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Which switch to use: #4, #5, #6, #8, #10?

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  • Member since
    December 2008
  • From: Heart of Georgia
  • 4,646 posts
Posted by Doughless on Tuesday, November 23, 2021 12:58 PM

Lastspikemike

 

 
cuyama

 

 
L
A #4 Wye will have, in effect, two #4 frogs cast together as if each diverging route were to be from the straight through route on a #4 turnout.

 

Not correct (semantics aside). For most manufacturers such as Walthers and PECO, what they call a "#4 Wye" turnout is actually the equivalent of a #8 frog. Very gentle curve through the turnout on either leg. 

 

 

 

A prototype #4 turnout will diverge at twice the angle of a #8 turnout. I'm  not following how 2 x 4 is not = to 8 in railroad land?

If this is the case for model turnouts then logically a #4 Wye will behave the same as two successive #4 turnouts. The angle of divergence from tangent of a #4 Wye  will be the same 7 degrees or so as a #4 turnout. 

So two #8 frogs back to back = a #8 frog. In railroad land 4 divided in half = 8....what a surprise....

 

As has probably been covered, the frog # represents the angle between both tracks.  Its just that with a wye, there is no tangent since the frog is essentially "rotated" a bit compared to normal, making two equal diverging paths.

So the #4 frog in a wye has the same effect of a #8 frog if there was an actual tangent route.

And a #3 wye uses a #6 frog, and a 5 a 10.

- Douglas

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Posted by Lastspikemike on Tuesday, November 23, 2021 1:38 PM

That's the most useful explanation so far to help the OP to get the hang of these frog numbers.

Alyth Yard

Canada

  • Member since
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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Tuesday, November 23, 2021 1:53 PM

 

 

Lastspikemike
It's hard enough to understand that 8 is a smaller number than 4.

 

Ever buy wire? Just sayin'.


 

 

 Frog-1 by Edmund, on Flickr

 Frog_fig9 by Edmund, on Flickr

 Frog_0001 by Edmund, on Flickr



 

 

Seems like we've covered this territory before.

        THAT thread wound up being locked. Indifferent

        https://cs.trains.com/mrr/f/88/t/289313.aspx

  

Good Luck, Ed

  • Member since
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  • From: Southeast Texas
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Posted by mobilman44 on Wednesday, November 24, 2021 5:21 AM

Hi,

Without getting involved in math, let me attempt to answer your query....

I've made (with success) HO double crossovers of both "6s" and "8"s, using Atlas code 100 trackage.  Both size turnouts allowed for my largest locos (E units, BLI 2-10-2s and 4-8-4s) to cross with ease.  The big locos certainly looked better crossing on the #8s vs. the #6s, but both worked well.

Of course the higher number turnouts cost you space - which may or may not be a factor.

As far as the separation of parallel tracks, the length of the diverging track is as important as the turnout number.  From what I gather, different mfg. turnouts have different lengths on their diverging tracks.  You certainly could add spacer tracks, and with care, you could shorten the diverging tracks as well.

All said, we need to tailor the turnout type/number to the layout space we want to use.  And if we are using bigger locos and longer cars, the higher number turnout we use the better.

 

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

  • Member since
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Posted by John-NYBW on Wednesday, November 24, 2021 7:42 AM

Generally speaking, longer is better but eats up space so like so many things in this hobby, it becomes a tradeoff. I have a large layout so I have room to use the longer turnouts. A #10 is getting close to prototype. I've found #8 handles the largest locos and passenger cars and it is my standard for mainline crossovers and sidings. I had to replace an Atlas #8 and didn't have another on hand so I've put in a #6 temporarily paired with a #8 to create a crossover and it has handled all my locos with no problem. I haven't ballasted it yet and am debating whether to replace it with a new #8 or leave well enough alone. I use #6 in my yard and spurs although I have cheated in some tight industrial areas and used a few #4. My shortline which branches off my mainline and runs shorter equipment uses a mix of #4 and #6.

  • Member since
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Posted by Lastspikemike on Wednesday, November 24, 2021 8:23 AM

I've tried mixing frog numbers in a crossover or even a yard lead. I found the slight angle difference troublesome. So I took out the #8  and fit a matching #6 which looks better to me and seems to work better although in both cases it was a diamond crossing frog angle that caused the mismatch. Maybe turnout to turnout isn't so noticable.

The other 120 degree crossing was in a line of #5 yard ladder turnouts and the angle mismatch really stuck out so I started the ladder with a #6 to keep the track angles consistent. I eventually took out the diamond crossing in the yard ladder. 

Alyth Yard

Canada

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  • From: Vermont
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Posted by Ablebakercharlie on Wednesday, November 24, 2021 11:20 AM

SeeYou190

My general rule for turnouts is to use the biggest one that will fit.

Everything in my collection will negotiate a #5 turnout, but bigger is always better.

-Kevin

 

 

My 2 cents -  This answer really is the answer.  Short and sweet and simple.

  • Member since
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  • From: Mpls/St.Paul
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Posted by wjstix on Wednesday, November 24, 2021 1:39 PM

Draw a line on a piece of paper. Take a ruler, and make a dot 1/8" on one side of the line, and another dot 1/8" directly across the first dot, but on the other side of the line. The two dots are 1/4" apart. 1/8" + 1/8" = 1/4".

If a straight track ends at a wye, and the track on the right diverges on the angle of a no. 8 turnout, and the other track diverges the other direction like a no.8 turnout, the frog has to be a no.4 frog.  

Stix
  • Member since
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Posted by Lastspikemike on Wednesday, November 24, 2021 2:00 PM

wjstix

Draw a line on a piece of paper. Take a ruler, and make a dot 1/8" on one side of the line, and another dot 1/8" directly across the first dot, but on the other side of the line. The two dots are 1/4" apart. 1/8" + 1/8" = 1/4".

If a straight track ends at a wye, and the track on the right diverges on the angle of a no. 8 turnout, and the other track diverges the other direction like a no.8 turnout, the frog has to be a no.4 frog.  

 

As has been pointed out, not quite. The mathematics of angles isn't quite so easy.

However, for model railroads it is accurate.

Unless your example is intended to reflect the actual frog calculation as in 1:8 x 2 is 1:4 which your example matches but that is not obvious. Frogs aren't laid out by angles but by ratio as I understand things. The angle results from the  ratio of divergence. The frog number system no doubt arose when frogs were made as castings. You'd need to know the angle before you got to the rails so the track would have to be laid to the frog angle. Welded in place frogs need not form a particular preset ratio or angle.

Alyth Yard

Canada

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  • From: Huron, SD
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Posted by Bayfield Transfer Railway on Wednesday, November 24, 2021 5:17 PM

My last layout, I used entirely #5 turnouts and operated 72 foot centerbeams and 6 axle diesels with no problems.

Larger is always better, but #5 will take pretty much all equipement, if not at warp speed.

 

Disclaimer:  This post may contain humor, sarcasm, and/or flatulence.

Michael Mornard

Bringing the North Woods to South Dakota!

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