Peco streamline C100 library

[BritsTukker]

With standard turnouts, it is often the case that if you concatenate many turnouts together using the curved sections, you may not get a true circle as there may be a short straight section at the toe of the turnout.

With such items as curved and Y-turnouts this should not be the case as the whole unit is curved. I've been experimenting with the Peco SL-86/87/97/98 items. The library refers to the curved turnouts as 12º - this is the difference in curvature between the large and small radii. The large radius subtends an arc of 7º, and the small radius an arc of 19º. Thus ten units concatenated using the outer radius form an arc of 70º, and ten units concatenated using the inner radius form an arc of 190º. Peco specifies the small radius as 762mm (30") and indeed, I get a circle of radius 762mm using the inner radius. However, Peco specify the large radius as 1524mm (60"), but if I use the library to concatenate a string of these using the large radius, they end up on a curve with radius 2080mm (~82").
Using the small Y turnout, each arm subtends an arc of 12º, so you need 15 to make a circle, and the Peco-specified radius is 610mm (24"). Connecting 15 together using the library I indeed get a circle - but with radius 697mm. For the large Y turnout, the subtended angle is 6º and indeed you need 15 to form a 90º arc - but the radius comes out at 2080mm (as for the curved turnouts) and not the 1828mm (72") specified by Peco.

So the question is: is the library correct and if so what am I doing wrong, or does the library need some adjustments?
Has anybody else seen these discrepancies?

I attach two files to demonstrate what I mean.

[Jeff]

I haven't checked Peco HO/OO, but I know that something similar applies to Atlas N scale. It's impossible to create a parallel set of tracks if you use their sectional track for a crossover, and even worse when you try to make a double crossover. The turnouts are something like 2.5 degrees off the correct angle. (and boy did THAT tick me off!).

[glakedylan]

my experience has been that the Anyrail track libraries are exact and trustworthy, and that the actually track as advertised by manufacturer is not accurate to that description/definition. so in planning, i always go by what Anyrail informs me of in angle and length and often curve flex track to the radius i need to be exact knowing the actual sectional track is not to those exact specifications, in turnouts, radius of curves, and length of straight tracks.

peace,
Gary

[David]

The radius that Peco provides is not the real circular radius of the diverting leg of the turnout.
It is some sort of 'effective' radius, or perhaps 'minimum' radius, as the segments do not follow a perfect circular curve.

We've used the Peco templates and in some cases the real parts to make sure they're accurate.

David.

[BritsTukker]

Thank you, gentlemen, for your comments. Since posting the first note I, too, resorted to printing out the Peco templates for the large turnouts and taping them to the kitchen floor to do actual measurements. Two observations come from that exercise:
1 - you get as much slop with the paper printouts as you do with the real track.
2 - Anyrail wins hands down - there's no way the Peco-specified radii represent reality.

Motto: Anyrail Rules - OK!

A happy Friday to one and all.