4 ms·
No, it is the same thing. What is counter-intuitive is that the body of the car is going directly downwind. The thing is, the sails of the car (the propeller)
by gvb 16y ago
No, it is the same thing. What is counter-intuitive is that the body of the car is going directly downwind. The thing is, the sails of the car (the propeller) are not going directly downwind, they have an angle of attack relative to the wind because they are angled relative to the car body. Ignore the car body and draw a propeller blade, the actual wind, and the apparent wind WRT the blade.
An iceboat is a better example than a sailboat. They go substantially faster than the wind. They can do this because their sails are very efficient in terms of being able to sail a very low angles of attack and because they have very low friction WRT their motion.
According to this article,
http://www.idniyra.org/articles/IceboatSailingPerformance.html http://www.idniyra.org/articles/IceboatSailingPerformance.ht...
the iceboat in question could sail 8 degrees off the wind and achieve a speed 7 times the wind speed.
Picture the propeller of the vehicle being a sail at a very small degree angle of attack (e.g. 8 degrees) while it is "sailing" in circles. Rather than pushing the vehicle body directly like with an iceboat, the energy is coupled to the wheels to drive the body at an arbitrary (but fixed for the vehicle in question) angle relative to the "sail" angle of attack.
- herdrick 16y agoOh.... Wow. That's awesome. Thank you!
- electromagnetic 16y agoCould you shed light on how well this vehicle would perform 'sailing into the wind' as it were? (Obviously with modifications to its transmission)
- ThinAirDesigns 16y agoIt is likely that the team from San Jose State University will use this vehicle to answer that very question during the next academic year, but it will involve a bit more work than just transmission changes. While it is true that with only ratio changes the vehicle can be made to drive directly upwind, it would not be all that efficient as the airfoils currently on the vehicle are propeller blades and not turbine blades. A set of properly cambered blades will need to be fabricated and installed and then the test could be done. One thing to remember is that when traveling upwind, the apparent wind over the chassis will be higher for any given multiple of wind speed. Upwind at 1x WS gives the same apparent wind as going 3x downwind. The current 'record' for directly upwind is ~64% of wind speed. http://www.gizmag.com/the-first-race-for-wind-powered-vehicles/9953/ http://www.gizmag.com/the-first-race-for-wind-powered-vehicl...