Further Information

Notes

In the table, the first column of dimensions gives the prototype size, the second shows the exact scale equivalent for a scale of 7mm=1ft (43.5429:1). The third column gives the rounded 7mm scale equivalents which are the basis for the ScaleSeven Standards. These have been set at the values shown after consideration of such matters as the effect of the scale factor and manufacturing tolerances. The fourth column converts the rounded dimensions back to prototype for comparison purposes.

The 7mm scale ratio is 1:43.5429.

Dimension 11 gives the theoretical clearance at crossings.

Dimension 12 gives the clearance on straight track.

Dimension 13 gives the clearance on curved track.

Maximum gauge widening is required at 5-1/2 chains radius, ie 8ft 4in radius in 7mm scale.

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Track and Wheel Standards

Basic Design Dimensions for Standard Gauge

Do not be misled by the large number of decimal places in some dimensions. This does not imply an accuracy that cannot be achieved. The figures have been produced for the purposes of establishing the ScaleSeven Standards and have been calculated to a high degree of accuracy to ensure that the use of the scale ratio does not introduce undesirable distortions.

These standards are for Standard Gauge (4ft 8-1/2in). Use these links for Irish 5ft 3in gauge or GWR Brunel 7ft 0-1/4in broad gauge standards.

 

Dimension

Prototype

7mm Equivalent

Prototype

 

Size 
(inches)

Exact 
(mm)

Rounded 
(mm)

Equivalent (inches)

             

1

Track Gauge (min)

56.5

32.9583

33.00

56.572

2

Gauge Widening (max)

0.750

0.4375

0.45

0.771

3

Tyre Width

locomotive (nom)

5.500

3.2083

3.21

5.503

wagon and coach (min)

5.00

2.9167

2.90

4.971

4

Back-to-back (max)

53.625

31.2812

31.30

53.657

5

Effective flange

1.125

0.6562

0.68

1.131

6

Back-to-back + effective flange (4+5)

54.750

31.9375

31.98

54.823

7

Check gauge (min)

54.750

31.9375

31.98

54.823

8

Crossing flangeway (min)

1.750

1.0208

1.00

1.714

9

Over check rail faces (max)

53.000

30.9166

31.08

53.280

10

Crossing flangeway – effective flange (8–5)

0.625

0.3646

0.32

0.549

11

Check gauge – (back-to-back+one effective flange) (7–(4+5))

0.000

0.000

0.00

0.000

12

Track gauge – (back-to-back+two effective flanges) (1–(4+(2x5)))

0.625

0.3646

0.34

0.583

13

Back-to-back – over check rail faces (4–9)

0.625

0.3646

0.22

0.377

14

Track gauge + gauge widening – (back-to-back + two effective flanges) ((1+2) – (4+(2x5)))

1.375

0.8021

0.79

1.354

             

15

Over tyre faces

locomotives

64.625

37.6978

37.67 (min)

37.77 (max)

64.577 (min)

64.745 (max)

wagon and coach

63.625

37.1145

37.10

63.600

Notes

In the table, the first column of dimensions gives the prototype size, the second shows the exact scale equivalent for a scale of 7mm=1ft (43.5429:1). The third column gives the rounded 7mm scale equivalents which are the basis for the ScaleSeven Standards. These have been set at the values shown after consideration of such matters as the effect of the scale factor and manufacturing tolerances. The fourth column converts the rounded dimensions back to prototype for comparison purposes.

The 7mm scale ratio is 1:43.5429.

Dimension 11 gives the theoretical clearance at crossings.

Dimension 12 gives the clearance on straight track.

Dimension 13 gives the clearance on curved track.

Maximum gauge widening is required at 5-1/2 chains radius, ie 8ft 4in radius in 7mm scale.

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