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

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Which switch to use: #4, #5, #6, #8, #10?
Posted by 1arfarf3 on Sunday, November 21, 2021 9:47 AM

What does each one accomplish that another one may not? Advantages, disadvantages, etc.

In using 2 switches to create a crossover in parallel main lines, what is the centerline distance of main lines for each number?

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Posted by tstage on Sunday, November 21, 2021 10:16 AM

Each increase in size numerically makes them longer physically with a corresponding smaller diverging angle.  And the smaller the diverging angle; the faster speed your trains can negotiate the crossover.

The center-to-center (CTC) distance between the mainline track would be contingent on how long the diverging track is when the two diverging tracks are abutted together.  Each manufacturer's turnout (switch) may and most likely will be different from one another.  You may need to place a piece of flex track in-between so that the CTC distance of your mainline track is adequate enough for two passing trains running in parallel.

Other considerations are 1) how much room will you have on your layout for a crossover and 2) how long are your longest locomotives?

Tom

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Posted by SeeYou190 on Sunday, November 21, 2021 10:20 AM

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

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Posted by Lastspikemike on Sunday, November 21, 2021 10:29 AM

Frog number and parallel track center lines are not related.  Track centres result from the length of the diveringing routes which vary between Atlas Customline, Model Engineering  or Peco Code 83 which give you usable >2" track centres right out of the package to Atlas Code 83 super switches (#6 only) or the new Walthers which assume you will cut down the diverging routes to fit your desired track centers. These latter types give you track centres of about 2.5" out of the package. For Walthers there's a nifty article in the October MR magazine on page 26-28 showing how you can build a crossover with no rail joints in the connecting track which I am determined to try out. It's a bit of work but not too complicated. Or you can just cut down the diverging routes equally and fit rail joiners.

As a general rule you would try to use the highest frog number you have room for, especially for crossovers. Reason is a crossover creates an S curve which can cause derailment depending on train speed and the frog numbers used to make it. The larger frog number stretches out the S bend making higher speeds feasible.

Fit smaller frog numbers only if you have to in order to fit your desired layout configuration. 

Double curved turnouts are generally described by the radius of each route. Walthers is planning on making some pretty handy sizes quite soon.

Wye turnouts are described by a frog number equivalent to half the actual frog angle. 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.

A good general guide if you have room would be to use #5 for yard and siding tracks, #8 or even #10 (Walthers is making these and do does Atlas I believe) for mainline crossovers and #6 everywhere else. Use Wye only when you can't avoid it. For model railroading those curved turnouts can be very handy in several situations. One is to extend a passing siding into the curves at each end of a straight, just for example. Reason is we are severely constrained by obstacles like walls and wives and money (lack thereof) and are forced to bend our track back on itself long before we wish to.

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Posted by selector on Sunday, November 21, 2021 1:53 PM

Lastspikemike

Frog number and parallel track center lines are not related... {I stopped reading here...}

I'm going to take a wild stab and guess that geometry isn't your long suit.  Track laying probably included.

Of course they're related, in the same way the diameter of a circle is directly proportional to the radius, and the circumference has the same relationship, with the calculating benefit afforded by Pi (3.14159).

Suppose you had a turnout, but instead of a diagonal diversion it is a 90 deg diversion.  We call them crossings, but I digress.  Does the angle of the diversion differ from that of a #8 frog?  Yes, it does.  And how far does one run the diversion in either case before one should consider truncating the length to create a parallel track?  Wouldn't that also depend on the angle of diversion?  Why yes, it does.  

As in so many things, it isn't just one factor, and one can ignore the others that actually matter.  As the angle of divergence changes, so must the length of the diversion if.......IF...one wants a parallel track that doesn't encourage contact at any point when two items are following those proximal parallel routes.  

To help situate this, suppose the divergent angle is that of a #8.  You place two turnouts opposite each other points-wise, and the length to complete the transit over to each other totals 6".  Wait, you decide to use a #6 instead because you're daft, if capricious and crafty, and find that now you must trim one of the diverging lengths.  Oh yes you will.  Try it and see.  You'll also have the kink in the middle of the cross-over route, and if you know geometry, you'll know why.

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Posted by richhotrain on Sunday, November 21, 2021 3:24 PM

selector
 
Lastspikemike

Frog number and parallel track center lines are not related... {I stopped reading here...} 

I'm going to take a wild stab and guess that geometry isn't your long suit.  

Nor is guessing. Laugh

Rich

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Posted by gregc on Sunday, November 21, 2021 3:47 PM

1arfarf3
In using 2 switches to create a crossover in parallel main lines, what is the centerline distance of main lines for each number?

the frog number (e.g. #4, #6) is a measure of the frog angle (see Turnouts) in terms of the ratio of the distance from the tip to the separation of the rails.  the larger the frog number, the smaller the angle

in a crossover, a longer distance will be needed the smaller the angle.

the distance from the points to the frog, the lead length, is also longer the smaller the angle.

