Locomotive Length and Curve Radii

Discussion in 'Track Planning' started by Christopher62, Jan 18, 2007.

  1. Christopher62

    Christopher62 Member

    My most recent discouraging discovery as I attempt to rediscover model railroading after a 30-year hiatus is that certain long locomotives will not be able to negotiate a tight curve on an HO scale track. Can someone give me the specifics on this? Thanks all!
  2. TruckLover

    TruckLover Mack CH613 & 53' Trailer

    Most of us run 22" radius or greater but it depends on how big of engines you want?

    Running Steam or Diesel? What is the biggest locos you will be running?
  3. Christopher62

    Christopher62 Member

    Thanks Josh for the speedy response. I know I want to run diesel. And I would like to run the more modern prototype models. I just received a new catalog from Athearn and some of the "cooler" (for lack of a better word) looking engines seem to be extra-long. I want to model the Atlas Yardmaster layout (8x4) but now I'm concerned about length vs. curve radii.
  4. railohio

    railohio Active Member

    For the modern six axle power you'll want at least a 22-24" radius curve. The larger, the better.
  5. Russ Bellinis

    Russ Bellinis Active Member

    Do you have room for a 5 x 10 (ping-pong table size)? If you do, you could take any 4 x 8 plan and increase your curve radius to operate longer equipment. the problem with 4 x 8 is that a 22 inch radius gives you a 44 inch circle. That only leaves 1 1/2 inches to the edge ot the table on both sides, and severely limits what youcould add inside of the oval.
  6. 60103

    60103 Pooh Bah

    There's no fixed answer for this because all the model manufacturers take different liberties with the mechanism. A brass model might take a 36" curve while a cheap train set version might be missing a lot of underframe detail and make it around 18". (Remember that for years Lionel manged to get its trains around a 15" radius and many around a 13". In O gauge.)
  7. Christopher62

    Christopher62 Member

    Thanks guys. This is all pretty much as I expected. Yes, I have the room to go larger, but being my first serious attempt at a model railroad I am worried about biting off more than I can chew. That's why I want to stick with the basic, standard 8x4 layout. At least I know to keep all this in mind when it comes time to buy the locomotives.
  8. Russ Bellinis

    Russ Bellinis Active Member

    If you can go with the 5 x 10 suggested earlier, you can get a max of 26-28 inches for a return curve and use the any 4 x 8 track plan stretched slightly to accomodate things. The difference is the cost of a second sheet of plywood and a little cutting and fitting. I would not go any bigger than 6 feet wide on an island type layout with access all the way around because you will have trouble reaching the middle.
  9. Christopher62

    Christopher62 Member

    Thanks again for the input. Say, what's the final verdict on layout height? The consensus seems to be 40".
  10. Russ Bellinis

    Russ Bellinis Active Member

    The higher the layout, the better the view, since modelers like to see their model trains from a trackside view; but the downside is that you can reach farther with a waist height layout than a shoulder height layout. Other things to consider is your height, do you have children who would want to look at the layout or help operate, is your wife intterested in the layout if married and how tall is she? I'm 6 feet tall, the modular club I belong to specifies a 40 inch rail height from the floor. I find that is too low for me to operate comfortably, and I would prefer 48-56 inches. On the other hand when we display our trains, people with small children either have to lift their children up to view the trains or provide them with step stools to get up high enough to view the trains.
  11. MasonJar

    MasonJar It's not rocket surgery


    The "standard basic 4x8" can be a bit of a misconception... especially as a small and/or beginner layout. It's all related to size...!

    The room size

    If you want access to all sides in order to be able to reach everything, you need a room of at least 8x12. That's a small bedroom or home office space. Think about the room you are going to put it in, and decide if it would be better to put a shelf type layout in the room.

    The layout size

    The square footage of the layout is the other aspect of the size question. A 4x8 is 32 square feet, while a 2 foot wide shelf around the same 8x12 room gives you 64 square feet of modelling space. It also allows for wider curves, and more linear features than the typical oval.

