Crossovers and S curves in yards

[MVW]

Hi all,

I posed this question on another forum ... and have drawn a range of opinions. I'd like to see if there's any consensus here.

I've always been a big adherent to John Armstrong's advice for planning reliable trackwork. One commandment I've followed religiously is provoding a section of straight track between turnouts in a crossover or to break up an S curve, with the straight track at least equal in length to the longest equipment that's going to be run over it.

My question: Is this equally important in yards, where trains will be moving at restricted speeds? I've never fudged this rule before, but I'm asking because I've seen photos of layouts where it at least appears that this rule is ignored. I'm just about to begin construction on my first major yard in N scale, and I would prefer not to sacrifice real estate to tangents I may not need.

So ... what's your experience? And I'm stressing the word "experience." I'd prefer to hear evidence instead of opinions.

I'm using Atlas Code 80 flex and Custom Line #6 turnouts. Modeling the transition era, so probably no rolling stock over 50 feet and '50s-era switchers.

Thanks in advance!

Jim

[conrail98]

I used to think the same as you until I started commuting by the interlocking and approaches to the Delair bridge and the Pavonia yard throats. There are tons of S-curves between turnouts facing in opposite directions. You are correct that operating at low speeds, S-curves become much less of a problem point, however, the prototype seems to make the diverging routes as close together as possible, thus shortening the straight distances between switches,

Phil

[pwnj]

I responded on the other forum, too, but I wanted to give a good example of where the S-curve rule just does not apply.  Take for example a nice yard ladder off a straight mainline.  Start with a left-hand switch, then immediately into a right.  There's your S-curve.  And this is just plain prototypical.  Or let's say you're going from a single-track main to a double.  Do you use a wye switch?  No, you use a #6 and an appropriate curve to bring it parallel.  Again, S-curve.  Now, as Randall had said on the other board, if you're going to be running long locomotives and/or equipment (passenger, etc.), you'll certainly want to use long switches at the very least.  And I do agree that trying to avoid them is a good thing.  But don't knock yourself out, because the railroads certainly don't.

[Ed Kapuscinski]

As a counter point to Phil's comment, which is absolutely correct, is that the prototype curve radii and switch geometries are MUCH larger that anything in the model world.

For example, you might not run into the issues when you have #22 turnouts and curves where the radius is measured in 1000's of feet, but when you scale that down to an 11" radius curve into a #6 turnout, the physics change (distances between things, mainly).

In N scale, you don't want a single car in the s curve. In real life, the turnouts themselves are long enough that that's physically impossible.

[conrail98]

As a counter point to Phil's comment, which is absolutely correct, is that the prototype curve radii and switch geometries are MUCH larger that anything in the model world.

....In real life, the turnouts themselves are long enough that that's physically impossible.

Actually, the one that amazes me on the prototype's I mentioned above is the approach to the Delair bridge:

http://maps.google.com/maps?q=Delair,+Pennsauken,+NJ&hl=en&ll=39.972062,-75.066463&spn=0.001198,0.002411&sll=37.0625,-95.677068&sspn=40.460237,79.013672&vpsrc=6&hnear=Delair,+Pennsauken,+Camden,+New+Jersey&t=h&z=19

Those two switches are close enough together to have a car in each, particularly the trash flats they run out of Pavonia,

Phil

[Ed Kapuscinski]

Oh yeah, but the divergent angles and lengths are far from the size they'd be using model railroad sized turnouts.

[pwnj]

Yeah, that's a good point, Ed.  Now I have seen some pretty tight S-curves in some of the urban rail yard settings though. 

[Brakie]

As I mention on the other forum unless you operate your yard engine at light speed you won't have any issues.

[pwnj]

(searching for the light-speed option in the DCC programming handbook...)

[conrail98]

(searching for the light-speed option in the DCC programming handbook...)

I prefer ludicrous speed

[wm3798]

As I mention on the other forum unless you operate your yard engine at light speed you won't have any issues.

Well, yes and no.  When I laid out the east end of my yard, I tried to get away with a left when I should have used a right.


These are Atlas c55 #7's.  I figured I'd have plenty of leeway especially at low speeds.

Well, it didn't take long for this switch to become a total pain.  In short order, I dug around the turnout box and replaced it with a right, and I haven't had a problem with it since.


The main issues, oddly enough, came from pulling trains out of the yard, not so much pushing them in...

Lee

[TrainCat2]

I prefer ludicrous speed

Do you prefer that now, now?

Actually, the one that amazes me on the prototype's I mentioned above is the approach to the Delair bridge:

http://maps.google.com/maps?q=Delair,+Pennsauken,+NJ&hl=en&ll=39.972062,-75.066463&spn=0.001198,0.002411&sll=37.0625,-95.677068&sspn=40.460237,79.013672&vpsrc=6&hnear=Delair,+Pennsauken,+Camden,+New+Jersey&t=h&z=19

Off topic a bit, but that is a nice compact batch plant. Just add online delivery of the raw material and you have a great lineside industry.

[MVW]

Thanks, all, for the responses. And Lee, thanks for the photos of your yard.

Lee, how about that S curve in the middle of your second photo, where you have a RH turnout (next to the tanks) followed on the diverging route with a LH turnout. Did you sneak a small straight section in there between turnouts? If so, what length? And is this area trouble-free for you?

And looking a bit deeper, just beyond that string of three hoppers, do you have a RH turnout immediately following the LH curve? Same questions: Is there a straight in there, and is it trouble-free?

Sorry for all the questions. I guess I'm one of those "measure twice, cut once" kinda guys. I hate re-doing work I could have gotten right the first time.

Thanks!

Jim

[wm3798]

Neither of the other two situations cause me any grief.  If you look at the first image, the big problem was probably more the kink  in the line more than the S.

[inkaneer]

Actually, the one that amazes me on the prototype's I mentioned above is the approach to the Delair bridge:

http://maps.google.com/maps?q=Delair,+Pennsauken,+NJ&hl=en&ll=39.972062,-75.066463&spn=0.001198,0.002411&sll=37.0625,-95.677068&sspn=40.460237,79.013672&vpsrc=6&hnear=Delair,+Pennsauken,+Camden,+New+Jersey&t=h&z=19


Those two switches are close enough together to have a car in each, particularly the trash flats they run out of Pavonia,

Phil

If you measure those switches you will find there is a distance of about 135-140 feet between their respective points.  That means that no one car will be in the "S".   What you want to avoid is having a car in the "S" where both ends of a car are moving in a direction other than the long axis of the car.   Also as stated before those switches are not as sharp as our #'s 4, 6, 8, or 10 so the diverging angle is not as great.