#4 vs #5 turnout

[DSchmitt]

From  Railway Track and Maintenance by RR Russell Tratman

Frog Number  Frog Angle

#5   11 deg  25 min

#6     9 deg  32 min

#8     7 deg  10 min

#10   5 deg  44 min

#20   2 deg  52 min 

Chart in book is in 1 deg increments from 5 to 20

Tratman lists three ways of measuring frog number .  #1 is "measure the distance, in inches, between between the points where the width over gauge lines is 2 in and 3 in, this distance giving the frog number."

In drawing posted by 7j43k  - where A is 2 inches and B is 3 inches, C is the Frog Number. 

[gregc]

after re-reading Ed's post, I realize this is what he was describing

the discrepancy between what Randy reported, 9.46 deg or 9d 27", and the other value of 9.53 or 9d 32" is that the frog angle is not calculated as a right triangle.   There's no assumption that a frog is on a right or left handed turnout, but the same as if for a wye.  Makes less of a difference for smaller angles

frog angle = 2 * atan (0.5 / frog-number)

frog angles based on right-angle and isosceles triangles

     4    14.04 d   14d  2"    14.25 d  14d 15"
     5    11.31 d   11d 19"    11.42 d  11d 25"
     6     9.46 d    9d 28"     9.53 d   9d 32"
     7     8.13 d    8d  8"     8.17 d   8d 10"
     8     7.13 d    7d  8"     7.15 d   7d  9"
     9     6.34 d    6d 20"     6.36 d   6d 22"
    10     5.71 d    5d 43"     5.72 d   5d 43"
    20     2.86 d    2d 52"     2.86 d   2d 52"

 

 

[Anonymous]

I just use the printable turnout plans from fast tracks, cut ties to match, build the frog with the frog jig, points with point jig and eyeball the rest.

[tomikawaTT]

To distill the original question to its essential essence:

I handlay all of my specialwork, so I'm certain that my #4 turnouts (on my end-of-the-coal-hauler module, built in 1980) and my #5 turnouts (in the hidden staging yards at Nonomura, built within the last decade) are built to the proper dimensions.

That said, one of my long-wheelbase 2-Co+Co-2 EF18 or EF58 class juice jacks can slither through a #5.  Trying to force it through the curved route of a #4 will put it on the ground, every time.

Why?  Those motors require an honest 24 inch (610mm) radius to operate.  The closure rail of a #4 turnout has a radius too tight for the long rigid wheelbase.  The axle under the center of the carbody gets pinched over the rails on whichever truck hits the tight spot first.

Chuck (Modeling Central Japan in September, 1964)