View Full Version : Train Length Questions

26th Mar 2007, 09:43 AM

I have a 7 1/2 foot long layout; on the flat section my Atlas 4-axle RS1 can pull a train as long as the entire layout. I'd never run one that long normally, and that locomotive can't pull that many cars up any incline at all. My 4-axle Intermountain F3 is quite heavy and can pull up my 3% grades. The A/B lash-up has an easier go of it, but I don't know if it could pull 2x that many - the layout's not big enough and I don't have that may cars (yet :? )

My rolling stock is a mix of Micro-Trains and Atlas. The MT cars seem to have a bit less rolling resistance.

26th Mar 2007, 11:54 AM
Train length can also be determined by the size of your layout, that is the length of your main line. For example, I have a main line run of 185" on a shelf style layout. so I limit my trains to 10% of the main or 18"

26th Mar 2007, 03:13 PM

I have to disagree with you about 'train lengths being determined by the length of the main line'.

Not so, though this may NOT be North American practice.

Within the British Commonwealth, train lengths are determined by the length of the Crossing Loops (Passing Sidings) at designated locations.

For simplicity, herewith a definition of a Crossing Loop: 'A crossing loop is a place on a single line railway where trains in opposing directions can "cross" each other. Trains in the same direction can also overtake.The crossing loop connects to the main track at both ends of the station, though a dead end siding, which is much less convenient, can be used. Ideally, the loop should be longer than all trains needing to cross at that station'

The 'Loops are the determing factor in train lengths because they hold any trains that need to go past each other and frequently a train that goes into a loop has to be held until the other train it is crossing, (passing) arrives.

Obviously, if a train is in a loop, it should be 'inside' the loop itself, (and any signals which are protecting it), and clear of the points that control access to said Loop from the Main line, because if the occupying train's 'tail' is still hanging out on the 'Main, nothing can get past from either direction.

(There are ways to get around the 'hanging-out ' aspect, which I won't go into here, because they tend to be one-off situations)

Therefore. because of the need to fit any train that is in a loop safely inside the loop tracks and NOT leave it obstructing the 'Main, train lengths are modified accordingly.

On the basis of all the above, as you can see, unless the RR mangement directs otherwise as a result of specific circumstances, the length of a train that will occupy a Crossing Loop (usually the smallest one on the line) determines the lengths of ALL trains that are running on that particular line of railway.

"TVR - serving the Northern Taranaki . . . "

26th Mar 2007, 08:33 PM

I have to disagree with you about 'train lengths being determined by the length of the main line'.

I believe he was referring to the length of the layouts mainline, not an actual mainline.


26th Mar 2007, 09:32 PM
I agree completely - and stand by what I wrote. :D

It isn't the length of the Main Line which determines train size, irrespective of whether or not it is in N-scale, HO or full-size - the determining factor is the length of the Crossing Loop, for the reasons I gave.

As an example: Putting a 15-wagon train into a loop that only holds a maximum of 10 wagons leaves 5 wagons still out on the Main line, and as long as the 5 wagons are still out on the 'main, blocking it, no-one is going anywhere.

If there is a train sitting on the main line trying to get past the train in the loop at the same time, nothing is going to be able to move until the offending 5 wagons are somehow removed.

With 10 wagons on a 10-wagon capacity loop, everthing works well, nothing is blocking the 'main, and the train that is on that line can get past and proceed on its way.

As I said, crossing loop (or passing siding) capacity determines train length - even in N-scale. :lol: :lol: :lol:

"TVR - serving the Northern Taranaki . . . "

26th Mar 2007, 09:44 PM
Ahh Hah! you are correct! Having reread your post and explanation, that makes perfect sense! So... in reference to the original question... do what Komata said! :lol:


26th Mar 2007, 10:46 PM
As an example: Putting a 15-wagon train into a loop that only holds a maximum of 10 wagons leaves 5 wagons still out on the Main line, and as long as the 5 wagons are still out on the 'main, blocking it, no-one is going anywhere.

Not true in the least :lol:
This has always been a problem, and is becoming more of a problem now that train lengths are getting much longer. Without going into a long post with lots of detail, i'll say that it happened on the CN Bedford Sub not a month ago, where two trains had to meet, both were in excess of 8000 feet, and the closest siding long enough was about 40 miles west of where the trains were. They ended up meeting on a 5500' siding. The eastbound (Q149) got there first, dropped the last 4500 feet off beyond the west end of the siding, and pulled in to the clear, leaving his conductor on the cut of cars. The westbound (M307) showed up, leaving the last 3000 feet of his train beyond the east end of the siding. He pulled through the siding and coupled up to Q149's dropped cars, and shoved them to the next siding up the line. Q149 pulled through, coupled to M307's cars, pulled them back into the siding he was just in, then backed further up the line to couple to the rear of his train, which was in the siding. Q149 picked up the rear of his train and proceeded east into Halifax. M307 then backed up into the siding to get the rear of their train, and proceeded westbound. This is a VERY long process, though, with lots of walking on the part of the conductor. It's avoided if at all possible, but it does happen.


26th Mar 2007, 11:33 PM

Thanks for your follow-up on my very simple example.

You may have notice that I had commented in my inital post 'though this may NOT be North American practice. ' - this was very delibrately done because North American RR practices can tend to be somewhat different to those in the rest of the world - and your posting certainly confirms that this is the case.

The idea of propelling trains and doing what you desribed is amazing - and, for all sorts of reason associated with terrain and safety, highly unlikely to occur on most of the world's railways.

For what it is worth, NZ's solution to larger trains has been to build longer crossing loops and space them further apart, adjusting train lengths accordingly - the situation you have described would simply never occur out here - our systems aren't arranged that way, largely due to our terrain, and as a result of local practice being tailored to our our circumstances.

Thanks though for sharing it with us - its interesting to see what others do.

"TVR - serving the Northern Taranaki . . ."

29th Mar 2007, 12:24 AM

How many 40ft freight cars on a flat stretch can a single engine atlas
RS3 pull?
or an S2?
or an U23B?

Generally, you can estimate 10-50 cars, with 15-25 being the norm for most road engines. Even different locos of the same make, model and run will vary from one another by a couple of cars. Not having any RS3s, S2, or U23s (blech), I can't speak for any of those specifically. I do want to add some RS units to my roster though. Just like the looks of 'em.

How does a MU lash-up work? 2x length?
Generally not actually double. Unless the engines are exactly speed matched, you won't get double. Figure to add 90% of each engine's capacity for a close match. Poor speed matches give lousy additives because the faster engine is dumping a lot of work into pushing/dragging the slower engine along. When you get an opportunity to test this, try using a single PA or E series loco to pull even a little switcher. Basically, if its a good day, all its going to do is drag the poor thing without even turning the lit'l guy's wheels. On a bad day, the only thing moving will be the big locos wheels as it spins in place. That's the dynamic of poor speed matching.

How long is 3 40ft cars coupled together?
10" using MT couplers. A MT 40' boxcar is 3 3/8" tip to toe. Couple three together would give you 9 9/8", i.e. 10 1/8", but there is overlap between the couplings, so I just knocked an 1/8" off. Cars equipped with Rapidos would probably add 1/4" to the length of three cars.

No surprise, I'm a newbie working from magazines and dreams.
Tom Magazines and dreams are good places to start from.