Can an HO, 6 axle, SD40-2 and a 4-8-2 handle the degree of curvature in an Atlas 280 Custom-Line Mark IV Wye Turnout (19 degrees, 12 feet)? If not, what is the smallest wye (HO, code 100) that both locomotives can handle? I would prefer a 3-way turnout instead if I could find one for a low price. All of the 3-way wyes I've found so far are more expensive than I'm willing to pay ($44 and up). The curvature of the turnouts really wouldn't matter at all since I would only be using it in the straight position. The turnouts would actually turn "off-layout" in each direction and be in place purely for representation. Thanks in advance for any help. -Brandon
Brandon, I have one of the Custom Line wye's on my layout. I'm not sure about the 4-8-2, but I think the SD40-2 will handle it fine, based off the performance of my Athearn SD45. I have an older blue-box SD40-2 which I don't operate anymore, but it always handled no. 4 turnouts o.k. Pat Moreland, Union Mo.
Although most manufacturers use the term “wye” to describe the turnout about which your questions are centered, the more accurate term is “equilateral” turnout. The Atlas line of turnouts is an entity unto themselves. For example, the Atlas number 4 turnout is really about a number 4.4, and the “wye”, which is not listed with a frog number, is about a number 2.9. Frog Number = 1/tan theta , where theta is the frog angle in degrees By the way, the Atlas turnout Custom Line Wye frog angle is 19 degrees 12 minutes not 19 degrees 12 feet. (The single tick or quote mark denotes minutes in this case). Degrees of angle may be expressed in decimal degrees or in degrees-minutes-seconds. So 12 degrees 12 minutes equals 12.2 degrees. While the frog angle is an important consideration to use when selecting a turnout, one other turnout dimension ultimately determines what type of equipment can operate through a given turnout, i.e., the Radius of the Turnout Curve (ROTC). This curve is a circular curve, which begins just past the heel of the switch, and it ends at the end of the angle bar at the toe of the frog. This dimension should not be confused with a dimension called the Radius of the Equivalent Curve (ROEC), which extends from just before the point of switch to just before the theoretical point of frog. The radius of this curve is determined by the frog angle, the distance between the point of switch and the point of intersection, and the length of the switch points, which are in most cases straight. The Equivalent Curve might also be described as the substitution curve radius, that is if the ROEC of a model turnout was 43 inches, then the turnout could be placed anywhere in a circular curve of that same radius, and the alignment between the PS and the heel of the frog would align with the circular curve. The ROEC > ROTC. The Atlas literature states, “…making the curve leg equal to a regular 18” radius section. “, so the ROEC is equal to 18”, and therefore the ROTC will be slightly less. This might be a problem for the steam locomotive.
That is a very detailed description by Karl, the track guy's like that a lot. Equilateral switches are somewhat rare on most railroads. Sometimes they were used at one end of a old siding, when they wanted to increase the speed on both tracks. The speed was increased to around 30, for both sides. As longer turnouts was engineered, the need for this type switch dropped off. Globe or Lou after Louis Menk , depending on your time period was a wye switch at East Monett. Some turnouts now, are in the 50 MPH range. One such I helped to install at Red Oak, Iowa, I stood and watched trains over the switch. 50 is real fast through a turnout. Finally, I called the Division Engineer in Lincoln and expressed my concerns. He said it was engineered, for 50 and that is what they want, so I removed the slow order. The first train through their said it was really smooth. I watched several trains through the turnout. I really struggled with the speed, course that is part of the life of track people, always concerned about some spot on the track. About a year later Amtrak derailed, on this turnout, the cause was that the spring wing didn't close. It was equipped with a retarder, the first of its kind (on a No. 24), it was supposed to stop the wing slapping against the point so as to keep it from shaking itself apart. So much for that. The wye on my layout works nice, so long as the speed is low and the weight is right on the cars. They look real neat and wye's was a part of the old way of railroads. In the right location they bring realism to your pike. The wye in Monett, was where they cleaned out the diner.
At Valley Park, MO, the double track became single with a number 20 equilateral turnout. The Frisco had a 50 MPH speed limit through this track work. View is looking RR east. Unfortunately the lens that I used to capture this picture fore-shortened the turnout's appearance. BTW, the photo was taken from a public road crossing.
Thanks for the great information, Karl and William. If I recall correctly, Oma and Norris just south of Tulsa are both equilateral turnouts.
Ryan, the switches at Oma and Norris are in fact equilateral turnouts. If the rain stays away tomorrow I will snap some pics and post them. I live mid way between the two, not far from the right of way.
The old rule of thumb was two times the turnout minus five for the speed. It does not hold for all turnouts, but sounds good. I don't remember having equilateral switches on too many railroads. Most of them stuck with the left or right hand. Sometimes a equilateral was used at the top of a hill, so the train taking the siding would not have to slow down, preventing a break into or stall. That was the case for Red Oak, Ia and am thinking also Globe. Anyone know what the grade was at Globe Hill?
I'm still hoping for an answer to that question. What is the radius of each curve in the wye? All I can find out is that it is 19 degrees, 12 minutes but that really doesn't tell me what I need to know in terms I can understand. - Brandon
The Atlas literature states, “…making the curve leg equal to a regular 18” radius section. “, so the ROEC is equal to 18”, and therefore the ROTC will be slightly less. This might be a problem for the steam locomotive.
Thanks. I didn't realize that a "custom line" wye would have almost the same radius as a "snap track" section or turnout. What is the smallest wye a 4-8-2 can run through? #6? #8?
