Ok, I’ve heard/read it said a million times, “avoid S-Turns in your layout”, but I’ve never heard/read why that is…
Why are S-turns Bad? Is it something to do with pulling line and center of gravity?
How short does a S-Turn have to be to be troublesome?
Are Long, Snaky S-Turns okay?
Thanks,
Trevor[:)]
The biggest problem is that with an S-curve, one car will be moving left and the other right. This causes the greatest coupler offset, and if the couplers can’t swing far enough, pulls the cars right off the track.
A very large radius S curve, one that would be more for appearance than an actual curve to get around something, unless you are building in a hanger and can use giant radius curves everywhere, is usually ok. Or make sure there is a straight section in the middle that is at least as long as your longest car.
–Randy
Passenger cars are especially bad in S-curves, because of the long overhang past the truck pivot.
You also need to watch turnouts causing S-curves. If you have two parallel mainlines for example, you should use No.6 or larger switches to avoid a bad S-curve (although if you only run short equipment you might squeak by using No. 5’s.
Plus sharp S-curves just don’t look good, they have a ‘toy train’ look to them. As Randy suggests above, adding a straight section between the curves will operate better and as a bonus look better !!
Another danger of S curves is if the curves are on a grade and with the train going in slightly different directions the pull is to the center line of the track, and it will pull the train off of the tracks. If you are thinking of an S curve my advice would be to make sure you are not over 1 and a half to 2% grade, make the raduis large (around 30" or more), have transitions in the curves with a relatively straight section in the middle. This will look better(much like mountainous track snaking along a river) and will prevent most operating problems.
good luck
Randy Johnson
Get a copy of John Armstrong’s book, “Track Planning for Realistic Operation”. He covers all the types of s curves that can creep into your trackplan as well as how to avoid or minimize them.
Enjoy
Paul
If I have separations (uncoupling) or derailmants, it is almost always at a grade-top transition, at a turnout, or on my one s-curve. I wanted one on my mine spur grade, and the 0-6-0 has no problem with that. But, if I take my Hudson up there for a lark, it is hit and miss.
I agree that s-curves can be eye-catching, and add visual appeal. Later, though, they are just a pain. If I ever redo any track on my layout, that one curve will get ripped out for sure.
I have a 20" radius “s” curve and i don’t have any problems with it.
I read somewhere that if the need for a “S” turn is not avoidable, that you should put a piece of straight track inbetween the two curves the length of your longest car, in my case an 85’ passenger car.
I have done this with no problems.
Gordon
I have an “S” curve with 30" rad and a 4" straight between them and have had no trouble.