On Sat, Aug 30, 2003 at 02:19:39AM -0700, Paul Johnson wrote: > On Sat, Aug 30, 2003 at 01:44:43AM +0200, Arnt Karlsen wrote: > > ..2 reason diesel-electric locomotives are popular; they are > > about as clean as your average power utility, and they dont > > put heavy loads on the power grids. I remember, at the GEC Hirst Research Centre in Wembley, London, being struck by the fact that the maximum power draw of the whole site, 3.5MW, was the same as a Class 87 on full bore belting down the West Coast Main Line which ran past the site. > Nope, and nope. Diesel electrics are popular because they give the > most bang for the buck. ...and because (in Britain) the introduction of diesel-hydraulics was cocked up badly, for silly reasons like the idea coming from those nasty Germans we'd just fought a war against; also because of commonality of transmission technology with straight electrics; worldwide, a lot of country B seeing country A using diesel-electrics and copying them, often buying similar designs from the same manufacturer, making the whole process easier and cheaper. Diesel-hydraulics are in many ways a much better idea than the diesel-electric - simpler, more reliable, lighter, no need for complex high-power electrical control gear, inherently good resistance to wheel slip and transmission overheating which makes them good choices for heavy freight trains and/or heavily graded routes. The reasons they're not more widely used are historical/political rather than technical. Hydraulic transmission does seem to be making a comeback, though - diesel multiple units in Britain since the 80s have all used hydraulic transmission, with great success. It's far more reliable than the mechanical transmissions on older DMUs, small and light enough for underfloor mounting, and much cheaper than the experimental diesel-electric version that was also built. > Vastly more efficient than gasoline engines > and mechanical transmissions (it's 2003, why can't I get a diesel > electric car?) Well, you can get plenty of diesel cars; electric transmission is out, though. It would be cripplingly heavy for a car, less reliable than a gearbox and less efficient than a manual gearbox. A car with hydrostatic transmission would be feasible, though - similar weight to mechanical, similar reliability and loses sufficiently little in efficiency that you'd make it up by maintaining better matching between the engine and the load. And of course the hydrodynamic-mechanical transmission principle, as in the British Class 35 "Hymek" locomotives, is widely used in cars. A diesel-hydrostatic motorbike is one of my projects. > with fewer moving parts than the steam engines it replaced. Huh? > This makes them dirt cheap and bloody reliable. There's also the fact that diesel engines, generators, motors and the other components of a diesel locomotive are produced by mass-production methods, whereas steam locomotives were constructed on more of a craftsman basis. Maturity of technology has a lot to do with it as well; in the early days of dieselisation they'd cost over twice as much as the equivalent steam loco, and reliability sucked badly. > The > railroads really couldn't give a damn about how much electric they're > using since they're not having to string thousands apon thousands of > miles of overhead lines (another costly expense railroads don't bother > with unless they can get economic benefit from the typically heavier > and faster trains that electrified lines run). and *maintain* all those flippin' wires... I think a bottom-contact third rail system, using aluminium rails with steel wearing faces, on around 3kV, would be a better bet; similar electrical losses, and a whole lot more robust and easy on maintenance. (But maybe I'm biased by knowledge of the UK East Coast Main Line electrification which was a real cheapo job and blows down whenever too many cows fart at once.) Electrification works better in densely-populated areas (Holland) or mountainous areas with lots of hydro-power (Switzerland) than somewhere as big as the US. -- Pigeon Be kind to pigeons Get my GPG key here: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x21C61F7F
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