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Re: OT: Debian Mailinglist server slow?



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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