Road racing motorcycle aerodynamics

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eikka99
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Road racing motorcycle aerodynamics

Post by eikka99 »

Hello,

does anyone know research, an article, a book, anything, concerning road racing motorcycle aerodynamics?

What I am looking for is comparison or description what are the reasons road racing machine looks like it does.

I have read basic articles and books about aerodynamics and why motorcycle has to be certain shape to be good for aerodynamics. And naturally that Mr Spaldings' book too.

But, as we all know, current design, or design from previous eras, is not the best possible for aerodynamics. For example front wheel has to be open, probably because they are wanted to look like road bikes for obvious commercial reasons and for example bike designs in 1950 or earlier probably were 'best practice' what it comes to aerodynamics. And during any era, they also have to look cool.

So if you have any pointer to any information about the reasons and regulations or perhaps fashion related standards of racing bikes throughout the eras, please let me know.

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speeddog
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Re: Road racing motorcycle aerodynamics

Post by speeddog »

Road racing motorcycle aerodynamics are severely constrained, predominantly by two factors.

First, the rider must have easy access to any position on the motorcycle, so that they can get maximum cornering speed, best acceleration or deceleration, etc.
They need to move forward and back, and hang off as much as they want, side to side.

Second, the aerodynamics is compromised by the current rule structure.
Bodywork cannot extend forward of the front edge of the tire, or behind the rear edge of the rear tire.
In side view, the whole front rim must be visible, and 180 degrees of the rear rim must be visible.

Th combinations of 'working room' to allow the rider to move, and just those four dimensional restrictions dramatically reduce the effect of streamlining efforts.


More details here:
http://www.fim-live.com/en/library/

2014 FIM Road Racing World Championship Grand Prix Regulations
http://www.fim-live.com/en/library/?tx_ ... 20919a4c93

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Grahluk
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Re: Road racing motorcycle aerodynamics

Post by Grahluk »

In short it not only has to go fast in a straight line, it has to go around corners well too. Ideal aeros aren't ideal for both. I think there's something in the rules that goes back to a safety concern that may or may not apply to today. Within those constraints or considerations I think GP bikes maximize some aero principals. Actually the little bikes do it to a greater extent. Smooth slippery surfaces with only enough feature to draw away heat or guide air in. Overall shape that tries to guide air up and over the rider's head & shoulders & across their back in a tuck like a single turtle back. Street sport bikes boggle my mind. I think they just try & make them look cool. Japanese enlist a Manga comic artist & Italians enlist a pornographer for their designs. Or at least it appears that way.

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Re: Road racing motorcycle aerodynamics

Post by Hanuman »

Grahluk wrote:In short it not only has to go fast in a straight line, it has to go around corners well too. Ideal aeros aren't ideal for both. I think there's something in the rules that goes back to a safety concern that may or may not apply to today. Within those constraints or considerations I think GP bikes maximize some aero principals. Actually the little bikes do it to a greater extent. Smooth slippery surfaces with only enough feature to draw away heat or guide air in. Overall shape that tries to guide air up and over the rider's head & shoulders & across their back in a tuck like a single turtle back. Street sport bikes boggle my mind. I think they just try & make them look cool. Japanese enlist a Manga comic artist & Italians enlist a pornographer for their designs. Or at least it appears that way.
I guess we need to define 'aerodynamics' or at least distinguish it (as Speeddog did) from streamlining.
The big problem with bikes is that since downforce is pretty much useless, from a side view of the bike an 'ideal' teardrop shape means the centre of pressure is (under existing rules and architecture) going to be above the CoG, so it is always acting to flip the bike over. Witness the early M1s and their Aprilia 125/250 type bubble upper fairings, which have graducally been whittled down to a vestigial screen. The big upper screens also don't seem to help in side winds.
I also think this was the theory behind the early RCVs minimal fairing - that it's better to have a neutral bike that is minimally affected by Aero forces than try to streamline it and make the thing unpredictable.
As you wrote, Grahluk, I reckon a large proportion of GP aero concerns flow through the bike rather than over and around it - airbox entry and radiator entry and exit ducting.

