The Transcontinental PRR

[eric220]

Ed - Thanks for taking the time to do that. I'm going to have to give it deeper consideration when I get home, but a couple of things jump out at me.

A-The yard that you have purposed for the departure yard is an interchange yard with the coal mine branch. That needs to be somewhere in the plan, although I don't necessarily object to a departure yard in that area.

B-I had given thought before to running the main under the hump, so again, not necessarily opposed to it. I'm not so sure about how it's connected, though. Also, I presume that part of the purpose of moving the lead is to allow the class tracks to be longer. As it's currently designed, the warp-speed-controller requires that the grade under the downhill side be the same width all the way from the end of the ladder to the crest.  The hump can't move any further to the left without a MAJOR redesign of the whole area.

C-Not really thrilled either. That area is on my short list for tweaking, but it's already built. I'm open to rebuilding it if necessary, but it's going to take a LOT of convincing to make me think it's necessary.

D-I really wanted a crossover there exactly for that reason, but I couldn't make it fit. Don't think it's going to happen.

Like I said, I'm going to have to ponder this more when I get home and have the design in front of me.

[eric220]

OK, I'm home and doing some math and figuring and other stuff.

As cool as it looks, I don't think the main under the hump idea is going to work.  In scale, most humps that I've researched only come out to 1.5" (or less) tall.  The taller hump at UP's Bailey Yard works out to 2.5" tall, but that's the largest classification yard in the world.  Apart from that, just to get up 2" in the most optimistic alignment, I'm looking at 3%-4% grades on the up slope.  Given that I'm not partial to that alignment, it's probably going to wind up at more like 5%-6%.  I am planning on implementing something like Lemosteam's magnet-and-steel-wire solution to increase traction of the hump locomotive, but that still seems too steep.  Also, specific to Ed's suggestion, there's just not room for a meaningful lead behind the shops there, even if I totally rebuild the ladder.

I like the idea of putting in a dedicated departure yard.  At the same time, putting it in the location of the current interchange yard causes some issues.  That will force departing freights either down the branch line, the yard lead, or westbound on the eastbound main (in other words, the only track the departing westbounds don't have access to is the westbound main).  They then have to go all the way around horseshoe before they can move through the universal crossover to the westbound main.  On the other hand, distributing traffic across the different tracks of the curve might not be a bad thing.  More contemplation on this subject is needed.

I messed around a bit with the idea of a dedicated departure yard (which would do double duty as the interchange yard in this arrangement) and came up with this:



Assuming a hump height of 1.25", there's enough length in the lead for around a 2% grade.  Movement from the arrival yard to the classification yard is still over the continuous running contingency track.  I added an engine pocket for the hump engine.  The idea would be that the trim engine would pull the cut to be classified from the arrival yard to the hump lead, and then the hump engine would attach to the correct end to push it over the hump.

[eric220]

OK, I've spent way too much time in front of the computer today screwing around with various ideas, and here's what I've come up with.  Ed's proposed departure yard could be used as both an arrival and departure yard.  The original A/D yard is repurposed as a storage/supplemental arrival yard.  If there's room in the primary A/D yard, trains to be classified would go straight there.  If the A/D yard doesn't have room, the incoming freight would drop off its cars in the supplemental arrival yard, and there would be a transfer move once there's capacity.  The supplemental yard would also serve as visible staging, holding through freights like the TrucTrain that wouldn't be classified, but rather are waiting on a power change.



Slightly closer view of the 5-track A/D and 8-track class yards.



The track in front of the left ladder is for cabins.

[eric220]

Good grief... Have I really done nothing of consequence on the layout in nearly five months?  I could have finished the helix and gotten a good start on the lower level in that time.  Oh well, other priorities right now.

In my spare time, I've been playing around with the yard again.  This is more of just another thought than anything else.  I thought that the hump might make more sense at the front, since that's were a lot of the action would be.



The other advantage of this arrangement is that it moves the hump away from the mains.  I'm a little worried about the retarding system interfering with trains passing on nearby tracks.  If it's just the runaround, like in this latest rendition, traffic can be controlled much more than if it were the mainline.

I'm still toying with the idea of finding a way to run the main under the hump, since that would be prototypical for the westbound hump at Altoona, which is geographically consistent with the location of this yard.  I'm not sure if I'll be able to find a way to pull it off, but I think it's worth investigating.

[davefoxx]

Don't forget that while the hump climbs over the main, the main line can also, at the same time, "dip" under the hump.  You can split the difference over both of the over- and under-tracks and reduce the grade and/or the length of the grade on the hump.

