Quote:
Originally Posted by alvaro84
With or without rider? And how does it change with the size of this rider? And what about a passenger? 
Anyway, a tail section which can be used as a topcase sounds like a good idea to me. (Did you mention it here or in another topic, I wonder.) |
The references for better understanding of this matter are; Aerodynamics of Road Vehicles Edited by Wolf-Heinrich Hucho Chapter 10 Motorcycle & The Racing Motorcycle A technical guide for constructos by John Bradley sections 4.3 & 4.4.
I believe this Cd figure [from Hucho] is with the rider. Generaly the Cd does not change with the size of the rider, what does change is the frontal area and the total drag force. In the same way that two sheets of plywood of diferent sizes being pushed through the air have the same Cd but the larger peace will require more force [due to its larger area] to go at the same velocity.
The affect of the Pasanger is all over the map; if the passange sites high bend the rider they will add to the frontal area and may also add to the Cd. If the passanger is tucked in beind the rider they may lower the Cd.
The Cd is the affect of the shape of an object; a flat peace that is square has a Cd of 1.17, a parashut has a Cd of 1.4, a cylinder parallel to air flow has a Cd of 1.1 to 0.83 depending on its length, a fully streamlined body has a Cd of 0.04, a large bird has a Cd of 0.40...
The Cd of a tree changes with respect to wind speed; the higher the wind speed the lower the Cd!
10m/s Cd = 0.43
20m/s Cd = 0.26
30m/s Cd = 0.20
isn't nature interesting?
