train lengths

[fwright]

I wish I could memorize Joe's and Chuck's answers for the times I get asked to design an HO 4x8 layout to run 20 car trains - using 1980s to present equipment no less.  I've talked myself blue in the face trying to explain why a normal maximum train length of 56 actual inches (and often 20% less, depending on track configuration) is the best one can do and have functional (and reasonably realistic) operation.

The train length issue (IMHO) is the single best argument for ditching the 4x8 in favor of the added complexity of building an around-the-walls plan with its duck under or removable section in the average bedroom.  Or, find ways to be contented with the train length limitations of a 4x8.  Historically, locomotives, cars, and train lengths all grew as time went on.  The only real exception was the early diesel period (1930s to early 1950s) when car and train lengths were relatively stagnant, and the new diesel locomotives were actually shorter than their modern steam brethern.  Except for the early diesel period, the earlier the era you model the better it looks on the confines of a 4x8.

Iain Rice has written some useful rules of thumb on train length that I agree with.  For shelf layouts, he says longest train should be 1/4 to 1/3 of the shelf length.  He also states that once a train is longer than 13ft, the extra length is not perceived because you can no longer see both ends of the train at once from normal viewing distances.  View blocks can sometimes create the same effect with shorter trains.  And my rule of thumb addendum for table layouts is that both ends of the train cannot be on the turnback curves at the same time - but if you use the rules for passing, staging, or yard tracks you will be even more limited anyway.

my thoughts, your choices

Fred W

[johncolley]

This whole question is just one of the reasons I model the late '40's. Even though I run a 4 unit FT on the point, all my cars are 36-40 feet, so my trains appear to be longer just because there's more cars between the head end and the crummy! Beiber at one time had a 4 track yard at the south end of 4, 000 feet length ( for those mathematically challenged that's a 100 car train), nowadays they use the run around of 8,000 feet for a siding. The times, they are a changin'! jc5729

[markpierce]

Joe and Chuck both get a score of 100%, that is, their answers agree with mine.  Maybe if I wave Joe's and Chuck's responses in front of the faces of some modelers I know (who have not yet designed and built a well-functioning layout), they will now come around to our way of thinking before they make serious mistakes.  Thanks.

Mark

[jfugate]

My article on layout design analysis spends a lot of time discussing train length and the effects it has on layout design.

You can have trains longer than passing sidings and yard tracks and can deal with them, although they will slow things down a lot. But a train longer than a reverse loop will not work -- the laws of physics says two objects cannot occupy the same space at the same time -- so the front of your too-long-for-the-reverse-loop train will collide with the back of the train once it reaches the end of the loop!

With passing sidings, the key is opposing trains. As long as one of the two opposing trains will fit, the other train can be any length -- you can get the trains past each other with a bit of advance planning. But if both trains are too long for the siding, you'll need to do a double-sawby maneuver. Such a maneuver is fun once in a while but it would get old if it was standard operating procedure. This means passing siding length has a major impact on train length if you want opposing traffic to flow smoothly.

With visible yards on the layout, a too-long train can always "double the yard", which means you split the train in two and it takes *two* yard tracks. This practice is not uncommon on the prototype so it could be an acceptable operating procedure as long as you are aware that it will slow down yard operation somewhat.

Finally, too-short staging tracks can be a problem, since it will make you "double the yard" in staging as well. Requiring trains to do this in a visible yard on the layout is one thing, but requiring this in staging is going to get old, so my recommendation is *don't*. Staging track length has a major influence on train length.

My layout design formulas piece discusses these issues as well, and describes how to work the relationships on your layout design to get an optimum train length in all the design factors. There's nothing like finding out what will work and what won't work on your design *before* you build it!

[Dave-the-Train]

Since I'm in the process of finalizing a layout design, I've been thinking about the same things.