DFF

[eric220]

Don't forget that while the hump climbs over the main, the main line can also, at the same time, "dip" under the hump.  You can split the difference over both of the over- and under-tracks and reduce the grade and/or the length of the grade on the hump.

That will likely be an integral part of any main-under-the-hump design.  The major problem is providing a viable lead from the A/D yard to the hump.  The path to get cars from the former to the latter is not entirely clear at this point.  I'm not even sure that there's enough room to make it work.

[eric220]

I think I am on to something.  I have been racking my brain, trying to figure out how to get the already half built arrival/staging yard (the curving yard all the way on the left) in line with the hump, while at the same time eliminating the need to run over the main.  Then the thought occurred to me to flip the hump yard around.



The only movements that require crossing the main are moving cabins off the end of trains, moving power from the roundhouse to the departure yard, and moving cars to be re-humped back to the hump lead.  This also allows the return of the dedicated A/D yard for the coal mine.

The main drawback to this design is that the eastbound main has to split off form the other tracks very close to Horseshoe.



I can probably hide the disappearing track with scenery to make it less obvious, and the curve itself is intact, but I'm still not sure about it.  Thoughts?

[MichaelWinicki]

Interesting approach Eric.  A couples challenges with it, the first coming off the curve like that.  Yeah, hiding it will help but it's just so abrupt that it takes some realism away from the curve.

Second challenge I have is the amount of trackage/depth from front to back. 

[eric220]

Michael, I those are the same challenges that I saw.  I've taken a stab at tweaking it to resolve them, and came up with this:



This arrangement requires the aforementioned scheme of dipping the main under the run up to the hump, but there's room to do it on reasonable grades.  The dip would begin just before the duckunder at Homer, so it shouldn't be too distracting.

[MichaelWinicki]

Eric, on the right, where the 4 tracks go through the underpass and enter the curve... is that one of the legs of the "Horseshoe"?

[eric220]

Michael- yes.  Here's an overall of the lower level as it currently stands:



I know that MG and Altoona are on the wrong sides of the Curve, but unfortunately, that's dictated by the shape of the room.

[MichaelWinicki]

I wish you had at least a little "leg" room between the yard and the curve.   Going from the yard and slam, bam you're right on the curve... Well.

If it were me I would definitely test out the feasibility of the "hump" yard before I committed to it, meaning is it going to work the way that you think that it should. 

That big distance and loop-around for several feet from the AD yard, bothers me in that it doesn't seem like a real RR would do it that way.  On the real RR, time=$ and crews would be spending huge amounts of time on the balloon track between the AD and Hump yard, but I understand you have to do what you have to do in order to make it work.

[eric220]

A little more leg room would definitely be nice, but I really don't see how to make it happen. There's a good opportunity for a scenic divide at "Homer" that should visually isolate the scenes pretty well.

I have most of the materials to test out my concept for the hump yard.  That's actually one of the next projects on my list, once I have the needed time/funding.  I plan to build it as a module that can be inserted into the layout once construction reaches that point.  I'm actually really excited about giving it a try.  All of the preliminary testing that I've done has been very encouraging.  If it doesn't work out, it won't be very hard to alter the design to turn it into a flat yard instead.

Yeah, the ramp up to the hump yard is too long, but not by much.  At a 2% grade, it requires most of that distance to gain enough altitude to clear the mains underneath.  How does the prototype handle that climb?  The prototype yards that I researched had humps that scaled out to between 1.25" and 2.5" tall in N scale.  There has to be some distance for the run-up.

[MichaelWinicki]

Here's an image of a PRR hump yard in my area.

The yard was designed and built by the PRR in 1905.

There are actually 2 humps there (near the light tower).  A "North" hump (top) and a "South" hump (bottom).

On the North hump cars were shoved from right to left.

On the South hump cars were shoved from left to right.



The image dates from about 1945.

[davefoxx]

Eric,

I have to say that I'm confused.  I don't understand why there is three yards in Altoona.  The hump yard is obvious, as is the arrival/departure yard.  What is the third yard?  If one yard was removed that might be enough to declutter the area and give you a little breathing room between Altoona and the Curve.

In my opinion, I don't see a hump yard working very well in N scale.  The cars will probably roll too fast or, if the cars are too light, you'll be dealing with derailments from uncontrolled hard coupling, especially if truck mounted couplers.  If you are going to build the hump, this would be one reason that it would be wise to have the hump yard up front.  Michael's point about a northbound and southbound hump should be well taken.  Potomac Yard was built this way, too.

My preference would be a flat yard for classification and an arrival/departure yard.

DFF