What is a HO switch equal to?

[Anonymous]

What radius is a no. 4 no.6 no.8 no. 10. any input would be great

[jrbernier]

No real radius - The 'angle' is the key here. The radius of the points to the frog can vary as to the manufacturer. A #4 is 'about' 18-20" radius, a #6 is about 30" radius....

Jim Bernier

[Anonymous]

The John Armstrong book, Tracklaying for Realistic Operation, lays it out better than ever. He has a table that tells you the closure rail radius for each frog Number. This would be what you would go by to keep trackage up to the minimum standard radius you set for your curves. The closure rail is the rail between the end of the points and the frog. Track through the frog is straight. This is what throws people off, so he also gives a "substitution radius" or the radius the switch will replace as a whole unit. The frog number is the angle of the two tracks where they cross. And as stated above it can vary from manufacturer to manufacturer. Atlas even has mislabeled a #4 1/2 as a #4. In short, you need to have the switch on hand to determine how it fits in a curve.

[Anonymous]

Switches or turnouts have multipal radiuses within them. The number given shows the ratio of the turnout, at the frog. A number 4 has four units of distance traveled compaired to 1 unit of diversion. A number 6 has a 6 to 1 ratio and so on.

[Don Gibson]

QUOTE: Originally posted by jrbernier

No real radius - The 'angle' is the key here. The radius of the points to the frog can vary as to the manufacturer. Jim Bernier

AMEN!
NMRA HO standards are based on divergent RATIO at the frog and the only 'curveture' is within the points - which varies from manufacturer to manufacturer. Some have claimed a #4 is equivalent to 36'' r. I have my doubts because it's closer to 18" through the points. A curved point rail is only secured at two ends. That is liitle to hold a 'bend' in a rail with a 'straight' memory...
Which might explain why a Broadway 4-8-4 will exibit some bind running through my current number 6 turnouts.

BK and RAILWAY ENGINEERING make their turnouts with curving continuous-rail points. I have found that makes a difference.

My Edit:
I run Steam and coupled 76" wheels require tighter adherance to specs on turnouts than Diesels.