NG gauge query

[steve1]

I’ve just been reading an article in the Bachmann Collector’s Club mag about Welsh NG lines.

 

What stuck was how so many of them had a gauge that ended in half an inch. Why was this does anyone know?Surely it would have made more sense to go to a full inch, either up or down? For example 2ft instead of 1ft 111/2ins.

 

Thanks

 

steve

[Bill Eaton]

Possibly, it is the nearest imperial measurement to a metric figure that is a round number. For example, 600mm (a common gauge in continental Europe) works out at 23.62205 inches, which to the nearest 1/8th of an inch is 1 foot 11 5/8ths inches and to the nearest half inch is 1 foot 11 1/2 inches.   

[NCB]

13 hours ago, steve1 said:

I’ve just been reading an article in the Bachmann Collector’s Club mag about Welsh NG lines.

 

What stuck was how so many of them had a gauge that ended in half an inch. Why was this does anyone know?Surely it would have made more sense to go to a full inch, either up or down? For example 2ft instead of 1ft 111/2ins.

 

Thanks

 

steve

 

It happened a lot, on other gauges as well. This is what Wikipedia says about the broad gauge:

The gauge initially proposed by Brunel was 7 ft (2,134 mm) exactly but this was soon increased by 1⁄4 in (6 mm) to 7 ft 1⁄4 in (2,140 mm) to accommodate clearance problems identified during early testing. George Stephenson was to add an extra half inch to his original 4 ft 8 in (1,422 mm) gauge for the same reason.

 

I suspect that it's to do with tightening on curves.

 

Interesting that the broad gauge was almost exactly 50% more than the standard gauge.

 

Nigel

Edited February 8, 2021 by NCB

[The Johnster]

The Ffestiniog was the first of the '2 foot' (actually 1'11  5/8") gauge railways, in the world, and presumably adopted this specific gauge because the relevant quarry tramways had already established it as a standard, though why that size and not the round 2' I have no idea.  But it does occur to me that the original 2' dimension might have been an axle length.  Just guessing, of course.

[Nearholmer]

I’m 99% sure the Festiniog was built to 600mm gauge at a time when leading engineers in Britain were calling for metrification.

 

Several of the others began with less obscure gauges, but measured between the centres of the railheads - things became odd when the point of measurement was changed to the gauge-face, particularly for the Penrhyn, whose original rail was elliptical-section.

 

 

Edited March 8, 2021 by Nearholmer

[Jub45565]

A lot of early gauges were defined by rail centres, rather than between rails.  It is obviously easier to lay with a gauge bar between the rails - and if you get worn rail or buy new heavier rail then the centre measurement would change.  It makes a bit more sense in quarry scenarios with double flanged wheels loose on the axles, though the absolute gauge is a bit less of a concern there.  Then when you change to defining by between rails it just changes the stated gauge, rather than any actual change in the dimensions used.

 

The FR is technically 597mm.