I’m wanting to expand my layout sometime in the future, and my idea is to connect the current layout to a new section using switches to split off from the curves. My outer loop uses standard 22" radius Atlas snap track. Are there any switches that will fit perfectly in place of a piece of this track? If not, what switch would fit best with a little flex track improvised into the curve?
there was a recent thread asking the same question
Atlas makes a #4 switch that is designed to replace a section of 18" radius track. The entire diverging route of the switch, with a small curved extender piece is designed for this pupose. Atlas makes a conventional #4 switch that does not replace an 18" radius track.
The diverging section of almost all other comercial turnouts are straight. There is also a section of straight track leading to the switch points. While the curve of the switch points to the frog may be described by an effective radius, it doesn’t mean the diverging section of a turnout can replace a section of curved track with the same radius.
Edit: I read the post as asking about a curved turnout. Hence my answer.
Atlas briefly had a customline curved turnout. http://www.atlasrr.com/Trackmisc/hocode83curvedturnout.htm I never saw one in a store and maybe it was just vapor track. Your choices are going to Peco or Walthers and perfect won’t happen. Others know the exact radius of these turnouts. I will just tell you to beware of creating an S curve as you create a new extension.
That’s called a SnapSwitch and the frog is significantly sharper than a #4. In code 83, these are Atlas model #s 540, 541, 542, 543 (left or right, manual or remote)
They are also available in 22" radius. Code 83 Atlas model #s 544, 545, 546, 547. It seems like this would be the best fit for the Original Poster’s needs.
There is also an 18" radius SnapSwitch in Code 100 (I don’t think there is a 22" radius in C100).
The Atlas Customline “#4” is actually a #4½ frog and as you noted, does not fit smoothly into a curve.
Atlas makes a 22" snap-switch that is the exact same geometry as a 2" straight section leading into a 22" radius curved section. So that should do what you need as long as it can be positioned where you have straight track leading into a 22" radius curve.
eg, http://www.modeltrainstuff.com/545-Code-83-22-Manual-Right-Hand-Switch-p/atl-545.htm
Although having said that, note that the train on the “mainline” will be going through a fairly sharp frog (less than #4), which may not be ideal. Likely worth mocking-up to try with the most demanding rolling stock before installing.
#5 has an R-equivalent of R24". You might have to do some trimming here and there though to get it to fit perfectly.
#4 switches really come in two types. #4 is just the angle of the frog. Some #4 switches meant to replace a R18 section keep curving past the front. However some just go straight past the frog. You have to hand examine the geometries to determine which is the case. Obviously the one’s that go straight will need more trimmed off the diverging route if you are trying to go into a curve.
That does not seem to be correct. The tightest part of the curve through an NMRA #5 is equivalent to about a 24" radius per RP-12 (Called the Curve Rail Radius and only a few inches long). But that says nothing about the curve that the entire turnout would fit into (which varies a bit from manufacturer to manufacturer.) That’s called the substitution radius, and it’s not found in the current NMRA RP.
For a #5, the substitution radius is more like 31”-34” or broader, depending how the turnout is constructed. Fast Tracks, whose turnouts are built to match the NMRA RP, specifies a 31” substitution radius for a #5 built to the minimum length on their fixture. A true #4, built to the absolute minimum length of the fixture, might be worked into that 22” radius curve with a lot of rework around it. But it’s still not a circular curve, there is a bit of straight leg on the diverging path.
SnapSwitches (as noted above) or the PECO C75 or C100 “Small” (with its 24" curved diverging leg and #4½ frog) are probably the best alternatives.
This can be easily seen with a few minutes’ investigation with CAD or the actual parts and flextrack. Any commercial true #5 wouldn’t ever fit into the Original Poster’s 22” curve.
Great, thanks for all the info! Looks like the track manufacturers aren’t going to make it easy for me. Oh well, I do know how to modify track to smoothly fit a radius, so it should turn out alright with some work.
Darth, check out John Armstrong’s “Track Planning For Realistic Operation”- the second or third chapter (can’t remember exactly which) had an explanation of the radius of the closure rails, and its correspondence to the frog types. It should have exactly what you’re looking for, in tabular form.
I may be incorrect. I am remembering the number from “Track planning for realistic operation”…going upstairs to grab book off shelf
Page 78…It says "#5 HO Radius of closure rail is 26" ". Oops…I hate when I goof up like that. My appologies.
The “Snap” Switches have a tangent that replaces a 9" straight section and a curve that with its extender, replaces a 18" R curve section.
Properly Speaking the numbered switches do not replace any part of a sectional circle, and do not have a radius at all. There is the straight track and a diverging TANGENT at the angle determined by the frog number.
Since the diverging track is a tangent it cannot be part of a circle. You can curve either way once past the switch body but that will never align with a curve of any given radius.
Just for the hell of it, I made a semicircle of Walthers code 83 turnouts in XtrackCAD and measured the width required to turn 180 degrees. The number 5’s gave a “radius” of 52". With number 4’s it came out to 34.5.
I have printed these full size and they match the actual track components perfectly.
That’s the substitution radius which varies from mfg to mfg based on how much track appears before the points, and if the diverging route continues to curve past the frog. It’s different from the Radius of the closure rail which is from the points to the frog.
The NRMA standard i think calls for 1.5" before the points. But not every mfg follows this standard. I pay attention to the Radius of the closure rail because with long cars like passenger cars, the trucks have a tendency to hit underbody details if they turn too much. I can trim down the R-sub if i need to.
Confused yet? lol
Of course it is. Had you forgotten that was the OP’s question?
You do of course realize that your long cars can handle a tighter radius closure rail than they can a longer curve of the same radius? Your trucks don’t reach their maximum turn until both trucks are fully in the curve. Curves of a length less than the car don’t cause the trucks to turn as much as curves as long as the car. Because a passenger car can straddle a closure rail, the frog angle is actually a better predictor of truck turn.
It’s the guy with large rigid steam locomotives without blind drivers that needs to worry about closure rail radius.
Despite your best effort, no.
Chill Carl
It’s all good and happy new year.
Needless to say, it will be interesting getting this all together, but I at least have an idea now of what to do. So, thanks everyone for all the details! I never paid too much attention to switches before.[:)]