I like your Quasar. How does it handle? Range? What is it based on? Homebrew chassis I suspect? I could hack up the Honda VF but that would result in a hash me thinks. Makes me want to re-evaluate the three wheeler, nah I got a jones to carry two passengers once in a while.
Jeff On Wed, Mar 12, 2008 at 2:01 PM, Paul Compton <[EMAIL PROTECTED]> wrote: > For starters you need to look at Cedric Lynch's streamliner > > http://www.bikeweb.com/node/1412 > > Cedric could achieve 80 miles at a constant 40mph on four Optima Yellowtops. > > It's pulling about 1.5Kw from the battery at 60mph. > > Secondly forget Cd. > > To measure the Cd (coefficient of drag) of an object, you place it in an > airstream of known speed and measure the FORCE exerted on the object. The Cd > is then the force divided by half of the reference area (more later) times > the air density times the velocity squared. > > Of course what you actually wanted to know for your design calculations was > the original force value. Instead you have to try and recreate it from > dubious data. > > Cd was only ever intended to campare the relative aerodynamic efficiency of > simple shapes. It has however become a marketing tool and stated figures are > very often distorted. All you have to do is exagerate the frontal area and > the Cd goes down. > > The reference area is usually the frontal area (but was it gross width by > gross height or an actual outline figure?), but not always. If you're > dealing with slim airfoil shapes then the frontal area is very small and in > any case you're trying to keep the airflow attatched over the whole surface, > so plan or total surface area is more likely to be used. This has applied to > some of the solar racing cars where very low Cd figures have been quoted. > > There is a great deal of total bollocks talked about aerodynamics, much of > it in centres of learning. They still spout the obvious nonsense about > airofoils generating lift because the air has further to flow over the top > surface and is therefore travelling faster and according to Bernouli's > principal at lower pressure. > > This ignores: > > Paper planes with no airfoil shape. > Chuck Gliders, ditto. > Planes flying upside down. > The number of planes with symetrical airfoil profiles. > Quoted aircraft wing loadings that would require a DIFFERENCE in speed > between top and bottom surface exceeding the total speed. > > I threw a paper plane at my Physics teacher when he tried this crap out on > my class! > > Airfoils generate lift primarily by changing the direction of airflow. The > trick is to do this with minimal drag and that's where the shape comes in. > > Borrow a copy of 'The Leading Edge (aerodymanic design of ultra-streamlined > land vehicles)' by Goro Tamai; published by Robert Bently Inc. The maths is > tough going, but the discussions, descriptions, and pictures are invaluable. > > > Paul Compton > www.evguru.co.uk > www.sciroccoev.co.uk > www.batteryvehiclesociety.org.uk > > > www.morini-mania.co.uk > www.compton.vispa.com/the_named > > >