I think one of Tony Foale's books had some reasonable analysis of aero development of race bikes. It has some pretty graphs and primitive CFD images, too.

eikka99
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Re: Road racing motorcycle aerodynamics

Post by eikka99 »

Thanks for commets so far!

I think aerodynamics as everything in bike racing is a thing you have to find the most effective compromise. If you think of ever growing radiator it has needs that fights against the perfect aerodynamics. Rider positioning is of course very important part.

But! What I really was looking for, is that why does 60ies bikes look so different than bikes today? Tear drop mentioned, and this detail has been known for a long time that it's optimum shape concerning aerodynamics. Why bikes then are not shaped like tear drops?

50ies bikes look quite edgy, not even rounded in some parts. If I claim, designs in 50ies didn't even were ment to be perfectly aerodynamically shaped, do I get beated? If the answer is yes or no, what was the thinking behind it? I know today bikes are wind tunneled and aerodynamics is properly tested and they try to find best possible compromise.

Or was it just that (for example) in 60ies people in general didn't think aerodynamics that much and bikes were equally bad in it? I don't believe it's so as it was mid-50ies when the had that design where front wheel was covered, the design that is not allowed today. Then why 60ies bikes look so different?

Or am I just stupid and 60ies bikes are good for aerodynamics and since then improvement has just been very small and todays bikes are just manga or porn inspired as someone mentioned?

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JanBros
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Re: Road racing motorcycle aerodynamics

Post by JanBros »

eikka99 wrote: But! What I really was looking for, is that why does 60ies bikes look so different than bikes today?
so do cars, airplanes, televisions, ...

bikes i the 50's might have had an "I thinck this will be aerodynamicly correct" , but was it truly ? was it ever tested ?
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Kropotkin
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Re: Road racing motorcycle aerodynamics

Post by Kropotkin »

JanBros wrote:
eikka99 wrote: But! What I really was looking for, is that why does 60ies bikes look so different than bikes today?
so do cars, airplanes, televisions, ...

bikes i the 50's might have had an "I thinck this will be aerodynamicly correct" , but was it truly ? was it ever tested ?
Moto Guzzi had a wind tunnel they used to design their dustbin fairings. One of the very first, I believe.
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Re: Road racing motorcycle aerodynamics

Post by Hanuman »

Kropotkin wrote:
Moto Guzzi had a wind tunnel they used to design their dustbin fairings. One of the very first, I believe.
Not sure if this is allowed, but here's a link to a 1951 article on the Moto Guzzi wind tunnel. Interesting stuff.

http://wildguzzi.com/forum/index.php?topic=60862.0


As for aero vs aesthetics. I seem to recall some Mockett (?) designed bodywork that was used by Harada or Kocinski, with a big droopy tail section that supposedly added a bit to top speed. But was reportedly killed off as it was so bloody ugly.

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Kropotkin
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Re: Road racing motorcycle aerodynamics

Post by Kropotkin »

Hanuman wrote:
Kropotkin wrote:
Moto Guzzi had a wind tunnel they used to design their dustbin fairings. One of the very first, I believe.
Not sure if this is allowed, but here's a link to a 1951 article on the Moto Guzzi wind tunnel. Interesting stuff.

http://wildguzzi.com/forum/index.php?topic=60862.0


As for aero vs aesthetics. I seem to recall some Mockett (?) designed bodywork that was used by Harada or Kocinski, with a big droopy tail section that supposedly added a bit to top speed. But was reportedly killed off as it was so bloody ugly.
Really great article! Thanks! Perfectly happy for anyone to link to anything which is relevant. It's displaying copies of articles on this website that gets me into trouble, not linking to them elsewhere.
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Re: Road racing motorcycle aerodynamics

Post by Kropotkin »

Image

Ducati 2010...
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Re: Road racing motorcycle aerodynamics

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Image
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Re: Road racing motorcycle aerodynamics

Post by Hanuman »

Suzuki had similar little winglets on their RG, I think.

Talking of little details, I was scanning through an old Aprilia promo CD "New Challenges for the new Millenium" (yeah, it's old, 2000. Really Hi-Res photos of the bikes and riders, including some of the 500...( and the likes of Nohles, Sanna and Borsoi, what happened to them?)