1. The length of the reversing section is an absolute limit for any train with metal wheels, even for DC.  However, there are ways to make the reversing section electrically longer than its actual length between rail gaps (I use MZL wiring, DC control, so electrical sections aren't totally cut and dried.)  In the case of a loop, the rear marker(s) have to cross into the reversing section before the locomotive leaves it, but the isolating gaps can be so close to the frog that sideswiping is a distinct possibility.
2. Arrival and departure tracks should be long enough to handle normal length trains.  An unusual movement might double in or double out, but that should not be considered the normal way of doing business.
3. Classification tracks need only be long enough to absorb the normal cut for the destination being assembled on the track.  Several tracks may be pulled so that an outbound train can be assembled, properly blocked, on a departure track.  On the other hand, yard leads should be as long as possible, preferably long enought to handle a complete train - especially hump yard leads.
4. Mainline sidings should be long enough to handle a normal train.  A longer train can meet or pass if the shorter train can get completely into the clear.  Double sawbyes are interesting for the two train crews involved, while the rest of the operating staff goes to lunch.
5. Unmentioned in the original question, but absoluely critical: No trainshould be too long to get completely into the clear on an off-scene staging track.  This may require close attention to which train is being sent to which track.

Just my opinions, formed over several decades of trying to operate like a railroad.  In my case, train length matches that of my prototype (and is actually quite short.)  The physical plant is being sized to the trains, not vice versa.

Chuck

So well put it's worth repeating.

Wish I could be that concise Chuck!

[tomikawaTT]

Since I'm in the process of finalizing a layout design, I've been thinking about the same things.

1. The length of the reversing section is an absolute limit for any train with metal wheels, even for DC.  However, there are ways to make the reversing section electrically longer than its actual length between rail gaps (I use MZL wiring, DC control, so electrical sections aren't totally cut and dried.)  In the case of a loop, the rear marker(s) have to cross into the reversing section before the locomotive leaves it, but the isolating gaps can be so close to the frog that sideswiping is a distinct possibility.
2. Arrival and departure tracks should be long enough to handle normal length trains.  An unusual movement might double in or double out, but that should not be considered the normal way of doing business.
3. Classification tracks need only be long enough to absorb the normal cut for the destination being assembled on the track.  Several tracks may be pulled so that an outbound train can be assembled, properly blocked, on a departure track.  On the other hand, yard leads should be as long as possible, preferably long enought to handle a complete train - especially hump yard leads.
4. Mainline sidings should be long enough to handle a normal train.  A longer train can meet or pass if the shorter train can get completely into the clear.  Double sawbyes are interesting for the two train crews involved, while the rest of the operating staff goes to lunch.
5. Unmentioned in the original question, but absoluely critical: No train should be too long to get completely into the clear on an off-scene staging track.  This may require close attention to which train is being sent to which track.

Just my opinions, formed over several decades of trying to operate like a railroad.  In my case, train length matches that of my prototype (and is actually quite short.)  The physical plant is being sized to the trains, not vice versa.

Chuck

[Virginian]

I am at a loss.  How can any of the factors listed NOT have a direct impact on the maximum length of trains run, UNLESS items 2, 3, and 4 are just there for looks and you do not intend to use them.  The trains cannot be longer than the reverse loop, if you intend to run them thru said loop.

[markpierce]

I've had disagreements with associates about the effect of certain track lengths upon train lengths.  I'm not concerned about track grades, track radii, locomotive type or weight, etc.  The following are the factors that concern me, presuming the modeled cars include metal wheels and trucks, metal floors, lighted cars, and end-of-train helper locomotives:

   1.  The length of the reverse loop (electrically).

   2.  Yard arrival and departure tracks.

   3.  Yard classification tracks.

   4.  Passing sidings along the mainline.

Please tell me the effects the above factors have on train length, and why, and how the above limitations can be overcome.  I have my own opinion, but that doesn't mean I'm  correct or that my opinion is accepted by other modelers.  I'd appreciate your comments.  Maybe you can convince my doubters, or not.

Mark Pierce