I’m mulling over a few ideas for a future layout. I’ll be running 89’ flat cars, superliners and long wheelbase 6-axle diesels. Will I get into trouble trying to use, let’s say 24"-26" radius curves for hidden tracks?
Also, if I use broader curves for the visible layout and crank it down to 24" radius in hidden parts, am I askng for problems? For example, if a track starts into a curve at 36" then as it enters a tunnel or viewblock is tightens to 24"…is that bad news?
Trying to cut down the radii of hidden curves can be asking for major trouble.
Even with the formual above, if you try to “cheat” in hidden areas that have little or no convenient reachablity is just asking for trouble.
Don’t forget in hiddedn areas you also have to allow for harmonic rocking and swaying of cars as well as overhang of the cars. The longer t he cars, the bigger the overhang on the smaller of the radii hidden. And that is assuming they will stay on the track in the tighter radii curves.
Most equipment lists a minimum required radius. So long as you have adequate clearance and meet or exceed the minimum, yes it will work and yes it can lead to problems though a 24" radius is more than we get from all the old sectional Atlas track. Best bet is to make up a test section and see if your rolling stock works correctly on it. It will look funny but it is hidden trackage right? And of course you do want to be sure you can access the area as well. Hope that helps. J.R.
Also remember that if double track’ any decreasing radius on those turn will need track spacing possibly greater than 2 1/2". If you push that radius down to even 26-28" you may need at least 2 3/4" centers. I would check this on a mock up before laying track. I think using 24" would be inviting nothing but trouble.
Tom, in a word, “yes”. If there’s anywhere that you have so-so trackwork, a hidden part of the layout is NOT the place to have it. Trying to cheat on track radius, as has already been posted, is just asking for trouble. Long passenger cars with body mounted couplers, long wheelbase locomotives, etc. are just a few examples. If they’ll derail anywhere, it’ll be where trackwork is a problem. 24" may be fine for most of your motive power/rolling stock, but some cars (I hear Walthers passenger cars tend to be quite unforgiving) will NOT “like” the tighter radius.
Murphy’s Law is rigidly enforced on all layouts and never more rigidly than in hidden trackage. Here is an actual photo of “the enforcer”: [}:)]
A case can be made that your broadest (and least derailment prone) curves and best laid track should be in hidden trackage. (Some guys who hand lay every visible inch of track , Code 83 or 70, on their layouts are happy to use prefab Code 100 flex in hidden trackage).
I have never tried this, and never seen it tried, but it would be interesting to accurately tally every time in an operating session someone has to nudge an engine, or put one wheel or an entire truck back on the rails, or hold a turnout point tightly so that an electrical connection can be completed, or “wrassle” with a stubborn coupler, such as nudging it so it can couple with a mate, or hold a finger down on a car so it won’t tip going through a sharp turnout. Tally it up and then think about how any of that would be done in hidden trackage.
Since an ounce of experiment trumps ten tons of opinion (including mine) here’s a quick way to determine what your minimum radius can be - on all track, not just hidden track.
Build a test spiral. Starting from a tangent, transition to a 36 inch radius, then reduce the radius two inches every thirteen (the length of your longest car.) Run your cars into it in several different configurations:
Separately. This will tell you where the trucks begin to bind and the wheels begin to strike parts of the underframe.
Coupled to cars of the same length. Now you know the radius where corners come together.
Coupled to cars of different length. Now you know where coupler side thrust starts doing terrible things. Worst case for you would probably be a humongubox coupled to an ore car. My worst case is a container flat (standard JNR design) coupled to the extremely short six wheel tender of a C56 class 2-6-0.
Having learned where things DON’T work, add two inches to establish the radius at which things can be expected to work. Note that this doesn’t include coupling and/or uncoupling. In hidden track, you should simply be running complete, unbroken trains.
Chuck (Modeling Central Japan in September, 1964 - with LOTS of hidden track)
Tom, in a word, “yes”. If there’s anywhere that you have so-so trackwork, a hidden part of the layout is NOT the place to have it. Trying to cheat on track radius, as has already been posted, is just asking for trouble. Long passenger cars with body mounted couplers, long wheelbase locomotives, etc. are just a few examples. If they’ll derail anywhere, it’ll be where trackwork is a problem. 24" may be fine for most of your motive power/rolling stock, but some cars (I hear Walthers passenger cars tend to be quite unforgiving) will NOT “like” the tighter radius.
Wishful thinkng I suppose, I have a 10’ x 20’ room, which seems pretty big, until you start filling it with 36" radius curves.
Interesting idea Chuck, thanks, you’re always helpful.
(I wish there was a place that you could rent Kato Unitrack from, take it home…hmmm, that didn’t work, go back and swap it for larger radius and try again.)
yes, a lot of plans for 8x4’s with a 18" radius. With a 36" radius you could compare your layout with a 5x10.; not really an empire.
BTW as long as you are just pulling those cars and use easements a 30 " radius would do fine. It is said by an other poster too, cars with different length’s combined in one train are a “PITA”.
Planning can be very tough, accepting the possibilities of your space might not be that easy. I’ve grown up with designing by squares. Your layout is about 3 squares wide and 6 squares long when using a 36" radius. Just nice for a very basic station length wise. If you would accept different cars from another era or / and focus on switching you could build a layout in need of a crew.
My Santa Fe in Oklahoma uses 36inch radius curves on visible and 36-38inch on hidden track. I am talking mainline and passing tracks along with staging tracks. Just because you can’t see the train on the hidden curve doesn’t mean you can cut down the radius, if you do, you are asking for trouble. In fact, I try to make my hidden curves a little wider for extra security.
My layout, which is mainly ATSF, UP, SP and Amtrak is in the house loft in the UK. Because of space limitations, I have had to use some 24 inch radius curves on the main line. Running six axle locos is not an issue but the full length Walthers passenger cars are.
To enable trouble-free running, where the 24 inch curve extends more than around 20 degrees, I have used Atlas fixed radius code 83 curved track and the baseboard must be absolutely flat. The Walthers cars, as you probably know, don’t have any torsional “give” between the trucks and uneven baseboard will cause derailments. This track has been successful and I run Superliners, Streamline cars, Heavyweights and Bi-Levels the latter in push-pull mode. Also, as noted by other guys, track centres need to be spaced accordingly.
The use of this small radius is not something I would do out of choice, however, “needs must”.
Chuck’s wise advice to build a test spiral (which I did for my own layout, using brass flex track that I got at nearly give-away prices at a swap meet) reminded me of yet another point that might save your plan: in John Armstrong’s Track Planning for Realistic Operation, he reports on an experiment that showed that passenger cars will derail or have problems when a tight radius meets a tangent, but those same cars can run on that very same tight radius IF there is a spiral easement curve between the tangent and the tight radius. His research was amusingly called “the co-efficient of lurch.” Worth reading and worth testing because while the end result takes up more space than the tight radius that doesn’t work, it is nonetheless still less space than the very broad radius that does work.
The 2011 Model Railroad Planning has an article on easement curves and presumably there is a calculator stil up on this website to go with that article although i have yet to find it! There are also NMRA templates out there.
Armstrong’s basic point is one which others have made – in our track planning and track laying, we do not take full advantage of what flex track or hand laid track can do for us and far too often we are still caught up in tinplate style thinking that our radius is a fixed curve and meets a fixed tangent.