"Artemus" wrote in message
...

"Jon Elson" wrote in message
...
I was at the local ice cream place that is adjacent to one of the local
train tracks.
The Amtrak pulled up to exchange passengers at the nearby station. A
bit after it stopped, I heard a very familiar and unexpected sound.
It was a large air compressor driven by a 60 Hz 3-phase motor. I'd
guess from the sound it very well could be a Quincy, and I'd guess maybe
15-25 Hp 4-cyl 2-stage, with pneumatic unloaders.

Anyway, it struck me as just a tiny bit odd they'd use an electric
compressor, as they have mechanical power available off the Diesel
engine.
I also noticed the Diesel didn't seem to change speed when the train
accelerated, so I'm guessing they run a single engine at 60-Hz
synchronous speed all the time, so they can distribute 60-Hz power for
air conditioning, etc. to the coaches. So, no aux engine for the
non-traction power.

Anybody know anything about this?

Jon

From http://science.howstuffworks.com/diesel-locomotive.htm

This 270,000-pound (122,470-kg) locomotive is designed to tow
passenger-train cars at
speeds of up to 110 miles per hour (177 kph). The diesel engine makes
3,200
horsepower, and the generator can turn this into almost 4,700 amps of
electrical
current. The four drive motors use this electricity to generate over
64,000 pounds of
thrust. There is a completely separate V-12 engine and generator to
provide
electrical power for the rest of the train. This generator is called the
head-end
power unit. The one on this train can make over 560 kilowatts (kW) of
electrical
power.

See also http://en.wikipedia.org/wiki/Diesel_locomotive
about 1/2 way down "Propulsion system operation"

I think technically they're called "diesel-electric" locomotives. 560 kW is
a lot of toasters!!

The hp of diesel-electrics varies from 330 hp (used for the "work trains" in
subways) to 6,600 hp behemoths, that are so large they can't navigate
certain areas of track. 3,200 hp is indeed a good-sized locomotive.

The diesel-electric strategy greatly simplifies the mechanicals, and gives
very sensitive control of the traction motors, AND allows the electric
motors to brake regeneratively (produce electrical power), altho this
regenerated power is not always utilized but is often bled through gigantic
banks of iron resistors, which can glow red hot under heavy braking.

The steel wheels alone of these locomotives are proly thousands of pounds
each, as the wheels on bitty subway cars (NYC) weigh 700-800 lbs each -- no
axle, no bearings, just the wheel..

History channel had this guy, a railroad conductor in the NE, do a train
reality show, which was really perty inneresting, if you could get past his
own personal issues/drama.
They might have some shows archived, altho I'm sure they're more innerested
in $29.95 for each dvd.
--
EA






Art