An Aerodynamic Device or Fender

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Discussion Overview

The discussion centers on the purpose and aerodynamic implications of a plastic component mounted below the number plate on certain motorcycles. Participants explore whether this component serves as an aerodynamic device that could provide an advantage at high speeds, or if it primarily functions to protect the motorcycle's components from dirt and debris. The scope includes theoretical considerations of aerodynamics, practical applications in racing, and the potential impact on performance.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants suggest that the component may redirect airflow downward, potentially reducing drag by avoiding the engine's fins.
  • Others argue that the component does not provide any discernible aerodynamic advantage due to the motorcycle's design and racing conditions.
  • A participant mentions the need for computational fluid dynamics (CFD) studies or wind tunnel tests to determine the aerodynamic effects accurately.
  • Another viewpoint is that the component may serve to improve engine cooling by redirecting airflow, rather than enhancing aerodynamics.
  • Concerns are raised about the applicability of studies on SUVs to motorcycles, highlighting the differences in their aerodynamics.
  • Some participants emphasize the importance of even minor aerodynamic improvements in close races, where finishes can be determined by fractions of a second.
  • There is a suggestion that the component primarily protects the fork suspension from debris rather than contributing to aerodynamic performance.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the aerodynamic benefits of the component. Multiple competing views remain, with some asserting it offers no advantage while others propose potential benefits related to airflow management.

Contextual Notes

Limitations include the lack of empirical data from CFD analyses or wind tunnel tests, which are necessary to substantiate claims about aerodynamic performance. The discussion also reflects varying interpretations of the component's design and function based on different racing contexts.

AMPOWN
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Please advise if the plastic white component mounted below the number plate on these motorcycles is or is not an Aerodynamic device that could afford an advantage at 100+ MPH over an identical motorcycle without this device? Users claim it is to keep dirt out of the hole in the bottom of the neck of the triple trees that hold the forks. I submit, if that be the case, why not just simply use a piece of lightweight tape instead of this heavier part?

The components in question are below the number plates on the #4 and #59 Motorcycles. I submit they re-direct air downward, thus avoiding the fins of the cylinder on the engine, and force it to run under the chassis, where it creates far less drag than running through the fins on the cylinder.

http://amaproracing.com/images/content/story/Springfield_featured.jpg

American Motorcyclists Association AMA in Daytona Florida Tech Directors state that they feel this device affords zero aerodynamic advantage. And they also contend that it is not a fender to keep dirt off the lower Triple Trees. We are trying to determine just what the hell this thing is then?

Thanks in advance for your input.
 
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http://i481.photobucket.com/albums/rr177/mikebike11y/Picture1-16.png

Side view of the curve of the component in question.
 
My opinion is that this feature will not give any discernible aerodynamic advantage on those bikes (with wide bars, tyres, no fairings, race numbers etc), but you'd need at least a CFD study (and possibly a wind tunnel test) to tell for sure.
 
I looks more like it would redirect airflow over the engine to cool it down better.
 
The finish in these races after 25 laps on a mile dirt oval is .001 - .045 seconds at the finish line for the top five bikes. Last race the finish difference was .000 measured using AMB-IT Transponders. Photograph was used to determine the winner.

With that said, if this component would reduce drag at any percentage, it could make the difference in the outcome of one of these contests.

Looking at this CFD Study, one notes that a very minor change in shape of the SUV body, reduces drag.

http://csus-dspace.calstate.edu/xmlui/bitstream/handle/10211.9/123/Thesis - Final.pdf?sequence=1
 
You can't take a study done on an SUV and apply it to a dirt bike. They are totally different animals. Honestly, like brewnog said, based on the information you have provided I can't think of any possible aerodynamic advantage to the part in question.
 
More no the machines these are mounted on.
While they race on hard packed clay surfaces, these machines exceed 145mph on the long straights. They are not Dirt Bikes like Moto Cross. Over 100hp weighing 300lbs, they race on oval tracks, many used for horse racing. Drafting to the finish with six or more in line is common for the 25 laps on the Mile tracks. Typical finish has four or five crossing the finish line less than .003 seconds apart at over 140mph.
 
And despite all of that, there is still no discernible aerodynamic advantage conferred by these devices. I am sorry, but unless you hire someone to do a full CFD analysis, the best we can all say is that it appears to not offer an advantage.
 
It looks to me like protection for the fork suspension. You don't want rocks and other debris denting or damaging your shock/suspension rods.

Its a rounded cover for a thinner, rounded rod, I doubt it has any positive aerodynamic effects.
 
  • #10
Just curious, but what is your personal concern? Are you a rival competitor?
 
  • #11
Allenman said:
I looks more like it would redirect airflow over the engine to cool it down better.

That and keep spray from the tires in wet weather out of the rider's face.
 

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