MicroEngineering #6 turnout to 2" parallel main tracks?

Michael Wagner Jul 13, 2021

  1. Michael Wagner

    Michael Wagner TrainBoard Member

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    I am thinking through a pusher/puller or shuttle station stop where a very short LRV on the inbound pulls into a station on the straight leg of switch, continues into the station, stops, reverses direction pulls out on the diverging leg of of a switch to the outbound track, which parallel to the inbound track ion a 2" center.

    I plan to use a #6 ME turnout setup as with an automatic switch control - sort of like a spring switch - the train will always arrive om the inbound track and depart on the out bound track - it will never reverse and go back out on the inbound track.

    If I understand the math right, a #6 turnout has an effective turnout angle of 7.5 degrees - arctan(1/6) = 7.5 degrees.

    The center line radius of the turnout is 34.6 degrees, so I think the curved portion of the turnout is about 4.5" inches long, because a 7.5 degree arc of a 34.6 in radius is 4.53 inches.

    I think that means that the last 4" or so of the diverged track must be straight, and I am pretty sure that is what I observe looking at the template.

    I think that to bring the diverged leg back to parallel, I will need a short piece of straight track to extend the straight portion of the diverged leg of the turnout, and then a 7.5 degree curve of some radius..

    I think that there is relationship between the length of that straight joining track and the radius of curve - but I do not yet understand the geometry to do that calculation.

    I think that one way to think of this is to think of two ME #6 turnouts joined together to create a crossover.

    What length of straight track would I need between the two turnouts would I need for a crossover between two parallel tracks spaced 2" on center?
     
  2. acptulsa

    acptulsa TrainBoard Member

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    Ess curves aren't a good thing, but there's something worse. Putting in a straight as long as your longest locomotive or car eliminates the problem. Your 4 1/2" straight should do that in N, but presents a nightmare scenario in HO, because reverse curves aren't good, but reverse curves with a short straight in the middle is an engraved invitation to the derailment gremlins.

    If a straight as long as your longest car is not an option, and it rarely is in crossovers, then your best bet is to make the curves as broad in radius as possible, and make the left and right curves abut each other. The left hand curve should begin right where the right hander ends.

    Of course, if you choose LRVs that are single-unit and use no couplers, reverse curves, with or without straight track in the middle, are no problem. But if you don't design with an eye toward the possibility that you'll find and fall in love with LRVs that run in multiple, well, you know how Murphy's Law works.

    Flex track is good stuff. With flex, you can come off your switch and ease the track out to the center spacing you want oh, so gently and smoothly. For that application, I strongly recommend it. It may not be easy to work with in SCARM, but it is on plywood. It may not make as pretty a SCARM, but it makes a better railroad.

    Sprinters, by the way, are articulated. Reverse curves won't bother them until you start coupling articulated pairs together.
     
    Last edited: Jul 13, 2021
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  3. Sumner

    Sumner TrainBoard Member

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    As mentioned above I think once you start laying the track you will find that it is going to work out. If you don't have it now possibly think about getting a few turnouts and some track and experiment with it.

    [​IMG]

    Above is a copy of a Fast Track template for their N #6 turnouts. I took it and used Fusion 360 to look at the angles. The two I measured are right around 9 degrees. ME's might be a little different and so might say an Atlas turnout. I'd get what you are going to work with and experiment with it.

    I've built about 40 #6's off of those templates and actually use 11 degrees when I doing track plans using Sketchup to work on what I'd like the layout to be. It will get me close and give me a fudge factor when the real track goes down

    Good luck and have fun,

    Sumner
     
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  4. acptulsa

    acptulsa TrainBoard Member

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    Thank you for posting that. If that's absolutely accurate, the switch is unusual in that all the track ends line up in a straight line. Many switches don't. The ends of the rails on the diverging track line up on a straight line perpendicular to their angle.

    Most switches are sectional track friendly. The switch in that diagram is easier to connect flex track to, as the outer rail of flex track retracts as you curve it.
     
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  5. Michael Wagner

    Michael Wagner TrainBoard Member

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    There must be something about turnout numbering I don't understand.

    I had thought that a number 6 turnout meant that the diverging turnout diverged by one units for every 6 units of length.

    The way that I thought about it was that a hypothetical #1 turnout would diverge by one unit for every one unit of length - by definition, that is a 45 degree angle.

    If that is true, then a #6 turnout, which diverges 1/6 as much as this hypothetical #1 turnout, should have an angle of (1/6 * 45 degrees),, which is 7.5 degrees.

    I also though of the turnout as implementing a right triangle - from high school geometry. If the straight leg is the "adjacent" side, and the amount of divergence is the "opposite" side. and the diverging track is the (curved) "hypotenuse." In that model, the opposite over the adjacent is 1/6 - the tangent of the angle of the diverging track. The arctagent of 1/6 is 7.5 degrees - which matches the answer I got with my more intuitive method above.

