Peco Code 55 large switch geometry issue

[Basilisk]

I think there is a geometry issue with the large straight Peco Code 55 switch (point) SL-E388F and SL-E389F in the AnyRail library as the angle is identical to the smaller switches (points) which are 10 degrees.

But according to various information the large switch (point) has only an 8 degrees angle as can be seen here. This is also evident when placing these switches with some tracks.

I did use the search feature but couldn't see this issue mentioned anywhere.
Cheers, Peter

[David]

Welcome Peter!

All Peco code 55 turnouts have an angle of 10 degrees. I've just verified this once again with my contact at Peco.

[VictorPM]

I have seen and commented on that pdf by Mueller before... I think the approach is a bit too theoretical.
The way he says: "the angle HAS to be 8°, if it would be 10° the curve would be too long".
Bottom line: measure the actual angle of the actual piece, and you know. The radius of the curve is not necessarily 914 mm, and not necessarily perfectly tangential.
Turnouts usually have three endpoints, 2 of them under an certain fixed angle, and the actual curve mostly is a bit vague.
Even if a turnout fits perfectly in a system (other brands).

Edit: in this online catalogue it says: the frog angle is 8°, and the end angle is 10°. So there you go.
http://blaetterkatalog.weinert-modellbau.de/#page_300

What bothers me most though in that pdf is the comparison with Fleischmann Piccolo turnouts. Suggesting that its curve really is a 15° part of a 430mm radius circle. Then he really has no idea.

Greetings, Victor

[David]

@Victor:
We always use the actual endpoint positions and their outgoing angles in our turnout definitions, and indeed, most of the time the diverting leg is either a straight-arc-straight combination (arc being a part of a perfect circle), or a curve with no fixed radius at any point along the diverting leg.

[Basilisk]

Thank you, David and Victor, for your comments. I use AnyRail for a long time and love the simplicity and flexibility to do things!

But I still think the correct angle is 8°. Please let me explain why I think so.

Here a simple layout done in AnyRail with the large Peco Code 55 Switch SL-E389F.

The parallel distance of the two tracks comes to 28.5mm

And here how it looks like on the bench with the help of some spacers to get the accuracy.

All looks good and the same as in AnyRail, so what is the problem you may think.

Before I show you the problem in close up, let's do the same with an 8° turn-off angle.

As can be seen, 2° difference have actually a rather noticeable effect!

And if you look carefully, you notice a small kink in the 10° setup which isn't the case in the 8° setup. Here a close up of the two.

Also note the gap in the lower rail on the 10° setup, indicating that there is an alignment issue.

After reading Victor's comment that the frog angle is 8°, and the end angle is 10° as shown in the document from his link, I had another closer look. Now if the frog angle is 8°, and the end angle is 10°, shouldn't the track be a curve between the frog and the end? But the samples I have here are dead straight and 8° is a perfect match from frog to the end.


10° not so.

And there is again the kink and the extended gap in the lower rail.

And here again the comparison of the two.


I know that the pictures could be a tad better, but I think they do show that the turn-off angle has to be 8° and not 10°. Or do you still think 10° is correct?

Cheers, Peter

[David]

@Peter: thanks for the research and clear pictures! Indeed, a few degrees difference has a great impact on the overall geometry.

I have contacted the design lead of Peco yesterday, and he told me the angle is 10 degrees, so we keep with that.

Of course it can happen that in the production process the rail cuttings can be slightly off causing differences.
In AnyRail, you can always connect track at a slight angle in case you prefer an 8 degree connection, but I think it is better to follow the manufacturer's intention.

[VictorPM]

Thanks Peter for the insightful pictures! 
I'm still not sure though if Peco really meant this to be used as an 8° turnout, considering the rest of the switches and crossings program.
But maybe I'm also thinking too much in systems and schemes 

[Basilisk]

David, I understand your point of view. For what I like to do, a 10° turn-off is what I need to create a scissors crossover like that using 2x SL-E390F, 1x SL-E388F, 1x SL-E389F, 1x SL-E393F and a lot of cutting.

Unfortunately it doesn't work well with the large points as they are not 10° (that is how I spotted the issue). And I checked over 20 of them and they are all identical.

But I have to admit, I was wrong as the turn-off isn't 8° degrees on the large point. Isn't the saying, a picture is as good as 1000 words - so here we go.




And a close-up.


And on te actual switch.

Looks to be 8.5° and definitely not 10°. The drawings are done in Solidworks and are accurate.

Any chance to point your contact at Peco to this thread (or send them these pictures) as I am curious where they are getting the 10° from.

Cheers, Peter

[David]

Peco has looked at this thread and will get a precise measurement for us later.

However, the main thing is that Peco has intended it to be 10 degrees, but with the older tooling they use (predating CAD) for this particular product, it might not come out exactly at that. They are sure it will never cause an actual problem when it is used with the intended angle of 10º.

[Basilisk]

Hello David, thank you for getting in touch with Peco. I am looking forward to hearing their comments.

Cheers, Peter