So my layout, out of necessity, has two helixes, one at each end of the Highland Line. Eastbound is Hartford, and westbound is Holyoke/Westfield, the New Hartford branch, Waterbury, and Maybrook, depending on the train. These are about 2% on a 28" radius curve. The other grade on the layout is on the Berlin Line, also a 2% on a 28" radius curve.
Passenger Train LengthThe longest passenger train is 5 or maybe 6 cars. Presently, only one of those cars is brass. Most of the trains are 3 or 4 cars. The short trains can be handled by any of the motive power called to do so - Atlas RS-1, Athearn RS-3, Crown Custom I-2. The longer train, 131/136, receives power from Boston, which means either a DL-109 (Life-Like/Walthers or brass), or the BLI I-4. So that's not a problem. Other passenger service, depending on the era, is either the Comet or RDCs. So passenger service is no issue at all regarding the helixes.
Freight Train LengthFreight, on the other hand, is a different story - at least in one case. The major issue here is motive power, and the main limitation is steam.
Cedar Hill-Holyoke Freights (NY/YN)The Holyoke freights won't be an issue. They come into Whiting Street yard on level track. They could leave a dozen or more cars at Whiting Street before hitting the 2% grade to New Britain (on a curve). Even the J-1 seems to be able to handle 15+ cars on that track, although it will primarily be handled by an S-2, RS-2, or RS-3, and the RS units often ran two or three at a time. The H-16-44s could also be on this run. So these trains could be 30+ cars westbound.
Eastbound, they are limited by whatever the motive power can pull up the helix. But we can add as much new tonnage, probably 12-15+ cars in New Britain, because it's downhill to staging. So they could still be 30-car trains leaving the layout.
Because of staging limitations on the Berlin line, the only way I'll be able to do that is to have the through train crew member actively splitting the train as it enters staging, then removing cars to make room for a later train. Something we might do from time-to-time with the right crew.
New Hartford Local (HDX-5)Of course, the New Hartford local, with either a K-1-d or an S-1, will be much shorter. I'm not sure the K-1-d will handle more than 8 cars up the helix, perhaps less. I'll need to get as much weight into it as possible. The Atlas S-1 can handle at least a dozen cars.
Maybrook Freights (OA/AO)The Maybrook freights, on the other hand, could potentially be very long...or not. Starting in '47 these were hauled by an FA-1/FB-1/FA-1 set. The Life-Like Proto 2000 locomotives are great haulers, and starting in '51 I could even add an FB-2 to the consist. But the brass L-1s on the other hand, won't be able to handle as much tonnage.
The good news is, that by the time they get to New Britain, all they have left is New Britain and Hartford cars. But that could still be 12-15+ cars for New Britain, plus that many or more for Hartford. One reason I'd like to be able to have a sizable cut for Hartford is the ability to have a decent string of reefers on the front with an equal or greater size cut of general freight. So maybe 8 reefers plus 10-12 cars, plus another 12-15 for New Britain. So I'll be able to do a 30-40 car train here with the ABA sets.
The westbound has only empties and loads coming from Hartford. This works out well, because I can max out the train coming up the helix, and add on the outbound from New Britain to go down the helix, just like the Holyoke freights.
OptionsThe point is, even on a layout as small as mine, it is possible to potentially run some very long trains. If I do get to run 30-40 car through freights, it will look "right" because most of the area they are running through is 70%+ to scale. The reality is, in this era it was still possible to see 100+ car trains heading to Maybrook.
Even if I can't run trains that long, we can simulate them anyway. We most likely won't be running the overnight trains (often two Maybrook, one Holyoke, and even a Bridgeport to Hartford train). Instead, long cuts of cars will be waiting for the crew when they arrive at work, just like the prototype. We can extend that approach by leaving the long cuts for the evening/overnight freights when the crew goes home, instead of running those trains. This would be easier for the YN freights to Cedar Hill due to insufficient staging.
In the meantime, as we're prepping the layout it sounds like a good job for Joseph - test 30-40 car trains and see how the layout handles it.