> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of William "Chops" Westfield
> Sent: 04 December 2009 23:32
> To: Microcontroller discussion list - Public.
> Subject: Re: [TECH]I'm microjetting to work today!
> 
> 
> On Dec 4, 2009, at 3:00 PM, cdb wrote:
> 
> > The car uses lithium polymer batteries combined with a diesel
fuelled
> > microturbine. The car can travel 80 miles on battery alone, and then
> > the turbine fires up and recharges the batteries on the fly
> 
> I recall hearing that this is essentially how/why a diesel-electric
> locomotive works.  Apparently you can make a diesel motor run VERY
> efficiently if it has a fixed target RPM and/or load, while electric
> motors do the "variable speed" thing without losing nearly as much
> efficiency as an IC engine would.

For some values of very ;)  In terms of diesel engines it's not so much
fixed speed but low speed (100's of RPM rather than 1000's) that is
really important.  Low speed two stroke supercharged diesels are the
most thermally efficient ICE's available, exceeding 50% under some
conditions.

The main advantage of diesel-electric drivetrains is the absence of a
mechanical transmission and to allow smooth, step-less control of power.
An electric motor also has almost ideal characteristics for a
locomotive; maximum torque is available at zero speed, right when you
need it.

Mike

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