OO Handmade Points

[Moses of the Mail]

Can any one tell me where I can obtain frog angles for different radius points in 4mm scale  (16.5mm gauge/finescale)

 

Thanks

[martin_wynne]

The best way is to use Templot to display turnouts of different V-crossing angles and switch sizes, and read off the radius values for each.

 

For each turnout there are several different radii which may interest you, but the main two are:

 

1. the turnout radius between the heel of the switch (blades) and the V-crossing (frog). This is usually the smallest radius within the turnout and corresponds to the actual radius in the rails.

 

2. the substitution radius (called the External Geometrical Radius in Templot) which is the "average" radius from the straight track to the exit from the V-crossing. This is the radius of curved plain track into which the turnout could be substituted. This is the radius which is usually quoted by manufacturers -- the actual radius in the rails is often much smaller.

 

What sizes are you looking for?

 

For example here is the full data from Templot for a straight B-7 turnout in 00-SF having a regular-type V-crossing.

 

Note that you would get different radius results for generic and curviform type V-crossings, for a different track gauge (16.5mm), for different switch sizes, etc. Also of course if the main road is curved. Often you can get an easier radius by using the old-type loose-heel switch geometry instead of REA switches.

 

You can see the big difference between the turnout radius 49.6" and the substitution radius 94.9"

template generated at 12:34:46 on 22/11/2014 using Templot v:2.11.a
scale = 4.0 mm/ft     scale ratio = 1:76.2
track gauge = 16.2    flangeway gap = 1.0
template: straight
rail head only (bullhead): rails vertical
------------
LH turnout:
REA semi-curved  B-size left-hand switch (unjoggled)
1 in 7.00 RAM  ( 1 in 7.04 CLM ) regular V-crossing
square-on timbering
------------
adjacent track centres main side = 44.67
adjacent track centres turnout side = 44.67
angle at TXP crossover mid-point (CTRL-5) = 8.13 degrees ( 1 in 7.0 RAM )
angle at TVJP turnout road vee joint (CTRL-6) = 8.13 degrees ( 1 in 7.0 RAM )
------------

turnout-road centre-line radius (at turnout-curve) = 1259.29

switch-curve radius (rail gauge-face) = 2452.0
turnout-curve radius (rail gauge-face) = 1267.39
switch-curve radial centre: X = 228.94  Y = 2443.62  (from CTRL-0)
turnout-curve radial centre: X = 293.17  Y = 1260.76  (from CTRL-0)
V-crossing entry-straight (curve-end to fine-point) = 14.0

switch front (rail-joint to switch-toe) = 21.67
virtual lead (switch-toe to fine-point) = 210.19
actual lead (switch-toe to blunt nose) = 211.95
blunt nose to timber A = 1.33
width of blunt nose = 0.25

wing rail reach length (main-side) = 16.0
wing rail reach length (turnout-side) = 16.0
check rail overall length (main-side) = 52.0
check rail overall length (turnout-side) = 52.0
------------
smallest radius on this template = 1259 mm ( 49.6 " )
total angular swing on this template = 0 degrees (in main road)
------------
nominal gauge :   00-SF    16.2  mm    4 mm/ft     1:76.2    00 Special Fine EM dims
------------
template location on trackpad :

rotation :  X = 0   Y = 32.1   K = 0 degrees
   shift :  X = 0   Y = 0.0
rail-end :  X = 0   Y = 24.0

peg from origin :  X = 0   Y = 32.1   K = 0 degrees
peg from notch :  X = 0   Y = 32.1   K = 0 degrees


track centre-line radius at peg = straight
internal geometrical radius = 1603.76  ( 63.14 " )
external geometrical radius (substitution radius) = 2409.77  ( 94.87 " )
------------

 

regards,

 

Martin.

 

edit: meaningless overall length deleted. Overall length to vee rail joint is 289mm.

[Donw]

Turnouts have a switch radius, then the closure radius and then the crosing which may be straight or curved.  Martin has explained how the overall substitution radius is the average of these. However if you want to fit a turnout into a curve you can create a turnout on the curve this can be done in Templot. Start with a curved turnout then using F6 curve the main away from the diverging road until the smallest radius is the value you want.

Don

[hayfield]

Can any one tell me where I can obtain frog angles for different radius points in 4mm scale  (16.5mm gauge/finescale)

 

Thanks

 

 

Moses

 

I am a bit confused at your request as what you have asked could be understood in a few different ways.

 

For instance when building scale turnouts now most use the crossing angles 1 in 5, 1 in 6, 1 in 7 etc

 

Where as Scale way and older points (GEM, Graham Farish etc) used radii 24", 36", 54" etc

 

Now Peco from what I understand use the same crossing angle, but change the crossing length to give small, medium and large points

 

As you can see what is known as the Frog (or common crossing) can be something different depending on what you are trying to achieve and which system you are using. Donw is quite correct in bringing Templot to your attention as it can produce a plan with either a displacement radius or with an actual radius, but the frog/crossing angle will differ depending on which method you use.

[DLPG]

I have started to hand built my own turnouts. what do you guys think of the Traintronics slow motion point motors? Bought a couple to try, yet to be installed.

[Donw]

My choice is tortoise.

Don