Jonesresidence
New Member
Hello, I'm lost on the math side of things in determining the amount of track necessary and the max radius of a turn. Could someone point me in the right direction on figuring this stuff out? Thanks and merry christmas
Radius? 2x4 n scale layout
- Thread starter Jonesresidence
- Start date
TrinityJayOne
N gauge fan
With sectional/static track it's easy, as most pieces are built to some round number radius and the packaging would indicate what it is.
To work out how many pieces you would need to complete the desired turn you need to know the angle of the pieces being used, which is completely independent of the radius. For example you may have a 30° piece that forms an 11" radius turn. To make a complete 180° turn you would need 6 of these pieces, and the resulting turn would have an 11" radius. The same turn could be formed with 15° pieces that also form an 11" radius turn, but you would need twice as many because they would only be half the length of the 30° pieces.
With flex track things become a bit more complicated, unless the curve you're investigating is a nice easily-measured angle like 90 or 180° (just use a tape measure in these situations). Otherwise there is a way to do it with maths, but that particular topic was never dear to my heart.
You may wish to check out a layout designing program called SCARM. It's very easy to work with, can create simple 3D renders of your layout, and most relevant here it can produce a shopping list of all the parts you've used so that you know what to buy.
To work out how many pieces you would need to complete the desired turn you need to know the angle of the pieces being used, which is completely independent of the radius. For example you may have a 30° piece that forms an 11" radius turn. To make a complete 180° turn you would need 6 of these pieces, and the resulting turn would have an 11" radius. The same turn could be formed with 15° pieces that also form an 11" radius turn, but you would need twice as many because they would only be half the length of the 30° pieces.
With flex track things become a bit more complicated, unless the curve you're investigating is a nice easily-measured angle like 90 or 180° (just use a tape measure in these situations). Otherwise there is a way to do it with maths, but that particular topic was never dear to my heart.
You may wish to check out a layout designing program called SCARM. It's very easy to work with, can create simple 3D renders of your layout, and most relevant here it can produce a shopping list of all the parts you've used so that you know what to buy.
Radius is measured from the center of the track. You need to add an inch for the width of the track plus clearance to the edge of the table. 11" radius would put the edge of the track at the edge of the table, a no go situation. 10" flex or 9-3/4" sectional would leave about a inch on each side of the table. You still need to be careful not to knock cars onto the floor. If you can cheat the width a few inches its worth it.
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jdetray
Well-Known Member
The following diagram may be helpful. It shows how an 11-inch radius curve would fit on a layout that is 24 inches deep. As you can see, an 11-inch radius curve puts the track very close to the edge of the layout, which as others have pointed out, can easily result in trains going over the edge and onto the floor.
As for the length of the curved portion, for a 180-degree curve (half of a full circle), the formula is:
length = pi x r
In this case, r = 11 inches and pi is approximately 3.14, so
length = 3.14 x 11 = 34.54 inches
So it will take about 34.54 inches of track to make a half circle with a radius of 11 inches.
- Jeff
As for the length of the curved portion, for a 180-degree curve (half of a full circle), the formula is:
length = pi x r
In this case, r = 11 inches and pi is approximately 3.14, so
length = 3.14 x 11 = 34.54 inches
So it will take about 34.54 inches of track to make a half circle with a radius of 11 inches.
- Jeff
otiscnj
Well-Known Member
Tray is correct about the track radius definition. I've seen in the last couple of years that train set manufacturers these days often show the dimensions of their set's included track as being the outside diameter of the circle or oval, rather than the radius, at least with HO. I got into the hobby so long ago, it doesn't matter now, so I don't know if this type of difference helps or hinders new people today.
jdetray
Well-Known Member
I'm not sure who "Jim" is, but there are two different track planning programs mentioned in this thread.
I drew the example in Post #4 using XTrackCAD, a popular free program that has been around for years.
Also mentioned is SCARM (Simple Computer Aided Railway Modeller), a relatively new free program that is growing in popularity.
Both have extensive track libraries, including Peco. They are both very capable programs, but you must be willing to get past their initial learning curves.
- Jeff
