Track mysteries explained

Degree of Curvature

Switch #s

Track manufacturers

9-27-06

Degree

of curve

Radius

feet

1/20.3

Radius feet

1/32nd

Radius feet

1
5,729
282.2
179.0
5
1,146
56.5
35.8
10
573
28.2
17.9
15
383
18.9
12.0
20
288
14.2
9.0
25
231
11.4
7.2
30
193
9.5
6.0
35
166
8.2
5.2
50
118
5.8
3.7
60
100
4.9
3.1

Curves as an angle

Main Line High Speed track will use 1/2 degree maximum if possible. With the French TGV it is better to pull a 2% grade than go around a curve at 168 MPH. On the other end of the scale the Uintah had 60 degree curves 5' in 20.3. Most tight Rio Grande narrow gauge curves were 20 degree.

The mystery of track curvature? From the beginning of railroading curves were rated in degree of curvature. This was because measuring the actual radius or diameter was almost impossible. It would be impossible to find the radius of a curve with cliffs and mountains in the way. Also with a small segment was hard to find the center. So we just stretch out a chain 100 feet long and measure the angle from the tangent. In “G” gauge there are many scales so I picked the two most diverse; 1/20.3 and 1/32. Everybody else in somewhere in between.

The Prototype curve data at left is from a wonderful book I bought at a used book store. The book is “Trautwine” the “Civil Engineer’s Pocket-Book” twentieth edition 1919.

Switch #
Radius feet
1/20.3

Radius feet

1/32nd

Radius feet

4
150
7.4
4.7
5
235
11.6
7.3
6
339
16.7
10.6
7
461
22.7
14.4
8
602
29.7
18.8
10
941
46.4
29.4
12
1356
66.8
42.4
16
2410
118.7
75.3

Switches are rated in Numbers

Main Line High Speed track will use very large radius switches if possible. A number 16 is a 1/2 mile radius. In switch yards where space is limited they use as tight as required. LGB and Aristo make 2 foot radius switches. Never use them with anything but a 0-2-0 (more on that later).

4 foot radius will work but use only 5 foot or bigger for best results.

Some manufactures use the numbers but, it is only a guide and not really to scale. I don't think I'll be using true #16 switches since my lot is only 100 feet wide.

The Prototype switch sizes at left are from a wonderful book I bought at a used book store. The book is “Trautwine” the “Civil Engineer’s Pocket-Book” twentieth edition 1919.

Manufacturer Code Material
LGB 332 brass
Aristo Craft 332 brass and stainless steel
Accurcraft 250 brass
Micro Engineering 205 and 250 nickel silver
Llagas Creek 215 and 250 aluminum & nickel silver
Peco 200 and 250 nickel silver
Old Pullman 205 and 250 nickel silver
Sunset Valley 250 aluminum & nickel silver
Bachmann 332 steel bent over plastic
Lionel 332 formed sheet brass
New bright 332 plastic
Who Makes what?

Well there are a lot of track manufacturers out there and Trains West stocks al lot of them and can get about all of them. Here is what I know.

Nickel Silver will blacken beautifully

Aluminum costs the least

Brass blackens well, conducts well, easy to work

Stainless never needs cleaning, always bright

Bachmann will really rust

www.trainswest.com

Rail

lb./yd.

Actual size inches

Scale 1/20.3

Scale 1/22.5

  Scale 1/24

  Scale 1/32

40

3.500

0.172

0.156

0.146

0.109

45

3.688

0.181

0.164

0.154

0.115

50

3.875

0.191

0.172

0.161

0.121

55

4.063

0.200

0.181

0.169

0.127

60

4.250

0.209

0.189

0.177

0.133

70

4.625

0.228

0.206

0.193

0.145

80

5.000

0.246

0.222

0.208

0.156

90

5.375

0.265

0.239

0.224

0.168

100

5.750

0.283

0.256

0.240

0.180

110

6.250

0.308

0.278

0.260

0.195

120

6.500

0.320

0.289

0.271

0.203

140

7.000

0.344

0.311

0.292

0.219

Model Rail is sized by code.

The code is 1/1000ths of an inch for height. Code 250 is .250” or ¼” high. Code 332 is .332” or 21/64” (slightly over 5/16”).

D&RG laid 30 lb./yd. rail at the start but soon went to heavier rail because of it’s better durability. 60 lb./yd. rail was typical for most narrow gauge railroads by 1900.

The largest available rail for main line standard gauge today is 150 lb./yd.

The Prototype rail sizes left are from a wonderful book I bought at a used book store. The book is “Trautwine” the “Civil Engineer’s Pocket-Book” twentieth edition 1919.