Turnout Radius Size Question
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Edit - OK I can't stand it.
An Atlas #6 (Mark II style not the superswitch) has 10 degrees of departure angle (according to them not my measurement). This means the frog is a 5.6 or 0.1767 radians. Call this theta.
The cord of theta can be measured by the square root of (1 - COS(theta) squared) + SIN(theta) squared or 0.1796
The cord of an Atlas measures 9 7/8".
The formula is: radius cord(theta) = 9 7/8
so reconfiguring to get Radius = 9 7/8 / cord (theta).
then substituting values from above, Radius = 54.9"
Then to check it out practically,
I got a protractor and laid two straight edges at 10 degrees.
I took an Atlas #6 turnout and moved it perpendicular along one edge until it fit. It fit at 54".
this switch (and curved in general) supposed to be more problematic then usual so i wouldn't put it on mainline. it worked fine in a spur however
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trailrider
Well-Known Member
Appears that way to me.
Rico
BN Modeller
Are you looking at HO or N scale? I believe there are differances in the two.
There's a website out there that lists all the makes, can't remember where.
Here's Peco's turnouts: http://www.barcourt.com/peco.htm
Maybe try Atlas' forum?
Just remembered Atlas has a few types of switches too.
There's a website out there that lists all the makes, can't remember where.
Here's Peco's turnouts: http://www.barcourt.com/peco.htm
Maybe try Atlas' forum?
Just remembered Atlas has a few types of switches too.
Last edited by a moderator:
Beachbum
Member
My Atlas Custom Line Code 83s #4 diverging rails are actually straight from about an inch before the frog to an inch after so the diverging route isn't really curved.
However, if I lay a 22-inch radius curve over the turnout starting at the points, it matches the diverging route quite well. Not sure about a #6, maybe a 24-inch?
However, if I lay a 22-inch radius curve over the turnout starting at the points, it matches the diverging route quite well. Not sure about a #6, maybe a 24-inch?
GandyDancer
Member
sorry duplicate see below.
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GandyDancer
Member
No. I would guess closer to 33". But the bottom line is that a standard North American turnout does not have a radius. The proper way to do it is to create two separate radius. One from the end with the points and the other from the end of the diverging track. The two centers of the radii would be offest by the degree curvature of the turnout (9.46 degrees for a real #6 and 10 degrees for an Atlas) and the length of that piece of track.
Edit - OK I can't stand it.
An Atlas #6 (Mark II style not the superswitch) has 10 degrees of departure angle (according to them not my measurement). This means the frog is a 5.6 or 0.1767 radians. Call this theta.
The cord of theta can be measured by the square root of (1 - COS(theta) squared) + SIN(theta) squared or 0.1796
The cord of an Atlas measures 9 7/8".
The formula is: radius cord(theta) = 9 7/8
so reconfiguring to get Radius = 9 7/8 / cord (theta).
then substituting values from above, Radius = 54.9"
Then to check it out practically,
I got a protractor and laid two straight edges at 10 degrees.
I took an Atlas #6 turnout and moved it perpendicular along one edge until it fit. It fit at 54".
Last edited by a moderator:
hamltnblue
Active Member
There are two different Atlas #4 switch offerings. One has a 22"r turnout, the other is mostly straight.
Selector
Well-Known Member
You can't use a radius for N. American style turnouts. Instead, eyeball what seems to fit and go with that, but try not to have a sharp curve leading into any of the three entrances/exits. Try to have their approaches straight for at least the length of a truck or the driver base of a steamer....ideally...not always achievable.
Instead of a radius, the routes are straight through and beyond the frog for a reason. What you can use somewhat is known as the 'substitution radius', and on a #6 turnout to NMRA specs, that is about 42" or a bit more...I forget...but it is over 40".
-Crandell
Instead of a radius, the routes are straight through and beyond the frog for a reason. What you can use somewhat is known as the 'substitution radius', and on a #6 turnout to NMRA specs, that is about 42" or a bit more...I forget...but it is over 40".
-Crandell
Cjcrescent
Master Mechanic
GandyDancer
Member
Atlas
The original curved Atlas turnouts were exactly that dimension; however, they stopped making them in 1984 or so and are getting very hard to find in the secondary market (ebay, swap meets, etc.). I buy them whenever I see them. Model Power made them up until a few years ago, unfortunately most of those were brass. Peco makes one that is about 17 3/4" inside radius, but I don't remember the outside radius.
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tankist
Active Member
peco. the bigger radius is 24 however.
this switch (and curved in general) supposed to be more problematic then usual so i wouldn't put it on mainline. it worked fine in a spur however
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