and cougars skulking through the bush, not rodents. Smaller canines and felines can hear ultrasound since they prey on rodents, which DO communicate partly in the +20 000 Hz range.



:winkFun fact: Dolphins can "hear" and communicate in frequencies up to 150 000 Hz! This is even better than bats.

And then there's me. Can't hear squat in the Female frequencies. :grin
 
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Your comments on the CTX remind me of the crosswind handling characteristics of the Honda Pacific Coast (PC800, '89-'98 ). Bike tilted a bit when hit by gusts -- sometimes quite a bit -- but always tracked straight. .
Part of the secret when you design aerodynamic bodywork is to put more drag at the back than the front.
There is a theoretical point called “centre of pressure” - Where the added up wind forces can be said to be acting (like centre of gravity).

If this is well to the rear the airflow aligns the nose into the wind - generally a good thing, creating stability and allowing you to continue your course.
If the centre of pressure is too far forward the airflow pushes the nose and out of alignment - a very bad thing that gets worse as the nose is pushed further out line and will try to turn the bike off course or completely around.

Similar to why rocket fins and arrow fletching are at the back not the front.

Wind tunnel tests can show up any unexpected steady state issues with this but it also matters with sudden gusting or passing a truck. The BMW test track had a huge fan that blew a crosswind over the track so that test riders would be sheltered in still air by a wall and then be delivered a measured amount of sudden crosswind so that the course deviation could be measured, recorded and filmed.
 
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