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Critical dimentions for scale modellers.

Critical dimentions for modellers of
British standard gauge railways
in the popular modelling scales.

Standard Dimentions.

Standard dimentions as defined by the British Railway Modelling Standards Bureau
with additions for British `N'gauge and 2mm finescale by Ozz Scott.
British N gauge, 1/148 scale.2mm Finescale, 1/152 scale.

Platforms, station buildings and bridges.

Track, platforms, buildings and bridge dimentions.

Tunnel and overbridge dimentions.

Track, tunnel and overbridge dimentions.
Standard Dimentions
Ref
Letter
See
Note
Prototype
(Ft)
N gauge
(1/148)
2mm
finescale
TT3
(3mm)
HO
(3.5mm)
OO
(4mm)
EM
(4mm)
O fine
(7mm)
A
1
08.00
16.50
16.00
24.00
28.00
32.00
32.00
56.00
B
1
06.25
12.89
12.50
18.75
21.75
25.00
25.00
43.75
C
1
12.50
25.78
25.00
36.75
43.75
50.00
50.00
87.50
D
2
03.00
06.18
06.00
09.00
11.50
12.00
12.00
21.00
E
10.50
21.65
21.00
31.50
36.75
42.00
42.00
73.50
F
13.50
27.84
27.00
40.50
47.25
54.00
54.00
94.50
G
05.50
11.34
11.00
16.50
19.25
22.00
22.00
38.50
H
3
09.50
19.59
19.00
28.50
33.25
38.00
38.00
66.50
J
05.65
11.65
11.30
17.00
19.75
22.50
22.50
39.50
K
09.00
18.56
18.00
27.00
31.50
36.00
36.00
63.00
L
05.30
10.93
10.60
16.00
17.25
21.25
21.25
37.00
M
03.50
07.21
07.00
10.50
12.25
14.00
14.00
24.50
N
00.75
01.54
01.50
02.25
02.50
03.00
03.00
05.25
O
4
06.50
13.40
13.00
23.75
21.50
31.50
31.50
45.00
P
4 *
11.15
22.99
22.30
38.00
40.00
50.00
45.00
80.00
Q
03.50
07.21
07.00
10.50
12.25
14.00
14.00
24.50
R
1
15.00
30.93
30.00
45.00
52.50
60.00
60.00
105.00
S
5
13.00
26.81
26.00
39.00
45.50
52.00
52.00
91.00
T
5
19.50
40.21
39.00
58.50
68.25
78.00
78.00
136.50
U
5
06.75
13.92
13.50
20.25
23.75
27.00
27.00
43.75
V
1
05.33
10.99
10.66
16.00
18.50
21.25
21.25
37.25
W
6
04.71
09.00
09.42
12.00
16.50
16.50
18.00
32.00
X
1
06.00
12.37
12.00
18.00
21.00
24.00
24.00
42.00
Y
1 +
02.40
04.95
04.80
09.00
09.50
11.00
10.00
17.50
Z
1
01.00
02.06
02.00
03.00
03.50
04.00
04.00
07.00

NOTES

1 = Minimum.
2 = Standard (minimum for prototype 2ft 9in).
3 = Maximum.
4 = Prototype dimentions are minimum.
5 = In `N', `2mm fine' `TT-3', `OO' and `O' coarse gauges, an extra 1.8mm, 2mm, 3mm, 5mm and 7mm respectively is necessary on curves.
* = Dimentions are for straight running roads (Center to Center), for siding increase as above. (see 5)
+ = Dimentions are for straight platforms, increase on curves as necessary.
6 = In British N gauge, 9mm gauge track is used. The correct 1/148th scale track gauge works out at 9.7143mm all models are built to suit available 9mm gauge trackwork.
The track gauge (W) is measured between the inside faces of the rails, not the rail centers as marked on the above diagrams.

Thanks must go to `Model Rail' magazine for publishing the BRMSB standard dimentions for `TT3', `HO', `OO', `EM' and `O fine' scales in the July 2000 issue which prompted me to add the dimentions for `British N gauge' and `2mm finescale'. The N gauge dimentions are for British 1/148th scale.

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Copyright Notes

All content, images and photographs on this site are Copyright ©1999/2000 Ozz Scott unless stated otherwise. Copyright holders will be fully credited for images where copyright is held by a third party.

The labelled diagrams on this page were drawn by myself (Ozz Scott) and were based on the diagrams published in the July 2000 issue of Model Rail magazine.

The standard dimentions for `TT3', `HO', `OO', `EM' and `O fine' scales are those defined by the British Railway Modelling Standards Bureau.