I've heard the opposite.....that it causes the air pressure to not flow over the truck if the tailgate is down. I've never seen any difference in my truck up or down Rich wrote: I drive with the tailgate down when I use the pickup unloaded. It does save fuel because up, it can scoop up enough air pressure at 50 mph to cause significant drag. I have seen some kind of rubber or polymer sheet on some pickups with big holes in the sheet stretched across the back, and no tailgate. I assume it is intended to reduce drag but at higher speeds it seems that perhaps some significant drag may develop to obviate the purpose. ----- Original Message ----- From: "Dave Tweed" To: "'Microcontroller discussion list - Public.'" Sent: Wednesday, June 27, 2007 5:11 PM Subject: RE: [EE] Simple fuel-saver, so they say > Tony Smith wrote: >> > Most instructive for saving money were 3 demos >> > >> > Jeremy Clarkson's London-Edinburgh-London trip in a V8 on one >> > tank of diesel and similar tests on the track by both >> > Mythbusters and a NZ motoring program. You can save >> > substantially by driving conservatively, including reducing >> > drag (windows and tailgate up) and weight (didn't Top Gear >> > calculate it costs UKP6 a year to haul a moustache around ?) >> >> In the second round of tailgate testing, there was a rather neat >> demonstration of E=MV^2, otherwise known as 'going twice as fast >> takes four times the effort'. >> >> They ran the test at ~50 MPH (55?), and used 5 gallons or so. >> The next run was at 25 MPH, and only used 1.25 gallons. (#s >> might off a bit...) >> >> They never commented on it, but it was interesting to see a 'real >> life' example. > > That has nothing to do with e = 0.5*m*v^2 (instantaneous energy), > and everything to do with the fact that most forms of resistance > (air resistance, rolling resistance, etc.) are proportional to v^2. > This means that the total energy (work) required to travel a given > distance tends to be proportional to v^2, and the power required > (work per unit time) is proportional to v^3. > > -- Dave Tweed > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------------------------- Get the free Yahoo! toolbar and rest assured with the added security of spyware protection. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist