I see a lot of posts for yard design here so hopefully this is the right forum to ask this newbie question.
Is the max length of any train dictated by the length of the A/D track? Or is it possible to pull through the A/D track, uncouple half of the train, move the cars with a switcher, then back the rest of the train into the A/D? Does this scenario exist in prototype? I guess the same question applies to putting a consist together in the yard. Would there be separate parts of the total train on different tracks due to yard length?
If you have a Arrival track with room for example… 2 engines, 15 cars and a caboose.
A train arrives holding 25 cars plus caboose.
You need to have a switcher drill track at least as long as your arrival/departure track and enjoy direct access to this track.
Back to that train. You already know you will fill this one track and need to double up onto another yard track.
If you find yourself with a yard more than 70% full after arriving, you are approaching meltdown with being able to process the cars and build new trains.
Yards do one thing. Build trains and get it OUT of there ASAP. Yards like to be empty as possible to keep the system moving.
It is possible, but it slows down operations, so if done, it would usually be best to do it not every train or many trains.
Your track arrangements will need to allow a locomotive to have access to at least one end of the train so that it can switch the excess cars onto another yard track. (Don’t trap your switcher on the switching lead or locomotive pocket by the long train unless the road engine has room at the other end to switch the cars.)
It was very common in older and smaller yards for the tracks to be shorter than the length of a train. A train would have to “double” (or triple) in or out of the yard. Normally the train did it without the yard engine helping. They would pull through and open track untill the caboose/last car cleared in the track and then start putting the part that hung out on the other iend in as many tracks as it takes to clear up. Going outbound the train would be built in several tracks and the crew would couple into a track, pull it out, couple into the next track, pull it out and couple into the next track, and so on, until the train was together. the last track had the caboose on it.
Just from observing the UP railyard near where I live (obviously this isn’t a model), the a/d tracks are long enough for all but the longest trains. Every once in a while you’ll see one that won’t quite fit. The switching lead is only half as long as these though and that’s fine. One thing that I have seen them do on the longest departing trains is to have as much of the train that will fit on the a/d track waiting. The rest of the train is sitting waiting on one of the sidings. Keep in mind this takes up usable space but depending on how long your classification tracks are you may be able to keep these last few cars towards the front of the siding with other cars for later trains still on the same siding behind them.
When these longest trains depart, the road engines grab the cars from the classification siding themselves. They pull onto the switching lead and then back onto the rest of the train on the a/d track. When trains this long arive, they pull as far as they can and then detach the engines to get them out of the way. The switchers immediately grab the first cars that can’t fit within the a/d tracks and get them out of the way. I’m not sure if they just go ahead and switch them to where they need to be or not.
It can be done. You just need to plan accordingly. You also need to have a yard setup that can physically handle it.
Double overs are a fact of life on the prototype, so why not on the model? Yes it does slow things down, but in some operations, that is exactly the point. It does affect yard fluidity, and that isn’t good, but it is a small price to pay. Most prototypes insist that yardmasters give absolute priority to the arrival and departure of trains. A drill track is not required, as double overs using the main track as a drill have been done for years, with the inbound or outbound road power being used.
Since you have prototype operating experience, maybe you could clear up a question for me: What is a “drill track?” I see this term used in what seems like several different situations and don’t know when it is appropriate. Maybe you could tell me how your prototype used the term.
“Drilling” was the back and forth process of switching cars, a term used mostly by eastern and southern roads. On the SP we called them tail tracks. So a “drill” track was a track, many times stub ended, but not always where a switch engine could work without fouling a main track or other switching leads. The railroad would try to make the track as long as the longest track to be worked, although that was frequently impossible. Where switchers used a main track, there might be a tail track or drill, but more often than not, the railroad didn’t see the need.
‘Drill Track’ and ‘Yard Lead’ are basically the same thing. Just different local terms. The Milwaukee Road yard in South Minneapolis was known as the ‘Garden’ yard, and when switching it, crews would talk about ‘weeding the garden’.
Correct. The definitions are many and complex and are influenced by railroad and even local location on the same railroad. For example at SP’s Taylor Yard the outbound engine lead became the “20 lead” and was double ended whereas in Oakland, The Homestead Lead wound up eventually being dead ended as a tail track. Clear as mud??
Many of my mainline trains have to double the yard.
At one track are the engines with one block of cars. When departure time comes they go to the main and back to the other A/D track and couple to the rest of the train with caboose.
Analog is the mathod for the arrival.
You see from the left: layover track (with the diamond), main, three A/D tracks, class tracks and run around track.
The GBW had 3 A/D tracks that were used to for assembling trains. They had pipes going to each of the A/D tracks so they could “air-up” before the road power hooked up and assembled the train.
Another scenario… have a switcher waiting on the ladder, cut off part of the train clear of the ladder for the switcher to take into any available class track. Meanwhile, the rest of the train pulls all the way onto the A/D to where the lead car is near, but short of, the fouling point. The road engines can then cut off and go to service. jc5729 John Colley, Port Townsend, WA
The unfortunate result of doubling on some layouts is that the front of the train has entered the next town before having to back up to collect the rest of the train. [sigh]
While that’s certainly possible, its very unlikely for a real railroad to do that. Too much chance that if you make the wrong cut and any one of the pieces is longer than the track its going into it will frog the road power or the switch engine in where they can’t get the rest of the train in the clear.