    The fact that my calculations do not match observations - by my calculations, a #5 turnout should have an angle of 9 degrees - tells me that something I think I know must be wrong.

    Does a #6 turnout not really diverge by one unit for every 6 units of length?
     
  6. acptulsa

    acptulsa TrainBoard Member

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    Yes, I think you have it right. I've seen reliable sources say that. Time to empty the ashtray, though. Here come the butts.

    But remember the curved leg is curved. The angle is measured at the frog, and you'd have to trace that frog angle back to find that ratio.

    But even switches on real railroads vary, and woo woo woo is notorious for playing fast and loose with those numbers. The Atlas #4, for example, has always been nearly a #5.

    But practice is practice, and theory is mostly good for letting you practice your math.
     
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  7. Sumner

    Sumner TrainBoard Member

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    The template is what is used and matches their build jigs if you use them but you are correct in how to cut the rail ends at both ends of the turnout. When you build them you leave the rail ends longer than the template or jig. Then cut them however far out that you like as you described. They don't show the extended lengths on the template or the build jig but tell you to do that.

    Yep, pretty much only at the frog area. Before and after that can depend....;)

    Yep, why I suggest obtaining some of the track and turnouts you will be needing anyway and laying them out in some test sections. I've also found, at least with the turnouts I've made, at least 2-3 inches of straight track before and after the turnout seems to make it a lot more reliable. Maybe commercial turnouts might be more forgiving. Of course the radius of a curve before/after is going to influence that. On my test track the radius is 12 inches and the short straight sections made the turnout work really well.

    Sumner
     
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  8. Michael Wagner

    Michael Wagner TrainBoard Member

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    Just so I understand the “the angle measured at the frog”, here is the ME #6 turnout template. Checking with a straight edge, the centerline of the diverging leg is straight pretty much from where it crosses the rail of the straight leg of the turnout.

    My assumption was that if I measure the distance between some point on the straight part of the diverging track and a point just below it on the straight track, that distance would be about 1/6 of the distance from centerline at the leading edge of the points to wherever I draw that perpendicular line.

    From what you are saying, that is not true?

    Part of the reason I am focusing on the math is that I am curious, but the other part is that I expect to use a ME flex track, and I have been told several times that once I have bent ME flex track, it is very hard to unbend it. I think that will make experimentation challenging.

    http://microengineering.com/Turnout_Templates_Micro_Engineering_HO_no_6.pdf
     
  9. acptulsa

    acptulsa TrainBoard Member

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    You're trying to get me lying.

    As I understand it, if I understand it, you draw two straight lines through the frog to the straight rail. One is perpendicular to the straight rail, and the other is aligned straight through the frog. The straight rail between those two intersecting lines should be six times the gauge of the track, or 3.9" in HO, on a #6 switch.

    Hopefully someone will correct me if I'm wrong.

    The points themselves don't seem to enter into it. Only the frog angle determines the switch number.
     
    Last edited: Jul 14, 2021
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  10. CSX Robert

    CSX Robert TrainBoard Member

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    Nope, angles don't work like that. Try the same logic in the opposite direction - a 1 in 1 is 45°, so a 2 in 1 must be 90°, but wait 90° is straight up, or infinity in 1.


    I don't know how you got that, but it's not correct. The arctangent of 1/6 is 9.46°, which matches what Fast Tracks lists for the diverging route angle in their #6 template: https://www.handlaidtrack.com/assets/downloads/tt-n-t-6.pdf
     
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  11. Michael Wagner

    Michael Wagner TrainBoard Member

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    Thanks for this - it all makes sense now. I misread a web calculator - instead of doing arctan(1/6), it was doing arctan(1)/6.

    So the calculation was incorrect, but the geometry works the way that I think it should work.

    This is very helpful.
     
  12. Sumner

    Sumner TrainBoard Member

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    Not really true if you have a tool ...

    [​IMG]

    .... like the one above. They use to be pretty easy to find. I finally found one in Canada prior to getting my 3D printer. Now I can print them and so can anyone else with a printer. I have that tool on my site ( HERE ). With it or one like it you can curve ore straighten ME track in seconds. If you don't have a printer I've seen people make them with other means. I've only used ME code 55 and love it since it is easy to curve and holds the curve making it very easy to put in place.

    I also ...

    [​IMG]

    [​IMG]

    ... have the same type of tool on a compass where you can use the compass to layout a track's centerline or to actually bend the track to the desired radius. You can find any of this stuff ( HERE ) along with the links to the print files on my thingiverse.com account,

    Sumner
     
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