Reference on rail Size

Rail Sizes for

Protoypes and

Model Railroad

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Information on Prototype Rails and Sizes

There are web sites with valuable information on this fascinating (or mundane) topic. Scale model railroaders are often concerned about the size of rail they are using. The railway historians among us try very hard to produce model railroads that contain rail that matches the rail used by the prototypes being represented at the matching point in history.

The quest for a perfect representation is made difficult by several factors. First, the rail in use in 1840 may be different from that in use in 1845 at the same geographic location. It is almost certainly different from the rail in use in 1945 at the same spot. So, time is an important variable.

Second, rail is and has been manufactured by different organizations to varying tolerances. So, even if rail was specified a certain way, there is no assurance that the actual rail that was used is a precise match to those specifications.

Third, the steel used to make the rail varies in its resistance to wear. The technology in use by the powered locomotives and the idler wheels on rolling stock varies in its abrasiveness. The weather and traffic density are other factors governing wear on rail. So, rail that met certain specifications when newly installed may not meet those specifications when nearly worn out and ready for replacement.

Fourth, there are differing specifications for the cross-sectional profile of rail. That means that two pieces of rail which are 6 inches tall may have different weights for a standard yard-long piece.

Rail in use by the railroads is typically referred to in the modeling press by a single number: the weight of one yard of one rail. Many of us have assumed that the factors listed above can be neglected. That is OK to a certain tolerance. However, as some of us attempt greater and greater precision in our efforts to duplicate the real world in miniature, these tolerances and small differences become significant.

Some model railroad references assume that all 90 pound rail (a one-yard long piece of rail weighs 90 pounds) is the same and should be represented by rail that is .060 inches tall in HO scale. Sadly, that assumption is not supported by historical information nor by current manufacturing practice. In the chart below, we can see that brand new, 90 pound rail in HO scale might be as short as .057 or as tall as .065, depending on cross section. That sort of variance is found in several of the common rail sizes. The variances are proportionately larger in larger scales and smaller in smaller scales.

Model railroad rail is normally specified with a “code” number. For instance, some commonly available HO track is code 100. The code number stands for the number of thousandths of an inch of rail height. So, that code 100 rail is .100 inches tall. If we knew the weight of rail to be 90, then HO rail that satisfies the requirement might be code 57, code 65 or somewhere in between. That is of course, for brand new rail. Worn 90 pound rail will be shorter (and no longer weigh 90 pounds per yard).

The following links provide some additional, detailed information and some convenient compromises.

urbaneagle...RRrailsizes

pearcedale...track

harmersteel...railsections

nmra.org...rp-15_1

Comprehensive, World-Wide Rail Specs and S-Scale Conversions

S-Scale Glossary

The table on the Harmer Steel site listed above, contains information about rails. It shows information about differing cross sections for rail with nominally the same weight per yard in US pounds. The following table is based on the rail that is currently available from Harmer Steel. These folks produce railroad rail for lots of railroads. They offer rail that matches existing track.