    The cost "size"

    Estimates for a finished railroad, not including the engines and rolling stock are often quoted as anything from $10 to $100 per square foot. Of course the sky is really the limit, but let's assume you balance RTR structures and commercial landscaping materials with some DIY and scavanged /repurposed materials. Even at $20 per square foot, you are looking at over $600, plus whatever control system, locomotive(s) and rolling stock you want. To say nothing of the books, collectibles, pictures, club memberships and so on that are often part of the hobby.

    So depending on your resources (time, space, money), perhaps the 4x8 is not a beginner layout after all...

    It certainly does offer many advantages though - and one of the more famous model railroads - The Gorre and Dephetid - was a 4x8 that grew (and grew, and grew...).

    If your plans include the around the walls in a bigger room, I suggest that you simply start on a small (maybe even only 2x6) part of it. You will be forgoing continuous running - which for some is an overriding concern.

    But having been down the road of a "failed" 4x8, I do not miss continuous running at all, and I am happy now with my modular approach, where things are built 2x4 feet at a time. That way, something I learn can immediately be incorporated into the next module, not the next layout.

    I hope this perspective is useful. It is after all, only my $0.02 :) If after this "editorial", you still are convinced of that a 4x8 is for you, check out www.gatewaynmra.org. They do fabulous things with 4x8's (and smaller).

  12. Christopher62

    Christopher62 Member

    Good advice as always guys. Russ, I'm 5-10, no kids as of yet, and my wife is not coming anywhere near my trains! When I get home I'm going to get out the tape measure and experiment around with various heights. I have a ping-pong table so I can use the as a guide I guess. I like the idea of not having to stoop or bend over to access the layout, but then again at the end of the day I want to be able to sit down comfortably and drink a beer and watch my trains go 'round.

    Andrew, space is not a concern. You've certainly given me something to consider with the island vs. shelf layout.
  13. Russ Bellinis

    Russ Bellinis Active Member

    I too like the shelf layout concept, but didn't want to suggest it if you had your mind made up to do an island. To me the beauty of the shelf is that the train seems to go someplace instead of around in circles. With a shelf, you can build at shoulder height and still reach the back of a 24 - 30 inch shelf (my arm length is 35 inches). Going around a room, you will have enough linear feet to put in some elevation changes. If there is only one door in the room, you could make it in the middle of a mountain and actually run the train over the top of the door to eliminate any duck unders. You can start with a switching layouton a 6 foot long shelf, and when it is done, add another as Andrew suggested, and when you are done, it will run all the way around the room. Then you can kick back and watch trains run with your beer if you want to.
  14. jetrock

    jetrock Member

    The problem with the "standard basic" 4x8 layout is that it dates to a time when the "standard basic" model railroad car was either a 40 foot boxcar or a 60 foot "shorty" passenger car, diesel locomotives tended to be shortish B-B locos or relatively small steam, and model companies were more concerned with getting their equipment to run on sharp curves than a realistic appearance. Today, the modern modeler has 80' auto-rack cars and multi-unit container car carriers that are built to very accurate standards, which often mean that the 22" radius one can fit onto a 4x8 simply isn't enough. Big diesel locos with six-wheel trucks are a little more forgiving but they don't tolerate sharp track either.

    So, really, if you can't go a foot beyond a 4x8 then you're going to be limited to smaller or older equipment. Expanding from a 4x8 to a 5x9 isn't a much bigger amount of space (one foot longer and one foot wider) but you can fit up to a 28" curve if you must have a loop, and they don't dominate a room much more than a 4x8. (Of course, the "simple, basic 4x8" can dominate a room all by itself, but that's another story.)
  15. Christopher62

    Christopher62 Member

    Thanks Jet. That all makes perfect sense. I guess I could manage a 5x9. And when I say manage I don't mean space-wise - I am fine there, I mean manage as in what I want to tackle as my first serious foray into a model railroad. Well, looks like I will be doing more research over the weekend.
  16. Triplex

    Triplex Active Member

    The point is, even a 5x9 will offer much less advantage than an around-the-walls layout, with one caveat. In rooms around 100 square feet, to take full advantage of the around-the-walls space, you need a duckunder, lift-out or swinging gate.
    This is only really practical in a large room, since trains can't climb steep grades.
    I heard $1 (US) per square inch, several years ago.
  17. pgandw

    pgandw Active Member

    Take a look at http://www.layoutdesignservice.com/lds/samples/betterbeginnerlayout.htm. This is an improved "first real layout", and is not that much more difficult to build than an island layout.

