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