ScaleSeven | 5ft 3in standards

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.

Track & Wheel Standards

Basic Design Dimensions for 5ft 3in gauge

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

The figures have been interpolated from the Standard Gauge dimensions for the purposes of establishing the ScaleSeven Standards for 5ft 3in gauge permanent way, and have been calculated to a high degree of accuracy to ensure that the use of the scale ratio does not introduce undesirable distortions. The difference between Standard Gauge and 5ft 3in is 6-1/2in (3.75mm at 7mm scale).

Acknowledgements to Dennis Mowatt for compiling these standards.

Dimension			Prototype	7mm Equivalent		Prototype
			Size (inches)	Exact (mm)	Rounded (mm)	Equivalent (inches)

1	Track Gauge (min)		63.0	36.75	36.75	63.0
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
3	Tyre Width	wagon and coach (min)	5.00	2.9167	2.90	4.971
4	Back-to-back (max) (Standard dim is 5ft)		60.125	35.073	35.05*	60.086
5	Effective flange		1.125	0.6562	0.68	1.131
6	Back-to-back + effective flange (4+5)		61.250	35.729	35.73*	61.250
7	Check gauge (min)		61.250	35.729	35.73*	61.250
8	Crossing flangeway (min)		1.750	1.0208	1.00	1.714
9	Over check rail faces (max)		59.500	34.708	34.83*	59.709
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	71.125	41.4478	41.42 (min)	71.006 (min)
15	Over tyre faces	wagon and coach	70.125	40.8645	40.85	70.029