    4x8s (or even 5x9) in HO scale are in fact quite small layouts - they have a number of limitations that have to be respected to have a successful layout in that space. I define a layout as successful when the owner is happy enough with it after the track is laid and the wiring done to continue to operate it and scenic and detail it.

    Biggest limitation is that very little that is more than 60ft scale long will operate happily around the 18"-22" curves found on a 4x8. Even the Walters 80ft heavyweight passenger cars require 24" minimum radius, and there have been reports of individual cars that couldn't manage that. For reliable operation with body-mounted couplers, minimum radius has to be 2.5 times the length of the longest car. Using a 2X multiplier is possible, but generally requires truck-mounted couplers on the long cars and simplified underbody detail.

    But as time has progressed, prototype railroad equipment has gotten larger and larger. 60ft to 89 ft long cars are commonplace in modern railroading.

    The other severe limitation on an island layout is train length. It is very difficult to get a passing siding more than 56" long on an 8ft board with 180 degree curves at the ends. That 's a train of 7 40ft cars, caboose, and short engine. In most track plans, you are going to be at least one car less. And if you modern longer cars, trains are going to have even fewer cars.

    If you look carefully, virtually all the 4x8 project railroads in Model Railroader use 1950s or earlier rolling stock and switching engines.

    my thoughts, your choices
  18. Christopher62

    Christopher62 Member

    Thanks for the input guys. Very thorough stuff. Though as I previously mentioned, this is my first foray into the hobby (as an adult that is) so I don't think I'll be going around the room (which is the entire basement) or up and over any doorways... That's a bit too much. Most likely I will attempt one of the pre-designed Atlas layout plans on a modest 8x4 or 5x9 table, just to see how it turns out. I realize I will have to forego the long locomotives, train length and sweeping curves... Nonetheless, if I can get the track laid and figure out the wiring, get some trains running, try my hand at scenery and detailing, etc... I can always expand later. Additionally, I am planning a move within the next year or two, so that figures into the equation - not wanting to start a project that I can't finish, or build something so large as to be too unwieldy to disassemble and move.

    As always, thanks for the advice and keep the suggestions coming!
  19. jetrock

    jetrock Member

    It helps to think of a layout in terms of square feet. A 4x8 layout is 32 square feet. A 5x9 layout is 45 square feet. I have the beginnings of an "around the room" layout, the room is 25x11 square feet, and right now it's a shelf layout that, once I finish this next module, will be around 30 square feet, as a series of modules built 4-8 square feet at a time. Truth be told, in terms of the amount of room dominated by a layout, a shelf layout can be a lot more modest than a 4x8.

    Very often these days, an "around the room" layout refers to "around the spare bedroom," an area of maybe 10x10 feet, not an "around the entire basement" house-spanning empire. Going up and over doors, as mentioned above, isn't really practical, but a bridge across the door isn't that much of an engineering project. So we aren't suggesting that you build all the way around your basement--more like a larger rectangle around part of the basement.

    If you're moving, definitely look into modular/sectional construction. I moved last year, and since my layout was built as a series of shelves I simply disconnected the wiring and lifted the modules into the back of my station wagon. I built simple shelving units to set the modules onto, which took a weekend to build in my old garage and a weekend to rebuild in my new basement, but if you don't want to leave screw holes you can set shelf layout modules on top of short bookcases or storage shelves.

    One other factor to consider is that all of those "pre-designed" Atlas layouts were pre-designed back in the 1950s, once again, when smaller locomotives and 40-foot boxcars were the rule. None of them were designed with modern equipment in mind. So a pre-designed Atlas 4x8 with modern Atlas diesel locomotives and modern cars will not be a very good fit. Modern equipment sometimes requires modern layout design--which often means going beyond the "basic 4x8" and into the world of the "basic shelf layout."
  20. Christopher62

    Christopher62 Member

    Thanks Jet. More grist for the mill. I will take all this under advisement.

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