I’m trying to figure out the turnout number for an HO scale turnout. I know that it’s the length from the point of the frog to the end of the rails divided by the spread. Measuring it, I get a spread of 1 10/16" in a length of 3 7/16" Converting to all sixteenths to make the math easier that’s a spread of 26 in 55. Dividing that gives me a slghtly over a #2 turnout. Now, looking at this turnout, there’s no way on earth it’s a #2. That’s almost a right-angle bend! It looks like at least a #4 or larger. What am I doing wrong here?
Measurement would be more correct if the frog angle were compared to a chart giving the associated number of turnout. Otherwise, try the length from point rail tips to the void at the centre of the frog, divided by the diversion distance from the through route’s centre line measured to the same point in the frog as before. Maybe that will come closer.
Methinks you’re measuring to the centerline of the track with your 1 5/8 inch dimension. The actual measurement should be between the gauge edges of the two rails that meet at the point of the frog.
Try measuring from the 1/2" spread point back to the point of the frog. If that’s 2 inches, the turnout is #4. If it’s 2 1/4 inches, it’s an Atlas #4, which is actually #4.5.
Chuck (modeling Central Japan in September, 1964)
Hello “Seamonster,”
Frog numbers can be measured in any units you like, but the ends of the turnout rails have nothing to do with it. Find the point where the frog rails have diverged by one unit, then measure the number of units back to the point of the frog. That’s the frog number.
So long,
Andy
Thanks, Andy. That was it. 1 cm. divergence and 4.5 cm back to the point of the frog so it’s a #4 1/2 turnout. And that’s what it looks like. It’s easy when you know the right way. Thanks again.
And that sounds like an Atlas Custom line.
It was on a friend’s layout so I don’t have the package here to refer to, but it was a Walthers turnout.