I like to make my curves have curvature transition easements. When using sectional track (rather than flex track), I start the curves with a section of larger radius than I will use for the bulk of the curve. For instance, with Kato Unitrak curves of 13.57" or 15" radius, I will put a 15° section of 19" radius track on each end to get a similar effect. It helps operations, and looks bit better, too. I am trying to lay out a track arrangement that needs 3 concentric curves and still use 13.75" as my minimum radius. Unfortunately, Kato does not make 16.375" radius single track sections, so I am having some trouble making the outer curve. Kato does make super-elevated, double track curves with 16.375" outer radius and 15" inner radius, so I could make the 2 outer curves with those, and the inner curve with standard 13.75" radius single track. The ties won't match, but I have paint pens to fix that. But, I am not sure that I can do the same thing for curvature easements with the super-elevated track that I do with Kato flat track. Kato super-elevated track needs, and Kato provides, vertical easement sections, but, those sections do not appear to also have any easement for the horizontal curvature. So, I want to use Kato "easement sections" for their 18.875" / 17.625" super-elevated curves on my 16.375" / 15" super-elevated curves to get a curvature easement effect. But, I do not know if they use the same amount of super-elevation on all of their super-elevated curves, no matter what radii those curves have. If so, I can use the easements for one radius to mate with a different radius to get my desired curvature easement effect. But, if, like the real railroads, the amount of super-elevation is different for different curvature, then Kato's easements for one radius will not properly mate with the super-elevated curves for a different radius. (In that case, I am going to have to "fudge" the 16.375" radius curve with various sections of 15" and 19" radius flat track.) So, my question to the group is: Does anybody know whether Kato super-elevation easement sections for 18.875"/ 17.625" curves will properly mate with their sections of 16.375" / 15" super-elevated curves? I also am asking if anybody has had problems with using the super-elevated track that Kato makes. One review (on the website for a well-know Baltimore hobby store) said that locomotives tend to stall on the super-elevated curves, and blamed that on the super-elevation.
I just tried it and the sections mated perfectly. A test car ran smoothly over the joint. As far as blaming stalling locomotives on superelevation, I've never had that problem, and quite honestly that sounds silly.
How vital is it that the three tracks appear perfectly concentric? If the visual effect is not so important, you could use short straight sections from the Kato assortment packs (20-091 or 20-092) to space another track with the 19"/15" radius curve combination outside the middle one.
Sounds silly to me too. If the curves were super elevated enough for the wheels on one side to try to lift off the rail and lose contact at slow speeds, then... ...it would look more like Darlington Speedway than a railroad.
Thanks for the replies. I did make a curve that is nearly 16.375" in radius by using 19" and 15", and it looks pretty good to the eye. The 15" curve inside it starts with a 19" segment for easement, so that was the obvious way to start the outer curve. The rest of the outer curve is another 19", then alternating 15" and 19" segments around to the far easement section, which makes the end of that curve another double 19" pair. I ran out of UniTrak sections, and need to order more to see if the sections can be joined up with proper spacing and no kinks on the far side. Using that arrangement also allows me to push my crossovers into the curve with #4 turnouts, giving me some additional room in the straightaways. But, that requires taking a Dremel to 2 turnouts, which I am contemplating at the moment. That would also be a good test of how well the famous Kato #4 turnout fix works to prevent point-picking in this rather demanding configuration. Since I now know that the super-elevated easements will work, I may decide to try one way one one end of the oval, and the other way on the other end. This whole thing is an experiment, at this point. I just didn't want to buy a bunch of expensive pieces and then immediately find that they won't work, together.
