PRR Track Plan

[DKS]

Subsequent to posting the previous rendering, I removed all of the extra spacer tracks between the switches and crushed it down until there was nothing that could be squeezed out of it. Then I overlaid the rendering on the original plan at the same scale.
 

[davefoxx]

I understand the double crossover at the beginning of the throat, but I do not understand the second crossover immedately adjacent.  If this yard had multiple tracks (more than just two) prior to the throat, then it would make sense to have multiple crossovers, so that trains could get around each other or a switcher could get in there without fouling the rest of the yard.  But, here, there are only two tracks beyond the double crossover.  Since anything crossing in the double crossover will block both tracks, the yard does not appear to need the multiple crossovers.  If you eliminate some of the extraneous crossovers, that will save you yard throat length.

Dave Foxx

[eric220]

Dave F. - The purpose of the first double crossover is to allow trains from the two outside platform tracks to reach either throat track. There is another crossover before they join the mains, so you're right, I may not need that.

DKS - Well, it appears that you are correct, sir. That's one of the pitfalls of designing with a vector art program instead of a dedicated track layout program: I know the diverging angles, but I often forget to take into account the total length of the turnout. There is a partial solution here. The Atlas #5 turnout is 6" long, but there's over 1.5" of track before the points that could be trimmed off. In looking at the diagram, it looks like there are 7 turnouts down the middle that butt up into each other and define the length of the throat. 2 are slip switches. That leaves 5 turnouts that I can trim 1.5" off of, saving 7.5 inches. I'm at work at the moment, but I'll try playing with it when I get home and see what I can come up with.

[bbussey]

Eric,

I agree with Dave Foxx - wouldn't you gain another foot of yard area if you eliminated the two crossovers that follow the primary double-crossover?  It seems that all of the trackage in the passenger yard is accessible from either main due to the primary double-crossover.

As an aside, David K Smith introduced me to the AnyRail software, and it is a major plus in working out conundrums such as this.  It is far easier to learn than the other track design software packages out there, it is affordable, and it allows you to output the schematic 1:1 if necessary.  I did that with my layout-in-progress - output the New Haven area 1:1 to a PDF and took it to a printing house to output on roll paper, so I could properly plot all of the flex track.

[DKS]

There is a partial solution here. The Atlas #5 turnout is 6" long, but there's over 1.5" of track before the points that could be trimmed off. In looking at the diagram, it looks like there are 7 turnouts down the middle that butt up into each other and define the length of the throat. 2 are slip switches. That leaves 5 turnouts that I can trim 1.5" off of, saving 7.5 inches. I'm at work at the moment, but I'll try playing with it when I get home and see what I can come up with.

I wonder about this whole approach. Crushing the throat down to the bare minimum length using trimmed #5 turnouts, IMO, is a major cosmetic compromise, particularly for a passenger terminal, where you've got long passenger cars twisting through a highly compressed maze. I might also be a bit concerned about performance as well; shoving a string of coaches through this beast sounds like a risky affair. You may want to re-think this whole area of the layout to improve both the appearance and the performance.

[eric220]

I agree with Dave Foxx - wouldn't you gain another foot of yard area if you eliminated the two crossovers that follow the primary double-crossover?  It seems that all of the trackage in the passenger yard is accessible from either main due to the primary double-crossover.

I've revised the the throat design several times. I settled on this design because it was a good balance between simplicity (2 double slips, down from 6 in my original design) and the aesthetic complexity associated with passenger terminal throat tracks. It also allows simultaneous movement to or from any two platform tracks. If I remove the double crossover, I can still accomplish simultaneous movement, but the two outside tracks only have access to one throat track. It's not a crises, because there is one additional double crossover before the throat rejoins the mainline, and there's actually another double crossover on the main in the next block. If I remove the pair of crossovers associated with the slip switches, my operating potential is drastically reduced. That design would allow simultaneous movement only if one train were coming from track 1-3 and the other from 4-6. For instance, I would not be able to have one train arrive on track 6 while another departed from track 5.

[bbussey]

I wasn't as clear in my query as I should have been.  My question is, if you have the double crossover that is depicted on the right side of the diagram, why do you need the two standard crossovers at the beginning of the coach yard?  Aren't all the coach yard tracks on the left accessible from both mainlines on the right due to the double crossover on the right?

I understand the Track 1-3 / Track 4-6 simultaneous action - but isn't that what signals and dispatchers are for?  It seems that you may be sacrificing more in real estate than you realize just to accommodate the rare three-passenger-consist meet at the yard throat.

Another thought - if you must keep the multiple crossovers, why not use FastTracks instead of Atlas at those spots?  A FastTracks #6 double crossover on the right side would save you at least six inches.

