OK, This should be No 1000 - So ask me a Technical Locomotive Question

[locomutt]

QUOTE: Originally posted by M636C

Guys,

I'm worried about how much time I've wasted making postings on this Forum (mainly) and I've realised that they have generally been technical reponses to locomotive questions.

So here is an invitation to ask any questions you haven't asked yet!

Peter

Well Peter, [#welcome] to the Four Star Club!!!![:D]
I doubt that you have wasted any time in posting. I for
one am very interested in what you say. Now understanding
the technical stuff is another story.[:)]

Okay I'll bite;"How many locomotives;does it take to screw in
a light bulb" or does that go to another "union" to do[?]

[Anonymous]

QUOTE: Originally posted by M.W. Hemphill

Welcome to the four-star time-wasting club!

Here's your question:

Are you ready?

Why?

FOFLMAO...

LC

[M636C]

QUOTE: Originally posted by kolechovski

Well, actually, I'm not sure. I just remember once seeing the needle on the amp meter going to the left, and it went well into the red. I can't remember if brakes were in use or not.

My first answer was a bit flippant, but it sounds as though you have seen motors acting as generators.

To return to first principles, a DC machine can act either as a generator or a motor. This is fairly obvious in a locomotive fitted with dynamic brakes. Normally, you provide power to the motor and it turns and does work, or you apply power to the field and it turns by outside forces and acts as a generator.

But in fact, if a motor is turning faster than the voltage applied to it wants it to turn (the speed of a DC motor is controlled by the voltage across it), the "Back EMF", the voltage generated by the motor internally will exceed the voltage from the generator and will start driving the generator as a motor (since it isn't connected to the dynamic brake grids). This will show up as "negative amps". It is most likely to occur when running down grade with the train pushing the locomotive, possibly through a short dip where application of dynamic brake would not be required.

Peter

(the system is slowing down here, I'll be back later!)

[M636C]

QUOTE: Originally posted by Junctionfan

I haven't asked this at least but what does the automatic brake do and what are the positions? I see things like SV and RL on the thing and don't know what they all do or stand for.

The mysteries of the Westinghouse system are generally beyond me!

But in the interests of continued good relations with Canada, here we go:

The "Automatic" brake is the air brake that applies the brakes on the train, as opposed to the "Independent" brake that applies the brakes only on the locomotive (or group of locomotives).

The brake is called "Automatic" because if the train breaks, or the pressure in the brake line is released, the brakes apply automatically. This is the opposite of the way the very early systems (or "Direct") air brakes worked. The change was made for safety purposes so that if a train broke a coupling, it would stop with brakes applied on both sections.

This means that the system is pretty complex and relatively slow acting compared to direct air brakes. The key feature is the "triple valve" that allows the single air pipe to provide:

a the signal to apply the brakes
b the signal to release the brakes
c to charge (raise the pressure in) the air reservoirs on each car

When a train breaks, or an air brake "application" is made, the pressure is "reduced" in the train line, and the difference between the pressure in the line and that in the air reservoirs determines the amount of braking you get.

I expect SV stands for "service" and this is a standard type of brake application, as opposed to an "emergency" application that drains the train line and allows all the pressure in the reservoirs to apply on the brake cylinders.

I also assume that RL is "release", and in this position, the pressure in the reservoirs is removed from the cylinders by sending a signal down the line. On a big train you can hear the sound of the air going down the line, in some cases. The system then recharges the brake reservoirs for the next application.

A problem is that if you are on a steep grade and make successive applications close together, you can run out of air pressure in the reservoirs. That is why you also have dynamic brakes, and the "independent" (locomotive only) brake which can be used instead of the "automatic" to conserve the air pressure in the train.

If this seems meaningless, I'll try again.

Peter

[kolechovski]

Junction...here's a hint:

http://www.imagedump.com/index.cgi?pick=get&tp=178235

[kolechovski]

Well, actually, I'm not sure. I just remember once seeing the needle on the amp meter going to the left, and it went well into the red. I can't remember if brakes were in use or not.

[M636C]

Mark,

In my current work environment, many people wear "readiness" badges.
I don't have one.
So, by definition, I'm not ready, and can't answer why I would be!

Peter

[M636C]

QUOTE: Originally posted by kolechovski

Very good...here's a question about running in the red...what causes negative amps?

Is this question related to the flow of electrons being opposite to the conventional flow of current, or is it a reference to motors acting as generators?

Peter

[Anonymous]

QUOTE: Originally posted by M.W. Hemphill

Welcome to the four-star time-wasting club!

Here's your question:

Are you ready?

Why?

Because!

Is there a limit to how manu locomotives can be MU'ed? Do they need to be some what similar in performance and setup?

Congrats on the 4th star.

[Junctionfan]

I haven't asked this at least but what does the automatic brake do and what are the positions? I see things like SV and RL on the thing and don't know what they all do or stand for.

[kolechovski]

Very good...here's a question about running in the red...what causes negative amps?

[mloik]

QUOTE: Originally posted by M.W. Hemphill

Here's your question:

Are you ready?

Why?

Mark,

Very good! Reminds me of the last episode of "The Prisoner".

Michael

[Kozzie]

Peter - Well done! from your down under colleague! [:)]

I knew it wouldn't be long! [:)]

Keep 'em coming!

Dave

[vsmith]

OK how many locomotives does it take to screw in a lightbulb?

Congrates on the four star promotion!
[bday][bday][bday][bday]

[M636C]

Guys,

I'm worried about how much time I've wasted making postings on this Forum (mainly) and I've realised that they have generally been technical reponses to locomotive questions.

So here is an invitation to ask any questions you haven't asked yet!

Peter