I am wanting to draw plans for a 10.25/7.25Inch gauge layout to build in the near future. does anyone know how to work out the scale for locomotives and rolling stock and buildings and for loading gauge's. I am in New Zealand where our gauge is 42in but would like to include standard gauge equipment as well as my "Ho" includes both British and American..
Thanks Jim Hall
I would think there are some standards or common practices for large scale trains in NZ, so I would go looking for those first, before embarking on an uncommon or personally devised scale:gauge ratio. Advantage #1: there would be a fair amount of parts etc available, reducing the amount of scratchbuilding required. Advantage #2: there will be a community of large-scale modellers that will provide help and sociability.
But to answer your questions:
Divide the prototype track gauge by the model track gauge. I assume you want 7.25" to represent 42" gauge. 42/7.25 = 5.79, so the absolutely correct scale would be 1:5.79
If 10.15 gauge represents standard 4' 8.5" gauge, then 54.5/10.25 =
5.31, so the absolutely correct gauge would be 1:5.31.You could build each prototype to the exact scale, which would make the standard gauge trains about 10% oversized compared to the narrow gauge (NZ)_ trains. Or you could compromise, and build both kinds of trains to the same scale, say 1:5.5, which would make the standard gauge narrow, and the narrow gauge wide for the trains.
As for buildings: I suggest 1:6 scale, making the buildings undersized, but that would make the trains look relatively bigger (which is an advantage in creating the illusion of massive locomotion.) In HO we often use "selective compression" to model large buildings to a size that doesn't overwhelm the trains, so using the same trick for large-scale trains would be OK.
Loading gauges: find the actual loading gauges (google is your friend), and calculate the scaled down dimensions in your chosen scale. All you need is the standard gauge one, it will automatically be large enough for the narrow gauge trains.
HTH & have fun! Wolf K.
In message , Jim Hall writes
There is a miniature railway that runs both 10.25 and 7.25 (one common rail for the two gauges) at Eastleigh, Hampshire. I was involved as a volunteer guard (and The Fat Controller for Thomas events!) when I lived nearer. They have various contacts with the 7 1/4 gauge society so may be able to put you in touch with people in NZ Web page at
Divide the prototype gauge by the model gauge to get a scale ratio.
eg 1067mm (NZ gauge) divided by 260.35mm (10 1/4") = 4.0983291.. That's near enough to 1:4 0r 4:1 scale. If you end up with a ratio that is too far out to be rounded neatly then you need to go down, not up as it's better to have too narrow a gauge than too wide a gauge. Normally we beef up valve gear, bogie side frames etc and need greater clearances to get our rolling stock around curves.
Greg.P.
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