Turnout

A "wye" is an equilateral switch, each route diverges the same angle from the centerline.  For a the same angle of divergence as a #6, the same curvature in the "turnout", you would use a wye switch with a #3 frog.

A "lap" or "3-way" switch is what is shown in the picture.  A lap switch has two "regular" switches of opposite hands overlapped.  A #6 3-way switch would use two #6 frogs.

A #6 3-way switch would use

Plus a third frog near #3 (but slightly larger because the diverging tracks haven't reached as much of an angle at the point the two curved routes intersect). 

he's asking about the next turnout

come to think of it

Code 100 Y's

I'm not sure how to express it as a frog number, and I can only speak of Code100's I have in inventory. I have 3 sizes,...
a) the small radius Peco Y that appears to have a 24" radius
b) the large radius Peco Y that appears to have something over 60" radius
c) an Atlas custom line one that appears to have a 24" radius

Jim, your photo inspired me to possible add one more track to my freight yard,...by splitting one of my proposed tracks into 2 tracks via a small radius Peco 'Y', or one of those Atlas Y's

PS: ..aren't you glad to know you inspired me to seek out even more trackage....ha...ha

Dave, turnout names I

Heck no Scott, no handlaying.

Peco code 100 different, not the droids I'm looking for

measure

Who knows what they mean by "nominal radius?" To me nominal just means "not exaclty". 

If you've got one of the switches, lay it on top of a #6 regular turnout and it should be apparent whether it's curving more sharply or not. 

If you don't have one, you can perhaps use one of the track planning programs to print out one at actual size, assuming you trust that the program has correctly modeled the geometry of that turnout, then lay a #6 on top of the paper.

Wonky numbers on that listing!

That is odd, curiosity made me look at the peco site ( https://peco-uk.com/collections/peco/products/wye-turnout-4th-radius2).  The #4 wye should have the same radius and diverging angle as a #8 turnout.  I think their specs are messed up.  The angle listed for the #8 is 7.15 degrees, and the angle for the #4 wye is 14.3 degrees, which makes sense (#4 frog is twice the angle to get the same diverging angle for the wye).  The radius should be nearly identical, which the frog angles listings confirm, however the #8 radius is listed as 1702mm (67”), whereas the #4 wye is 978mm (38.5”).  That doesn’t even agree with where you got your data from.  So something is wonky with that radius.

But that page I linked to and the page for the #8 on the same site both have links to download a pdf file that’s a full scale template of the turnout.  So download them, print them out, and I bet you’ll find the curves are almost identical.  And probably clearly larger radii than the #6 turnout, which you can also download a template for there.

I have some  Atlas wye

I have some  Atlas wye switches on my railroad and the radius on both legs is greater than 24"...possibly around 26 or 28 ".

If you can still find find Code 83, Shinohara/Walthers wye switches they are fairly gradual and a #5 is often a good choice.

Enjoy, railroading.

Barry

It's not the frog that counts

My understanding is that a closure rail has a straight portion at the frog end, a fixed-radius curve in the middle, and a straight or spiral curve portion at the points. If the straight portion at the frog end is made longer and the fixed-radius portion in the middle is made sharper the whole switch can be made shorter (because the closure rail "closes" on the stock rail faster). That is what has been done with the #4 wye, it is substantially shorter than the peco #8 turnout, so it must have a sharper curve in it's closure rail.

It's only a shortcut to compare frog numbers, it's the minimum curvature of the closure rail that determines whether long equipment can negotiate the switch, not the frog number.

Frog angle and according

Frog angle and according radius are not connected. There are many radii possible when designing a turnout with a given frog #. The difference between #4 wye and #8 standard turnout not mentioned here is their length. The #8 is 322 mm long, the #4 wye 183 mm. To get the shorter length you need a smaller radius.
Regards, Volker

Maybe if you can still find them....

Walthers Shinohara code 83 line offered three way turnouts and wye turnouts in their extensive line of turnouts and tracks.

Since Shinohara has stop production, may be this will be not easy to find....check second hand market, may be.

Wye is shorter due to double diverging, not sharper radii

The length is different, but it’s not because of a smaller radius, it’s because both routes diverge from the tangent.  In other words, if you put a #8 left and a #8 right turnout on top of each other aligned on the straight legs, the #8 left diverging route and the #8 right diverging route should like up perfectly with the two diverging routes of the #4 wye.

Maybe if you can still find

Marc, I already have the Walthers/Shinohara code 83 3-way (mentioned in the OP), however I might still need a Walthers code 83 wye for the main yard if I can be sure the Peco doesn't have a sharper closure radius than the standard #6.

I did sell my Shinohara code 100 3-way recently because I in staging where I use code 100 I wanted to reduce the number specialty turnouts there.

Ken, I'll check out that template.

i'm wrong

ken is right. 

