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Hi guys, I've got a small (33" w by 72" l) oval layout and I've got an issue with the dimensions of one of my switches.

My layout's curves are mostly 15 inch radius Atlas code 83 22.5 degree pieces, with a single 18 inch radius piece in each of the semicircles. The two 18 inch radius pieces are diagonally across the layout from each other, where a curved piece is missing in the picture and diagonally across from it in the lower left corner. I want to replace the missing 18 inch radius curve piece with a switch so that I can have a track continue straight off the board to connect to another module. I can't use a switch with a larger radius because of the width restriction. I also want to use off-the-shelf track pieces if possible.

Basically, my issue is that the packaging for the Atlas 543 Right Manual Snap Switch plainly says that it is a direct replacement for an 18 inch radius curve piece - and even shows this in a diagram - but it is most certainly not. You can see in the picture where I've laid an 18 inch radius piece on top of the switch that they're not even close to matching up.

I'm not married to Atlas, brand-wise. Peco and Hornby seem to make a 2nd radius 22.5 degree frog angle turnout, but both of those are code 100 rail.

Does anyone know of a code 83 switch/point/turnout that fits my needs?
 

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You seem to be trying to put a larger curve inside a smaller one. The outside loop should be 18", and the inside 15".

Unless you're trying to duplicate the diagram on the package shown. Then, you need to match the radius, 18" & 18", or 15" & 15".
 

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Well, I have some bad news for you: the Snap Switches are, in fact, a replacement for an 18" curve section. Knowing that, there are 3 possibilities: 1) a defective piece (it happens
-- and Snap Switches aren't known for their quality engineering); 2) You don't have the "test" piece perfect lined up over the rails; 3) the 1/3 radius piece that you installed is kinked and not forming a perfect track piece.

However, you can't use anyone else's turnout. Even the cheap ones that do incorporate an 18" curve segment have a different geometry. The better ones don't incorporate a curved diverging track at all -- the have straight diverging legs like real railroads do.

If you're having a problem with things lining up, it's probably because you need a second 18" radius piece at the opposite end of the curves as well.

Your best solution, though, would probably be to get a couple of pieces of their Code 83 flex track and use that to make a curve of the correct radius.
 

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You have two choices as I see it.
Assuming you(1) cannot enlarge your module/layout table (2) have locos and rolling stock that can negotiate tighter curves.
1. Custom build a 15" radius turnout.
2. Make the center loop out of flex track with approximate 14" radius curves. (Red section in the layout design below)
 

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You can see in the picture where I've laid an 18 inch radius piece on top of the switch that they're not even close to matching up.
wasn't there a short curved section of track that came with the turnout?

When you attach that to the turnout, the turnout can replace the end section of an 18" curve and a little bit of straight track
 

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Well, I have some bad news for you: the Snap Switches are, in fact, a replacement for an 18" curve section. ...
They are not direct replacements as you stated. Two snap switches and two small add-on tracks take the place of 2 sections of curved track, as shown in the diagram above on the back of the packaging.
 

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the curved section from the non-diverging rails end at the same angle as the turnout with the small curved section of track.

one turnout + short curved section replace one section of 18" curved track.
 

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If you have a circle of track, and replaced a curved section with a snap switch and an add-on piece, I don't think it will fit. you need 2 switches and 2 add-on pieces.
 

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You all (spoken with a southern USA accent) need to read the OP first post. He is trying to do this in 33". Cannot be done with 18" or 15" sectional.
 

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You all (spoken with a southern USA accent) need to read the OP first post. He is trying to do this in 33". Cannot be done with 18" or 15" sectional.
While the OP said 33" width and 18" radius track, what shows in the first pic seems to be his 18" radius oval on his board, albeit dangerously close to the edge.

And it's "Y'all". :D
 

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Keep trying till it hurts

Well, I tried again and got it to work in the Atlas software. You need to use the short piece of curved track that comes with the turnout, and some short straight sections to make it work. The Atlas part numbers are on the drawing.
 

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My layout's curves are mostly 15 inch radius Atlas code 83 22.5 degree pieces, with a single 18 inch radius piece in each of the semicircles.
this is pretty clever. I had never read about anyone ever doing this before.

I did some math and calculated that the two 18" end sections, allowing the use of the Atlas Snap turnouts, increases the diameter by less than 1" (0.8").

So while the 15" radius curves require ~31", the 18" section can fit within 33"
 

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They are not direct replacements as you stated. Two snap switches and two small add-on tracks take the place of 2 sections of curved track, as shown in the diagram above on the back of the packaging.
I didn't say, nor mean to imply that one snap switch took the place of a full section.

However, yes, you absolutely CAN substitute a snap switch for a corner of an oval and have the straight route continue at a tangent for a sliding, without a matching configuration on the opposite side of the layout.
 

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Discussion Starter #18
Hi guys, thanks for all the replies.

The picture I took of the two pieces on top of one another has the switch with the optional 1/3rd 18" radius piece attached. As you can see, it makes the piece as a whole too long to drop in, and there's not enough angle because the switch's diverging track straightens out as soon as it clears the straight rails.

And to clear a few things up that I have seen discussed, I am only doing a single loop of track, not a outer and inner, as some commenters have stated.

Dennis has the right idea, though as you can see, even in Atlas's own software, the 543 switch plus the 534 1/3 18" radius curve piece is longer than the 532 full 18" radius curve piece.
 

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Dennis has the right idea, though as you can see, even in Atlas's own software, the 543 switch plus the 534 1/3 18" radius curve piece is longer than the 532 full 18" radius curve piece.
No, really. I insist. By deliberate design and intent of the manufacturer, the Snap Switch plus the short curved segment is an exact match for the longer curved segment. I can't tell you how many times I personally did it when I was using sectional track (a lot of years ago, now).

I'm sure you know that appearances can be deceiving, so if your photo appears to show something that we all know is factually incorrect, then there must be something else wrong somewhere, either a defective piece or user error. Figure out which, and the problem is solved.

Let me share this. On the last layout I built with sectional track, I was swearing up a storm because the ends of the adjacent tracks didn't line up like the the planning software said they would. And I got very frustrated. I ripped out the offending section and asked my brother to help me re-lay the track. We hadn't been working for 5 minutes when he said, "DO you know you have a section of 22" radius track in here?" D'Oh. Problem solved.
 
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