Approx radii of a #2 and 1/2 wye

Model Railroader General Discussion (Model Railroader)
1

Does any body know the approximate overall dimensions and approximate radii of a HO scale code 70 #2 nad 1/2 wye? Need the info for a possible track revision. Thanks

Old Fat Robert

2

You have to specify a brand to talk about radius - the number is only indicative of the angle of the frog. The radius can and will vary from brand to brand, or line to line.

3

Robert,

Here’s what I found out from this .pdf page on turnouts:

The two routes curve in opposite directions, which can save space in some tight situations. A #4 wye matches the frog angle of #8 turnouts and a #3 wye matches the frog angle of #6 turnouts. However, the closure radius of a wye turnout is much smaller than the closure radius of the matching conventional turnout.

Here’s what the same .pdf says about closure radii of the following turnouts:

  • #4 - R15"
  • #5 - R26"
  • #6 - R43"
  • #7 - R49"
  • #8 - R67"
  • #10 - R117"

At a minimum, it will be under R15" and, perhaps, a single-digit radii. Pretty tight for all but the smallest of switchers and rolling stock.

Tom

4

The only one I am aware of is one made by Shinohara. I have e mailed them but have yet to receive a reply.

5

My error. I meant to say the only one I know of is made by BK Enterprises aka Trout Enterprises. I am sorry if I mislead anyone.

Old fat Robert

6

Tom: Thank you for your input. You obviously have a greater grasp of this subject. Using the info you supplied, I computed the difference between a 4 and 5 at 57%. Following that logic (?) I came up with a radius of about 8.5 inches. That will certainly do for an interurban line that has a single 40 foot trolley in operation.

Robert

7

Not necessarily a greater grasp, Robert…Just a knack for googling an answer.

Anyhow, glad that helped. I actually saved that .pdf file into my Train folder for later reference.

Tom

8

Wye turnouts are half though, they split the difference between the right and left leg, rather than having all the radius in the diverging leg. So a 2 1/2 wye is going to have a frog angle and radius equivalent to a #5 turnout. It won’t be under the 15" radius of a #4 turnout.

–Randy

9

Dang, Randy: You just shot my track plan theory down!! ALthough I must admit that what you said makes a lot of sense. Thank you for the input.

Old fat Robert

10

Looking at the Fast Tracks site for HO fixtures.

A #4 wye turnout jig (smallest they offer) has a diverging radius of 43". The equivalent straight turnout, a #8, has a diverging radius of 67".

So a 2 1/2 will be something less than 26" for a #5 per NMRA RP12.3.

Multiplying 26" by 43/67 = 16.69". Note that this may not be a valid extrapolation. It’s also possible that the actual turnout is made to have a larger diverging radius.

I suggest you get a 2 1/2 wye and measure it.

Good luck

Paul

11

Thanks Paul. I am attempting to get my hands on one. As mentioned before, I have e mailed the only maker that I am aware of for specs. Am waiting for their reply.

Robert