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Posted by RR_Mel on Sunday, November 21, 2021 4:52 PM

I went with code 83 Atlas #6 turnouts for my mainlines and #4 for my yard.  My longest locomotives easily negotiate the #6 turnouts at full speed (70MPH scale).  They also negotiate the #4 turnouts at yard speed (under 15MPH scale).

My longest rolling stock is scale 72’ and all negotiate the #4 turnouts, early on I had several 85’ passengers cars that also cleared the #4 turnouts.  The 85’ cars looked ridiculous on my small 14’x 10’ layout.

I built a #6 double crossover for 2” CTC track separation that works perfectly at full speed.

https://melvineperry.blogspot.com/2012/06/june-25-2012-my-double-crossover.html





Commercially manufactured code 83 double crossovers won’t pass my Rivarossi deep flanges without problems but the Atlas turnouts work perfect with deep flanges.
 

Mel


 
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Posted by Lastspikemike on Sunday, November 21, 2021 9:48 PM

gregc

 

 
1arfarf3
In using 2 switches to create a crossover in parallel main lines, what is the centerline distance of main lines for each number?

 

the frog number (e.g. #4, #6) is a measure of the frog angle (see Turnouts) in terms of the ratio of the distance from the tip to the separation of the rails.  the larger the frog number, the smaller the angle

in a crossover, a longer distance will be needed the smaller the angle.

the distance from the points to the frog, the lead length, is also longer the smaller the angle.

 

I dunno but I just measure the track centres. Use Peco turnouts to build crossovers and the track centres will all be the same, about 2", regardless which frog number you use. Even their #7 curved turnouts make crossovers with 2" track centres.

The 90 degree example was perhaps the most amusing.

I assure you my knowledge of geometry is just fine. As is my understanding of its relationship to algebra and at one time to the calculus although at present I doubt I could perform a differential calculation much less an integral. 

Track centers depend on length of diverging tracks connecting the turnouts. Frog number is irrelevant.

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Posted by JDawg on Sunday, November 21, 2021 10:39 PM

   The op's question has been answered very well by many more knowledgeable than I.

   To reiterate, the larger the number, the shallower the angle of the diverging route and thus the larger and longer a turnout. #4-#10 all hold a place in model railroading. Going to run huge steamers? Get #6-#10. Running small steam with some early GP's? #4s will suffice.

   It's all in your equipment, and more importantly, the space you have to work with. My layouts neccesitate smaller turnouts. Like a peco #2. They look great in industrial areas and allow me to create fun track formations. I use 6's and 8's too however. They look right at home on the mainline.

   It come down to three things. You're equipment, your space, and your preference. Notice the common word?

 

Psst! The answer is your!

JJF


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Posted by cuyama on Sunday, November 21, 2021 11:37 PM

I don’t think anyone so far has given the most useful answer. Frog number and minimum radius should be in balance. If your minimum radius is 22” in HO scale (for example), that’s roughly equivalent to a #4½ (what Atlas labels their “#4”). So a #8 turnout in that situation would be wasteful overkill, since your trains must negotiate the much-tighter curves. If you let folks know your minimum radius, someone may be able to help. (Some others will only talk.)

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Posted by gregc on Monday, November 22, 2021 5:09 AM

yes, the distance between the track centers can be whatever is desired, perhaps requiring a short piece of connecting track.

but the overall length of the crossover will be longer depending on the frog number

 

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Posted by riogrande5761 on Monday, November 22, 2021 6:24 AM

cuyama

I don’t think anyone so far has given the most useful answer. Frog number and minimum radius should be in balance. If your minimum radius is 22” in HO scale (for example), that’s roughly equivalent to a #4½ (what Atlas labels their “#4”). So a #8 turnout in that situation would be wasteful overkill, since your trains must negotiate the much-tighter curves. If you let folks know your minimum radius, someone may be able to help. (Some others will only talk.)

Byron

I noticed also that the asnwers have been lacking.  Good point that using long turnouts when curve radii are sharp makes little sense.  As for talking, so true!

1arfarf3

What does each one accomplish that another one may not? Advantages, disadvantages, etc.

In using 2 switches to create a crossover in parallel main lines, what is the centerline distance of main lines for each number? 

As others may have mentioned, the higher the switch number, the broader/longer it is and it can handle longer rolling stock, as a rule. 

The #4 (Atlas is a #4 1/2) are used on small 4x8 layouts due to space restrictions but do not work well with long rolling stock.

