Freight Yard Ladder Turnouts

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Active Member
Peco Turnouts in a Yard Ladder

I'm still working on the possibilities with my freight yard ladder configuration. I'm using Code 100 track.

There was a time at the beginning that I was considering whether it might be possible to utilize the Peco 'Set Track' turnouts due to their short length. I have REJECTED that idea as the curved diverging tracks are too sharp of a radius.

Next came the use of the Peco 'streamline' turnouts, .... 'small radius size'. One of the major appealing factors about these turnouts is the 'effective radius' of curved portion of these turnouts,...24" inches. My thoughts were that any of my trains that could negotiate a 24" radius curve track, could negotiate these turnouts.
( and yes I understand there could be some instances where long cars coupled to short ones MIGHT experience some problems here).

My next thought was what if i were to do some trimming of these turnouts so to make them fit even closer together? That experiment was less than satisfying when i laid out a string of 4 trimmed turnouts (templates), and compared them a string of untrimmed turnouts. The total length of the ladder was only approx 1.5" difference,....not worth the effort to do all that cutting/trimming.

Thoughts then turned to whether I could utilize the even broader radius of the 'medium size' Pecos. I laid out a string of these alongside the small radius ones. You can see there is quite a difference, so they were unacceptable to me.


Active Member
Further Justification, Peco Sm Radius (24") in Ladder

I was doing some research on utilizing some Peco 'small radius' turnouts in my freight yard ladder design. I found this very interesting conversation, with lots of good and intelligent contributions. I've highlited some of the quotes that caught my eye, and concerned themselves with those Peco turnouts I'm interested in.

This is the question that opened the discussion
What is the difference between a #4 turnout and a #5 turnout?

You can find extensive detail in the NMRA turnout dimensions Recommended Practices area and other related pages:

In practical terms, a #4 is pretty sharp. Some locos and long rolling stock (like 80' cars) may not take it. A #5 is much more forgiving. I used #5s in my yards, #6 for mainline takeoffs and one #8 for a smoother mainline split.

...from a profession layout designer
This is true for PECO N Scale and for PECO HO Code 75 and Code 100, but the newer PECO HO Code 83 is accurately defined by frog number. PECO N scale Code 55 uses a #6 frog for all the turnouts, but the curved diverging leg has different radii for Small Medium, and Large, for example. PECO HO Code 75 and 100 typically have a #4½ frog, again with different diverging radii past the frog. So they are “exact”, but the curved diverging leg is the determining factor.

The second (and more important) is that the lower the frog number, the sharper the effective curve through the turnout. That means that longer cars and engines will be less likely to derail running through a #5 than through a #4.

For this reason, it's a good idea to match the turnout frog to the minimum radius elsewhere on the layout. To take an extreme, there's no point in using #8 turnouts with 18" radius curves in HO -- the curves will restrict the equipment that can be run.

As a general rule of thumb for HO, the tightest point through various frogs is:
"True" #4 is roughly equivalent to 14"-15" radius
Atlas "#4" (actually #4½) roughly equivalent to 18"-19" radius
#5 roughly equivalent to 24"-25" radius

These calculations are from a series of datasheets published by the National Model Railroad Association. An out-of-date link was given above, the newer version of the website is a downloadable zip archive of .pdf files found at this link:

I'm okay with designating their turnouts using the small-, medium-, and large- scheme, but that just doesn't sound very railroady, so I'm calling my medium- and large-radius turnouts #6 and #8 respectively. Mainly because that's what they appear to be as trains pass through them.

I'm nit-picky about a lot of things but the slightly non-prototypical appearance of my PECO trackage and turnouts is not one of them. That stuff is well-made and very reliable

My contention is that Peco uses #6 frogs for all their turnouts. And as cuyama and others have pointed out, what happens downstream on the diverging route varies from manufacturer to manufacturer.

...photographs of N gage code 55 Electrofrog turnouts. I measured the frog sizes:


So then I would call them #6S, #6L, #7

To distill the original question to its essential essence:

I handlay all of my specialwork, so I'm certain that my #4 turnouts (on my end-of-the-coal-hauler module, built in 1980) and my #5 turnouts (in the hidden staging yards at Nonomura, built within the last decade) are built to the proper dimensions.

That said, one of my long-wheelbase 2-Co+Co-2 EF18 or EF58 class juice jacks can slither through a #5. Trying to force it through the curved route of a #4 will put it on the ground, every time.

Why? Those motors require an honest 24 inch (610mm) radius to operate. The closure rail of a #4 turnout has a radius too tight for the long rigid wheelbase. The axle under the center of the carbody gets pinched over the rails on whichever truck hits the tight spot first.

Iron Horseman

Well-Known Member
There is another factor here I didn't see in the discussion above. It was said that all Peco turnouts have a #6 frog, what wasn't said explicitly is that the Peco code 100 track is not a North American style turnout, it is more European. This means that it doesn't "kink" as much at the points as a USA turnout would. This is a good thing when trying to get trains around the tighter corners. I love the Peco code 100 small radius turnouts for this reason. I think they will serve you well in this application.


Active Member
My latest experimenting with the ladder and the freight yard,...again laid out on my living room rug.

The left hand edge of the rug would be the wall of the shed. The first track inboard represents that track along that side of the shed that enters the helix structure and goes down to the staging tracks down below.

The next 2 tracks inboard of that are the mainline track and its opposing end that has looped around in a circle inside the helix and reemerged....dbl mainline.

The next 2 tracks inboard are primarily 'diesel engine servicing' tracks. That long white rectangular shape is meant to be a fueling / sanding / lube stop for diesel engines. One of those tracks will bear off and go into a repair shop down the way (not shown). That one service track close to the mainline will rejoin the mainline on its other end.

The next 4 tracks in are mostly freight yard.

The final 2 tracks in are primarily feeding the steel mill complex, but I imagine the dead end portion at the upper end could be a cabeese storage track (and that cross over track shown will be of the opposite variety, and further down the line towards the mill.

Some additional photos I took so that I might dimension them and make some sort of record to help me remember the possibilities when I go to lay them out on the plywood decks. Unless I completely redesign this ladder due to someone else's superior design, my ladder will have 4 Peco smalls and 2 Peco dble-curves at the head as shown. All of those Pecos smalls have 24” diverging tracks. Other crossover tracks in the yard will be either Peco smalls, or could be Peco mediums.

A difference perspective on this complex.

The big white blob there is the Tichy 400T coaling tower. The tracks I have running under it are not exactly scale as I did not have enough sectional track of the correct radius to lay in there. Suffice it to say that the minimum curves for any of the 'big steam' track will be 24”. And that also goes for the large curve going over into the peninsula area.

It happens to turn out that I do NOT need the original 30” deep shelf for this yard. As you can see by the tape measure I could manage with just 29”, or maybe even 28”. That would allow for a bigger aisle.

Turns out that the also be made slightly wider on the other side as well due to the 22” inner circle radius and the track along the edge of the peninsula. I've depicted that here with an increase in the paper aisle width.... is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to