After some more analysis, i believe the lead length for a proper wye with 30" radii diverging rails comparable to a #6 turnout is only 4.5", the frog angle is 17 deg and is a # 3.3

Ken Rice said: The length is

Ken Rice said: The length is different, but it’s not because of a smaller radius, it’s because both routes diverge from the tangent.  In other words, if you put a #8 left and a #8 right turnout on top of each other aligned on the straight legs, the #8 left diverging route and the #8 right diverging route should like up perfectly with the two diverging routes of the #4 wye.

No, a #4 wye is two #8s symetrically to the centerline. You can build a #4 wye like you describe at the end but there is no need to do so. As Greg's drawings show there are almost limitless combinations of length and radius. Peco chose a smaller length with a smaller radius for whatever reasons but most likely to save valuable layout space.

And it the smaller radius compared to their #8 straight turnout that makes the shorter length possible.
Regards, Volker

So Volker,The Peco #4 code

So Volker,

The Peco #4 code 83 wye sounds like it will not be suitable for me if the curve radius through the wye is smaller than what is typical of a #6 standard turnout.

That being the case, it's a no-go.  And there is another factor as to why a Peco #4 wye is less suitable.  S-curves.

If you look at the photo linked where the wye in the yard splits the two inner tracks, it forms and S curve in both cases.  S-curves usually demand broader curves to minimize the negative geometric effects, especially on long cars.

Solution appears to be either a bigger wye, like a #5 or larger or just don't replicate that yard ladder configuration.  Pity Peco doesn't seem to make a larger wye as I like the finger flick feature.

No, a #4 wye is two #8s

That's what I was said, perhaps not clearly enough.

Well given how easy it is to try the experiment and the fact that a picture is worth 1000 words...

You are quite correct, they did use a tighter radius.  The ends of the upper leg on the wye are aligned with the #8 template underneath (held up against the window) and you can clearly see how much tighter the #4 curve is than the #8 curve.  The points of the two aren't even quite aligned due to the sharper curve even though the stock rail ends are.

Well I learned something today!

Jim, I don't know if the Peco

Jim,

I don't know if the Peco #4 wye works for you. The radius is 38.5'' according to a previous post. The NMRA RP 12 gives a radius of 35.4'' for a #6 turnout.

Here are links to Peco wye drawings.

Small radius wye, code 75, curve goes through frog; length 148 mm, radius 610 mm, angle 24°
https://cdn.shopify.com/s/files/1/1541/1303/t/4/assets/Turnout_Plan_SL97-1532337814149.pdf?4050807787022905029

Large radius wye, otherwise as before; length 220 mm, radius 1828 mm, angle 12°
https://cdn.shopify.com/s/files/1/1541/1303/t/4/assets/Turnout_Plan_SL98-1532337916591.pdf?2678604210228259804

Code 83, #4 wye, straight through frog, radius 38.5'', length 183 mm
https://cdn.shopify.com/s/files/1/1541/1303/t/4/assets/Turnout_Plan_SL8348-1532342269014.pdf?5285622650598174636

The drawings show Streamline code 100 but the turnouts are available with the same geometry in code 75.

Here something else you migt be interested in: The German company Tillig offers its Elite-track. They offer kit of bendable turnout: https://www.tillig.com/eng/Elite_Gleissysteme_Weichen_Kreuzungen-Seite5.html

And here two manuals: https://www.tillig.com/dateien/Produkte/HOModellbahnen/EliteGleissystem/WeichenKreuzungen/85435_368552-EW5-H0_2016_07_13.pdf

and: https://www.tillig.com/dateien/Produkte/HOModellbahnen/EliteGleissystem/WeichenKreuzungen/85441_51_368065-Flex_2016_04_11.pdf

and: https://www.tillig.com/dateien/Produkte/HOModellbahnen/EliteGleissystem/WeichenKreuzungen/85445_368553-EW6-H0_2016_03_18.pdf 

The links are only provided on the German language page but are in English too.
Regards, Volker

Interestingly the Atlas wye

Interestingly the Atlas wye is a match for their number 6. So it is actually would be the equivalent of a right and a left number 6 on top of each other with no center track. The diverging angle for the number 6 is about 10 degrees and it is the same for the wye.

Different brands of track may deviate from this because of manufacturing and design goals. They are only close to what they describe as none are built to the NMRA standards like the fast tracks jigs are. This is not a put down on the makers of track just an observation.

Toll!  Vielen dank Volker. It

Toll!  Vielen dank Volker.

It sound like the Peco #4 wye is tighter than it's symmetrical half of the #8 but a bit wider than the #6 radius.  Question is, is the S-curve created by going through a #4 Peco wye into either of two yard tracks going to bother 89' rolling stock?

Parallel Lines: Examaning S-curves

The very first MRH magazine (1/2009) contains an article about S-curves: Parallel Lines: Examaning S-curves. Here is a link to the magazine: http://00200530.pdl.pscdn.net/002/00530/MRH01/MRH-2009-Q1v3.pdf

Perhapy you can find answers in this article.
Regards, Volker

Moderator's Note: You probably can't get the magazine from that link. Try http://macrodyn.com/assets/files/MRH-Q1/MRH-2009-Q1v3.pdf (right click and Save) instead.