Athearn hasn’t been able to provide any info. Does anyone know if a Genesis Big Boy (and Challenger) would negotiate a #4 Wye turn out?>P? If I recall correctly from my reading and a friend concurred, a wye’s number (4) divergent curvature would be twice the number of the turn out? (equal to a #8)?
I could see if I have room for a #5 but I doubt it and won’t get to that upper level for another month or more.
The loco is supposed to negotiate 22" radius curves. (I’d be using Walther’s Shinohar Code 83 HO).
I do not believe that a wye turnout # necessarily means that you can safely halve the actual diversion from the turnout’s major axis (ie, straight ahead, linear to its single ingress axis). I think a #4 wye turnout will look like a regular #4 flipped over so that it is symmetrical on either side. In that respect, it should be no worse than a regular #4 through either route…and that means it won’t be any better, either.
But I will continue to read in case I am mistaken. Couldn’t hurt to learn su’thin’. [:)]
-Crandell
Edit- I think I just learnt su’thin’. I went to handlaidtrack.com and looked at a #4 wye template. It sure looks to me like one side of it is much more in keeping with a #7-8, visualizing the major axis as a normal through route. So, it seems as if you are right!
What i have seen is that it will work as long as you have a gradual radius (24" or better) off the turnout. I don’t run steam, but a buddy of mine ran his UP challenger thru the wye on my layout and it negotiated the #4 wye turnout just fine. My radius is 30" off the turnout in both directions before connecting to a #4 right hand and at the other end a #4 left hand turnout to complete the wye (It’s a big wye) …chuck
If it helps at all, Cap’n G., I have a Fast Tracks #6 double slip turnout in my yard, and I haven’t found a single item that isn’t perfectly happy negotiating its various widely divergent routes. If a #4 wye equates to a single #8 on each side, that is a nice long turnout, as Chuck suggests above, and pretty much everything, even most brass steamers, should have little or no trouble.
Affirmative! The “number” of the turnout indicates the frog only. What decides the radius is the distance from the points to the frog. If you laid a #8L on a #8R turnout you would see why the frog angle becomes a #4 (because both sides are diverging) and the frog axis would be right on the incoming tangents’ centerline. I hope this clarifies. John
Thanks Mr. Clark. I don’t know my radius at the wye yet but pretty sure it will be 28" to 30". I have a paper template I’ve made that I’ll dig out and measure it.
Crandell, thanks for the additional info as always.
John Colley, I’ve followed up with a regular email to you… So…if Mr. Colley and my buddy are correct about the equals a #8 standard turnout, the Big Boy should be ok? I can’t think of any other variables (other than the radius of the approaching/leaving curves that might affect things…?
I was wondering when someone would get to that. A #4 wye = a #8 normal. A #3 wye = #6 normal etc. A Big Boy that can negotiate a 22" curve should have no problems at all with that large of a turnout.
I’m not going to say that it won’t do it but I sure as the dickens wouldn’t trust it on a regular basis.
According to NMRA RP-12.3 an HO-Scale #4 switch/turnout diverges from the tangent on a 43" radius off of the points; the (closure) rail radius, however, is only 15" and that is likely to give you headaches.
On the other hand an HO-Scale #5 switch/turnout diverges from the tangent on a 43" radius off of the points but the (closure) rail radius is 26" and that shouldn’t give you troubles.
Yup, maybe a hard concept to grasp but because the wye diverges in both directions, the frog is a no. 4 but the degree of replacement radius is the same as a no. 8 turnout. Check the Walthers line of track to see examples.
I have a #4 wye going into a car repair shop on my layout. I just ran a Rivarrossi Big Boy through it with no problems at all. I then tried one of my Proto 2-8-8-2’s and it too ran through it with no problems. I tried both at a slow and fast speed. Your Athearn Big Boy should do it as well.
Wow. No wonder beginners are so befuddled. I’d be interested to hear what people think about what RT Poteet was saying about the radii.
The majority of folks here think the #4 wye should work. I know that Proto advertizes the 2-8-8-2 to be able to negotiate #4 STANDARD t.o.s so I figured that loco would be ok.
It’s good to hear that the Rivarossi B.B. had no problems. I guess…final trial and error will be the ultimate determiner…hopefully I’ll have room to place a #5 on the layout IF I have problems. But won’t know that for awhile yet. Seems like the odds are at least good that at slow speed things might be ok according to big steam users with #4 wyes…Thanks TA for your confirmation run.
Based on my new understanding, you should have no trouble even with a brass engine through that turnout. The closure radius of a #4 wye is well outside 35".
