From: Mr. Sharkey >> Remember that the top of a tire is moving forward >> at *twice* the speed of the car
>I was discussing this a short while back with a friend. If the top of >the tire is moving at 2x, the axle is moving at 1x, then the bottom >of the tire would have to be standing still. But we all know that it >isn't, the entire tire is moving forward at 1x. that can't be true >either or else the road would need to be moving at 1x also or else >the tire would be skidding, but it's not. This must be what some of >those advanced math courses I never took were all about. Yeah; confusing, isn't it? Nevertheless, it's true. :-) >What I do know is that is the perfect case against open-wheel >vehicles and for enclosed wheels as much as possible. Exactly! Open wheels have huge aerodynamic losses from the top of the tire's 2x forward speed. But in race car, they often have an excess of HP, and need the extra cooling so the tires (and brakes) don't overheat. On a conventional car, smooth wheel wells and a close fit between the the tire and outer edge of the fender will reduce these losses. You wind up with a pocket of air rotating with the tire, so its speed and aerodynamic losses are reduced. >A belly pan would be nice too, but a lot of work... Right again. There is a lot of turbulence between the road and bottom of the car. But since you can't see it, auto manufacturers ignore it. Remember, the drag coefficients of cars are tested in a wind tunnel. The car, road, and tires are *not moving*. Only the air is moving over it. This eliminates the losses due to the spinning tires and road-belly pan, and gives them an deceptively low number to brag about in their ads. Lee Hart -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
