Selective Compression Of Wyes?

Discussion in 'Narrow Gauge Model Railroading' started by Mountain Man, Feb 10, 2007.

  1. Mountain Man

    Mountain Man Active Member

    Here is a question for those MMR geniuses who walk amongst us dispensing knowledge: :)

    While working on my layout design, I meanured out the protype lengths of the "legs" of the wyes commonly used - they work out to between 300' - 350' per side. That scales out to a triangle over 2' per side, which is difficult to shoehorn into an HOn3 layout.

    My question is: how much can the wye be selectively compressed and still function properly?

    Per my fledgling trackplan, 3 sections of 18" radius per side are required plus a staight section of flex to fit across the base of the wye. Does anyone have any practical experience with 15" curves on wyes? I'll be running 1890's 2-8-0's and 4-6-0's, which can allegedly handle such tight curves.

    BTW - in the prototypical region in which I am basing my design, turntables were virtually non-existent.
  2. cidchase

    cidchase Active Member

    You need enough straight at the end to accommodate a loco and tender. Whatever radius your loco can stand is fine. The relative shrinking of the radius is probably as much or more than the length, anyway. :thumb: (Modeler's Licence) Some old turntables were even turned by hand:)
  3. sumpter250

    sumpter250 multiscale modelbuilder

    A wye, needs to have legs (the sides of the triangle) equal to the maximum length of whatever is being turned on the wye. This also applies to the extensions at each corner, you have to clear the points. A narrow gauge train of five cars, a loco, and a caboose, will be approximately 235'. An outside frame 2-8-0 at 55', rolling stock at 30', and a long caboose at 30', this takes into account the length of the couplers. This is 2.7' . If you are only going to turn a loco and caboose, leg and extension each would be 85', or just under 1 actual foot. While you could probably be able to use 15" radius, I'd recommend 18" radius at the tightest. This is a 45 degree curve. I don't have formula handy to compute the actual length of 235 track feet layed in a 45 degree curve. The wye may have two curved and one straight side, or all three curved. In the case of the "straight" side, your looking at 1 extension, 1 side of the triangle, and 1 more extension....705' or 8'1-1/4". Remember, the thing you are turning has to clear both sides of the turnout on each corner of the wye.
  4. nachoman

    nachoman Guest

    My roundhouse 2-8-0s go around curves of 14-15" okay. One of them I had to file a bit off the inside of the clylinder casting to keep the pilot truck from shorting out against the cylinders.

  5. MasonJar

    MasonJar It's not rocket surgery


    I have no practical experience with wyes (they don't fit on a 2x4 module ;)) but I can't figure out why the legs (sides of the triangle) have to be as long as the longest train you wish to turn... I understand why the extensions must be so, but not the legs...? :confused:

  6. sumpter250

    sumpter250 multiscale modelbuilder

    Hmmmm......I haven't built a wye, and have only seen a couple. One was an ariel view, and showed legs and extensions as about the same length. Asking that question, stirs up brain cells that haven't been used in some time, the ones that deal with logic.:D I believe you have a valid point there. The legs can actually be shorter, as they are simply a connection between the extensions.
    I believe my brain is actually running slower than dial-up ! The wye I remember seeing the ariel picture of was set up with one leg on a passing siding, and the other two legs, because there was no other choice, were bridged across a river! Because the two were so long, the third (passing siding) also had to be long.
  7. pgandw

    pgandw Active Member


    You are right, the legs don't have to be a train length long to turn the train, only the extensions do.

    But if you use the wye as a run-around or passing track (often done in model layouts), then at least one leg has to be a train length long. Tail tracks still need to hold at least a locomotive in the run-around operation.

    The Atlas 4x8 layout Plywood Summit Lines uses a wye with 15" radius curves in HO standard gauge. The Atlas books show the built layout using one tail track as a mine loading spur, with 2 hoppers. An AHM Indiana Harbor Belt 0-8-0 is pictured doing the mine switching.

    just my thoughts, your choices
  8. Mountain Man

    Mountain Man Active Member

    There seems to be some confusion and I apologize for not being clearer: I am talking about the wye itself, not the spurs.

    Prototype wyes run 300' to 350' straightline distance between turnouts, which is a lot of real estate on a layout in any scale. Can this be selectively compressed without compromising operations?

    Or to put it more clearly, in the scale of HOn3, what is the smallest workable wye?

    Turntables are nice, but they were too expensive a capital investment to be used if any more reasonable means were available to the fledgling narrow gauge lines. Many of those lines lived out their entire existence without a single turntable anywhere - just wyes. There were no less than five of them on the 40 mile stretch of the F&CCR from Florence to Cripple Creek, and they would have added more but lacked sufficient level ground to lay them out.

    One narrow gauge line reluctantly put in a turntable at Corkscrew Gulch because it was the only way to get down the mountain, pick up a string of loaded ore cars, and get back up. There wasn't even room for switchbacks and not enough room for the stubs needed to make a successful ladder as done elsewhere, so they put in a 2-way-gravity-feed turntable, and then had to cover it with a snowshed to keep it working year round!

    I suppose I could put in a fancy turntable, completely out of character for the region, but that seems like the easy way out.
  9. 60103

    60103 Pooh Bah

    The most compact wye would be where 3 circles of your minimum radius meet, using matching curved wye turnouts. A slightly larger wye would use conventional wye turnouts, and be a bit bigger.
  10. Mountain Man

    Mountain Man Active Member

    I'm guessing that "matching curved wye turnouts" would have to be scratchbuilt?
  11. 60103

    60103 Pooh Bah

    Peco have a 24" radius wye in their code 100 and code 75 range.
    This could be used as a lead-in to an 18" radius wye; worth the sacrifice compared to building?
  12. Torpedo

    Torpedo Member

    Railway Engineering,, has code 55 HOn3 wyes available, including stub versions. They don't say what their effective radius is, but they do invite emailed questions. They are also narrow gauge fans.
  13. Mountain Man

    Mountain Man Active Member

    Thanks for the linki. Loks pretty useful!
  14. Torpedo

    Torpedo Member

    You are welcome. If you do order from Railway Engineering, I understand it is a good idea to do it early, as they do a lot of custom work and are frequently backed up.
  15. Mountain Man

    Mountain Man Active Member

    Also good to know!
  16. Canopus

    Canopus Member

    Pardon my ignorance but, what in the heck is a "wye"?
  17. Torpedo

    Torpedo Member

    Trackage generally in the shape of an inwardly curved triangle. It has three turnouts, one at each corner, and is often used to change the direction a locomotive or entire train is pointing. Wyes were cheaper than turntables to build and maintain, but took up much more real estate. They were often used where land was inexpensive.

    They were/are also sometimes used to connect a branch line to a main line, thus allowing the branch to be entered from either direction on the main. Same for leaving the branch.

    Also the term for a turnout in which the main and the diverging route curve away from each other, instead of the main going straight while the diverging route curves. Sometimes used for high speed passing sidings.
  18. Canopus

    Canopus Member

    Ah right, there is actually a British name for that, however it escapes me at this time. I think it might be "reversing loop", but I'm not sure.

  19. Torpedo

    Torpedo Member

    Here, a reversing loop is different than a wye. It is just a loop that is used to turn an entire train. Used at some passenger terminals and very common in trolley and interurban operations.
  20. Canopus

    Canopus Member

    Come to think of it yeah a reversing loop is just where the track turns back on itself. It'll come to me eventually.

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