My personal minimum is a #6 for yards ladders and sidings, and for crossovers, #8.  But my minimum radius is 32" or broader.

A cross over is basically an S curve, so you want it to be gentle to allow longer cars to pass through with hopefully no issues.

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Posted by ndbprr on Monday, November 22, 2021 7:35 AM

There is one other factor. Real railroad crossovers will be #16 and up. Even then they are reduced speed. The limiting factor is going to be how much space you have for the crossing.. if you are making a 4' x8' you are pretty much going to be limited to #4 turnouts. #6 and higher will eat up nearly all your straight section. As usual everything we do on modeling is a compromise of real railroads

  Best to draw your plan with a template that also has various turnouts on it. When I was 18 I designed a yard with 8 tracks and all the turnouts fit in a one foot length on my hand drawn plan. Didn't turn out that way in real life.

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Posted by Lastspikemike on Monday, November 22, 2021 7:45 AM

Frog numbers have no effect on track centres. The two ideas are not connected at all.

Using turnouts with smaller frog numbers will make a shorter and more compact crossover. That's the connection.

The track center distance is determined by how long the connecting track is which in turn results from the length of the diverging route of your chosen turnout.

The post with the diagram shows this very well. All track centres are the same but the higher frog number turnouts make a much longer total crossover. That's the dimension you have to pay attention to when choosing frog numbers. #4 make nice short but sharp crossovers while #8 make nice long space eating crossovers. Many of us fit #5 or #6 as a good looking compromise between too sharp or too long. 

The minimum radius of your layout can coincide with the minimum frog number you choose to use because there's no operational advantage to fitting a larger frog number turnout as the limit on operation will be the curve radius.

I still fit the highest frog number turnouts that will fit because they look better and the trains look better. The way your layout looks is and should be a very persinal choice. However, everyone has the same interest in how well a layout operates.

Derailments from choosing a minimum curve radius too tight or a frog number too small are discouraging for anyone. Trains that look right to one person but not to another is an entirely different situation. Build what looks good to you.

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Posted by cuyama on Monday, November 22, 2021 12:38 PM

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. 

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Posted by wjstix on Monday, November 22, 2021 12:58 PM

cuyama

I don’t think anyone so far has given the most useful answer. Frog number and minimum radius should be in balance. If your minimum radius is 22” in HO scale (for example), that’s roughly equivalent to a #4½ (what Atlas labels their “#4”). So a #8 turnout in that situation would be wasteful overkill, since your trains must negotiate the much-tighter curves. If you let folks know your minimum radius, someone may be able to help. (Some others will only talk.)

Byron

 

Depends on the situation. Imagine a layout built along one long wall of a basement on 24" wide shelfs. At the ends, it widens out to 4' wide to allow return loops of 22" radius. On the main part of the layout, you could use larger turnouts (say no.8s or 10s on the mainline, and no.6 for spur tracks) for a more prototypical look. The loops at the ends could be disguised by scenery. Yes, you could only run equipment that can handle 22" radius, but you wouldn't have to build the whole layout with that limitation.

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Posted by gregc on Monday, November 22, 2021 1:52 PM

wjstix
The loops at the ends could be disguised by scenery. Yes, you could only run equipment that can handle 22" radius, but you wouldn't have to build the whole layout with that limitation.

i think Byron is suggesting that the loops at the end could use a #4 wye instead of a #4 turnout to allow a greater radius and such that the "rest of the layout" is limited by a #8 turnout

(wow, never realized that)!

greg - Philadelphia & Reading / Reading

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Posted by cuyama on Monday, November 22, 2021 2:02 PM

wjstix
Depends on the situation. Imagine a layout built along one long wall of a basement on 24" wide shelfs. At the ends, it widens out to 4' wide to allow return loops of 22" radius. On the main part of the layout, you could use larger turnouts (say no.8s or 10s on the mainline, and no.6 for spur tracks) for a more prototypical look. The loops at the ends could be disguised by scenery. Yes, you could only run equipment that can handle 22" radius, but you wouldn't have to build the whole layout with that limitation.

Sure. But is that the OP's situation? After designing a couple of hundred layouts for others, no one's ever asked for this, except maybe in one scene.

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Posted by cuyama on Monday, November 22, 2021 2:04 PM

gregc
i think is suggesting that the loops at the end could use a #4 wye instead of a #4 turnout to allow a greater radius and such that the "rest of the layout" is limited by a #8 turnout

Doesn't matter how you feed the 22" radius mainline curve – it's still 22" radius and that's the determining factor for what will run reliably.

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Posted by Lastspikemike on Monday, November 22, 2021 2:28 PM

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....

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Posted by cuyama on Monday, November 22, 2021 3:47 PM

Rhetoric is not the same thing as knowledge.

