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AerodynamicsFrom $1
Table of contentsThis page is dedicated to the thing that slows your scooter down the most. At higher speed, all the tuning effort you do is mostly aimed at overcoming the forces of pushing you and your scooter through air.
Left is the Vespa landspeed record scooter which set the world speed record for a flying kilometre at an average of 171.102 km/h. Scooter Magazine stated this had a 21 Hp engine (at the crank). Right, speed can be gained through a simple Cuppini Screen, this photo shows an aerodynamic shape compared to the less aerodynamic shape of the rider. Drag Coefficient and Drag Areahttp://en.wikipedia.org/wiki/Drag_coefficient http://en.wikipedia.org/wiki/Automobile_drag_coefficient#Drag_area Drag area is a variation of drag coefficient that allows you to directly compare drag including the effect of the frontal area. In the example above ducking down, as everyone knows, makes you go faster. This is not because you are a more aerodynamic shape (though you may be) it is because you are smaller (less frontal area). Drag area allows you to see the important factors as a single number and this tells you what vehicle will actually require less power to push through air. Vespa Drag MeasurementsTo calculate drag, one thing you need to know is the frontal area of what is being pushed through air. Here are some area measurements roughly taken from a front on photo of a Vespa PX (no screen). For more information see the simulated results when they are available at Vespa CFD/3D Model, here the calculated frontal area of scooter and rider is 0.81518 m^2 Scientific StudyThere is a 2002 scientific paper available called the Aerodynamic Investigation of a Scooter in the University of Perugia Wind Tunnel Facility by Stefano Ubertini - Univ. of Rome Tor Vergata and Umberto Desideri - Univ. of Perugia. The report is on a 460cc maxi scooter capable of 160 km/hr and some of the information is highly applicable to Vespa riders, especially those going fast. Below is a summary of the important points:
The paper references a few other interesting papers. These have not been read fully but the abstracts provide some clues: The Effect of Handlebar Fairings on Motorcycle Aerodynamics states 'cross-wind response may be reduced with a fairing or windshield mounted'. Useful Linkshttp://www.tonyfoale.com/Articles/Aerodynamics/AERO.htm http://www.sae.org/technical/papers/ground_vehicle/AERDY Motorcycle Workshop. Part 2: Aerodynamics Tunnel Vision http://www.sportrider.com/tech/146_0106_aero/index.html What makes the Suzuki Hayabusa faster than the more powerful Kawasaki ZX-12R? A visit to the National Research Council wind tunnel provides the answer - From the June, 2010 issue of Sport Rider. By Bruce Reeve
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