Anyhow, in several shots the tip of the fairing noses on the 125s and 250s, you can see that Aprilia have applied what appears to be clear 'grip tape' (as in, clear adhesive sandpaper a la skateboards).
I can only assume this was an attempt to modify the boundary layer separation point...

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speeddog
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Re: Road racing motorcycle aerodynamics

Post by speeddog »

Just watched "Faster", and it had a short bit on Hopper testing this:

Image

http://www.bottpower.com/interesting-bodywork/

eikka99
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Re: Road racing motorcycle aerodynamics

Post by eikka99 »

Hanuman wrote:
Not sure if this is allowed, but here's a link to a 1951 article on the Moto Guzzi wind tunnel. Interesting stuff.

http://wildguzzi.com/forum/index.php?topic=60862.0

As for aero vs aesthetics. I seem to recall some Mockett (?) designed bodywork that was used by Harada or Kocinski, with a big droopy tail section that supposedly added a bit to top speed. But was reportedly killed off as it was so bloody ugly.
This is gold, thank you!

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bobkarol
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Re: Road racing motorcycle aerodynamics

Post by bobkarol »

Way back in Nov.30, 2014 elkka asked:

"does anyone know research, an article, a book, anything, concerning road racing motorcycle aerodynamics?...What I am looking for is comparison or description what are the reasons road racing machine looks like it does."

Even though this an old thread, I can contribute some sources not previously presented or possibly known to readers who may be interested. Here are references from my library, including the specifics on Tony Foale's book that was mentioned:

1. The Complete Motorcyclist's Handbook, by David Minton, 1981. Header: Aerodynamic Fairings (4 pages)
2. Motorcycle Chassis Design: the theory and practice, by Toany Foale and Vic Willoughby, 1984. Basic Principles: 3) Aerodynamic Effects (3 pages)
3. Motorcycle Tuning: Chassis, by John Robinson, 1990. Chapter 7: Aerodynamics (22 pages)
4. The Racing Motorcycle: A Technical Guide for Constructors, by John Bradley, 1996. Chapter 4.4: Minimizing Motorcycle Drag (28 pages)
5. Motorcycle Dynamics, by Vittore Cossalter, 2002. Chapter 3.1.1: Aerodynamic Resistant Forces (4 pages)
6. Motorcycle Handling and Chassis Design..., by Tony Foale, 2002. Chapter 5: Aerodynamics (31 pages)

The vintage dustbin fairing was banned in 1958, a scant two years before I began road-racing in Europe. The front wheel became exposed, and the forward fairing length was limited to a vertical line drawn above the front axle. Shortly after, narrower cut-away fairings were regulated in lieu of the new, sleeker Peel fairing design that fully enclosed the handlebars.

30 years later, fairing noses were permitted to extend further forward than the front axle. Longer fairing nose designs began to provide downforce and ram-air flow for the engine intake. Other than those accommodations, I believe fairing design standards have remained the same for more than 3 decades. Until recently that is...

As we know, a few years ago, fairing bottom, side and bottom winglets, plus lower wheel shrouds were daringly introduced by Ducati. These new aerodynamic enhancements were begrudgingly accepted by the other teams, who then quickly developed two of these three innovative features for themselves.

Given the FIM's progressive acceptance of these developments, I predict front and rear wheels eventually will become completely fendered (within regulation limits) and shrouded. Ducati is already more than half-way there.

Although the wheels will function visibly separated from the fairing, as they do now, the shape of the fender portions will begin to blend with the front and rear of the chassis fairing. This will significantly smooth the airflow around the lower half of the bike and the wheels to lower the overall Cf.

This new chassis and wheel streamlining configuration will become almost as aerodynamic as the the historic dustbin fairing, and it will incorporate all the current benefits: maximum downforce for braking and anti-wheeling, directed brake and tire cooling, and rear-tire water-spray dispersion.

I've been patiently waiting 60 years for design of the optimum streamlined fairing to come full circle. How soon will we see it, Ducati?

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