[DKS]

You know, you can have everything you need in the same space using #10 switches, configured like this:
 


Fits perfectly:
 


No double-slips, and no #5s. Simple, and you can get from any platform track to either mainline track. Granted, you can't have simultaneous movement, but how often will you be doing this, honestly? How much real estate are you willing to sacrifice and custom double-slip switches are you ready to build all for a few rare moves?

[wazzou]

That seems like an excellent solution DKS. 

[eric220]

I wasn't as clear in my query as I should have been.  My question is, if you have the double crossover that is depicted on the right side of the diagram, why do you need the two standard crossovers at the beginning of the coach yard?  Aren't all the coach yard tracks on the left accessible from both mainlines on the right due to the double crossover on the right?

OK, you're referring to the full crossovers on the left side (vertical on the diagram)?  Those are to allow trains from any of the three platform tracks to reach any of the three arrival/departure tracks of the coach yard (the three balloon tracks inside the mainline).  They also allow switchers working the coach yard to run around trains on the A/D tracks.

You know, you can have everything you need in the same space using #10 switches, configured like this:
 


Fits perfectly:
 


No double-slips, and no #5s. Simple, and you can get from any platform track to either mainline track. Granted, you can't have simultaneous movement, but how often will you be doing this, honestly? How much real estate are you willing to sacrifice and custom double-slip switches are you ready to build all for a few rare moves?

I definitely see the point to be made there about how much real estate is being eaten up by the more complex track work that I designed.  I've waffled back and forth about something short, simple, and more reliable like what you show, and something that gives more of an impression of the spaghetti tracks of a busy passenger terminal.  I thought that the version with two slips did a good job of compromising between the two.

I do have to say, you're absolutely right about simultaneous movement.  The only time that two passenger trains will meet on the throat is if I deliberately schedule it that way.  (And if I build it, I just might.)  I guess that's just one of my druthers; I want the throat to be complex enough to convey the feel of a large passenger terminal.  I'm willing to sacrifice some real estate to make it happen.  I'll have to play with it tonight when I can sit down in front of my designs and fiddle.

[DKS]

Incidentally, I designed an adaptation of Sunnyside for someone (coincidentally another Eric) that I present here as food for thought, since you're working on something along similar lines...
 

[eric220]

I wonder about this whole approach. Crushing the throat down to the bare minimum length using trimmed #5 turnouts, IMO, is a major cosmetic compromise, particularly for a passenger terminal, where you've got long passenger cars twisting through a highly compressed maze. I might also be a bit concerned about performance as well; shoving a string of coaches through this beast sounds like a risky affair. You may want to re-think this whole area of the layout to improve both the appearance and the performance.

OK, here's what I mean by trimming down the #5's.  Here are a #10 and a #7





Note the length of track beyond the throw bar.  4 ties.  Based on those images, which of the images below would you expect to be the correct #5?



I'm not really sure what is to be gained by the extra 1.25 inches.  That's the part that I'm talking about trimming off.  If I do that, the entire thing doesn't expand much from my guesswork version.  It's less than 5 feet.



If I take out the double crossover, the whole shebang comes in at a little over three feet.  (Oops, I just noticed that I neglected to extend two tracks the whole way, but it doesn't change the overall measurement.)



At that size, I could easily do it with unmodified #5's.  In which case, I might be able to go to #7's.  The hangup is the Peco double slips.  They are 10° crossings.  A #5 diverges at 11.3099°, and a #7 diverges at 8.1301°.  Neither is a perfect match, but the #5 is closer.  (Although now that I actually have the numbers in front of me, the difference is a lot less than I thought: 1.3099° vs. 1.8699°.)

#5


#7


I've got a double slip in Altoona backed up against a #5, and it works quite nicely.  The trains don't seem to be bothered at all by the slight jog.  I'll have to draw up a throat with #7's and see how it looks.  Unfortunately, I don't have time, as I'm expecting company any minute.

[Ed Kapuscinski]

Eric, I don't think you want to be using #5s in there. I think they're even too tight for industrial work, let alone a passenger terminal. I think you're going to get yourself into trouble trying to move passenger consists through them.

[wm3798]

One word of caution on trimming back the #5's... if you run them together like that in a ladder, a typical four axle road switcher will have one truck on the frog, and the other on the next set of points...  Make sure you power your frogs, or you will stall.  I'm still working on fixing this in my paper mill yard.

Lee

[bbussey]

... I'm not really sure what is to be gained by the extra 1.25 inches.  That's the part that I'm talking about trimming off.  If I do that, the entire thing doesn't expand much from my guesswork version.  It's less than 5 feet...

It is so the length of the straight path of the turnout matches an existing combination of straight segmented track pieces, i.e. a 6" segment plus one of the shorter segments - a necessary compromise for oval-based segmented track plans to work using existing track components without modification.