Obfuscation is not the same thing as help.

 

 

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Posted by doctorwayne on Monday, November 22, 2021 4:05 PM

cuyama
...what they call a "#4 Wye" turnout is actually the equivalent of a #8 frog. Very gentle curve through the turnout on either leg.

Absolutely correct...I have four #4 wye turnouts on my layout, three of them in a wye meant for turning locos and some short trains...the points follow exactly the 30" radii of the tracks in which they're installed - no jarring or jumping, just as smooth as if there was no turnout there at all.

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Posted by gregc on Monday, November 22, 2021 4:12 PM

Lastspikemike
I'm  not following how 2 x 4 is not = to 8 in railroad land?

the frog # is measured as the distance between the diverging rails.   but on a wye, neither is straight

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Posted by wjstix on Monday, November 22, 2021 4:30 PM

Yes on a wye the tracks are both moving away from each other, it isn't one track staying straight and the other diverging.

Think of it this way...imagine a straight line drawn on the benchwork. Then imagine a straight track centered over the straight line. That straight track then ends in a #4 wye. The track diverging to the right diverges from the straight line on the benchwork at the same angle as a no. 8 turnout would. The track diverging to the left also diverges from the straight line at the same angle as a no. 8 turnout. Since the two tracks are both diverging from the straight line, the result is a no. 4 wye turnout. 

OR

Think of it this way. Take a no. 8 right hand turnout, and a no. 8 left hand turnout. Lay one on top of the other so the straight tracks of the turnouts are one directly on top of the other. Then take a no. 4 wye and lay that on top of the two no. 8 turnouts. The angle of the tracks of the no. 4 wye match the diverging tracks of the two no. 8 regular turnouts.

It can be difficult to grasp. It's kinda like how 1/8 is half of 1/4, even though 8 is bigger than 4.

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Posted by selector on Monday, November 22, 2021 5:26 PM

The key is the frog angle.  On a straight turnout, one frog rail parallels the through route.  The opposite frog rail parallels the diversion.  What is the angle of the frog rails relative to each other?  Picture that. 

Now, along the same centerline, you have the same frog, but it services two diverging/flaring routes.  Won't the formerly parallel-to-the-centerline through frog rail now be angled to permit the second divergence, whether left or right?  If the angle of divergence relative to the centerline up to the points is a #8 turnout, the angle at the frog that permits two divergences is going to be twice the divergence as before...and so the angle now doubles to a #4.

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Posted by Water Level Route on Monday, November 22, 2021 6:56 PM

cuyama

Rhetoric is not the same thing as knowledge.

Obfuscation is not the same thing as help.

 

 

 

+1

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Posted by Colorado Ray on Monday, November 22, 2021 8:32 PM

Lastspikemike

 

 

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?

 

 

 

 

The frog angle is the arc tangent of the reciprocal of the frog number. 

ATAN(1/4) = 14.036

ATAN(1/8) = 7.125

14.036/7.125 = 1.97. Which is not = 2.

 

For a constant centerline separation, the length for a #8 crossover will be twice the length of a #4, but it's incorrect to say that the angle of a #4 frog is twice that of a #8.

 

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Posted by Lastspikemike on Tuesday, November 23, 2021 8:47 AM

Colorado Ray

 

 
Lastspikemike

 

 

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?

 

 

 

 

 

 

The frog angle is the arc tangent of the reciprocal of the frog number. 

ATAN(1/4) = 14.036

ATAN(1/8) = 7.125

14.036/7.125 = 1.97. Which is not = 2.

 

For a constant centerline separation, the length for a #8 crossover will be twice the length of a #4, but it's incorrect to say that the angle of a #4 frog is twice that of a #8.

 

Ray

 

Yes, I know. I was trying to keep it simpler.

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

Let's also not mention the Atlas #4 that isn't and the Peco and ME curved diverging routes....

Oh and 1.97=2 but does not equal 2.00

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Posted by Lastspikemike on Tuesday, November 23, 2021 8:55 AM

gregc

 

 
Lastspikemike
I'm  not following how 2 x 4 is not = to 8 in railroad land?

 

the frog # is measured as the distance between the diverging rails.   but on a wye, neither is straight

 

Your diagram illustrates the whole thing perfectly.

Frog numbers represent ratios rather than angles.  Makes sense that a higher number in the ratio would designate the frog number creating that diverging angle.

Of course trigonometry is about ratios resulting from angles. The whole thing derives from the surveying done for building railroads which uses trigonometry. Before that the same trigonometry allowed building of canals which facilitated later railway construction. And just incidentally facilitated the development of the theory of evolution but that really would drift off topic. 

Alyth Yard

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