turnout radius

[Anonymous]

I have a remedial question
the sizes of turnouts how do you know what the radius of the turnout is?
what does a #6, #8 and so forth mean in radius?

thanks

[Don Gibson]

Most HO turnouts are graded by ratio since they only curve from the points to the frog and are straight beyond that.

There are a few exceptions:
ATLAS 'Snap' switches fit into an 18" radius
PECO's "medium" switch claims fitting into a 36" radius, so does ELITE (both made in Europe) and Shinohara and Walthers offer Curved switches if you have the room.

These 'Curved Frog' turnouts ADVANTAGE is they can fit into a curve and keep the geometry intact, Their DISADVANTAGE is wheel flanges are more apt to pick the opening in the frog and derail.

In practice the #4 is the most popular turnout d'Jour for Yards and #6 for mainlines. The 4X8 plywood empire's limit is 22"r curves.. One can use larger turnouts,- but why?

[cacole]

I don't know about radius, but Peco turnouts diverge away from the main line at an angle of 12 degrees. Four Peco turnouts and a 24 degree Peco crossover can be used to form a double crossover.

[IRONROOSTER]

The turnout number is how many units of length it takes for the diverging track to get one unit from the thru track. Thus a number 4 turnout will have the center lines 1 inch apart after 4 inches, 2 inches apart after 8 inches.

John Armstrong's book "Track Planning for Realistic Operation" gives the equivalent radii for turnouts. There is one for radius of closure rail (rcr) and one for radius of substitution. The first is for individual locos/cars the second is for the train. rcr is always smaller. For a #6 turnout in HO they are 43" and 56". I highly recomment this book.

Enjoy
Paul

[Anonymous]

Kato makes it easy. No. 4 turnouts have a radius of 481 millimeters. No. 6 turnouts have a radius of 718 millimeters. Each of them has an arc of 15 degrees.