Signals: What I don't know . . .

[NW Mailing List]

I'm building signals for my layout, N&W is one of them.

I believe they would place signals logistically in the right locations. 
Its important to know what train may be ahead of your train in case of 
stoppage, brake failure, broken knuckle, which happens on grades.
If theres a circumstance you would recieve train orders that would 
circumvent a signal aspect.
Say a signal is supposed to be absolute stop the orders would tell you 
you may stop and proceed(slow and proceed).
Other signals may be designated stop and proceed  or indication or have 
a specific light on/off to indicate stop and proceed.

Signals tho they can indicate block occupancy, they say more what speed 
the train should run, thats true for advance signals having 2 or more 
heads, or like N&W the one head and additional lights.

A signal's designation is based on its location and what it protects and 
how to do it.

-Lynn-



On 8/5/2013 8:43 AM, nw-mailing-list-request at nwhs.org wrote:

> Subject:

> Signals: What I don't know . . .

> From:

> NW Mailing List <nw-mailing-list at nwhs.org>

> Date:

> 8/4/2013 5:05 PM

>

> To:

> NW Mailing List <nw-mailing-list at nwhs.org>

>

>

> As the saying goes, What I don't know about signals would fill 

> volumes.  So I would like to throw out the little bit that I think I 

> know and hopefully y'all can correct my errors and elaborate of the 

> things that are basically correct.

>

> It seems to me that there are three types of signals:  block, 

> interlocking, and the "glue" signals that connect the blocks to the 

> interlockings.  Basic block signals seem fairly straightforward. They 

> have one arm with a number plate below it.  The arm can display only 

> "clear" when the next two blocks are unoccupied, "approach" when the 

> second block in advance is occupied, and "stop and proceed 

> restricting" when the next block is occupied.  So the only thing that 

> determines the aspect that these signal present is the state of block 

> occupancy detectors for the next two blocks.  This doesn't seem too 

> complicated, but like everything else, special cases arise to muddy 

> the waters a bit.

> For example, suppose you're pulling a heavy coal drag up a 2% grade 

> and your locomotives are bout on their knees.  What you would not want 

> to happen is to encounter a signal at "stop and proceed restricting", 

> bring your train to a full stop only to see the signal go to approach 

> a minute later.  For one thing you might not be able to get your train 

> started again or at a minimum it might take a lot of time and effort 

> to get her going again.  So the way I understand it, to cover such 

> situations, the "restricting" aspect can be added to a block signal so 

> that the train only needed to slow to restricted speed (15 mph) 

> instead of stopping.  I think I remember seeing that this could be 

> accomplished by the addition of a circle "G" (grade) emblem under the 

> arm as well as, I suppose, by adding a second arm with only two 

> positions on the reverse diagonal.

> Conversely, if you're coming down a steep grade rather quickly with 

> that same heavy train pushing you, you might need a significant 

> distance to bring her to a stop.  In some cases where blocks are 

> short, it might take more than whole block to do this.  In such a 

> location, if you were to enter a block at speed, whose signal 

> displayed "approach", you might run past the next signal at "stop and 

> proceed restricting" before getting her completely stopped.  I believe 

> this would be the motivation for "advance approach" aspect.  I would 

> assume this would be done with a second arm with two lights on the 

> diagonal that would come on whenever the top arm went to "approach".

> As was stated in one of the notes in the safari thread, going from 

> signalled to "dark" territory was indicated by "restricing".

> Any other "block" signal aspects, special circumstances/situations?  

> I'll start on interlocking signals in a later message.

> Jim Cochran


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