Re: mini/microturbines in the railway?

Angelo, two minor comments...

First that the tractive effort that can be provided by a locomotive is
first determined by its weight (as discussed in my earlier posts), and
second by the horsepower developed by its engine. Reduce the weight of
the engine and you will have to increase the dead weight or ballast
carried by a locomotive in the form of a large block of concrete or
stacks of iron weights. Hence if all turbines have to offer is a better
power to rate ratio, this makes them less attractive to locomotive
designers.

The locomotive throttle designs you describe are termed "cam
controllers". When I was still in the railway business back around 25
years ago, they were still found in use on light rail tracked vehicles
like the legendary PCC Trolley Cars and even some of the "Green Line"
cars used on the MBTA here in Boston. The functioned by switching the
connections to the traction motor in a number of steps. I've long since
forgotten what steps on the cam controllers where which, but they
included "full series, full parallel" and a number of motor taps in
between. (Full series referred to connecting the armature in series
with the field magnet of the motor and of course full parallel
represented running the armature windings in parallel with those of the
field magnet or stator. I'm not sure of how the in-between steps were
implemented, but just guess I would assume that they consisted of a
number of different taps on the stator windings.) This method was, of
course, limited to the control of d.c. powered traction motors. By the
time a.c. powered locomotives like the GG1 arrived, control of the
traction motor(s) was fully electronic.

What may be interesting to some readers is the unique braking mechanism
employed by the PCC trolley cars. Old timers may remember that they had
an electro-magnetic powered brake shoe that actually pulled down to the
track and braked these vehicles by magnetically clamping intself onto
the rail. IIRC, I believe it was located between the wheels of each
truck. Damn system worked very well, but I am at a loss to explain
just how the PCC cars were braked when they lost contact with the
overhead catenaries supplying electical power to them or if they had an
actual braking mechanism on their wheels.

More curious still, I understand that the PCC cars are still in use in
some regions of our Nation. Why not, it it ain't broke, don't try to
fix it!

Just for your entertainment, here's a link to a photo of a PCC car that
was until recently used in Boston.
http://world.nycsubway.org/perl/show?14140

Here's another wonderful link about PCC cars...
http://world.nycsubway.org/us/pcc/

Yes, on this photo your can clearly see that the braking magnet was
located between the two axles of each truck.

Evidently NYC people are really into rail transit judging from the URL
of both of these. Still, for guys like me who spent far to many 18-hour
days working far away from our homes and families, it is not the type
of thing that most of us dwell on as a hobby! Still, looking at this
stuff after 26 years brings back many happy memories, although I've
never worked with a PCC car in my entire life! (My expertise at the
time was mainline and rapid transit signaling systems and centralized
traffic control...stuff like the control systems for the Washington DC
subway, MARTA in Atlanta, and the automated routing system running
freights like the "Queen of Los Angeles" from LA to St. Louis without
ever having the freight face a Restrictive Signal! Ah, my memories of
Springfield, MO...now that is another post likely for another
newsgroup! :-)

,,,And so you now realize that I am an electronics and computer Geek...


Enjoy, and kindest regards, Harry C.

.

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