Row	Nominal Weight per Yard	Height	Z-Scale	N-Scale	TT-Scale	HO-Scale	OO-Scale	S-Scale	O-Scale
1	12	2	0.009	0.013	0.017	0.023	0.026	0.031	0.042
2	16	2.375	0.011	0.015	0.020	0.027	0.031	0.037	0.049
3	20	2.625	0.012	0.016	0.022	0.030	0.035	0.041	0.055
4	25	2.75	0.013	0.017	0.023	0.032	0.036	0.043	0.057
5	30	3.125	0.014	0.020	0.026	0.036	0.041	0.049	0.065
6	35	3.3125	0.015	0.021	0.028	0.038	0.044	0.052	0.069
7	40	3.5	0.016	0.022	0.029	0.040	0.046	0.055	0.073
8	45	3.6875	0.017	0.023	0.031	0.042	0.049	0.058	0.077
9	50	3.875	0.018	0.024	0.032	0.044	0.051	0.061	0.081
10	55	4.0625	0.018	0.025	0.034	0.047	0.053	0.063	0.085
11	56	4	0.018	0.025	0.033	0.046	0.053	0.063	0.083
12		4.25	0.019	0.027	0.035	0.049	0.056	0.066	0.089
13	60	4.25	0.019	0.027	0.035	0.049	0.056	0.066	0.089
14		4.5	0.020	0.028	0.038	0.052	0.059	0.070	0.094
15		4.25	0.019	0.027	0.035	0.049	0.056	0.066	0.089
16	65	4.4375	0.020	0.028	0.037	0.051	0.058	0.069	0.092
17	70	4.625	0.021	0.029	0.039	0.053	0.061	0.072	0.096
18	72	4.75	0.022	0.030	0.040	0.055	0.063	0.074	0.099
19	75	4.8125	0.022	0.030	0.040	0.055	0.063	0.075	0.100
20		4.75	0.022	0.030	0.040	0.055	0.063	0.074	0.099
21		4.9375	0.022	0.031	0.041	0.057	0.065	0.077	0.103
22		5	0.023	0.031	0.042	0.057	0.066	0.078	0.104
23		4.9375	0.022	0.031	0.041	0.057	0.065	0.077	0.103
24	80	5	0.023	0.031	0.042	0.057	0.066	0.078	0.104
25		5.125	0.023	0.032	0.043	0.059	0.067	0.080	0.107
26	85	5.1875	0.024	0.032	0.043	0.060	0.068	0.081	0.108
27		5.125	0.023	0.032	0.043	0.059	0.067	0.080	0.107
28		5.1875	0.024	0.032	0.043	0.060	0.068	0.081	0.108
29		5	0.023	0.031	0.042	0.057	0.066	0.078	0.104
30		5.21875	0.024	0.033	.043	0.060	0.069	0.082	0.109
31		5.125	0.023	0.032	0.043	0.059	0.067	0.080	0.107
32		5	0.023	0.031	0.042	0.057	0.066	0.078	0.104
33		5.375	0.024	0.034	0.045	0.062	0.071	0.084	0.112
34	90	5.375	0.024	0.034	0.045	0.062	0.071	0.084	0.112
35		5.625	0.026	0.035	0.047	0.065	0.074	0.088	0.117
36		5.265625	0.024	0.033	0.044	0.060	0.069	0.082	0.110
37		5.625	0.026	0.035	0.047	0.065	0.074	0.088	0.117
38		5.53125	0.025	0.035	0.046	0.064	0.073	0.086	0.115
39		5.5	0.025	0.034	0.046	0.063	0.072	0.086	0.115
40		5.375	0.024	0.034	0.045	0.062	0.071	0.084	0.112
41		5	0.023	0.031	0.042	0.057	0.066	0.078	0.104
42	100	5.75	0.026	0.036	0.048	0.066	0.076	0.090	0.120
43		5.6875	0.026	0.036	0.047	0.065	0.075	0.089	0.118
44		5.5	0.025	0.034	0.046	0.063	0.072	0.086	0.115
45		6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
46		5.640625	0.026	0.035	0.047	0.065	0.074	0.088	0.118
47		6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
48		5.703125	0.026	0.036	0.048	0.065	0.075	0.089	0.119
49		5.75	0.026	0.036	0.048	0.066	0.076	0.090	0.120
50		5.75	0.026	0.036	0.048	0.066	0.076	0.090	0.120
51		6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
52		5.625	0.026	0.035	0.047	0.065	0.074	0.088	0.117
53	101	5.4375	0.025	0.034	0.045	0.062	0.072	0.085	0.113
54	105	6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
55		6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
56	110	6.75	0.031	0.042	0.056	0.077	0.089	0.105	0.141
57		6.5	0.030	0.041	0.054	0.075	0.086	0.102	0.135
58		6	0.027	0.038	0.050	0.069	0.079	0.094	0.125
59	112	6.625	0.030	0.041	0.055	0.076	0.087	0.104	0.138
60		6.75	0.031	0.042	0.056	0.077	0.089	0.105	0.141
61	113	6.8125	0.031	0.043	0.057	0.078	0.090	0.106	0.142
62	115	6.625	0.030	0.041	0.055	0.076	0.087	0.104	0.138
63		6.5	0.030	0.041	0.054	0.075	0.086	0.102	0.135
64	119	6.8125	0.031	0.043	0.057	0.078	0.090	0.106	0.142
65	122	6.78125	0.031	0.042	0.057	0.078	0.089	0.106	0.141
66	127	7	0.032	0.044	0.058	0.080	0.092	0.109	0.146
67	130	6.625	0.030	0.041	0.055	0.076	0.087	0.104	0.138
68		6.75	0.031	0.042	0.056	0.077	0.089	0.105	0.141
69	131	7.125	0.032	0.045	0.059	0.082	0.094	0.111	0.148
70	132	7.125	0.032	0.045	0.059	0.082	0.094	0.111	0.148
71	133	7.0625	0.032	0.044	0.059	0.081	0.093	0.110	0.147
72	136	7.3125	0.033	0.046	0.061	0.084	0.096	0.114	0.152
73	140	7.3125	0.033	0.046	0.061	0.084	0.096	0.114	0.152
74	152	8	0.036	0.050	0.067	0.092	0.105	0.125	0.167
75	155	8	0.036	0.050	0.067	0.092	0.105	0.125	0.167

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