On Sun, 25 Nov 2007 20:19:46 -0500, Red wrote:

Roger Long wrote:
The bigger the diesel, the more of a factor this is
which is why railroad engines are seldom shut down for maintenance.

Roger, I am under the impression that railroad diesels are run at pretty
high "idle". In fact when waiting for the various commuter trains to get
out of the way around here I get the impression of a pretty fast running
engine when they are stopped. They do not sound anywhere near idle. Is
this the case just when they are dropping off and picking up and/or is
there another time when they actually idle slower?
Red


I think that railway engines are basically generator prime movers and
run at a constant RPM all the time. At least that is the way a power
plant engine runs. It always runs at approximately rated RPM
and the governor makes small adjustments up or down to maintain the
proper frequency.


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

"Bruce in Bangkok" wrote in message
...


I think that railway engines are basically generator prime
movers and
run at a constant RPM all the time. At least that is the
way a power
plant engine runs. It always runs at approximately rated
RPM
and the governor makes small adjustments up or down to
maintain the
proper frequency.


A train engine will increase RPM as the electric load goes
up.

On Tue, 27 Nov 2007 14:54:25 -0500, "Scotty" wrote:


"Bruce in Bangkok" wrote in message
.. .


I think that railway engines are basically generator prime
movers and
run at a constant RPM all the time. At least that is the
way a power
plant engine runs. It always runs at approximately rated
RPM
and the governor makes small adjustments up or down to
maintain the
proper frequency.


A train engine will increase RPM as the electric load goes
up.


I guess I assumed that because they drove a "generator" that they were
generating A.C. .
Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Wed, 28 Nov 2007 10:26:59 +0700, Bruce in Bangkok
wrote:

A train engine will increase RPM as the electric load goes
up.


I guess I assumed that because they drove a "generator" that they were
generating A.C. .

They probably are but then rectify it to DC at some point like an
alternator. If so, the RPMs/frequency do not matter.

On Fri, 30 Nov 2007 21:02:07 -0500, Wayne.B
wrote:

On Wed, 28 Nov 2007 10:26:59 +0700, Bruce in Bangkok
wrote:

A train engine will increase RPM as the electric load goes
up.


I guess I assumed that because they drove a "generator" that they were
generating A.C. .

They probably are but then rectify it to DC at some point like an
alternator. If so, the RPMs/frequency do not matter.


Years ago I had a train guy, who didn't understand it very well, try
to tell me about how an electric locomotive worked. He was a bit vague
about 'lectricity but did talk a lot about some sort of coils or
resistance grid on the top of the engine that got very hot under
certain conditions.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Years ago I had a train guy, who didn't understand it very well, try
to tell me about how an electric locomotive worked. He was a bit vague
about 'lectricity but did talk a lot about some sort of coils or
resistance grid on the top of the engine that got very hot under
certain conditions.

My first job straight out of college was at the National Carbon Company in
Cleveland.

As I was being given a plant introduction tour saw a couple of guys at
bandsaws cutting carbon blocks into small pieces.

Was told these guys worked on piece rate and were the highest paid hourly
employees in the place.

All those little carbon pieces ended up becoming carbon brushes for
Electromotive train engine DC motors.

Lew

The hot grids referred to are resistance loads used to dissipate the
energy produced by the dynamic electric braking action employed as
part of the engine braking system.

Terry K