In a message dated 98-05-19 02:08:10 EDT, austins@IX.NETCOM.COM writes:

<< Isn't this ('hybrid') system just what railroad locomotives use - albeit
 with compression diesels instead of a turbine?  Never could figure out,
 though, why the diesel engine power isn't just run straight to the drive
 wheels...? >>

Trains use electric generators/traction motors as the "transmission". Think
for a moment of the amount of torque it takes to move a standing inertia of
38,000 tons from a dead stop to 1 mph. There is no physical gearbox or clutch
mechanism in the world that could handle that task.

By regulating the speed of the crankshaft of the Diesel, the engineer is
changing the speed the attached generator is turning, and thus, the output of
the generator. By then splitting this electricity to 8, 12, or 16 traction
motors, each motor (theoretcially) is moving a small percentage of a train's
standing weight, and has only a fraction of the load that a single
transmission would have to bear.

One last factoid: many engineers, after brining a long, heavy load to a stop
will back the train up slightly, (untill all of the hitches between cars are
slack). Thus, when the train starts underway again, the locomotive initially
is only pulling one car, and a fraction of a second later, two, then three,
etc. This way the standing inertia the locomotive must overcome is reduced to
the minimum, and only gradually increased as the rolling ineria increases.
Pretty smart, eh.

back to VW's now,

gmbulley
cary, nc